DEP<j\RTMENT

OF

PRIMARY INDUSTRY AND

FISHERIES

TECHNICAL ANNUAL REPORT

1996/97

November 1997

NORTHERN TERRITORY OF AUSTRALIA

CONTENTS

INTRODUCTION

HORTICULTURE DIVISION

AGRICULTURE DIVISION

PASTORAL DIVISIONS

KATHERINE

1ENNANT CREEK

ALICE SPRINGS

LAND RESOURCE MANAGEMENT DIVISION

RESOURCE PR01ECTION DIVISION

ANIMAL HEALTH DIVISION

FISHERIES DIVISION

PUBLICATIONS, CONFERENCE PAPERS, PRESENTATIONS

1

3

71

99

120

131

137

148

171

196

213

1

INTRODUCTION

The nature of the work of the Department of Primary Industry and Fisheries (DPIF) depends on the various demands placed upon it by the rural and fishing industries. These may require short or medium term projects to investigate a problem and offer advice or they may entail the implementation of a research project lasting over several seasons or even over decades in the case of such aspects as range management. Fisheries activity involves constant monitoring of marine populations, investigation and control of catch size and method of catch for each species. Fisheries activity also promotes the development of aquaculture to supplement or replace product gathered from natural sources. All DPIF activity is guided by a need to ensure that production is permanently sustainable as well as economically viable.

Short term investigatory work may be precipitated by industry emergencies such as the appearance of disease and these may be, directly or indirectly, affected by weather activity. This equates, in the north of the Territory, with the nature of the monsoon and, in the south of the Territory, the extent, duration and severity of drought conditions. Fishery activity is also to an extent a reflection of seasonal conditions.

After a dry year in 1995-96 the 1996-97 monsoon provided record rainfall in the Darwin and Katherine regions. The rains started early but finished very abruptly at the beginning of April. Pasture growth was good, and, as for the past several seasons, has rendered supplementation unnecessary in the Victoria River area.

Cattle properties in the north are now geared heavily towards the live cattle export trade which continued to expand. Arable properties have maintained the trend to replace field crops with hay crops to support the trade. A strong demand for land suitable for agriculture has continued and government initiatives to make more land available continued during the year.

Mango harvesting in the Top End was again affected by rain but total product rose as further areas entered production. The expanded area of banana planting in the previous year was reflected in a 45% increase in production and the value of the vegetable crop increased 10%. Interest in new tropical fruits continued and the Department maintained its policy of introducing new species from Asia for examination and appraisal.

One investigation not linked to seasonal effects was the examination of Top End flying foxes for evidence of equine morbillivirus and bat Iyssavirus. Both viruses were found to be present in the Territory.

The Barkly Tablelands had an excellent season, feed was abundant and stock again entered the dry season in good condition. The Barldy region also continued to contribute to the live export trade.

In the Alice Springs Region the severe drought continued, affecting properties over much of the region, particularly the western half. Cattle prices remained depressed and properties continued to experience hardship. The rabbit calicivirus has established in the region and rabbit numbers are much reduced leading to the re­appearance of hitherto suppressed floral species.

Table grapes maintained production in Central Australia as a major industry and there was limited but viable production of asparagus and hydroponic lettuce, the latter being supplied throughout the Territory and seeking overseas markets.

In the fisheries area there was a downturn in the prawn catch but higher prices resulted in an upturn in value. Other fisheries were stable. There was increased enquiry to DPIF about aquaculture but this has not so far translated into further commercial ventures. Recreational fishing tour operations expanded greatly and new regulations were drafted to control this industry. Consultation with Aboriginal communities led to the formation of six committees to develop commercial fishing enterprises.

A range of DPIF research projects were active with particular attention to the Timor Reef area and the demersal fishery.

Reporting follows a similar pattern to that in last year's Technical Annual Report and records the work of the programs and projects of each Division. The Department was reorganised during the year but reporting reflects the organisation as it was at the start of the year. The work may be experimental, developmental or regulatory,

2

with some Divisions engaged in all of these aspects. Reports are presented on a project basis wherever appropriate.

DPIF RESEARCH CENTRES

Fisheries Research J!;;::;) Darwin Aquaculture Centre

B.R.F. = C.P.R.S. = D.D.R.F. = K.R.F. = V.R.R.S. = Ti-Tree = A.Z.R.I. =

• Kalkaringi

Tennant Creek

Avon Downs

Berrimah Research Farm Coastal Plains Research Station Douglas Daly Research Farm Katherine Research Station Victoria River Research Station Ti Tree Research Block Arid Zone Research Institute

3

HORTICULTURE DIVISION

MANGOVAruETALTruALS

Project Officers: V Kulkarni and D Hamilton

Objective: The Australian mango industry is based on a single cultivar, Kensington Pride. The need for diversification into other cultivars can be justified on two grounds. Firstly, Kensington Pride has some major limitations such as erratic flowering and fruiting, severe sapburn, excessive tree vigour and lack of consistent attractive red blush on fruit. In the tropical environment of the Top End, these problems are further accentuated. While research in productivity improvement has given very encouraging results, introducing and evolving promising cultivars is yet another approach. In a national mango breeding project commenced in 1994, improvement of Kensington Pride is being attempted by crossing it with other donor cultivars.

This project has two objectives (1) Introduction and multilocation testing of promising cultivars from overseas and (2) Evolving superior seedling types from monoembryonic seedlings and multilocation testing of clonally propagated progeny of the selection.

Method and Results: Introduction and multilocation testing of new introductions : The new introductions from India and species introduced from S.B. Asia were planted out at Coastal Plains Horticultural Research Farm (CPHRF) and/or Berrirnah. It is proposed to test some of the most promising types, such as Badami Model, Vanraj, Kesar, Mahmuda, Hirnayatpasand and Nam Dok Mai selection T5 in grower properties.

Response from growers to volunteer their properties has been very encouraging. It is proposed to propagate the outstanding cultivars for evaluation on grower properties under a testing agreement. Conditions for such an agreement have been prepared.

Evolving superior seedling txpes from monoembryonic cultivars : From a large number of monoembryonic seedlings planted at CPHRF in 1983, one selection was found to be most promising. Tentatively named as S-113 after its site in field, the selection from 'Glen' seedling is similar to Kensington Pride in taste and fruit shape but has more attractive fruit with little fibre in flesh. Time of fruit maturity is on par with Kensington Pride. It is proposed to test its performance in grower properties along with the introductions mentioned above.

One more selection identified by us in a grower property is being registered with Plant Breeder's Rights. The selection has outstanding fruit quality especially fruit appearance, and has been bearing regularly for the last three years. It has been named as 'Celebration'. The selection is being described on guidelines used for international registration of mango cultivars. ' Celebration' is likely to be registered by 1998.

*****

MANGO BREEDING - NATIONAL MANGO BREEDING PROGRAM

Project Officers: V Kulkarni and D Hamilton

Objective: Although the supply of the Kensington Pride mango in Australia far exceeds that of any other mango cultivar, Kensington Pride has several inherent problems related to both production and quality which have a significant impact on producers and the market. Some of these problems can be controlled through the use of sound cultural practices and use of plant growth regulators but evolving superior genotypes to suit the needs is perhaps a more tangible approach.

To address this, a national mango breeding program was initiated in 1994 between CSIRO, QDPI, NT DPIP and W AAG. The primary aim of the program is to improve the performance of Kensington using the conventional

4

breeding method of transferring pollen from Kensington to other cultivars with certain superior characteristics such as:

* Dwarf growth habit * High productivity * Early maturity (NT) * Fruit size ( 400g) * Fruit colour ( blush) * Retention of the Kensington flavour * Reduced fruit internal disorders * Reduced sap burn and post harvest problems * Disease resistance * Longer shelf life

Other commercial cultivars of lesser importance, but with good potential and in need of improvement, such as Irwin, R2E2 and Nam Dok Mai were also included in the program. In addition to generating promising genotypes, the project also provides an excellent opportunity to study inheritance of various characteristics in mango.

Materials and Method: Donor cultivars with the desired characteristics were selected in 1994 when the collaborative project was initiated. The successful crosses were protected against insect pests and diseases. Well developed fruits at 'late egg' stage were bagged in onion bags. After fruit maturity and ripening, kernels were sown to raise seedling progeny of the crosses.

Progeny are being tested at two sites, one at South Edge Research Station in Queensland and the other at CPHRF in NT. Plant material of the successful crosses, therefore, is to be sent by all the participants to the two sites. Original seedlings are to be planted in the NT whereas grafts from these seedlings are to be planted in Queensland. After the initial evaluation, promising progeny will be further tested using clonally propagated material.

Resnlts and Discussion: This year, a number of successful progeny were generated by NT DPIF (173 as compared to 158 by CSIRO, 64 by QDPI and 83 by W A AG). Fruit set was better in early crosses in June and early July than late July and August. The total number of crossed progeny from 1994 till 1996 is nearly 1200. By the 1997 and 1998 seasons, this number is likely to reach the 1500 mark.

*****

REGULATION OF VEGETATIVE GROWTH, FLOWERING AND FRUITING

Project Officers: V Kulkarni and D Hamilton

Objective: Improvement of productivity in mango continues to be the foremost issue for mango. In the tropical conditions of Darwin, the commercial cultivar Kensington Pride suffers from intermittent and pre-flower flushing .. The resultant reduction in yield and delay of fruit maturity has a direct impact on productivity and profitability for an industry which relies heavily on the early domestic market. Soil application of paclobutrazol has been found to be an effective tool for improving flowering and yield and for advancing fruit maturity but the efficacy of paclobutrazol is diminished with untimely vegetative flushing. Prevention or removal of such untimely vegetative flush should then improve flowering and response to paclobutrazol.

This trial examines pre flower pruning together with post harvest skirting for improving yield and quality in a higher density situation.

Materials and Method: Grafted trees on Kensington Pride seedling rootstock planted at 10 X 5 m in a private property were used. Trees were initially trained for two years to form a strong framework and were 3 years old when the trial commenced.

5

Treatments included pre-flower pruning, pruning in combination with paclobutrazol (PBZ), pruning alone, PBZ alone and control.

Results and Discussion: Maximum flowering was generally obtained by the PBZ + pruning treatment followed by the PBZ alone treatment. Flowering was also early and synchronous in these treatments and was completed within six to seven weeks after pruning whereas in the other two treatments, it was distributed between six to ten weeks.

When yield was related to the canopy size, yield efficiency was highest in PBZ + pruning. By this time, control trees had attained significantly large canopies overlapping within the rows which adversely affected flowering and fruiting on these aspects. Visual pest monitoring also showed higher incidence of white scales not found in the well-lit canopies of the pruned trees.

One consistent observation was poor flowering on the south west aspect of the unpruned trees. Terminal buds on these shoots remained dormant through the floral cycle and emerged later as vegetative shoots. This effect was overcome by pruning treatment.

These investigations have shown that the flower-inhibiting effect of immature vegetative flush can be overcome with pre flower pruning and that such removal of unwanted growth during the reproductive cycle significantly improves yield of Kensington Pride. These results need to be elucidated with our existing knowledge of promotery and inhibitory mechanisms in operation. The combination approach has perhaps opened a way for a higher density planting system in the tropics. Experience has shown that heavy pruning after harvest and hedge row system may not be advantageous in tropics because of reinstatement of vigour and uncontrolled return growth.

Mechanical pruning is an area that needs to be looked into and has to take into account the needs of the technique. The option of mechanical or manual pruning will depend upon other factors such as, tree size and number of trees to name two. One option is a combination of mechanical pruning of the top and manual pruning of the sides.

*****

PROPAGATION AND ROOTSTOCKIINTERSTOCK TRIALS

Project Officers: V Kulkarni and D Hamilton

Introduction: Together with and possibly likened to erratic flowering and fruiting, excessive tree vigour is another major limitation with the commercial cultivar Kensington Pride. The tropical environmental conditions of the Top End further accentuate the problem of excessive tree vigour and low productivity. Strategies towards vigour control in this situation can be mediated through (I) management practices such as pruning and nutrition, (2) chemical means such as plant growth regnlators like paclobutrazol, (3) breeding and (4) use of rootstocks and interstocks. These techniques are being investigated.

Materials and Method: Two types of rootstock material are proposed to be used: (I) Use of seedling rootstocks which have shown promise in other cultivars. These include Vellaikolamban, 13-1 and Sabre in comparison with Kensington Pride as control. (2) Clonally propagated marcots of dwarf and ready to root cultivars such as Mahmuda Vikarabad introduced from India.

Results and Discnssion: (I) Rootstock trial using seedling rootstocks: It is now proposed to undertake the rootstock trials on grower's properties under testing agreements similar to the agreements for the varietal testing. Grower reaction to a call for volunteering their properties was very positive. Rootstock material of cultivars mentioned above is being raised to layout trials using SRD design in grower properties with Kensington Pride as scion.

(2) Use of clonally propagated rootstocks: In preliminary attempts, excellent rooting was obtained in marcotting in January - March. The polystyrene 'stubby holders' were found to be ideal as containers for marcotting.

6

Rooting was very profuse in Mahmuda Vikarabad and satisfactory in Kensington Pride. Further work is in progress to prepare grafted material on the marcotted shoot directly on the parent tree without any need to use nursery beds. Initial results seem encouraging. If this technique is successful, it is proposed to test the performance of the clonally propagated rootstocks in grower properties.

*****

ROOTSTOCKS FOR KENSINGTON PRIDE MANGOES

Project Officers:

Objective:

M Smith, M Hoult, J Bright, G Foard, S McAlister, C Brown, S Smith and M Langdrigan.

The aim is to identify rootstocks that will increase the commercial profitability of mango growing.

Materials and Method: Two rootstock experiments, with Kensington as the scion, were harvested in the 1996 season. The oldest of these experiments contains 9 stock treatments and has been reported on extensively in the past.

Results and Discussion: Results from this experiment in the 1996 season were largely consistent with those obtained over the past 5 seasons. The rootstock Sg. Siput again out yielded (124 kg/tree) all other stocks by a large margin, whilst Sabre was the poorest (27 kg/tree) yet again.

Sg. Siput has clearly emerged as a superior rootstock, resulting in significant commercial interest.

Quality assessments in the other Kensington rootstock experiment showed that stock influenced fruit maturity time, with Red Harumanis giving the earliest maturing fruit while Batavi delayed maturity.

*****

MANGO V ARIETALIROOTSTOCK EVALUATION

Project Officrs: M Smith, J Bright, M Hoult, G Foord and S McAlister

Objective: This work involves the evaluation of seven different scion cultivars (Glenn, Haden, Irwin, Kensington Pride, Kent, Tommy Atkins and Zill) on two different rootstocks (Sabre and ARC Common).

Materials and Method: Data collection in this experiment was completed during the 1997 season. Yields of most combinations were poor considering the age of the trees. This is believed to be due, in part, to inadequate nutrient additions in the latter years of the experiment.

Results and Discussion: Overall, the experiment revealed a number of interesting trends. For example, Kensington was found to give yields comparable (on a per tree basis) to most of the other cultivars, contrary to the beliefthat it is a 'low yielding' cultivar. However yield efficiency was lowest with Kensington. This cultivar also compared favourably with the others in terms of consistency of production from year to year.

Haden produced very well during the early years, but had slumped in the last few seasons. Conversely, Tommy Atkins was quite slow to come into production and had produced good yields in the latter years of the experiment.

All cultivars grown on Sabre rootstock produced markedly smaller trees and lower yields than on ARC Common, and it is not recommended for commercial use. One notable exception is the combination of Kent on Sabre, which resulted in small trees, with high yields. This combination would be well suited to high density planting.

7

Many of the problems in mango production that are often blamed on the Kensington cultivar, appear to be common to many other cultivars. It would seem that overcoming these problems requires more than simply changing to a 'better' scion cultivar.

*****

MANGO RESEARCH IN CENTRAL AUSTRALIA - CULTIV AR EVALUATION

Project Officers: G Kenna, J Mansfield and S Marte

Objective: The objective of this experiment is to evaluate the commercial production of mangoes in the southern region of the Northern Territory for the lucrative late season domestic market.

Materials and Metbod: In 1990 twelve cultivars were planted in a single row running north-south at a spacing of 3 m between trees. For nine of the cultivars there are two trees of each cultivar planted adjacent to each other. For the other 3 cultivars (Davis Haden, Keitt and Manzanillo Nunez) there is only one tree of each. All the trees are on Kensington rootstock except for the Manzanillo Nunez which is on Adelaide River Common rootstock.

Mature fruit were harvested and weighed. The date and tree from which this fruit was removed were recorded. From this information it is possible to compare the cultivars for differences in harvest patterns, fruit size and total yield (kg fruit/tree).

Results and Discussion: The cultivars which produced the earliest fruit were Irwin, Lippens, R2E2 and Sensation while the cultivars which produced the latest fruit were Keitt and Kent. In addition to Davis Haden, Keitt and Kent were also the highest yielding cultivars producing around 50 kg per tree. This is based on estimated yield (number of fruit collected by average fruit size) and not marketable yield as due to the wet summer in the Ti Tree area some fruit was damaged by fruit piercing moth. The fruit of the cultivar R2E2 averaged 720 g and this much greater than the other cultivars with most of these averaging between 440 and 570 g.

*****

MANGO RESEARCH IN CENTRAL AUSTRALIA - HIGH DENSITY PLANTING

Project Officers: G Kenna, J Mansfield and S Marte

Objective: Due to the slower growth of mango trees in the Central Australian region compared to those further north, research has been directed at maximising the yield per unit area by examining various high density planting designs.

Materials and Method: In 1990 a high-density planting trial was established by planting six plots in an east-west direction. Two plots are single row plantings of 5 trees each of Kent and Naomi at 2 m spacings between trees. Another four plots are double row plantings at a spacing of 2 m within rows and 2 m between rows. The two rows are offset to each other by 1 m. One row contains five trees and the other contains four. The cultivars grown in these plots are Palmer, Keitt, Kent and Springfels. All the trees are on Kensington rootstock.

Mature fruit were harvested and weighed. The date and tree from which this fruit was removed were recorded. From this information it is possible to compare the cultivars for differences in harvest patterns, fruit size, and total yield (kg fruit/tree).

Results and Discussion: The trees of the cultivar Kent planted in the single row plot showed a difference to the trees of the same cultivar in the double row plot. The single row planting produce mature fruit slightly later had almost twice the yield per tree of the double row planting (31 kg compared to 18 kg) and also had larger fruit (average of 505 g compared

8

to 433 g). The cultivar Springfels had an average fruit size of 669 g which was higher than for the other cultivars.

*****

IMPROVEMENT OF FRUIT QUALITY IN MANGO - IMPROVEMENT OF EXTERNAL FRUIT COLOUR AND FRUIT FIRMNESS BY CONTROLLING VEGETATIVE VIGOUR

Project Officers: V Kulkarni and D Hamilton

Objective: Besides affecting flowering and fruiting, excessive and frequent vegetative growth (flushing) in mango in the warm growing conditions of Darwin region is also implicated in problems associated with internal and external quality of fruit. The effect of pre flower pruning on elimination of this adverse effect on fruit quality was investigated in 1995 season with and without PBZ.

Materials and Metbod: Fruit from the pre flower pruning trial was used for this purpose, pruning alone and control on fruit quality was assessed to confirm visual observations made in the previous two years. A total of 48 fruits were taken randomly (six/tree) from each treatment were ripened at 20°C. and were assessed for external colour and internal quality when they were ripe to eat.

Results and Discussion: Red blush on the fruit: Pre flower pruning had a dramatic positive effect on development of red blush on the fruit. Average colour rating of the fruits, proportion of fruits with noticeable blush and quantitative measurement of the blush were significantly higher in the PBZ+ pruning and pruning alone treatments than in the unpruned treatments. There was no significant difference in fruit weight (540 to 585 g). Dramatic improvement in external fruit colour was obtained with pre-flower pruning. Differences were clearly visible in field. To a large extent, this difference can be attributed to less light interception in the pruned trees and the shading effect in the excessively vigorous trees.

Fruit firmness: Field observations suggested that fruits in the pruning treatments not only appeared more attractive but were also more firno than those from the unpruned treatments. Manual assessment with a fruit firmness index (FFI) and with a penetrometer to test pressure required to penetrate the fruit supported these observations.

It is tempting to attribute the ubiquitous quality- related problems in mango in the tropics to the excessive tree vigour and intermittent flushing during flowering and fruiting on one hand by being a source for the energy and on the other, by being a sink for nutrients and other metabolites during the course of fruit development and possibly through a hormonal pathway. It is proposed to investigate this aspect more closely.

*****

EFFECT OF LOCATION AND CULTURAL PRACTICES ON MANGO QUALITY

Project Officers: V Kulkarni, M Landrigan, D Hamilton and G Foard

Objective: Currently there is considerable interest in preharvest nutrition effects, particularly of calcium on fruit qUality. We decided to look at four sites in Darwin, experiencing perceived fruit quality differences.

Materials and Method: Four grower properties under different management systems were chosen. Leaf samples and soil samples were collected to build up profiles of inputs at each location. Samples of mature fruit were also assessed for quality and mineral content.

Resnlts and Discussion: Fruit Quality: With the fruit stored at 22°C there were some slight differences in quality of fruit from the Darwin growers. Fruit from Katherine was noticeably better in quality than the Darwin fruit. No decay and rots were

9

observed in Katherine fruit during the four week duration as compared to a much higher incidence in the Darwin fruit. Katherine fruit also took longer to ripen. Differences in the Katherine and Darwin fruit was even more significant when fruit were stored at lO°C. Grower 4 from Darwin had the highest incidence of decay and rots. Weight loss in fruit during ripening was also maximum in the fruit from G 4. Fruit from this property failed to develop any red blush.

Mineral analysis of fruit: Calcium content of the peel was much higher than that of the flesh. Calcium and potassium content of the peel and flesh of fruit from Katherine was noticeably high as compared to the Darwin samples. Fruits from G 4 which recorded a higher incidence of rots and lack of blush also recorded lowest calcium in the peel.

Mineral analysis of soil and leaf: Interestingly, property G4 which recorded relatively high rate of rots and low levels of calcium in fruit recorded lowest soil levels of calcium but unexpectedly higher levels of calcium in the leaves as compared with the other three properties. It is clear that the issue of nutrition and fruit quality needs long term research so that a suitable explanation can be found for these observations. There may be a need to evolve alternate ways to improve calcium levels in fruit

*****

IMPROVEMENT OF FRIDT QUALITY IN MANGO - EFFECT OF LOCATION AND CULTURAL PRACTICES ON MANGO QUALITY

Project Officers: M Landrigan V Kulkarni, D Hamilton, G Foard

Objective: Currently there is huge interest in preharvest nutrition effects, particularly calcium on fruit qUality. Work going on in Katherine examining productivity trends has been gathering data so we decided to look at a couple of sites in Darwin, experiencing perceived fruit quality differences. To gather some objective data, leaf samples and soil samples were collected to build up profiles of inputs at each location. Samples of mature fruit were also assessed for quality and mineral content.

Materials and Method: Four growers have been chosen who use different management systems in the orchard and who have previously had a range of fruit quality.

Fruit were tagged (at duck egg stage) on four trees in each orchard. About 30 fruit on each tree were tagged around the tree. At this stage soil and leaf samples were taken.

Fruit were harvested at commercial maturity (using visual observation and dry matter) and desapped for 30 minutes in the lab. No postharvest treatments were applied.

Resnlts and Discussion: Fruit Quality With the fruit stored at 22°C there were some slight differences in quality. Fruit stored at lOoC showed no noticeable differences between the fruit from different growers except one grower who experienced problems with rots, mostly anthracnose and the fruit had to be removed from storage after only 3 weeks. The incidence of rots in the remaining Darwin growers fruit were also high. No rots were seen on the Katherine fruit.

Mineral Analysis: There appear to be no obvious differences among the growers in respect of mineral analysis and this may explain why there were also very little differences in postharvest quality. This data really needs to be supported by several years work before any implications can be drawn. It will also be important to follow up on preliminary data out of Queensland (Peter Hoffman) suggesting little correlation between fruit quality and calcium content of the flesh.

*****

10

MANGO RIPENING RESEARCH - MODIFIED ATMOSPHERE STORAGE OF MANGOES

Project Officer: MLandrigan

Over the last few seasons LifeSpan have been working in conjunction with the W A Department of Agriculture and the W A mango industry to come up with some options for modified atmosphere packaging (MAP) of mangoes to prolong shelf life. With the development of a successful package and promising results after 8 weeks storage with W A fruit, it was suggested that trials be conducted with NT fruit to ascertain if they would perform similarly.

Materials and Method: Two trials were conducted. The first with fruit from Katherine (300 km south of Darwin) and the second with fruit from the Darwin region. 1. Fruit from Katherine was harvested on 24/10/96. Fruit had an average dry matter of 16.5% (a dry matter of> 14.5 % is considered desirable for commercial maturity). 2. Fruit from Darwin was harvested on 20111/96. Fruit had an average dry matter of 16.6%.

Fruit from both trials wer~ desapped for a couple of hours after harvested and washed in water and then dried prior to packing in the LifeSpan bags. Fruit from the Darwin region was dipped in a fungicide (Sportak®; 0.55 mLlL for 2 minutes) to reduce postharvest disease.

Fruit were then stored at 10°C and removals made at the following times; 4, 6 and 7 weeks. Assessments of fruit quality were made when the fruit had ripened, usually after 3 days at 22°C.

Assessments were made on skin colour using a rating scale (l=fully green; 6=fully coloured) and flesh firmness (1=hard; 5=oversoft). Disease was assessed using a five point scale (1=0% skin area affected; 2=1-5% skin area affected; 3=6-15% skin area affected; 4=16-30% skin area affected; 5=31-100% skin area affected).

Internal measurements on flesh colour (rating scale l=white flesh; 5=orange flesh) and total soluble solids were also recorded.

Results: The carbon dioxide and oxygen concentrations inside the bags were measured weekly. Values differed from those experienced in WA. One possible reason for this may have been the reduced weight in each bag (about 5 kg instead of the usual 7 kg).

1. Katherine Fruit Peel colour and fruit firmness were assessed immediately after removal from storage. Initially (after 4 weeks) fruit stored in MAP were less coloured and more firm upon removal. By 6 weeks, all fruit irrespective of MAP, had coloured to a rating of 5 (60-90% skin area fully coloured) and all fruit was at the edible ripe stage (rating 4). After 3 days at 22°C all fruit had coloured and was edible ripe.

Weight loss was significantly greater at all storage times for fruit not stored in MAP.

The rating for disease increased with time. At the first removal (4 weeks) the incidence of decay was lowest and had an average rating of 1.3 «1 % area affected). Whilst the percentage offruit effected was similar for the 6 and 7 week storage with MAP stored fruits, the rating increased from 2.5 (1-5% skin area affected) to 3.5 (6-15% skin area affected).

2. DaIWin Fruit Fruit were only assessed when ripe. The incidence of decay was high for all removals, whether the fruit were MAP stored or not.

This high incidence of disease may explain the reduced colour and softening compared to the Katherine fruit. That is, fruit may have been assessed earlier because of rots. The colour and firmness changes at week 6 and 7 were similar being a colour rating of 4 (>40% and <60% coloured 0 and a softness of 3 (moderate softening).

Weight loss again was significantly greater at all storage times for fruit not stored in MAP.

11

In both trials there were no differences between the MAP and non MAP fruit flesh colour and total soluble solids. It should be mentioned that some possible chilling injury was seen in fruit from Katherine stored without MAP for longer than 6 weeks. No noticeable chilling injury was seen in the MAP fruit. The chilling injury was expressed as a slight discolouring of the skin and a darkening of the flesh next to the skin.

These results suggest that under the conditions created in this trial, fruit could only be stored for about 4 weeks. Obviously care should have been taken to adhere strictly to the recommended weight and temperatures for these bags. Also it is interesting to note the somewhat poorer outtum of the Darwin fruit compared to the Katherine fruit. One reason for this may be the lower incidence of disease on the Katherine fruit due largely to environmental conditions. The Katherine growing environment would be quite similar to the Kununurra region.

*****

MANGO SAPBURN AND BROWNING AMELIORATION - MANGO SKIN BROWNING

Project Officers: M Landrigan and M Hearnden

Objective: Mango skin browning refers to the lYpes of skin blemishes (excluding sapbum) which appear on mangoes during postharvest handling and marketing. This research is part of the HRDC Mango Skin Browning Project co­ordinated by Rowland Holmes of QDPI. Last year QPDI put out an excellent guide to identifying the different lYpes of skin browning. Correct identification is essential to determine'the cause of skin browning. For the last three season we have been working with staff at QPDI to elucidate the causes of skin browning and initiate strategies for alleviating the problem.

Three experiments were conducted this season that looked at the following aspects: I)Effect of a range of concentrations of Mango Wash® on skin browning and sapbum; 2)Inducement of skin browning; 3)Effect of temperature differences on skin browning.

1) Effect of a range of concentrations of Mango Wash® on skin browning and sapburn

Materials and Method: Fruit were harvested from a grower's orchard in the Darwin rural area and dipped in one of the following Mango Wash® concentrations, 0.0, 1.0,2.5,5.0, 10.0 & 20 gIL. Within each group half of the fruit were dipped for 30 minutes and the other half for 5 minutes. Fruit were allowed to dry and sap was applied to one cheek of each fruit. Both skin browning and sapburn were assessed when fruit ripened.

A modified version of this experiment was repeated later in the season with fruit from the CPHRF harvested after a week of heavy rain. The following Mango Wash® concentrations were used 0.0, 0.25, 1.00, 5.00, 10.00 & 50 gIL and neither sap or detergent solutions were applied to the cheeks of the fruit after dipping. Dip times were 1 or 15 minutes.

Once again fruit were assessed when ripe.

Results and Discussion: Grower's property fruit: There were no significant differences between the 30 and 5 minute dip times therefore results presented have been combined.

The area where the absorbent pad was applied was assessed for damage and only lenticel injury was seen. The area where sap was applied was also assessed separately. No sapburn was experienced, only a combination of abrasion and etch (Skin browning score).

Colour development was unaffected by Mango Wash® concentration. The results, however, illustrate the random effect of Mango Wash® concentration on both lenticel injury and skin browning. Lenticel injury was not significantly different among the different Mango Wash® concentrations and levels recorded were low (<1). Where sap was applied there were significant differences with the amount of etch and abrasion recorded among the different detergent concentrations. However these differences do not necessarily provide a guide to the grower for the most effective concentrations. The lowest rates of Mango Wash® (1.0 and 2.5g1L) gave the

12

highest skin browning scores whilst the water and 20gIL had the least skin browning. This suggests that rates of Mango Wash® up to 50 gIL are no more detrimental to mango skin than water. No other forms of skin browning were experienced in this trial.

CPHRF Fruit: In this experiment there were significant differences between the two dip times, unlike in the previous experiment. This was probably due to the way the latter experiment was performed, i.e. sap was allowed to accumulate in the dip solutions. Thus fruit in the solutions for a longer time had more damage. At 15 minutes more fruit were more severely effected than those fruit dipped for only one minute. This confirms the belief that fruit held too long in contact with detergent solution that contain sap increases the chances of skin blemish.

From these experiments no upper limit for Mango Wash® concentration was established. Lenticel injury and etch and abrasion can be induced by water alone as well as by Mango Wash®. Concentrations up to and including 50.0 gIL (20 times the recommended rate) all can result in similar levels of injury. More important is the length of time fruit are in contact with the solution and the quantity of sap present.

2) Inducement of skin browning

Objective: The following experiments were designed to test the effect of a range of postharvest chemicals on skin browning. Three separate experiments were conducted. The first with fruit from Katherine (300 Ian south of Darwin)and the second and third with fruit from CPHRF. A third experiment examined the effect of time after harvest and fruit turgor as well as skin browning.

Materials and Method: Experiment 1: Fruit were harvested from KRS early in the morning, desapped for 30 minutes on racks then transported to the laboratory within 6 hours of harvest. The fruit were randomly distributed among the following treatments, resulting in 15 fruit per treatment; l)water, 2)Mango Wash® 2.5 gIL, 3)Mango Wash® 5.0 gIL, 4)Mango Wash® 50.0 gIL, 5)Agral 1.0%, 6)Coldpower 1 %, 7)Rogor® (aj. Dimethoate; Rhone-Poulenc) ImLlL, 8)Lebaycide® (aj. Fenthion; Bayer) 0.75 mLIL and 9)Sportak®(aj. Prochloraz; Hoechst & Schering) 0.55mLlL. The last three are postharvest insecticides and a fungicide. A further 3 groups of fruit were held at 22°C & 70 %RH for 24 hours before being treated with the following solutions, IO)Mango Wash® 50.0 gIL, 1l)Agral1.0%, and 12)Coldpower 1 %.

Experiment 2: The second experiment used fruit from CPHRF, involving a repetition of that at KRS. The only difference was the use of petri dishes to contain the solution and saturate the absorbent pad and skin. A few extra chemicals were included DCTron (Ampol) and Bioshield (Spray tech) at O.I/mLlL and LOC (Amway) at 1 % and a range of times fruit were left in contact with the solutions were used. These were 4, 6, 10 and 17 hours. Only the treated area was assessed for damage.

Results: Experiment 1: The results tells us that colour development was not effected by treatment in this experiment.

The only skin browning seen here was an enhancement of the lenticels. There were significant differences among the treatments with respect to skin browning. The Agral and the Coldpower, as experienced last season, gave the most intense lenticels and this injury was not reduced by leaving fruit for 24 hours, to allow the skin to become less turgid. Also 100% of the Agral fruit were effected at both times and for Coldpower the numbers were 80% immediately after harvest and 100% with time. The Mango Wash® results were again puzzling, with both the lowest and highest rates resulting in pronounced lenticels (-2). However this effect was reduced with the 24 hour after harvest treatments (0.2). The % of fruit effected was also reduced with the 24 hour after harvest. The reduced effect of Mango Wash® with time probably reflects its weaker penetrating power compared to Agral, a chemical specifically designed to be active at an interface.

The surface ofthe fruit not treated was also scored for area covered by lenticels and their intensity (using rating scale as in previous experiments). These results are interesting in that there are significant differences with both lenticel area effected and intensity on the untreated surfaces. This result may have biased the results for the

13

treated area. For example, the water treatment caused a lenticel score of 0.6 but the background level was similar (0.8), indicating, perhaps a lack of treatment effect.

The inability of the postharvest chemicals to induce skin browning may also be due to the fruit themselves. Fruit grown in Katherine are known for being 'tougher' due to the harsher growing conditions.

Experiment 2: Due to the complicated nature of these results I have reduced the fruit to not marketable and marketable and analysed the % of fruit in each solution time combination, that were not marketable. The cut off for marketable was fruit with an area score of 1 « 10% area effected) and / or an intensity score of 1 (faint).

Two hours in contact with the solution appears long enough to cause damage. And as seen in earlier experiments as little as 15 minutes may result in damage. Lenticel damage was the main form of injury with some etch occurring and a small percentage of fruit showing smear.

It is possible to rank the ability of the solutions to cause injury irrespective of duration of application. For lenticel injury Coldpower, Agral, Mango Wash, DCTron, LOC, and Lebaycide all had median values of greater than 50 % of fruit with lenticel injury. Water, Sportak and Rogor effected less than 30% of fruit with lenticel injury. With respect to the occurrence of etch, Coldpower, Agral, DCTron and LOC all effected greater than 30% of fruit. For smear the levels were too low to highlight differences.

Discussion: These three experiments highlight the random nature of response of fruit to treatment. It would appear that all postharvest chemicals including water are capable of causing il\iury. The most consistent form of injury able to be produced in these experiments was lenticel injury but damaged lenticels are also a result of 'natural' ripening processes, so these results should be interpreted with caution. It would also appear that not so turgid fruit are also susceptible to damage and that skin turgor is not the only thing predisposing the fruit to skin browning.

The fact that no skin browning (aside from lenticel damage) was seen on the 'tougher' fruit from Katherine perhaps provides evidence for regional differences in susceptibility.

3) Effect of temperature on skin browning

Due to speculation about the practice of dipping hot fruit into cooler dips and vice versa a small trial was undertaken to confirm the symptom, if any, from this practice.

Materials and Method: Fruit was harvested early in the morning at CPHRF. The fruit was uniformly distributed among 6 groups resulting in 10 fruit per treatment. One third of the fruit were placed in the sun for 2 hours to increase the core fruit temperature, another third was placed in the coolroom to reduce fruit core temperature and the remaining third was treated immediately. Two dips were prepared of Mango Wash® (2.5g/L) and fruit were dipped for 10 minutes.

Fruit were assessed for skin browning when ripe.

Results: The injury seen on these fruit was a type of sap burn/scald. There was a significant difference between the fruit dipped in the hot and cool dip. Fruit dipped at 29.7°C had more injury than fruit dipped at 38.3°C. The effect of fruit core temperature on skin browning was not significant.

Conclusions: The length of time and the amount of sap present in a postharvest solution appear the most critical conditions for skin browning to occur. Mango Wash® definitely is not as aggressive in continually causing injury as the chemicals Coldpower and Agral. However we are still yet to establish the most effective concentration for the application of Mango Wash®. Measurements of turgor may still prove useful as a guide to fruit predisposed to skin browning, though much further work would be needed here.

Finally it would appear that temperature of the dip may also have an important role to play.

*****

14

PRE-FLOWERING MANGO IRRIGATION TRIAL - HOW PRE-FLOWERING IRRIGATION, CULTAR AND SEASON INFLUENCE MANGO YIELD

Project Officers: Y Diczbalis, C Wicks

Objective: In the NT, irrigation is traditionally withheld from the end of the wet season until flowering. This period of stress is imposed to improve the flowering response. Questions were being asked by growers and researchers as to whether this stress period had a negative influence on fruit set. A three year trial was initiated in 1995 to determine whether irrigation through the dry period prior to flowering influenced flowering, fruit set and hence yield. The work was carried out on untreated and paclobutrazol (Cultar®) treated trees.

Materials and Method: In mid December 1994, 96 four and a half year old trees on a commercial farm were lightly pruned. Paclobutrazol as Cultar® was applied to half the trees at conventional rates in late December 1994 following pruning. An irrigation system was installed which allowed four pre-flowering irrigation treatments (50, 25, 13 and 0 mm1week) to be imposed from the end of the wet season (late April) until flowering (June-July). Following flowering, trees were fully irrigated (approximately 40 mm1wk) through to harvest. Measurements undertaken at the site included, weekly soil tension and total soil moisture (Neutron Moisture Probe and EnviroScan), daily maximum and minimum temperature, weekly photosynthesis and tree phenology (flushing, flowering etc) recording, flowering panicle number per tree and harvest measurements such- as fruit number and total tree yield.

Results and Discussion: In 1995 paclobutrazol treated trees flowered approximately a week earlier in mid July. Pre-flowering irrigation treatments decreased flowering in the untreated trees and increased flowering in the pac1obutrazol treated trees. Similar yields (38 kg/tree) occurred in the non irrigated untreated trees and the paclobutrazol treated trees irrigated at 25 mm1week. Paclobutrazol increased the number of flowering panicles per tree but there was no evidence of a similar increase in yield as fruit set was reduced. There was no evidence to suggest that dry conditions pre-flowering substantially reduced fruit set for either paclobutrazol treated or untreated trees, in fact the reverse may be said to have occurred. This suggests that tree yield may be limited by tree physiological factors, as yet unknown, and hence the tree can only support a certain number of fruit regardless of the number of flowers produced.

The trees were well pruned in December of 1995 and paclobutrazol applied. Flush number and length were monitored during the period prior to flowering. In 1996 the flowering was extremely poor. For all practical purposes there was no fruit on the trees in the trial block. However, as in 1995 the best yields were obtained in the untreated, 0 mm1wk irrigation treatment and in the paclobutrazol plus 13 mm1wk irrigation treatment.

Growth measurements suggested that paclobutrazol treated and untreated trees had the same number of flushes, but the average length of flushes were smaller for the treated trees. Photosynthesis measurements showed that as soil moisture declined after the wet season so did leaf photosynthesis. Temperature measurements show that the 1996 season was colder than the 1995 season. Despite this, the flowering response in the trial block was poor. Continued work this season and perhaps next season will hopefully allow us to pick up a pattern which helps explain the flowering behaviour of Kensington in the Top End of the NT.

The trial, which is continuing in the 1997 season, has raised a number of issues which need to be carefully considered by researchers and growers alike. In the Top End environment:

- Does the use ofpaclobutrazol increase yields or just the flowering response?

- If using paclobutrazol, small amounts of water pre-flowering may be beneficial to production.

- In trees not treated with growth regulators, pre-flowering irrigation reduces yield potential by reducing the flowering response.

*****

15

FOLIAR NITROGEN NUTRITION OF MANGO

Project Officers: M Smith, S McAlister, C Brown, G Foard, J Bright, M Hoult and D Jaensch

Objective: The nitrogen nutrition of mango remains an area of much debate and confusion. Over the last decade in the NT there have been major swings in the quantity of nitrogen recommended for commercial orchards. Current rates range from zero up to 300 g N per tree per year. Foliar application of nitrogen has received limited attention. The aim of this project is to determine any effects of foliar nitrogen application on the yield and quality of mangoes.

Materials and Method: The experiment was established in January 1996, with four rates of nitrogen (80, 40, 20 and 0 g N/tree) applied at four phenological stages (post-harvest flush, pre-flowering, fruit at golf-ball size, and all 3 of these stages). These treatments were arranged in a factorial design with 5 replicates and individual tree plots. Two additional treatments (of potassium nitrate pre-flowering; and window pruning in August) were included.

Resnlts and Discnssion: Harvest in the 1996 season showed no effect of treatment, as was to be expected so early in the experiment. However, measurements of vegetative activity (flush number, length, number of leaves etc.) made in April 1997, showed interesting trends, suggesting that the treatments were starting to have an effect. Furthermore, leaf measurements taken from the 2 extreme treatments in May 1997, confirmed that significant effects (p~0.004) were present.

Effects on yield and quality will be examined over the next 3 to 4 seasons, with treatments applied annually.

*****

MANGO BREEDING AT KATHERINE

Project Officers: M Smith, M Hoult, S McAlister and C Brown

Objective: Despite a strong preference for Kensington Pride in the Australian market, this cultivar exbibits a number of attributes that might be improved through breeding and selection. Hand pollination in mango is time consuming and therefore expensive. An alternative approach is to collect and propagate seed from a tree growing in close proximity to the desired pollen parent. This approach enables the rapid establishment of large progeny populations and has been employed with some success elsewhere.

Materials and Method: A population of 550 seedlings of the cultivar Glenn, were field planted in May 1994 from seed collected in December 1993, from various orchards in the Katherine area Seeds were collected from Glenn trees growing at 6 different pollination distances from Kensington Pride trees. These pollination distances make up the 6 treatments being examined in the experiment.

Preliminary observations were made on the first of the trees that had flowered and carried fruit in the 1996 season, just 2 years after planting.

A time budget was also prepared in order to help calculate the cost of this approach to mango breeding. In this budget, full account was taken of all time input into the experiment during the first 2.5 years.

Results and Discussion: Of the 550 seedlings planted, 32 died and 87 flowered during the 1996 dry season. This means that 17% of the population flowered after 2 years. Of the 87 flowering trees, 65 went on to carry fruit through to maturity. This represents 13% of the popUlation fruiting after 2 years growth. These figures are important because they show that it is possible to obtain early fruiting of monoembryonic seedlings even in a low-land tropical environment. Furthermore climatic conditions during the 1996 dry season were not particularly conducive to good flowering in mango.

16

The trees that fruited, carried between 1 and 36 pieces of fruit. Seed from these fruit were extracted and examined to determine whether they were mono or poly embryonic. Based on this examination, it was found that 32 of the 65 trees produced polyembryonic seed. Given that polyembryony in mango is controlled by a single dominant gene (Aron ef al. in print), these results suggest that almost 50% of the trees that fruited in 1996 were a natural hybrid between Glenn and a polyembryonic pollen parent (possibly Kensington Pride given that it was the dominant source of pollen in most of the orchards from which Glenn seed was collected). If this proves to be the case when more trees fruit in the 1997 season, then it has important implications for any future approach to mango breeding.

Seed from 19 of the trees that were polyembryonic have been included as rootstock treatments in an experiment due to be planted in 1997. Seed from trees that were monoembryonic have also been planted, as it is hoped that these seedlings may show a shorter juvenile period. That is, we hope to be able to select for a short juvenile period (assuming this trait is heritable in mango) and therefore speed-up future breeding work with this species.

In terms of time allocations, it was calculated that the first 2.5 years of the experiment required 412 person hours (49 minutes per seedling). This included land preparation, irrigation installation and maintenance, seed collection and dehusking, nursery growing, and all field maintenance. The nursery phase consumed over 70 hours, and would appear to be an area where improvements in efficiency can be made. It is anticipated that the final time input into this experiment (which is programmed to finish in 1999) will be around 1 hour per seedling. This figure needs to be considered with the relative success of the program (in developing suitable genotypes) when comparing this approach to other methods of mango breeding.

References: Aron, Y., Czosnek, H., Degani, c., and Gazit, S. (in print). The genetics of polyembryony in mango. Oral presentation at the 5th International Mango Symposium Tel Aviv Israel. 1-6/9/96.

*****

DIRECT SEEDING MANGOES

Project Officers: M Smith, S McAlister and M Hoult

Objective: A time budget of inputs into current mango breeding work at KRS showed that major improvements in efficiency could be achieved if it were possible to direct-seed mangoes in the field. This would avoid the time consuming nursery phase (>70 hr / 550 trees) as well as the expense of field planting trees from pots (>90 hr / 550 trees). By decreasing plant spacing from 3 x 4 m to 1.5 x 3 m and with the use of plastic mulch and a seedling planter, it was estimated that the time costs for the first 2.5 years of a project could be reduced from 49 minutes per tree to 11 minutes per tree. A preliminary experiment was undertaken to investigate the possibility of direct seeding mangoes.

Materials and Method: Ripe Irwin fruit were collected and planted through small holes punched into plastic mulch which had been laid over a cultivated seed-bed. Fruit were either: 1. planted whole (green mature); 2. planted whole (ripe); 3. planted after removing the flesh; or 4. the flesh and husk were removed and just the kernel planted. These 4 treatments were replicated 3 times, with 4 fruit in each plot. Planting occurred on 18 October at a spacing of 1.5 m between plants in the row, and 3 m between rows. Emergence and survival of seedlings were recorded.

Results and Discussion: For 2 weeks after planting, climatic conditions were very hot, dry and with bright cloudless days (mean daily max. air temp. 38.2 °C; mean daily max. grass temp. 56.4 0c). Seedlings that emerged showed necrosis of the stem at the level of the plastic mulch. Plants in the dehusked treatment were the first to emerge, and without exception showed obvious signs of stress. Emergence in treatments I and 2 was particularly poor, with less than 10% of seeds emerging in each case. Where the kernel alone was sown (treatment 4), around 42% emergence was achieved. The highest rate of emergence (58%) was achieved by only removing the flesh and leaving the husk around the kernel (treatment 3).

None of the 4 treatments were satisfactory in terms of establishing a population of mango seedlings. However the prospect of direct seeding mangoes should not be abandoned as our observations point to areas where

17

modifications may lead to increased success. In particular, seeding should take place as late in the season as possible, when there is a higher probability of cloudy conditions and increased humidity. Seed should be defleshed but not dehusked. A tall grass, such as sorghum, planted between the beds may help to keep temperatures down and provide shade for newly emerging mango seedlings. A north-south row orientation may also reduce stress on emerging seedlings.

*****

POLLINATION DISTANCE EFFECTS ON GLENN SEEDLING VEGETATIVE CHARACTERS

Project Officers: M Smith and L Granger

Objective: This trial was established in order to determine if seedlings from Glenn trees, growing close to a Kensington pollen source, were any different in vegetative characters from seedlings derived from Glenn trees located far from a Kensington pollen source.

Materials and Method: The vegetative characters of tree height, trunk circumference, number of branches, length of the longest branch, and average length of branches were measured on 3 year old mango seedlings of the cultivar Glenn. A total of 473 trees were measured consisting of six different treatments. These six treatments were the distance between the Glenn seed parent tree, and the closest source of Kensington pollen.

Results and Discussion: The character of 'number of branches' showed poor correlation with other measurements, and likewise the correlation between 'trunk circumference' and 'branch lengths' were poor. The 6 treatments had little influence on the correlations between vegetative characteristics.

There is no evidence for a pollination distance effect on any of the characters measured.

Whilst within treatment variation is undesirable in terms of detecting significant differences between treatments, high levels of variation can be desirable in terms of breeding for a particular characteristic. Where large variations are the result of genetic variation (rather than seasonal or environmental) and heritability is high, there exists considerable opportunity for genetic gain in response to selection.

Results confirm visual observations on the enormous variation that exists within a monoembryonic seedling population of mangoes and supports much evidence that mangoes are a highly heterozygous species. Future measurements will be concentrated on reproductive characteristics of the six different seedling populations.

*****

VARIATION IN MANGO PRODUCTIVITY

Project Officers:

Objective:

G Foord, J Bright, M Smith, M HouIt, S McAlister, L de Souza and MLandrigan

In 1996 the large variation in the productivity of Kensington Pride mango trees, between orchards and between trees within the saroe orchard continued. DPIF Horticulture staff are attempting to identify why such variations exist. This will help in the development of a 'Local Best Practice' model for the Katherine region. Other related projects will compile a record of the size and productivity of the industry and develop a model to predict productivity for the region.

Materials and Method: In 1996 the data set for this project extended to include an additional property on the Katherine River with Levee soil type. There are now 11 groups of three trees in orchards on three different soil types of different bearing ages and management practices. Data collection of phenology, nutrient status (at flowering and after harvest), fruit yield and fruit quality continued in the 1996 season.

18

Results and Discussion: As in 1995, 1996 data showed that productivity does not directly relate to orchard age, tree size or a number of other parameters.

Analysis of the data showed that the relationships between yield and leaf nutrient levels were different for young trees and mature trees. Leaf nutrient levels were generally unchanged from 1995 to 1996, despite changes in fertiliser inputs.

'Sporadic' flowering lead to an extended harvest season in 1996. Yields were generally lower than in 1995, which may be attributed to the mild dry season and highlights the need to collect data for a number of seasons as well as from a number of orchards. Most trees with relatively high yields in 1995, again yielded well in 1996, however, some improved dramatically when compared to the rest of the data set. Further collection and analysis of data is required to identify what, if any, management practices influenced this improvement.

Growers involved in this project are generally very interested in its progress and are modifying their management, particularly their nutrition program, based on data we collect.

This project seems to have provided us with more questions than answers. High leaf nitrogen levels had a positive impact on the marketable yield and yield efficiency of mature trees (7 years and over). However the negative trend displayed in young trees (4 and 5 year old trees) poses a whole new set of questions. It is somewhat surprising that the young trees with relatively low leaf nitrogen were larger and higher yielding than those with higher leaf nitrogen.

*****

NEW ROOTSTOCKS FOR KENSINGTON PRIDE

Project Officers: M Smith, M Hoult, G.Foord, L Granger, J Bright and S McAlister

Objective: In response to the prontising results obtained over past seasons with just a few rootstocks, it was decided to evaluate a far greater range of polyembryonic genotypes that may prove useful as stocks for Kensington Pride. The influence of soil type on rootstock performance also requires evaluation.

Materials and Method: An experiment with 64 different rootstocks was planted in ntid 1996 on a Tippera clay loam, while the second experiment with 97 different rootstocks is due to be planted in ntid 1997 on a Blain sandy loam. These treatments consist of polyembryonic genotypes from DPIP arboreta; trees identified by local nurserymen; polyembryonic types bred at KRS; seed supplied by overseas mango workers; and a lintited range of other Mangifera species. In both experiments each treatment is replicated five times with individual tree plots. Nearest-neighbour designs have been employed in an attempt to account for spacial variation.

Results and Discussion: Whilst differences between stocks in terms of vigour are already obvious, it will be some years before any meaningful data on yield and quality can be generated from this work.

*****

MORPHOLOGY OF POLYEMBRYONIC MANGO GENOTYPE SEEDLINGS

Project Officers: M Smith, L Granger and S Eastburn

Objective: More polyembryonic mango cultivars exist than can ever be evaluated as rootstocks in field experiments. Furthermore, the general absence of pest and disease problems makes the elimination of genotypes on the basis of pot screening (such as is done in citrus) inappropriate as a way of reducing material warranting field evaluation. Ideally we require a way of relating a genotype's performance as a rootstock to its performance as a seedling. Attempts have been made to relate vigour as a rootstock to root bark percentage, and to screen for salt tolerance in seedlings, but direct comparison between seedling performance and performance as a rootstock in

19

the field seems to be lacking. Some morphological characteristics of different polyembryonic seedlings were recorded in the hope that they may later correlate with results obtained from the field.

Materials and Method: Trees used at the Tippera site were from seeds sown in December 1994 and 1995, and were measured in February 1996. Measurements were taken from 4 to 6 seedlings of each genotype. The measurements included: seedling height; stem diameter; leaf number; leaf area; leaf biomass; bark thickness; bark density; wood density; and internode length. In total, 28 variables were generated for 276 seedlings.

Trees used at the Blain site were from seeds sown in December 1996, and were measured in May 1997. Six seedlings of each genotype were measured for tree height.

Resnlts and Discnssion: There was a wide spread in measurements for the morphological characteristics across the genotypes. It is also worth noting that what are referred to as 'commons' are obviously not all the same genotype.

Results for the second group of seedlings are largely similar to those for the first group in terms of tree vigour. Notable exceptions are 'Vella Colombar' and 'Nam Doc Mai' which grew poorly in the first planting (Tippera site), but were quite vigorous in the second planting (Blain site). This may be due to the younger age of seedlings when they were measured in the second group.

Measurements will be reviewed again once field performance data becomes available.

*****

GRAFT COMPATIDILITY OF MANGIFERA SPECIES

Project Officers: M Smith, T K Lim and L Granger

Objective: In recent years there has been renewed interest in Mangifera species other than Mangifera indica (which is the species of almost all cultivated mangoes). This interest has been stimulated by presentations at the 4th International Mango Symposium in Florida, the text of Kostermans and Bompard (1993), DPIP field collection trips to Borneo, and an increasing commitment by the Department to mango breeding and rootstock development.

Of fundamental importance to collecting, maintammg and utilising these different species, is their graft compatibility with M. indica. This project examines this compatibility.

Materials and Method: A range of budwood material has been grafted to various M. indica cultivars at KRS. The species that have been tried as scions include (as labelled): M odorata RIT6 BARC Pastures; M. quadrifida, RIT3 BARC Pastures; M. laurina (Depih) R2T2 BARC Pastures; M. torquenda RIT4? BARC Pastures; M foetida (Aqua) BFI R7T3; M. casturi (Round), Peter Gillett Qld.; M. casturi (Long) Peter Gillett Qld.; M. laurina RI TI? BARC Pastures; and Bouea macrophylla, C. Gustont Darwin. Between 3 and 10 grafts of each were attempted at various times during 1996.

Results and Discussion: Although of very limited scope to date, early indications are that many of the species currently available in the NT are compatible with M. indica, at least in the early years. The growth rates of scions such as M. laurina and M. casturi have been particularly impressive.

Although from a separate genus, graft sticks of Bouea macrophylla remained green for over 2 months, and in 3 cases, the buds started to push. Although none of the grafts were eventually successful, indications were that future success may be possible with this material and more intergeneric grafting would be worth evaluating.

It is important to identify which species are the most difficult to successfully graft, and to evaluate means of overcoming such problems. For example, during grafting, it was observed that species differ in the thickness of

20

their bark. In such cases, it may be worth examining a range of rootstocks since we have also observed large differences in trunk morphological features within M. indica.

Great care needs to be taken when ascribing a species name to a particular tree. Often this material has come with only tentative identification. Hence it is important to identify the individual budwood source trees in case these trees are later found to have been wrongly named. For example the tree in the BARC orchard labelled as M. foetida, is certainly wrong, and more likely to be M. laurina (still to be confirmed).

The benefits of having a wide range of genetic material available for rootstock and breeding work, may be of great commercial significance in decades to come.

*****

HEAT SUMS TO PREDICT FRUIT MATURITY IN KENSINGTON PRIDE MANGO

Project Officers: Y Diczbalis, C Wicks, M Landrigan

Objective: Mangoes are a climatic fruit. That is, they can be harvested when mature (hard green) and will successfully ripen into firm but succulent well coloured fruit. The ability to pick at the hard green stage is of considerable advantage to the industry in terms of packaging and transport, however, fruit maturity at harvest and the resultant quality of fruit on the market floor has been an important industry issue since the industry commenced. The maturity of Kensington Pride (KP), the main commercial cultivar, at harvest strongly influences the quality of the fruit at the soft ripe stage.

The current maturity indices used by industry include flesh dry matter percentage, flesh colour, fruit size and shape and to the industry's detriment, price. All of these methods are fallible and can be influenced by season, crop management, picker perceptions and greed. None of the currently utilised maturity indices allow an accurate long term prediction of harvest date to be made hence orchard management can be chaotic in the weeks leading up to anticipated harvest. The aim of this project is an examination of heat sums as an indicator of maturity. Heat Sums are a combination of the time for a particular event to occur and the average temperature experienced during the period monitored. Heat Sums take into account the fact that the rate of development of any biological process is temperature dependent. Hence the objective of this one season (1996) project was to examine the relationship between Heat Sums (Growing Degree Days), other fruit maturity indices, and fruit quality at the soft ripe stage to ascertain whether Heat Sums could be utilised as a mango fruit maturity predictor. Other fruit maturity indices examined at the same time included; dry matter percentage at harvest, flesh colour at harvest (as per the QDPI Mango Picking Guide), total soluble solids (TSS a measure of sugars) at harvest and specific gravity, ie. the ability of the fruit to sink or float in various solutions. Fruit quality measurements made at soft ripe included; peel colour, flesh colour, TSS, and titratable acidity.

Materials and Method: The work is funded by a commercial mango orchard, HRDC (Project number FR605) and the NT DPIP. It was carried out at a combined cost of $8,000. Three commercial orchards in the Darwin area were selected for the project, principally Acacia Hills Farm Pty. Ltd. the commercial contributor to the project. Temperature data was collected by maximum and minimum thermometer and electronic temperature data loggers from early flowering until harvest. Fruit were sampled from each of three flowerings (May, June and August) over a four week period at a range of Heat Sums. Fruit were transferred to the laboratory where they were desapped and divided into two groups with one half being sampled for fruit weight, specific gravity, flesh colour, TSS and flesh dry matter %. The remaining fruit were stored at 20'C and 70 % RH until soft ripe. When soft ripe fruit were assessed for fruit weight, peel colour, flesh colour, TSS and titratable acidity. Following the completion of data collection, all the ripened fruit were rated on the basis of stringent fruit quality criteria, for different levels of the maturity indices tested.

Results and Discussion: Our data showed that fruit quality, in particular peel and flesh colour, improved as the maturity of fruit at harvest increased. Heat Sum is as good or better maturity index than dry matter % at harvest with both methods able to account for greater than 90% of marketable fruit at Heat Sums greater than 1500 Celsius degree hours and at dry matter greater than 16 %. The best ratings for flesh colour, TSS and specific gravity at harvest were only able to

21

account for 75 to 86 % of marketable fruit and hence were not considered as good indicators of fruit maturity. The advantages of the Heat Sum technique for predicting fruit maturity are;

• it can be used as a true predictive tool from flowering, thus allowing for a improvement in orchard management and planning

• calculations are not affected by irrigation management, unlike dry matter % and TSS • the method is not affected by the bias selection of fruit prior to harvest.

It is not envisaged that the Heat Sum technique is capable of totally replacing currently used maturity indices, however, when used in conjunction with current methods it will allow for improved orchard management and improve the quality of mangoes on the market floor.

The scope of the experiment did not allow the reliability of the technique to be tested from season to season and over a range of growing environments. However, data already available from other seasons and regions suggests that the technique may be suitable across a wide range of environments and seasons. Immature fruit will continue to be a problem in the shed regardless of maturity indicator utilised, hence the development of a inline culling method is also crucial to the improvement of the final product. This study showed that specific gravity may have potential as a post-picking maturity sorter.

The full report to contributing growers and HRDC is near completion.

*****

PRODUCTIVITY RESPONSES OF ASPARAGUS TO DROUGHTING IN A TROPICAL ENVIRONMENT

Project Officers: J Bright, S Martin, M Smith, S McAlister, G Foard, M Hoult, and Y Diczbalis.

Objective: Asparagus has traditionally been grown in temperate climates where cool winter temperatures cause plant dormancy. Asparagus spears are picked as plants emerge from their dormancy period in spring. Dormancy induced by the cessation of irrigation prior to harvest is used, where possible, in tropical areas. The effects of such droughting are, in some cases, believed to be detrimental to the plant both in production and health. This project will quantify production results in response to droughting in terms of spear quantity and quality.

Method: Field and lysimeter trials were conducted. The field experiment involved the examination of 5 different droughting durations, namely 80, 40, 20, 10 and 0 days without irrigation, prior to harvest.

In 1994, asparagus plants (120) were transplanted in to 200 L lysimeters with various droughting treatments being imposed to examine the effects on crop production. A total of 20 treatments were developed using a combination of 4 droughting intensities and 5 droughting durations.

Treatments were as follows:­Moisture Stress (kPa): Droughting Duration (days):

10 o

50 10

100 20

dry 40

dry 80

Harvesting commenced on 12 June 1995 and lasted for 14 days. Harvesting for 1996 commenced on 28 June and lasted for one month.

ResnIts: Results from thel995 harvest show that at the extreme droughting lengths there is a greater proportion of reject spears. High reject spear production was evident in both the field trial and the Iysimeter trial.

In the Iysimeter trial drought duration significantly affected the quantity and quality of spears. Plants in the 50 kPa treatment took between 4 to 5 days to reach this tension, while those in the 100 kPa treatment required watering every 6 to 8 days.

22

Differing soil tensions had an effect on the production of grade spears (p=0.05). A high yield of first and second grade spears were produced in the field trial. The main reason for rejecting spears in the Iysimeter trial was due to flowering, while in the field trial, the predominant reason was the spears being too thin.

During harvest of the Iysimeter trial in 1996, it became obvious that the crop required harvesting twice a day. Spears that were too short in the morning, flowered and became rejects by the next day.

1996 results were similar to 1995 trends. Droughting duration appears to have an effect on the number and quality of spears produced. In both years, increasing drought duration resulted in a decrease in the amount of first grade spears produced. The amount of first grade spears is also low where there is no water cut off.

Root samples taken in the field trial show that the plant is capable of extending roots below 3 m in depth. However the bulk of the roots are found between 20 and 40 em depth.

The 1995 results suggest that a drought duration, prior to slashing and harvesting, of 10 to 20 days will result in higher marketable yields than longer, more extreme drought durations. This is also the case for the no drought situation i.e. better yields are achieved from the 10 and 20 day drought duration than from the 0 drought duration.

The field trial was not harvested in 1996 due to an outbreak of Colletotricum. We decided that it would be better to leave this planting to regenerate for a year. The block was slashed in August and the fern burnt. Various techniques are being applied to control the fungns.

The field trial will be harvested in 1998 and 1999 (funds permitting). 1997 will see the final harvest for the Iysimeter trail. Findings over the first two years of this project have conflicted with the recommendations of other tropical areas and in light of these findings an extra site may benefit us in understanding the management techniques of irrigation prior to harvest. It is important that we confirm findings from the Iysimeter experiment in field plantings. In order to achieve this we must first deal with the fungal problem that currently exists with this crop.

*****

ASPARAGUS CULTIV AR ASSESSMENT

Project Officer: J Bright

Objective: Currently UC157 F j is the standard asparagus cultivar grown in Northern Australia. The commencement of the 2nd International Asparagus Cultivar Trial provided an opportunity to obtain a wide selection of genetic material for comparison with UC 157 F j at Katherine.

Materials and Method: Seed of 18 cultivars were sown in June 1997 for evaluation at KRS, including:

UC157F j

Grande Tainanal Tainana 2 Tainana 3 JACQMA2004

Results and Discussiou:

Andreas Val Prima Larae Venlim PLA-2132 Dariana

Preliminary results will be available in late 1998.

Apollo Boonlim Cipres PLA-2232 Atlas JACQMA2014

Of particular interest will be the relative susceptibility of the cultivars to the disease Colletotricum. Should there be any plants showing resistance, it may justify larger plantings of that cultivar.

*****

23

BANANA VARIETY TRIAL

Project Officers: J Bright and G Foord

Objective: The aim of this experiment was to develop a database on the performance of various banana cultivars and identify cultivars suited to the climatic conditions of the Katherine region.

During 1996/97 we have made banana plant material available to local growers and the Katherine community. Making plant material available, we believe, will discourage illegal plant importation and prevent introduction of pests and diseases not yet experienced in Katherine bananas.

Materials and Method: A trial was field planted in February 1995. Observations were made on flowering and fruiting times, as well as bunch weights and fruit quality.

Results and Discussion: Most cultivars are performing well under Katherine conditions.

The cooking bananas Pacific Plantain, Horn Plantain and Pisang Gajih Merah (Saba), all produced good sized bunches (compared to their performance elsewhere). Indications are that these cultivars are well adapted to the environment at the trial site.

Goldfinger suffered slightly from leaf burn, but produced bunches (20 kg) that appeared cleaner (less marked) than some other cultivars.

Santa Catarinas Prata (Dwarf Ladyfinger) produced bunches that barely resembled ladyfinger fruit. However, the taste of the fruit was similar to ladyfinger. The plant was shorter, standing only 2.5 m at flowering, which is a big advantage with regard to wind damage.

Simoi produced huge pseudostems that reached heights of over 5.5 m making the fruit very difficult to harvest.

Some cultivars did reveal problems in this environment. Wain was very slow to establish and Sugar produced fruit that was particularly short and susceptible to splitting (which is typical of the variety in other regions).

Several people have requested planting material. Records of the material taken to each location, have been kept for future reference.

*****

BANANA NUTRIENT MONITORING

Project Officer: J Bright

Objective: Leaf and soil nutrient sampling are popular ways of determining the adequacy of crop management practices. In the case of banana, a large body of information exists as to what nutrient levels should be, and under what conditions, nutrients are likely to be limiting production. This work seeks to determine the extent to which commercial plantings in the Katherine area are meeting established standards.

Materials and Method: All commercial plantings of bananas in the Katherine area were sampled at 3 monthly intervals from January 1994 to January 1996. Both leaf and soil samples were taken, at each sampling date. Great care was taken to ensure samples were sufficiently large to be truly representative of each block.

Results: During the period of the nutrient survey. commercial interest in bananas declined rapidly, such that there was only one commercial property growing bananas at the last sampling date. This had a significant impact on the usefulness of the information gathered because between-farm comparisons were not possible.

24

It is also reasonable to suggest that the usefulness of the nutrient information was undermined by the low level of crop management, particularly in the area of irrigation inputs.

Despite these problems, there were some important lessons, that must be recognised if research resources are to be better utilised in the future. Firstly, it is essential to have access to good records of crop management, particularly fertiliser inputs. Leaf and soil samples should not be taken unless such information is available. Secondly, growers need to be in a financial position to adjust inputs in response to nutrient analysis results. There is little point in determining that a particular nutrient is critically low, if the grower is not in a position to correct it.

From the experience of this project, combined with banana production in research plots at KRS, it is felt that efforts should concentrate on regular applications of fertiliser in accordance with a fertiliser program. Nutrient analysis can then be used as a means of modifying the fertiliser program rather than directly determining what nutrients need to be applied.

*****

RATOON SELECTION INFLUENCE ON BANANA PRODUCTION

Project Officers: J Bright, G Foord, M Smith, S McAlister and M Hoult

Objective: 'Nurse technique' is a widely employed method of manipulating banana production to maintain year round production or to bring in bunches at periods of better prices. The technique involves the foregoing of the parent bunch to achieve a synchronised harvest and higher prices with the ratoon / follower, crop.

The main purpose of this trial is to obtain production during the dry season months when market prices are high and also to achieve consistent year-round production.

Materials and Method: The trial was designed with 3 ratoon selection dates (31 May, 15 August and 15 September) and 2 nurse treatments (parent pseudostem cut down on 20 September and parent pseudostem left to carry a bunch). Plots consist of 4 stools in a row, with each of the 6 treatments replicated 4 times within a randomised complete block design.

Flowering and harvest dates, bunch weights, and number of hands per bunch were recorded. In addition, the length and circumference of the middle finger on the third hand, and the number of fingers and weight of fingers on the third hand were measured.

Results and Discussion: Results from 1996 show significant differences in days-to-flower as a result of nurse management and timing of ratoon selection. Ratoons of parents that were nursed produced flowers 40 days earlier than those ratoons that were selected from parents that were not nursed.

Although there was no significant difference in days-to-flower between August and September ratoon selection, the difference between May and August, and May and September, selection dates did prove to be significant. May selected ratoons produced flowers 24 days earlier than those selected in August and 20 days earlier than those selected in September.

Significant differences also existed in days-to-harvest Where nurse management was implemented, the days-to­harvest was shortened by 30 days. Time of ratoon-selection did not appear to affect the days-to-harvest.

The period between flowering and harvesting was affected by time of ratoon selection. No differences were observed between July and September selections although there were differences between May and August (30 days), and May and September (22 days).

*****

25

NURSE INFLUENCE ON BANANA PRODUCTION

Project Officers: J Bright and G Foord

Objective: As a continuation of the bunch production timing trial it was agreed to incorporate nurse management along with ratoon selection. Having already established results from the ratoon selection timing trial we now thought it necessary to find out details of the effects of nursing at various times.

Method: This trial (which is a continuation of the KRS ratoon selection trial), utilises the second ratoon, being the nurse for the third fatoon from the previous trial. Nurse management treatments were applied in September, October, November and December 1996 and January 1997. The remaining treatment will be a no-nurse control.

Results: Results will be available in late 1997.

*****

BANANA NUTRIENT MONITORING

Project Officers: K Blackburn, M Traynor

Objective: A banana nutrition monitoring prograra was commenced in March 1994 consisting of bi-monthly leaf and soil analyses, to be correlated with grower fertiliser practises, over a three year period, to optimise banana nutrition. Initially the project set out to establish what the present situation was in regard to nutritional status of the plants and the frequency, araounts and type of fertiliser applied.

Results: Results in the first year (1994) over 5 sarapling dates showed that regular monthly fertiliser application was not always occurring especially during the wet season when access to the crop is restricted by water-logged conditions. Generally, for 1994, leaf and soil potassium and zinc levels were low throughout the industry and the high soil magnesium levels are affecting the leaf potassium and calcium levels.

During 1995, farm fertiliser applications becarae more regular with an average increase in the total araount of fertiliser used. However, growers could not provide any yield estimates to determine whether the improved nutrition has increased farm productivity although all growers agreed that production had imprOVed.

Again, high soil magnesium levels have affected both potassium and calcium leaf levels by altering the cation balance and restricting their uptake by the plant. Low soil potassium levels on most farms could be improved by small regular applications of potassium with 2 or 3 major applications at seasonal intervals. The maintenance of adequate zinc levels in the leaf is an industry-wide problem. High soil zinc levels on one farm have not resulted in adequate leaf zinc levels although foliar application of zinc is also used.

In 1996, all growers were more aware and concerned with their leaf and soil nutrient analysis and were basing their fertiliser prograras on the results of the regular saraplings. New plant crop blocks were selected at the beginning of the year as the older blocks being monitored were in their second or third ratoon. Three established growers replaced old banana blocks with new plantings based on undertree sprinklers with fertiliser injection systems for accurate nutrient control.

Conclusion: After three years offarm monitoring the results could be briefly summarised: • Regular monthly applications of nutrients should be strictly carried out to maintain a constant supply to the

growing crop. It is anticipated that, as the phenology of the crop is better understood, critical times for additional fertiliser applications will be determined. For exaraple additional potassium could be required in March/April before the onset of cool dry season conditions.

26

• The importance of precise lITIgation scheduling in bananas under local conditions cannot be over­emphasised. Unless this is achieved, the response from an improved nutrition program will not be obtained. Current irrigation scheduling is generally variable and water is insufficient during Sept.lOct.lNov. when climatic conditions are harsh and banana crops are under undue stress. New planting's on existing farms as well as two very large banana projects just commencing operations are using undertree sprinkler irrigation systems, rather than the traditional overhead method, and will be injecting fertiliser through the irrigation system at regular intervals. It is considered that this system will be more efficient in supplying the irrigation requirements and the nutrient demands of the banana crop under Darwin climatic conditions.

• Strategies for improving both zinc and potassium nutrition to ensure constant and adequate levels in the soil and plant will have to be developed. The high magnesium content in the irrigation water from bores is a concern and the effect on potassium availability may only be partially overcome by small, frequent applications of potassium fertilisers. Maintaining adequate zinc levels in the soil and leaf is an industry-wide problem and both ground and foliar application will need to be employed to overcome deficiencies.

• The use of nutrient ratio's such as the DRIS system, may offer more in analysing nutrient interaction over time in a banana crop, rather than attempting to define straight nutrient levels. There is a real need to develop the diagnostic technology necessary to improve crop productivity but grower feedback is essential for this to happen. Plant reserves and the cycling of some nutrients, such as potassium, need to be better understood.

• During the 1996 season a recommendation to increase potassium application to banana crops by frequent small amounts did improve lead levels of K but a subsequent reduction in the high leaf Mg levels was only evident on two farms. On all farms Ca leaf levels remained low although two farms had reasonable analysis but only just above the critical range.

• By the end of 1996 it was realised that raising the leaf K levels to balance out the excess Mg did not significantly alter the low leaf Ca levels. Although soil levels of Ca in most cases was thought to be adequate, addition of calcium compounds to the soil, without affecting the PH, is now considered essential. Gypsum applications would have to be used to dramatically raise soil Ca levels and this will have to be monitored to determine the effect on K and Mg levels in the leaf.

• Two local potential suppliers of raw gypsum were found in the Alice Springs district and negotiations have commenced to utilise this resource. Information on gypsum injectors from the USA has been obtained and the possibility of utilising this technology is being evaluated. The project will continue for at least another year or until the cation balance is partially restored in bananas. Other factors, such as high ammonium ions in the soil, may be affecting calcium uptake by the plant.

*****

BANANA EXTENSION AND INDUSTRY SUPPORT

Project Officers: K Blackburn and M Traynor

Objective: The Department seeks to exploit various ways of passing technical information to the industry.

Background and Activity: During 1996 the banana industry expanded to a total area of approximately 220 ha with 6 growers and the value of production rose 45% over the 1995 level to $4.3 million. The total production was 3,768 tonnes with 65% being transported to interstate markets while the remaining 35% supplied the local market. The large increase in production was the result of a new banana farm coming into production as well as significant expansion in area by three of the original growers.

The Banana Working Group was formed in 1993. It is chaired by ran Baker, Executive Officer (NTHA), and the DPIP work in closely with the grower members and the NTHA to discuss and implement R&D projects for the industry and any other. relevant industry issues. The Working Group meets 3 to 4 times per year, usually on grower's farms, and has been able to co-ordinate advisory services to growers and assist in the development of

27

industry initiatives. It has been able to unite as a group, look at its problems and present a united front to DPIP and its industry organisation, the NTHA, rather than individual growers requesting DPIP to work on their own problems in inefficient and short term problem solving exercises. Research results are presented regularly at Workshop meeting so growers are always aware of the progress of projects.

During 1996 there were 4 Working Group meeting on-farm and some of the issues covered can be summarised as follows: • Plant Quarantine measures introduced included the prohibition of import of ornamental bananas and other

seeded bananas which could form a wild population and be a sink for disease especially Bunchy Top virus disease. Other measures to control the movement of banana planting material from farm to farm or growing areas would also be considered.

• Local banana promotion through contributions of $7500 from the growers to have in-store banners, modules and pamphlets as well as TV advertisements.

• The banana quality manual commissioned by the Australian Banana Growers Council (ABGC) was reviewed by members of the Working Group and was found to have good ideas on management. However, the system it proposes has not found support throughout Australia so will not be adopted universally by the industry.

An in-store Quality Monitoring Project was conducted by DPIP at the request of the Working Group, in an attempt to identify the major defects that occur at the retail level and to pin-point where the damage was done. Assessments of a range of defects and blemishes were carried out in 3 major supermarkets at fortnightly intervals both in store coolrooms as well as the sales counter to determine the level of damage. It was found that the level of bruising cuts and skin rub was relatively high, using the ABGC Manual standards, but the level of insect damage was low. Quite a lot of skin damage occurred through excessive and rough handling of ripe fruit at the retail sales counter.

It was found that the ABGC Quality Manual had damage levels that were far too strict for NT use. As a follow on from the in-store Quality Monitoring Project it was decided by the Working Group that the NT should develop its own grade standards by being able, firstly, to recognise the defect and then to establish a level or allowance for it. Growers would bring ripe fruit to each meeting where the members would identify the defect, photos would be taken and the information used to develop a grading chart. There is no grade or defect chart available in Australia for grower use.

• Other matters of business attended to include: - A national ABGC sponsored benchmarking or best practice project - Some members to attend the Second National Banana Industry Congress in May 1997 - A PLU numbering system for supermarket sales of fruit is being considered - Farm bore water analysis compiled by DPIP - The NT involvement in the national Black Sigatoka Project - The registration of growers in the Chemical Users Course conducted by the NTU - The problems of standard carton sizes from the 2 major carton makers - The Lambell's Lagoon land release program.

• During 1996 value of the banana industry rose by 45% to $4.3m • Total production 3,768 tonnes - 65% interstate markets 35% local markets • Banana Working Group - Growers, NTHA and DPIP

plan and implement R&D projects for industry co-ordinate advisory services for growers 1996 activities included: seeded ornamental bananas prohibited input into NT local banana promotion invited guests spoke on areas of expertise ABGC Quality Manual reviewed by growers in-store Quality Monitoring Project defect identification and grade standards benchmarking project farm bore water analysis

*****

28

HONEYDEW MELON VARIETAL ASSESSMENT

Project Officers: K Blackburn and M Traynor

The objectives of this project were to assess recent commercial releases, to assist a Burdekin grower and to evaluate varieties with a local commercial grower.

Materials and Method: The following ten varieties were looked at: Honeymoon, Sweet Success, White Mist, Glacier, NW 456, Dewcrisp, Dewelle, NKS 735, SPS 882, Honeybabe

Trial Design: RCBD with 2 replicates

Results and Discnssion: Three cultivars, Dewelle, Sweet Success and Honeybabe were outstanding, Advantages of these cuitivars are:

• Bred for concentrated fruit set and once-over harvesting • Easier to pick - uniform maturity • Damage to plants at picking is irrelevant • Easier to grade - uniform size and shape • White Mist and Glacier did not rate as well • Grower observation plots confirmed trial results

*****

WATERMELON CULTIV AR EVALUATION FOR EARLY SEASON PRODUCTION

Project Officers: S McAlister, M Smith, J Bright and G Foord

There continues to be a steady flow of new watermelon cuitivars available to growers. Previous trials had screened commercial cultivars and identified Red Tiger as being superior for mid-season production at Katherine, on either plastic mulch or overhead irrigation. This cultivar is now commonly grown in the district.

The aim of this experiment was to examine the comparative performance (yield and quality) of 15 watermelon cultivars.

Materials and Method: The duration of this trial was from March 1996 to July 1996 at KRS, horticulture block. The trial was planted on 22 March 1996, with 82 days to fIrst harvest. First harvest took place on 12 June 1996, second on 27 June 1996 and the rejects on 3 July 1996.

The 15 treatments were arranged in a randomised complete block design with 2 replicates. Plots consisted of three adjacent rows, 7 m in length.

Regular observations of any differences between cultivars in terms of establishment, biomass, pest or disease susceptibility were recorded. Yields of marketable fruit (weight and number) were recorded from each plot, with a maximum of 3 harvests. At the completion of harvest the number of all remaining fruit was recorded.

At each harvest, three randomly selected, marketable fruit from each plot were assessed for external and internal colour, shape, internal splitting and rind thickness. A sensory evaluation was also conducted by staff and local producers

Results and Discnssion: Assessors consider most of the varieties to be suitable for commercial production, but showed a distinct preference for the quality of Red Tiger, and to a lesser extent Morocco and Red Devil. Watermelon appears to be a crop in which quality is far more important than simply yield per hectare.

Whilst there is a wide range of suitable varieties available to growers, there seems little justification for changing the current recommendation of Red Tiger as the preferred seeded watermelon for the region.

*****

29

BASAL NITROGEN RATES FOR WATERMELONS

Project Officers: M Smith, S McAlister, C Brown, J Bright, G Foord, and M Hoult

Objective: There has been no research work to establish base fertiliser rates for watermelons in the Katherine region. Commercial practices, in terms of base nitrogen application, vary widely from as little as 30 kg Nlha up to 140 kg Nlha. Growers have been advised to apply between 30 and 50 kg Nlha. Given that watermelons are the most widely grown annual crop in the region, there was a need to refine fertiliser practices.

Materials and Method: Nitrogen (as ammonium sulfate) was applied at 5 rates prior to plastic laying and sowing. The rates were 0, 30, 60, 120, and 240 kg Nlha. Plots consisted of 3 beds (1.2 m centres) of 10 m length. Data was collected from the central bed for 7 m of its length. Treatments were replicated 4 times, with the exception of the 0 kg Nlha treatment which was replicated 8 times. Phosphorus and potassium were applied at the rates of 90 and 70 kglha respectively at planting, and an additional 70 kg Nlha was applied to all plots as side dressings.

Petiole sap nitrate concentration was determined for each plot at approximately weekly intervals. Canopy height was also assessed at regular intervals. Although 3 harvests were made, only data from the first 2 were included in calculating marketable yield. At each harvest individual fruit were weighed and assessed for blossom-end rot and marketability. After the final harvest, aim square quadrat was cut from each plot in order to determine harvest index and nutrient content. Soil samples, to a depth of 1.2 m in 200 mm sections, were taken in all plots.

At the first harvest, 15 fruit from each plot were collected for post harvest assessments. Five of these fruit were assessed immediately, five assessed after three weeks storage, and the remaining five fruit from each plot assessed after 5 weeks storage. Each fruit was assessed for diameter, rind thickness, firmness, flesh and juice Brix, juice percentage of the flesh, and flesh colour.

ResnIts and Discussion: Base nitrogen rates had a marked influence on petiole sap nitrate levels from shortly after emergence right through until after final harvest. There was also an obvious influence on the rate and extent of canopy development. There was a clear optimum rate (120 kg Nlha) above and below which yields fell. Effects on fruit quality were less clear. It was expected that high rates of nitrogen would detrimentally effect fruit quality and post harvest storage. However there was little evidence for this other than perhaps a slightly paler colour in fruit from the highest rate of base nitrogen. It appeared that the optimum base nitrogen rate in terms of yield, was also optimum for fruit quality.

Although these results need to be confirmed in further work, it would seem that there is a need to substantially increase recommended basal nitrogen rates to around 120 kg N/ha.

*****

WATERMELON RESPONSE TO TEMPORARY MOISTURE STRESS

Project Officers: S McAlister, J Bright, M Smith, G Foord, M Hoult and C Brown

Objective: It is not uncommon to hear watermelon growers and researchers suggest that moisture stress for the right amount of time, and at the correct phenological stage can increase yield and qUality. However this suggestion that moisture stress may be beneficial in watermelons, is not supported by any scientific literature that we are aware of. The objective of this trial was to examine this claim.

Materials and Method: An experiment was designed in which plants were stressed at different phenological stages (25, 38 or 60 days after sowing (DAS)) and for different periods of stress (3, 6 or 12 days without water). These treatments gave a 3 (DAS) x 3 (stress period) factorial design and were assigned to plots within a randomised complete block design with three replicates. An additional control treatment received no moisture stress. Plots consisted of three beds 10 m in length. Yield was assessed from three harvests, with fruit quality effects determined at harvest, after 3 weeks storage, and after 5 weeks storage.

30

Results and Discussion: The no-stress control treatment out yielded all other treatments. There was a clear trend with moisture stress later in the crops development (38 and 60 DAS) having the most detrimental effect on yield. Stress at 25 DAS had little effect except where it lasted for 12 days. It was during the fruit filling stage (60 DAS) that moisture stress was most detrimental to yield. Plants stressed at this stage also had an increased incidence of blossom end rot.

Longer periods of moisture stress had a slight but detrimental effect on fruit Brix. Fruit from plants stressed at 60 DAS produced fruit which was firm at harvest, but deteriorate more rapidly in storage than fruit from other treatments. This is an example of the effect of pre-harvest treatment on post-harvest performance.

It is clear from this experiment that growers looking for high yields of high quality fruit with good post-harvest storage capacity should grow their watermelons without stressing them for moisture. Moisture stress is most damaging during the later stages of crop development.

*****

HERBICIDES FOR WATERMELONS

Project Officers: M Smith, S McAlister, G Foard and J Bright

Currently there are no herbicides that give effective weed control in watermelons. However a review of literature revealed a number of chemicals that had been evaluated internationally with some prontising results. This trial examined these herbicides for use in the Territory.

Materials and Method: Samples of two of the more prontising chemicals (ethalfluralin and clomazone) were obtained for trial purposes. Oryzalin (sold as Surflan®) which is commonly used in Australian agriculture was also included. Each of these 3 chemicals was applied at two rates, and the effect of mechanically incorporating the chemical was also compared with incorporation by irrigation. This gave a 3 (chemical) x 2 (rate) x 2 (mechanical vs. irrigation) factorial treatment design.

An additional 2 control treatments (no weed control, and regular hand weeding) resulted in an experiment with 14 treatments. Plots were 3 by 9 m, with each treatment replicated 3 times. The field selected for the experiment had been under intensive cultivation for over 30 years and was heavily infested with caltrop, portulacas, cape gooseberry and couch. Treatment effects on crop growth and suppression of different weed species was assessed visually by two researchers at two different dates. Harvests were also made on the oryzalin plots and the control plots. All other plots had been too heavily infested with weeds, or the plants too badly damage to warrant yield assessment.

Resnlts and Discussion: All treatments resulted in some level of weed suppression, although phytotoxic effects on emerging watermelon plants were also noted in most cases. In general, this detrimental effect on the watermelons was worse at the higher rate of each chemical, and was also worse where the chemical had been mechanically incorporated. Increasing the rate of chemical tended to increase crop damage more than it increased weed control. None of the treatments (other than hand weeding) gave acceptable weed suppression without also damaging the crop.

Future work ought to evaluate lower rates of application (without mechanical incorporation) as there may be a role for these chemicals in the early stages of crop development, after which mechanical weed control methods could be employed.

Alternatively, these chemicals could be used to provide weed control from planting until the plants start to spread, after which another chemical could be applied. The important thing that developed from this work is that there are chemicals that will allow watermelons to emerge while at the same time suppressing weed gennination.

*****

31

LEGUMES AS A GREEN MANURE CROP

Project Officers: M Smith, M Hoult, S McAlister, G Foord and J Bright

Objective: The current production system for annual crops in the Katherine area involves growing a tall grass (either millet or sorghum) during the wet season, ploughing this in around mid-February, and then sowing annual crops from March through to August. Whilst this system works well on sandier soils, the heavier 'Tippera' soils in the region lose their structure very quickly with cultivation making continual utilisation of areas difficult. Furthermore, the need to plough-in grasses in mid-February increases the risk of soil erosion on steep slopes, from intense rainfall which sometime occurs late in the wet season. There is therefore a need to develop an alternative production system in order to sustainably utilise heavier soils and those areas with significant slope.

Past work has identified one cowpea genotype (40323) that sets seeds very late (mid-May) and may be suitable as a mulch into which annual crops could be direct drilled. New work was undertaken to examine the suitability of this cowpea for an alternative production system.

Materials and Method: A 0.25 ha area of cowpea was sown (11 December 1996) adjacent to a similar sized area of Jumbo sorghum. The growth and development of both areas were observed throughout the wet season. Prior to ploughing-in the sorghum (28 February 1997) three 1m2 quadrats were cut from each of the two areas to assess biomass production. Three quadrats were also cut from a nearby area of Putland mungbean, planted 1 January 1997 for comparison. A further 3 quadrats from the cowpea area were taken (8 May 1997) immediately prior to the area being sprayed-out with glyphosate. Both areas were sown to watermelon nitrogen experiment on 15 May 1997.

Results and Discussion: The sorghum is clearly ahead, in terms of biomass, if all crops were to be ploughed-in around mid-February. However, because the cowpea does not need to be ploughed into moist soil with sufficient rain to help it rot down (a problem with the sorghum), and because it does not set seed early (a problem with the mungbean) it can be left to grow until May. Because of this, the actual biomass added to the soil per year from the cowpea, starts to approach the levels normally added by grass green manure crops.

The cowpea mulch presented considerable difficulties in terms of direct drilling, due mainly to the long spreading 'rope-like' stems that fouled the planting equipment. Whilst machinery modifications may help to overcome this problem, there may also be a need to identify legumes that can be more readily cut by coulter wheels. Results for the response of watermelons to the two different production systems will be presented next season.

*****

BAMBOO RESEARCH

Project Officers: K Blackburn and M Traynor

Objective: The bamboo research project is partially funded by RIRDC and is an Australian joint research investigation combining inputs from: • The University of Central Queensland, Rockhampton (principal Organisation). • Bamboo Australia, Belli Park, Eumundi, Queensland (Commercial grower). • Queensland DP!, Bundaberg Research Station. • NT DPIP, Coastal Plains Horticultural Research Station.

The objectives of the project, which was approved and funded in August 1994, are: • To identify suitable species for the production of bamboo shoots under Top End conditions. • To gain expertise in the cultivation of selected species and to develop cultural practises such as irrigation and

fertiliser scheduling for optimum shoot production. • To release trial quantities of fresh product to assess its market potential. • To collate and extend information on species performance.

32

There is, effectively, no production of bamboo shoots within Australia. Canned bamboo shoots are currently imported from SE Asia with a retail price between $3.00 and $6.00 per kg and an estimated Australian consumption of 1, 357, 000 kg (value $6 M) per annum. A potential export market exists for fresh shoots into Asian markets, particularly Japan, where they represent the largest category of imported fresh vegetables into the country (44 - 85, 000 tonnes pa.).

The two project officers visited Belli Bamboo Farm in November 1994 to attend the frrst RIRDC meeting on the project as well as attending a Bamboo Workshop conducted by the grower participant, Mr Durnford Dart. A visit was made to Bundaberg Research Station to discuss the co-operative project with researchers and to inspect the bamboo collection. On the return trip to Eumundi, a visit was made to Rollo Campbell's Tiaro Bamboo Nursery and varietal collection. The RIRDC meeting was attended by John Leonardi of UCQ, Peter Bindon of the Australian Bamboo Network (Perth), Mr Dart and the NT officers. The RIRDC project was discussed at length and much valuable information was collected to support the NT part of the project. The most suitable bamboo species were selected and arrangements were made to have the plants prepared and grown on for shipment to Darwin early in 1995 for trial establishment.

RIRDC/DPlF Bamboo Trial: This trial was planted on Friday 24 February 1995 with plants shipped personally by Mr Dart. The bare-rooted plants were planted directly into the freld under heavy monsoon conditions and to date no losses have occurred. The bamboo variety, Bambusa oldhamii, was chosen for the trial as it was less expensive than the two other preferred species Dendrocalamus asper and D. latiflorus.

The trial design is a 3x3x3 factorial arrangement with a split plot design 3 Irrigation Levels. 40, 60, 80% evaporation replacement. 3 Fertiliser treatments - to be implemented at about 18-24 months from planting to allow the plants to

establish frrst. 3 Replications.

During 1996 the trial plants made excellent growth with the culm diameters gradually increasing as the rhizomes matured. The thinning operation in April 1996 removed about 10-12 culms per clump leaving approximately 3 to 4 mature and 6 to 8 new culms for growing on. There was a mass of lateral branches in each clump which seems to be typical of B. oldhamii and makes thinning a labour intensive operation. In contrast, D. latiflorus has much less branch development which makes thinning an easier management activity. D. latiflores, after 2 years growth is impressive and is one of the best performers in terms of growth and short size. Bamboo leaf and soil samples were collected and analysed in mid 1996 to check against nutrient leaf standards set for a similar species, sugar cane. It was found that the general nutrient levels were quite adequate and the current maintenance fertiliser program was maintained.

It is anticipated that the treatments will be imposed on the trial in mid 1997, after the plants have recovered from thinning, and when it is considered that the rhizomes are advanced enough in development to handle the trial treatments.

The current RIRDC project was programmed to terminate at the end of June 1997 but recent information received from the UCQ, Rockhampton, confrrms that there is a very good chance that the project will be extended for a further 3 years.

Data collection will include: Number of shoots produced, size and height Diameter of culms at the 7th node above ground Leaf and soil analyses at regular intervals Soil moisture tensiometer and Environscan monitoring Phenology of shoot production in relation to treatments and to local conditions Variety collection: An older collection of bamboo (12 species) gathered from around the Darwin area is now 3 yrs old but has only been managed well for the past 2 years.

A new collection of bamboos (19 species) which include edible, timber, windbreak and ornamental types purchased mainly with DPlF funds. This collection includes 7 plants each of D. asper and D. latiflorus, which are 2 of the preferred 3 species for edible shoot production.

*****

33

CASHEW SELECTION AND EVALUATION

Project Officers: V Kulkarni and D Haroilton

Objective: The climatic conditions of the Top End are ideal for cashew. Economic analysis however has indicated that commercial success of cashew in NT would largely depend on availability of cultivars which can yield at least 4.5 tonnes of nutslh. Few of the existing cultivars can meet this target. Productivity can be improved either by evolving new genotypes or by developing new management techniques. New genotypes can be evolved by systematic crossing as well as through selection. This project aims at evolving new genotypes through selecting promising types from a large population of seedling progenies and evaluating them for consistency.

Materials and Method: Seedlings were raised from genetically diverse material derived from Brazil and were planted at CPRS in 1990. A total of 800 seedlings were tested. Evaluation of the seedling progenies for vegetative, floral and nut characteristics and yield of the trees resulted in 12 promising types of which five were judged to be most promising. These are, DPIF 5/9, DPIF 5/11, DPIF 5/13, DPIF 5/18, DPIF 5/19, DPIF 5/21, DPIF 5/22, DPIF 5123, DPIF 5/24, DPIF 5/30, DPIF 5/40 and DPIF 3/28. These selections were grafted on seedling rootstock for planting and testing at Wildman River Plantation in NT and Australian Cashews in Queensland. At least 5 grafts were prepared for each site. Four grafts in each selection were also planted at CPRS.

Results: Grafts planted at Australian Cashews have established well. QDPI researcher P.O.J. Farrel is monitoring the progress of this material. As a result of management problems faced by Wildman River property, the selections at this site failed to establish and will be replanted under the new management. There were a few mortalities at CPRS on account of cyclone Rachel. It is proposed to replant the selections at a new site.

*****

CASHEW VISUAL YIELD ASSESSMENT

Project Officers: G Foord, M Smith, M Hoult, S McAlister and J Bright

Objective: Over 800 trees of about 450 different cashew hybrids were planted in 1992 as part of the NTDPIF, QDPI and CSIRO hybrid evaluation program. This presented us with the task of assessing a large number of individual trees, in a short time, with limited resources.

The aim of this project was to test a visual ranking technique to record yields of cashew trees without hand­harvesting.

Materials aud Method: Yield was visually assessed in November, estimating yield by the number of nuts on the ground. Each tree was ranked from 0 to 5 (5=highest yield). Nuts were hand-harvested from the higher ranked trees, a selection of lower ranked trees and from trees that were hand-harvested in 1995. A linear regression was performed on the data from 1995 and 1996 harvests.

Results and Discussion: In 1996, leaf fall, caused by pesticide damage, made the visual assessment more difficult than in 1995. However, the correlation between visual ranking and hand-harvested yield in 1996 was strong (R2 = 0.5796).

The high correlation between yield data and the ranking system used supports the use of the visual ranking system for assessing the yield of individual cashew trees. We were able to calculate the yield of over 500 trees without hand-harvesting by simply multiplying the visual ranking by the 'y' value calculated. The visual assessment took 3 people about 2 hours and saved over 500 hours hand-harvesting and sorting time.

*****

34

CASHEW GERMPLASM ASSESSMENT

Project Officers: G Foord, M Smith, M Hoult, S McAlister and J Bright

Objective: Since 1995, cashew research in Katherine concentrated on a collection of hybrids planted at King Producers' Venn block, 20 km south of Katherine. Over 800 trees of about 450 different cashew hybrids were planted in 1992. These are a part of an NTDPIF, QDPI and CSIRO hybrid evaluation program to identify superior hybrids.

Early in 1995 it became clear that management systems developed elsewhere did not necessarily suit Katherine conditions. Pest management emerged as a priority, the main cashew insect pests (the Mango Tip Borer Penicillaria jocosatrix, Helopeltis Bug Helopeltis sp. and the Fruit Spotting Bug Amblypelta lutescens) attack new flushes. This project looked at developing a system that would encourage new growth at critical stages and limit unnecessary flushing through 'high pest pressure' periods without adversely affecting yield or nut size. At the same time we could identify superior hybrids.

Materials and Method: In 1996 we modified our irrigation and nutritional inputs outlined in the 1995/96 Technical Annual Report by withholding irrigation from the start of the wet season (December 1995) until the beginning of May, and applying all macro-nutrients in May, June and December.

Results and Discussion: The hybrid '1161' consistently yielded well, out yielding the next best in 1995 by about 10% and in 1996, and '1995 and 1996' combined, by >30%.

The new management system developed at Katherine and outlined in 1995/96 Technical Annual Report appeared to be effective. Compared to 1995, there was more uniform flushing and flowering, a general yield increase with similar nut size and a reduced reliance on chemicals for insect control. Withholding irrigation from the start of the wet season (November, December) until the beginning of May, represents a substantial saving of power and water resources, more than 0.4 megalitres of water per month per hectare could be saved. The more uniform flowering resulted in a more uniform nut fall. This will allow harvesting to take place over a shorter period with fewer passes with the machinery.

The next phase of this project is to frother evaluate the hybrid '1161' and a promising Brazilian selection in multiple tree plots. This will enable more accurate estimates of yields (per hal and the 'fine tuning' of cashew management in Katherine.

*****

CASHEW ROOTSTOCK SCREENING

Project Officers: G Foord, M Smith and M Hoult

Objective: Superior cashew genotypes identified at Katherine and at CPRS will be grafted and further tested at KRS. The availability of seedlines for rootstocks and information on their performance as a rootstock is limited (or non existent). Smith and Bowman (1994) conducted an experiment to assess the possible existence of iron­deficiency induced chlorosis as a problem in young cashew and to determine the relative susceptibility of a range of cashew seedlines to symptoms of chlorosis. Distinct differences were detected within 45 days of sowing.

In this experiment, we investigated the selection of available seedlines most likely to perform well, as a rootstock, on the alkaline, irrigated soils of the Katherine region.

Materials and Method: On 22 October 1996 the seedbed was prepared at KRS on Tippera clay loam. One kilogram per square metre (10 tonne per hectare) of calcium carbonate was incorporated into the soil.

Seed collected from 43 trees around Darwin and Katherine were sown in rows of 7 at close spacings (15 cm x 20 cm) and irrigated daily using T-tape®. Chlorosis severity was assessed on 27 February 1997.

35

Results and Discussion: October and November mean maximum temperatures and humidity were typically hot and dry. By contrast, December and January were particularly wet. Heavy rainfall caused local flooding and the trial area was inundated for up to ten days at a time. These extreme conditions were less than ideal. However, many of the 43 lines planted established well (>50% survival rate).

On 27 February 1997, most lines were severely chlorotic. Two lines from Darwin were very vigorous, with no chlorosis and two lines from Katherine, though less vigorous also showed no chlorosis.

Seedlines from Darwin, that performed well, were not available for the 1997 planting. Therefore, the seedline from Katherine that performed the best was selected because of its availability. Of the ten seedlines sourced in Katherine (collected from trees that yielded well in 1995), one did not germinate, two were severely chlorotic and only two were acceptable. In this instance, we had an 80% chance of selecting a stock with a low tolerance to elevated pH if we selected on availability alone.

References: Smith, M. W. and Bowman, L. (1994). Cashew Rootstocks: why and how. Working paper of the Seventh Annual Cashew Research and Development Workshop. Cairns, Qld. 17 May, 1994.

*****

SUPER·RED GRAPEFRIDT EVALUATION IN KATHERINE

Project Officers: M Houl!, M Smith, D Jaensch and P Gallasch

Objective: Redfleshed grapefruit are expected to be popular in Australia because they are visually more appealing and some are more palatable than the traditional white·fleshed cultivars. This trial is part of a national HRDC project that aims to assess red-fleshed grapefruit cultivars in a wide range of growing conditions around Australia.

Materials and Metbod: Eight cultivars of grapefruit were replicated 8 times, budded to 2 different rootstocks and planted in randomised, single tree plots in 1995. The 8 cultivars include: Marsh, Oroblanco, BCP3-Ruby type grapefruit, Henderson, Ray Ruby, Rio Red, Star Ruby and Flame (established 8 months later). The rootstocks used were Swingle Citrumelo and Carrizo Citrange. The trial was conducted at Katherine Research Station (KRS).

Trees were fertilised with either anunonium sulphate or 14:14:12 every 6-8 weeks at 80-100 g / tree / year of age. Copper (5 gltree) and zinc (50 gltree) were applied as foliar sprays every 6 months. Irrigations were scheduled according to soil moisture requirements as determined by tensiometer readings. Suckers were removed and trees skirted in June 1997.

Results and Discussion: All scion / stock combinations have established well. Some cultivars have exhibited better growth than others with Oroblanco, Rio red, Ray Ruby and Marsh showing good vigour and Star Ruby being the least vigorous. Scions on Swingle exhibited less micro nutrient deficiencies than Carrizo at the alkaline soil site of KRS.

Some trees flowered well and set fruit notably Ray Ruby, Rio Red, BCP3-Ruby type and Marsh. Yield and quality data will be collected for the first time in 1998.

*****

NATIONAL RED·FLESH GRAPEFRIDT CULTIVAR TRIAL· EVALUATION IN CENTRAL AUSTRALIA

Project Officers: G Kenna and N Isgro

Objective: There are three sites in Central Australia which have been established to evaluate newly imported redflesh grapefruit selections and a white flesh cultivar, Oroblanco Australia, as part of the national project.

36

Materials and Methods: A replicated trial planting was established at the Arid Zone Research Institute in August 1995. All cultivars are replicated on two rootstocks, Swingle and Carrizo. Trial layout is a randomised complete block design with 14 treatments and 4 replicates. A demonstration planting consisting of 14 trees was established at Ti Tree Research Farm in August 1995. A similar demonstration planting has also been established on Murray Downs Station, which is located approximately 140 kilometres south of Tennant Creek, in September 1996.

Results and Discussion: During the 1995-96 growing season it was observed that the variety Star Ruby reacted adversely to the very hot conditions experienced during the summer months. These growth patterns tended to be more evident on Swingle rootstock. Tree growth for all other varieties at all locations was satisfactory.

A number of trees growing in the replicated trial planting at the Arid Zone Research Institute in Alice Springs have carried a very small number of fruit. Preliminary investigation of these as they mature has indicated that the variety Rio Red has considerable potential for the Alice Springs region.

*****

GRAPEFRUIT CULTIV AR EVALUATION IN THE KATHERINE REGION

Project Officers: M Hoult, D Jaensch, S McAlister, J Grigg and M Smith

Objective: Hot conditions during fruit maturation, make the Katherine region ideal for quality grapefruit production. This trial aimed to rapidly screen several new red cultivars for their production performance in the Katherine region.

Materials and Method: Five super red cultivars, Star Ruby, Rio Red, Flame, Ray Ruby, Flame and Henderson, were planted on a range of rootstocks at Katherine Research Station (KRS) during 1992-1994. Henderson and Ray Ruby produced their first significant crop in 1996.

Yields were recorded and quality assessments made over a number of months using 5-6 fruit at each assessment. All fruit was de-greened with ethylene prior to evaluation. Quality assessments were made for Henderson, Ray Ruby and Rio Red in 1997.

Results and Discussion: The external colour of Ray Ruby was outstanding with most of the rind showing red background colour. Henderson tended to exhibit external colour only where fruit touched other fruit or foliage. The internal colour for Henderson and Ray Ruby was very similar with Ray Ruby being marginally darker. For both cultivars the colour was far superior to locally grown Ruby Blush. Rio Red also had good internal colour which was more uniform through the juice sacks than Ray Ruby or Henderson.

Internal quality was excellent with Ray Ruby and Henderson cultivars achieving Brix I acid ratios of 7:1 in late February 1996. Fruit matured early, had high percentage juice, intense colour and thin rind. In general fruit quality for 1997 was poorer than 1996, a possible reflection of the heavy wet season.

Rind levels in 1997 were similar for Ray Ruby but slightly higher for Henderson. Rio Red fruit was fairly course with thick rinds and bumpy stem end or 'sheep nose' like condition. This has also been observed in California USA for this cultivar. Internal colour was darker than Henderson and Ray Ruby with external colour similar to Ray Ruby. Fruit Piercing Moth (FPM) caused an estimated 5-10% fruit damage in 1996. However FPM was very severe in 1997 with 80-90% fruit damaged when the fruit was allowed to hang on the tree.

In general the quality of these cultivars was outstanding and indicates that there is potential for quality red grapefruit production in this region. Similar assessments will continue for 1998 season.

*****

37

LEMON CULTIV AR EVALUATION IN KATHERINE

Project Officers: M Hoult, D Jaensch, M Smith, S McAlister and J Grigg

Objective: With some manipulation of phenology, Top End lemons mature at a time when prices on the domestic market are at their highest, that is in January - March. This trial aimed to look at the production performance of various lemon cultivars in the Katherine region with particular emphasis on summer lemon production.

Materials and Method: Four cultivars, Meyer, Eureka, Lisbon, Villa Franca, were planted on Benton rootstock at Katherine Research Station (KRS) in 1992. Fino and Verna were grafted to Benton rootstock in 1993. Yields for the 1996 crop and 1997 crop were recorded and quality assessments made over a number of months using 5-6 fruit at each assessment.

Results and Discussion: Yields increased dramatically in 1997 with trees reaching 4 years. Fino and Verna cultivars (3 year old) produced their first crop in 1997 with Fino having one of the highest 'fIrst-year' yields of all the cultivars observed.

The quality performance of the lemon cultivars was encouraging. Percentage juice was high, even at the fIrst sampling date in December 1996. Quality for 1997 was poorer and juice levels reached a maximum of 44% for Eureka, 44% for Fino and 34% for Verna.

Rind thickness was very good with no cultivar exceeding 4 mm in 1996. Rind thickness was slightly higher in 1997 with Eureka, Fino and Vema having a rind thickness of 5.3,5.8 and 7.1 respectively. Fruit size was large, which may be a negative aspect for certain markets.

Overall the lemons were very good quality and could be harvested during a period of reduced supply on the Australian domestic market, that is January through to March / April, and for possible supply into Japan in late March-April. Apparently this is a period where the USA 'main crop' lemon season has finished and the southern Australian and South African 'main crop' season has yet to fully commence. All cultivars (except Vema) had fruit percentage juice greater than 44% for the 'main crop' by January. The most promising cultivars to date are Eureka, Lisbon, and Fino.

The only cultivar to signifIcantly be damaged by fruit piercing moth (PPM) was Meyer. For the other cultivars no damage was observed in 1996 and there was only very slight damage «5%) in 1997.

Yield and quality assessments will continue for the 1997/98 season. *****

BREEDING/SELECTION OF CITRUS VARIETIES

Project Officers: M Smith and M Hoult

Objective: Research work to date has demonstrated that much of the citrus germplasm currently in Australia is of limited commercial value under the hot dry conditions of the Katherine region. Consequently, efforts have been made to identify alternate sources of suitable material, and to investigate the possibility of breeding new material.

Materials and Method: Seed of a red-fleshed pommelo type from Israel were sown at Katherine Research Station (KRS) in September 1996, and transferred to the field in July 1997. A total of 46 trees from this material have been established (on their own roots). Seed from a low acid pommelo type (Leeman pamela) from Darwin were also sown at KRS and 24 trees field planted in May 1997 (again on their own roots). Nine seedlings from a pamela grapefruit cross (ex Zappalas Qld.) will be planted late in 1997. Controlled crosses were made between Marlsol clementine and Fremont mandarin at KRS in the 1995 season. Twenty two seedlings were produced from this cross and have been budded onto Cleopatra rootstock.

38

Seedlings of Fairchild mandarin (origin USA), Quit Duong mandarin (origin Vietnam), an easy-peel selection from Indonesia, and Chironja (origin Haiti) have been established. All 4 of these are polyembryonic and should come true to type from seed.

Ten seedlings of Temple (origin Jamaica) and 8 of Cam Sanh (origin Vietnam) will be budded onto Cleopatra for field evaluation. These two cultivars are monoembryonic and hence seedlings will show genetic variability.

Eleven seed lots were collected during the citrus season in Jamaica and Trinidad in 1997, most of them being from highly coloured easy-peel types. Delays in quarantine treatment meant that practically all of the material failed to germinate. The exceptions were three seeds of Ugli (also spelt Hoogly) and one of Ortanique. These will be budded onto Swingle rootstocks and transferred to the field for evaluation.

Results and Discnssion: Whilst currently of limited scope, it is hoped that some of the material may prove to be of commercial value to the region. Similarly, it is hoped that the material may also prove useful as breeding parents in the longer term.

*****

CITRUS ROOTSTOCK EVALUATION IN CENTRAL AUSTRALIA - MINNEOLA TANGELO, IMPERIAL MANDARIN AND MARSH GRAPEFRUIT

Project Officers: G Kenna, J Mansfield and S Marte

Objective: Citrus has shown some potential in the Central Australian region. The identification of compatible rootstocks, their effect on productivity, time of harvest and tolerance to soil and water characteristics in Central Australia is necessary for the successful establishment of a citrus industry.

Materials and Methods The trial was planted at Ti Tree Farm in 1987. Eight commonly used rootstocks: Rangpur (also known as Rangpur lime), Watkins rough lemon, Carrizo and Troyer citrange, Emperor and Cleopatra mandarin, Swingle citrumelo and Symons sweet orange were evaluated for their suitability as rootstocks for the Minneola tangelo, Marsh grapefruit and Imperial mandarin scions. Yield data and fruit characteristic measurements were taken until 1994.

Results and Discussion This experiment is currently being written up into a report. The results indicated there was a variation in the performance of the rootstocks under the three scion types, but Rangpur, Watkins rough lemon and Carrizo citrange consistently out performed the others.

*****

CITRUS ROOTSTOCK EVALUATION FOR MARISOL CLEMENTINE (CENTRAL AUSTRALIA)

Project Officers: G Kenna, J Mansfield and S Marte

Objective: Potential exists for commercial development of seedless mandarin cultivars for the early market niche. The identification of compatible rootstocks, their effect on productivity, time of harvest and tolerance to soil and water characteristics in Central Australia is necessary for their successful establishment. Materials and Method: This trial was planted in September 1991 to evaluate Marisol Clementine Mandarin on five different rootstocks (Watkins rough lemon, Carrizo citrange, Cleopatra mandarin, Rangpur cross Troyer citrange and C32).

Results and Discussion The trial was harvested in 1994 and 1995 but the data is of little use as the fruit are cross-pollinated and consequently are very seedy and not what would be expected if each cultivar was grown in isolation. This experiment is currently being written up into a report.

*****

39

PINK·FLESHED GRAPEFRIDT EVALUATION IN CENTRAL AUSTRALIA

Project Officers: G Kenna, J Mansfield and S Marte

Objective: White flesh grapefruit have met consumer resistance due to the perception that fruit is unpalatable (ie. it has high acid and low sugar levels). Pink fleshed grapefruit tend to have higher sugar levels and lower acid levels and have gained consumer recognition for this.

Materials and Method: The varieties available at the time of planting (Ruby, Foster and Thompson) were grown on four rootstocks (Symons sweet orange, Troyer citrange, Rough lemon and Swingle citrumelo) with and without mild strain tristeza.

The trial was planted at Ti Tree Research Farm in 1989 and yield data and fruit characteristic measurements have been taken.

Results and Discussion: This experiment is currently being written up into a report. The experiment was compromised by the introduction of phytophthora with the trees in the potting mix.

The results indicate that the mild strain tristeza had little effect on yield. Rough lemon and Symons sweet orange appeared to be the better rootstock, as scions on these had the highest yields and yield efficiencies. Of the scions, Foster had the highest yields.

*****

CITRUS CULTIV AR EVALUATION PLANTING IN CENTRAL AUSTRALIA

Project Officers: G Kenna, J Mansfield and S Marte

Objective: Commercial citrus production has been identified as having potential for Central Australia. There is a constant release of new selections sourced from overseas as well as new selections bred or selected in Australia. These need to be evaluated for suitability for the region.

Materials and Method: A number of trees of these selections, mainly easy peels and navel oranges, are established at Ti Tree Research Farm for evaluation. The potential of these cultivars is being assessed based on earliness, total yield, fruit quality and market acceptance.

Resnlts and Discussion: Fruit piercing moth has limited the evaluation of these cultivars by causing extensive damage to fruit during high summer rainfall seasons. However it appears that grapefruit may have some potential for the Ti Tree region since it appears to be less susceptible to damage. This experiment is currently being written up into a report.

*****

ROOTSTOCK EVALUATION FOR LEMONS IN VARIOUS SOIL TYPES IN THE KATHERINE REGION

Project Officers: M Hoult, M Smith, D Jaensch and L Granger

Objective: This trial was initiated in order to identify the most appropriate rootstock for commercial lemon production in the three major soil types in the Katherine region.

40

Materials and Method: Four cultivars of lemons were budded, in the nursery at Katherine Research Station (KRS) to 7 different rootstocks, resulting in 28 scion 1 stock combinations. Scion 1 stock combinations were replicated 4 times. Field layouts have been designed with scion 1 stock combinations randomly assigned to single tree plots.

The four scion cultivars are: Eureka, Lisbon, Fino and Verna. The 7 rootstocks are: Benton Citrange, Cox Mandarin, Lockyer Rough Lemon, Rangpur, Nelspruit hybrid 639, Volkamer Lemon, Swingle Citrumelo. Three trial sites, with 3 different soil types namely Tippera, Blain and River levee, have been identified for planting.

Results and Discussion: One site was established on the Tippera soil type in early 1996. At six months all trees had established well with Volkarner Lemon, Lockyer Rough Lemon and Rangpur having the highest vigour. Nelspruit hybrid showed moderate vigour while Cox Mandarin and Benton Citrange showed low vigour. Some trees showed slight iron chlorosis possibly due to the heavy rains saturating the soil in the 1996/97 wet season. Rangpur exhibited some anchorage problems as trees had poor stability. The Swingle Citrumelo stock were field budded on planting so no comparison was possible.

Trees were budded for the Blain soil type site and have been hardened off ready for planting in July 1997. The third site is expected to be planted in late 1997.

*****

GRAPEFRllT ROOTSTOCK EVALUATIONS FOR DIFFERENT SOIL TYPES IN THE KATHERINE REGION

Project Officers: M Hoult, M Smith, D Jaensch and L Granger

Objective: This trial was initiated in order to identify the most appropriate rootstock for commercial grapefruit production in the three major soil types in the Katherine region.

Materials and Method: Three cultivars of grapefruit were budded, in the nursery at Katherine Research Station, to 7 different rootstocks, resulting in 19 scion 1 stock combinations. Scion 1 stock combinations were replicated 4 times. Field layouts have been designed with scion 1 stock combinations randomly assigned to single tree plots.

The three scion cultivars include: Rio Red, Flame and Star Ruby. The 7 rootstocks include: Benton Citrange, Cox Mandarin, Cleopatra Mandarin, Carrizo Citrange, Trifoliate Orange (Poneirus trifoliata), Nelspruit hybrid 639, and Swingle Citrumelo.

Three trial sites on grower properties, with 3 different soil types namely Tippera, Blain and River levee, have been identified for planting.

Resnlts and Discussion: One site was established on the Tippera soil type in mid 1996. After three months growth there already appeared to be dramatic differences in stock/scion combinations.

Benton Citrange across all scions had very poor, weak growth or no scion growth at all. Trifoliate Orange was also weak and Carrizo Citrange showed moderate vigour. Swingle Citrumelo, Cleopatra Mandarin and Nelspruit hybrid were amongst the more vigorous stocks.

Cox Mandarin also looked very healthy and was a surprise given it was selected for Eureka lemon in the lemon rootstock trial. Star Ruby scions exhibited distortion of new growth flushes due to suspected herbicide drift, a common complaint with this cultivar overseas. Plantings at the other sites will be established in 1997.

*****

41

MANDARIN CULTIV AR EVALUATION IN THE KATHERINE REGION

Project Officers: M Hoult, M Smith and D Jaensch

Objective: Early cultivar assessments of mandarin production in Katherine were not encouraging given poor flowering, and low and erratic yields. With modification of management, using moisture stress to enhance flowering on certain cultivars, a re-evaluation of the potential for very early mandarin production was initiated.

This trial aimed to look at the production performance of various mandarin cultivars, including tangor and tangello types, in the Katherine region with particular emphasis on the early, easy-peel cultivars.

Materials and Method: Ten cultivars on a range of rootstocks were planted at KRS in 1993. Trees were first harvested in the 1996 season. Yields were recorded and quality assessments made over a number of months in the 1996 and 1997 seasons, using 5-6 fruit at each assessment.

Results and Discnssion: The most promising cultivar was Fremont with high yield, high fruit numbers and excellent internal colour and rind colour (after degreening) and significantly lower levels of granulation than other cultivars. But fruit size was small with noticeable levels of pith. Fruit thinning may be required to increase fruit size.

Murcott yielded well but most fruit was sunburnt with an insipid taste and considered unmarketable. Fina had little granulation and reasonable flavour. Imperial, Emperor, Red Imperial, Page, Sunburst and Ellendale had little or no flowering and produced few or no fruit. The poor performance of Imperial and Ellendale confirmed past observations of these cultivars in the Katherine district.

Nova matured reasonably early with a Brix: acid ratio of 11.5:1 in mid February. Internal colouring was good although moderate to heavy levels of granulation developed during the season. Juice content was relatively high at 41.1 %.

In both assessment years, fruit piercing moth caused severe damage with up to 90-100% of fruit damaged. Strip picking prior to severe infestations may not be an option given most cultivars are not mature at the onset of damage.

Cultivars such as Marisol, Nules, Oroval, Emperor and Imperial will be fe-worked in 1997 to other promising cultivars such as Topaz, Fallglo, Daisy, Shekwasha and Wekiwa. Assessments of yield and quality will continue for Fremont, Murcott and Fina in 1998 with some adjustments made to crop levels during the season.

*****

CITRUS MANAGEMENT IN THE KATHERINE REGION

Project Officers: M Hoult, G Foord, J Bright, S McAlister, M Smith and D Jaensch

Objective: Past experience has shown that the challenges facing the management of citrus around Katherine include: poor and erratic flowering over a number of months due to warm temperatures experienced during the flower initiation phase; control of unnecessary vegetative flushes to minimise citrus leaf miner damage; determining irrigation and nutrient requirements for high quality and yield; and control of pests and diseases.

An effective management system for citrus in the tropical environment of the Katherine region has been evolving over a number of years and this trial examines the use of irrigation scheduling and selective fertiliser use to improve yield. With some modification, this could also be adapted to the Darwin region.

Materials and Method: Irrigation was withheld for 6 weeks in May I June 1996. At 'wetting-up' a 1 % foliar low-biuret urea application was applied. Tensiometers, at 45 cm and 90 cm, were used to monitor soil moisture tension (SMT) and to schedule irrigation so that SMT was maintained below -40 kPa at 90 cm. Nitrogen (ammonium sulphate) was

42

applied at 80-100 g N/tree/year of age in July / August, potassium at 50 g Kltree/year of age and phosphorus at 10 g P/tree/year of age. Potassium and phosphorus were both applied in January / February. Two foliar applications of zinc heptahydrate at 2 gIL and one foliar application of copper oxychloride at 1.5 gIL.

Results and Discussion: Flowering was more prolific and concentrated for some cultivars after withholding water for 6 weeks. Observations of slow tree growth after this stress period suggests that the stressing period may need to be shorter in order to maintain tree health. The stress period applied in 1997 was reduced to 4 weeks. Flowering levels will be monitored to determine if shorter stress periods are able to induce good flowering.

By maintaining a SMT of less than -40 kPa at 90 cm in 3 year old lemons, a crop factor of between 0.74 and 0.86 applied (assuming 18 square meter canopy). This is considerably higher than crop factors used for citrus in other areas. This crop factor was determined on one season's data only and soil moisture monitoring will continue.

Fertiliser application in July/August produced strong vegetative flushes in the following weeks and greatly reduced the amount of flushing during the wet season. This helps in managing citrus leaf miner which is most prevalent during the wet season on young vegetative flushes. Reducing wet season flush also ensures maximum reserves are available for fruit production at this time.

Leaf nutrient levels were within the standard range except for zinc and copper. Nitrogen levels generally were on the high side and possibly reflect the high N inputs for maximising growth in young, non-bearing trees prior to the first harvest year.

The most troublesome pest in citrus has been the citrus leaf miner. However this is easily managed with horticultural spray oils, natural parasites and management of vegetative growth flushes. Fruit piercing moth may cause devastating damage to mandarin crops and to a lesser extent grapefruit and lemons. This pest will need monitoring over a number of years and would be a major limitation to commercial mandarin production as there are no known effective control measures apart from netting the orchard. Citrus mealybug, red scale and citrus butterfly larvae are largely controlled using biological control methods in which it is essential to maintain effective ant control.

*****

CITRUS IRRIGATION OBSERVATION, MONITORING AND SCHEDULING IN THE KATHERINE REGION

Project Officers: G Foard and M Hoult

Objective: The citrus planting at Katherine Research Station (KRS) provided an opportunity to closely monitor irtigation, record soil moisture tension and gain a better understanding of the irrigation requirements of citrus in Katherine on Tippera soil.

Materials and Method: After the water 'stress' period in May/June, lemons at KRS were irrigated to field capacity to a depth of >90 cm. Tensiometers at 45 and 90 cm depths were installed to monitor soil moisture tension and to schedule irrigation.

Results and Discussion: In July and August, a pattern developed. On the Tippera clay /Ioam of the trial site, we found that we needed to apply about 530 litres of water per tree when the SMT at 45 cm reached -20 kPa. This maintained SMT below -40 kPa at 90 cm. Applying 530 litres per tree, with a tree canopy area of 18 square metres (4 year old trees) is about 29 mm per irtigation.

In August, 5 irrigations provided a total of 145 mm. The total evaporation for August was 195.7 mm, this translates to a crop factor of 0.74. In September and October combined, 14 irrigations provided a total of 406 mm, the total evaporation was 488.1 mm, a crop factor of 0.83. November rainfall and irtigation totalled 175.6 mm, evaporation was 228.7 mm, a crop factor of 0.76. In December and January, rainfall exceeded evaporation and no supplementary irrigation was required.

43

These preliminary observations show that when using soil moisture tension to schedule irrigation in lemons, a crop factor of between 0.74 and 0.86 applied. This is consistantly higher than crop factors used for citrus in other areas. However, it must be stressed that we base this on only one season's soil moisture monitoring.

*****

EXTENSION SERVICES TO THE HORTICULTURE INDUSTRY (CITRUS) IN CENTRAL AUSTRALIA

Project Officers: G Kenna and J Mansfield

Objective: Commercial citrus production in the Alice Springs region is limited at the present time to a number of small plantings in the Ti Tree area. There is however considerable potential to expand this industry to produce early maturing high quality fruit for both domestic and export markets.

Considerable resources are allocated to providing results on various citrus research work which has been conducted in the area over recent years. This includes assessment of fruit quality, maturity times, rootstock performance and marketing information. Assessment of land and water resources suitable for citrus production is also made available to prospective developers.

Commercial citrus growers are supported with general information on management, postharvest handling, packing and marketing. Plant health certificates are issued for access of produce to interstate markets. Plants of the grapefruit variety Rio Red have been made available to a Ti Tree grower to encourage the planting of red flesh selections.

*****

COMPARISON OF TISSUE CULTURE AND OFFSHOOT PALMS

Project Officers: G Kenna, J Mansfield, KYoung, N Isgro, C Ellis and S Miller

Objective: There is some reservation within the industry as to whether off-types may occur in tissue cultured date palms and that not all palms produced are "true to type". Offshoots, suckers produced by the parent palm, are the standard method of propagation. However, tissue culture offers the possibility of introducing material which cannot be imported as offshoots due to quarantine restrictions. In addition, tissue cultured plants are cheaper to import than offshoot material and as they are in a sterile medium they do not require fumigation on arrival and are subject to significantly less airfreight costs. Another use of tissue culture besides being a means of importing plants is that it offers a method of rapidly multiplying up planting material within Australia. This experiment compared tissue cultured and offshoot palms of the same cultivar.

Materials and Method: Depending on availability, tissue cultured palms produced by two different methods of propagation were used -those from Date Palm Developments laboratory, England, produced by a callus multiplication method arid those from the Group of French Research on Date Palm (G.R.F.P.) laboratory, France which were produced using a bud proliferation technique. Information was collected on the flowering of all palms and the fruiting and fruit characteristics of the female palms.

Results and Discussion This project was terminated at the end of the 1996 season. The evaluation of the palms was partially funded by RIRDC for three years (1992-1995). The palms first started flowering in the 1992/93 season and data on flowering and fruiting was recorded up until the end of the 1996 season. Generally, the offshoot palms tended to flower and fruit earlier than the tissue-cultured palms, most likely because they were larger and older when they were planted. They also tended to yield higher, possibly because they had more leaves, more food reserves and became established faster. It is difficult to compare the performance of the tissue-cultured palm from the French laboratory against those from the English laboratory due to differences in planting dates. A detailed write up of

44

this experiment can be found in the RIRDC final report for the project DNT-llA ''Evaluation of Date Production in Central Australia".

*****

DATE CULTIV AR EVALUATION

Project Officers: G Kenna, J Mansfield, KYoung, N Isgro, C Ellis and S Miller

Objective: The aims of this project were to assess the performance of four international cultivars under Central Australian conditions and to determine their suitability as potential cultivars for commercial production in this region. Many years are required to thoroughly evaluate a new date cultivar because of varying climatic conditions, the effect that certain management and cultural techniques sometimes have on successful fruit production and the irregular cropping characteristics of young palms.

The four cultivars evaluated were Barhee, Deglet Noor, Medjool and Thoory. Barhee is a cultivar increasing in popularity overseas. The fruit is egg-shaped, quite soft and very sweet. It has excellent eating qualities at all stages of maturity. Deglet Noor is the leading commercial variety in the United States. It is a semi-dry date with sweet flesh and a nutty taste but it is susceptible to rain damage and has a long fruit maturation period. Medjool is one of the main cultivars grown internationally for the high value fresh fruit market. It produces a large, soft fruit with excellent eating qualities. Thoory is a dry date with an attractive appearance and a delicate flavour.

Materials and Method: Four cultivars (Barhee, Deglet Noor, Medjool and Thoory) were imported from England as tissue cultured plants. In September 1989 the palms were established in a statistical planting comprised of four blocks, with each block containing four randomly distributed single palm replicates of each cultivar. Information was collected on the flowering, fruiting and fruit characteristics of the palms.

Results and Discussion: This project was terminated at the end of the 1996 season. The evaluation of the palms was partially funded by RIRDC for three years (1992-1995). The palms first started flowering in the 1991/92 season and data on flowering and fruiting was recorded up until the end of the 1996 season. Some palms of Deglet Noor and Thoory produced flowers in the 1991/92 season, while it was a year later (1992/93 season) before some palms of Barhee and Medjool flowered. By the 1994/95 season, most palms of all cultivars had flowered. However, even by 1995/96 season, flowering patterns were still irregular as all the palms were not producing flowers every season. A pahn may flower one season and not the next. This was particularly the case for palms of the cultivar Thoory.

The overall trend seemed to be that Medjool was the earliest to produce fruit, normally followed by Barhee, while Deglet Noor and Thoory tended to begin fruiting later than the other two cultivars but they continued to produce mature fruit after the other cultivars had finished. However, the timing of when cultivars commenced and stopped producing fruit varied from season to season.

Even six and half years after planting the average yield of the palms was still low. When the average yield per palm is added together for the four seasons in which fruiting has been recorded since planting (1991/92 season not included), Deglet Noor has totalled 30 kg per palm compared to Barhee (20 kg), Thoory (19 kg) and Medjool (8.5 kg). Medjool produced the heaviest fruit in both seasons (around 16 g), while Barhee produced the next heaviest fruit in both seasons (around 10 g). Deglet Noor and Thoory seem to produce fruit of a similar weight (around 8 g).

The cultivars showed some genetic difference in dimensions. The cultivar with the longest and widest fruit of these four cultivars was Medjoo!. The cultivar with the shortest fruit of the four cultivars tended to be Barhee, however it was the second widest fruit after Medjoo!. Deglet Noor and Thoory were very similar in fruit length and diameter.

A detailed write up of this experiment can be found in the RIRDC final report for the project DNT-llA "Evaluation of Date Production in Central Australia".

*****

45

DATECULTIVAROBSERVATION

Project Officers: G Kenna, J Mansfield, KYoung, N Isgro, C EIlis and S MiIler

Objective: Throughout the world several thousand cultivars of dates have been recognised, but of these, those which have any commercial importance are limited to about 100 or so. Some cultivars are unique to a particular country but others, such as the top cultivars now grown in the United States, are grown fairly extensively around the world.

In western countries, dates are considered a confectionery or a dessert rather than a staple food. Consequently. consumers have a preference for fresh, dessert type dates and this has determined that the main cultivars grown here in Australia, and in most western countries, should be large in size, soft with a reasonable moisture content.

Careful attention needs to be given to the selection of cultivars likely to succeed in a particular location. The suitability of the cultivar to the climatic condition of that particular area (heat sum units, rainfall pattern) are of primary importance but other considerations include the adaptability of the cultivar to the soil conditions and management techniques, the amount of high quality dates produced, and the present and future markets.

The aim of this project is to establish a coIlection of the world's best cultivars. From this general observations can be made on potential cultivars for the area. In addition, it acts as a source of offshoot material. In the future, it is envisaged that planting material from the coIlection in Alice Springs could be sent to other areas to establish trials of these cultivars under different conditions.

Materials and Metbod: The germplasm collection is made up of a three male and eighteen female cultivars imported as offshoot and tissue cultured material from various international sources. The planting of the trial started in April 1990 and additions have been made as material has become available.

Results and Discussion: This project was terminated at the end of the end of the 1996 season. The evaluation of the palms was partially funded by RIRDC for three years (1992-1995). The palms first started flowering in the 1992/93 season and data on flowering and fruiting was recorded up until the end of the 1996 season. A detailed description of the results far each cultivar is presented in the RIRDC final report for the project DNT-llA "Evaluation of Date Production in Central Australia", From the infonnation presented it is possible to see the variation in the characteristics from year to year, the effect of palm age on these characteristics and for fruit size, the differences between the three harvest stages (kbalal, rhutab and tamar).

*****

EVALUATION OF A RANGE OF BUNCH COVERS TO REDUCE RAIN DAMAGE IN DATES

Project Officers: G Kenna, J Mansfield, KYoung, N Isgro, C Ellis and S Miller

Objective: The occurrence of rain on date fruit as it nears maturity can cause considerable damage to the fruit. This can cause a downgrade in fruit quality or render the fruit unmarketable. The primary damage caused by rain and humidity are: 1. Checking and blacknose - Checking results in small, transverse linear scars, chiefly near the apex. Although these ruptures tend to heal, the scars remain, and may downgrade fruit quality. Checking usually results if rain occurs just prior to the kbalal stage. If checking is severe, particularly in the cultivar Deglet Noar, it can be followed by darkening and shrivelling of the tip, known as blacknose. If the fruit is badly affected it may be almost worthless. 2. Splitting and tearing - In the late kbalal stage, the fruit is subject to severe splitting and tearing if exposed to direct contact with water. 3. Excessive hydration of the fruit - in some soft cultivars, contact with rain may cause sugar to concentrate on the fruit surface, producing a sticky skin, and a poor appearance.

Secondary damage to the fruit can result, usually in the late kbalaI stage, due to fruit rots caused by fungi which are active during prolonged periods of high humidity. In addition, souring and fermentation of fruit can occur,

46

usually in the rhutab stage. It tends to occur in the centre of heavy bunches during periods of high humidity following rain.

However, cultivars vary in their susceptibility to rain damage. Some being more sensitive than others. By planting cultivars resistant to rain damage, losses can be reduced. But these cultivars are still susceptible to damage by vertebrate and invertebrate pests. Therefore, commercial orchards need some way of protecting bunches. The problem has been to provide a moderately dry atmosphere and favourable temperatures around the bunch but at the sarne time adequately protect it from rain, birds and insects. This problem would be relatively simple if it were not for the water vapour constantly transpired from the fruit surfaces. Moisture from uncovered bunches is quickly dissipated into the surrounding air. In covered bunches, however, some of the moisture may become trapped and the resulting condition tends to promote water injury and fungal attack. The aim of this project was to evaluate the effectiveness of a range of material when used as bunch covers.

Materials and Method: Bunches were covered in the Kimri (green/unripe) stage of development just before the Khalal stage (early ripening). This period was usually around January. The covers being tested were made from a range of materials including banana bags (plastic bags used for covering banana bunches), muslin, nylon, shadecloth, Tyvek® (a spinebonded polyfilm material used to make disposable overalls) and weedmat. In each season, where possible the bunches on each palm were covered using different materials. Bunches were covered in the 1992/93, 1993/94, 1994/95 and 1995/96 seasons. In the first two seasons preliminary observations only were made as not many bunches were available. However in the 1994/95 and 1995/96 seasons individual bunch information was recorded.

Results and Discussion: The ideal bunch cover would be one possessing all the following attributes: 1. Waterproof during heavy rains, 2. Allow free circulation of air throughout the bunch in periods of high humidity, 3. Allow easy entry for picking ripe fruit, 4. Exclude vertebrate and invertebrate pests, and 5. Be economical to manufacture and fit to the bunch.

Unfortunately, the covers trialed here, did not have all these attributes. In the 1994/95 season, when rain fell regularly throughout the maturation period, covers made of shadecloth and nylon appeared to be most effective in preventing losses due to rain darnage, as they allowed air circulation in and around the bunches. Although they will only keep light rain off the fruit, good air circulation appears to be imperative in the prevention of mould growth following rain. Covers made of dense material (plastic banana bags and weedmat) appeared to be the least effective in preventing rain darnage. This was probably due to condensation build-up and lack of air circulation in and around the bunches, leading to excessive mould growth and fruit rots. It should, however, be noted that on these relatively young palms the fruit bunches hang quite close to the ground and the problem of condensation build-up in these covers may not be as prevalent in older palms where bunches are higher off the ground and better air circulation is possible. By contrast, in the drier season of 1995/96, the denser materials, particularly the plastic banana bags, tended to reduce losses due to vermin and bird darnage.

This project was jointly funded by the RIRDC and the DPIF. It was terminated at the end of the 1996 season. A detailed write up of this experiment can be found in the RIRDC final report for the project DNT-llA "Evaluation of Date Production in Central Australia".

*****

PARLATORIA SCALE ERADICATION

Project Officers: G Kenna, KYoung, N Isgro, C Ellis, D Kennedy and R Mills

Objective: Parlatoria scale is a major pest of date palms in the Alice Springs area. The scale which was introduced into Australia in the early 1900s and into Central Australia in the 1950s threatens the long term viability of the commercial date industry in Australia. It causes palms to become unthrifty and may also infest fruit which either causes it to be downgraded in quality or renders it unsuitable for sale.

47

The insect has infested Mecca Date Gardens and Arid Gold Farm and plantings at the Arid Zone Research Institute. A large percentage of palms growing in and around the Alice Springs town area are infested with the scale and there are also palms in a number of areas throughout the region which are infested. In most instances the scale has been spread by the movement of infested plant material.

Materials and Method: A serious attempt to eradicate the scale from plantings at the AZRI, Mecca Date Gardens and Arid Gold Farm was commenced in 1991. The program involved; 1. The provision of assistance to Arid Gold Farm to apply insecticide sprays to all palms on the propetty. 2. The provision of chemical to the owners of Mecca Date Gardens and Arid Gold Farm for scale

eradication. 3. Foliar application of insecticides at three weekly intervals to palms in the Dahlenburg Block research

planting. 4. Foliar application of insecticides at three weekly intervals and six weekly trunk injections to palms on

De Fontenay Drive at the AZRI with monocrotophos. 5. Three weekly !mnk injection with insecticides to mature palms at the McEllister Block at the AZRI. 6. Three weekly foliar sprays of insecticide to offshoots held in nursery rows at the McEllister Block at

theAZRI. 7. Removal of dead and unthrifty leaves from all palms. 8. Removal and destruction of infested offshoots from palms in the research planting. 9. Inspection and treatment of all offshoots by immersion in dimethoate before leaving the AZRI. 10. Insecticides used for foliar sprays are alternated between maldison and dimethoate.

Results and Discussion: The resources required to conduct such a program over a number of years have been considerable. Progress in the eradication of the scale is being made. The numbers of live scale on palms at the AZRI are declining and have also declined at Mecca Date Gardens and Arid Gold Farm. A survey to monitor the rate of decline by sampling grower properties and the plantings at the AZRI will be conducted in late spring - early summer 1997.

Further methods of eradication have been considered in consultation with the Entomology Branch. This includes the trial release ofladybird beetles as predators of the scale. Red chilocorus (Chilocorus circumdatus) and Blue chilocorus (Chilocorus baileyi) have been released onto heavily infested date palms which are being grown as ornamentals. Their ability to survive the Central Australian climate and their effectiveness at controlling parlatoria scale are yet to be assessed.

*****

INTRODUCTION OF NEW DATE PLANTING MATERIAL INTO CENTRAL AUSTRALIA

Project Officers: G Kenna, J Mansfield, N Isgro and C Ellis

Objective: The number of date cultivars under commercial cultivation throughout the world is considerable. The fruit characteristics of these varieties are many and varied. They range from very soft sweet fruit of average size to fruit which is slightly drier, firm, sweet and has a large fruit size and other varieties which are quite low in moisture and have a sweet nutty flavour. These fruit characteristics together with maturity time and the ability of the fruit to withstand rain as it nears maturity are considered important for commercial date production in the Central Australian region.

Materials and Method: A planting of 21 varieties of date palm has been made at the Arid Zone Research Institute at Alice Springs. As these palms begin to bear fruit they are assessed for palm growth and yield. Fruit characteristics are also assessed. This planting is increasing as new varieties are imported from overseas as tissue cultured material. A new addition to the planting in the near future will be the cultivar Sukkary which was imported in 1994 and has been grown in a controlled environment until the plant reaches a suitable size for planting out.

Resnlts: Assessment of the plantings is continuing.

*****

48

THE PROVISION OF OFFSHOOTS OF IMPORTED DATE CULTIV ARS TO THE DATE INDUSTRY IN CENTRAL AUSTRALIA

Project Officers: G Kenna, J Mansfield, N Isgro and C Ellis

Objective: The need to encourage the development of a commercial date industry in Central Australia by the provision of offshoot material is a DPIF priority.

Method: The pastoral industry in this region has been considering options for diversification. This includes the establishment of date palms for small scale commercial production. Where adequate resources are available including supplies of water small plantings of palms are being established with assistance from DPIF.

Planting material taken as offshoots from palms imported as tissue cultured material for research purposes is also being supplied to these pastoral properties in an effort to encourage this diversification.

*****

MANAGEMENT, POST HARVEST AND MARKETING INFORMATION FOR DATES

Project Officers: G Kenna, J Mansfield, N Isgro and C Ellis

Considerable research work has been conducted on many aspects of date production in this region. This information has been collated into a report which is to be published in the near future. The report details various aspects of date palm management including irrigation scheduling, plant nutrition, weed control and yields and fruit quality characteristics of a range of varieties. Marketing information is also shared with growers as many fruit wholesalers in the larger domestic markets are eager to obtain supplies of quality dessert dates produced in this region.

*****

EXTENSION SERVICES TO DATE INDUSTRY

Project Officers: G Kenna and J Mansfield

Extension services have been provided to the date industry on a regular basis. This includes information on research results on all aspects of date production including machinery for more efficient management of plantings. Marketing information includes passing on enquires for the supply of fruit to wholesalers on domestic markets and the promotion of the Central Australian dessert date industry in various media including newspapers, magazines, radio and television.

*****

EVALUATION OF A GROWTH PROMOTING CHEMICAL AND ITS EFFECTS ON TABLE GRAPE QUALITY

Project Officers: G Kenna, J Mansfield, KYoung, N Isgro, C Ellis and S Miller

Objective: A new generation plant growth regulator is being researched in India. The substance is sold commercially as Combine® and is a naturally occurring brassinosteroid.

The chemical Gibberellic Acid (GA) has been used for many years by table grape growers to improve the berry size and quality of seedless table grapes. There are a number of problems associated with its use such as the accurate timing of spray applications and the effectiveness of the sprays in achieving the desired results. While increased berry size may be achieved, the effectiveness of spray applications for berry thinning and bunch stretching, which is necessary to offset the increase in berry size, is not always possible. The manufacturer of Combine® claims that it will increase berry size in table grapes independently of GA, yet it also has a synergistic

49

(complementary) effect when used with that product. Research work in India recommends that a small amount of GA be used in combination with Combine® for best results. The product can be used on seedless and seeded varieties.

Preliminary work to assess the potential of Combine® for the Central Australia table grape industry was carried out in 1994. The assessment was carried out at Territory Grape Farm on the varieties Flame Seedless, Menindee Seedless, Sultana and Red Globe using two methods of application - dipping and hand spraying. Results from this preliminary work indicated that the use of a Combine®/GA solution has the potential to improve table grape bunch quality in all varieties, particularly when the bunches were dipped. While individually dipping each bunch in solution is the recommended method of application, this is considered uneconomic under Australian table grape production conditions.

Further research on the chemical was considered necessary, and in the 95/96 season it was trialed again at Territory Grape Farm using two varieties, Menindee Seedless and Red Globe. The use of Combine® on the early maturing white grape Menindee Seedless was of particular interest as the use of GA on this variety can cause a severe decline in yield in the season following application of the chemical. The use of Combine® with a very small amount of GA may have the potential to increase berry size and bunch quality without compromising future yields. Results from this work indicated that there were no improvements in fruit quality when Combine®/GA was applied to the cultivar Red Globe however there were significant improvements in fruit quality when the same solution was applied to the cultivar Menindee Seedless.

In the 96/97 season another field trial was established to investigate two issues which had been identified concerning the use of this chemical in the cultivar Menindee Seedless the previous season:

1. Research in the previous season had indicated that there was a significant increase in bunch weight in those vines treated with Combine®/GA however there was no significant difference in berry weight or berry diameter. It was concluded that the treated bunches may have had more berries per bunch which contributed to the increase in weight. This needed to be confirmed.

2. If this chemical is to have a place in modern table/grape production in this region it must be able to be applied by spray application rather than by dipping individual bunches as is the method of application recommended by the manufacturer.

Materials and Method: The experiment was conducted in a commercial table grape planting of Vitis vinifera cultivar Menindee Seedless located at Territory Grape Farm, approximately 200 km north of Alice Springs. The vines are planted at 3.3 m (between rows) and 2.8 m (between vines). The vines are cane pruned on two cordon wires. All cultural practices are as for this cultivar in this region.

Each bunch on the treated vines was sprayed to runoff with a Combine ® /GA solution. Two sprays were applied as per the manufacturers recommendation for hand dipping of bunches. One spray was applied on the 8 October, 1996 and the second spray was applied on the 17 October, 1996.

All the data collection vines were harvested on the 19 November 1996. All the bunches from each vine were weighed and bunches less than 300 g were discarded. The weight of bunches over 300 g was recorded.

From each vine, two bunches were taken for destructive analysis. All the berries on a bunch were stripped off and then counted. They were then measured for berry diameter using sizing rings and from this the average berry size was calculated. All berries on the sampled bunch were then placed together in a container and weighed and average berry weight was obtained. Following this, these grapes were squashed and the Brix reading was recorded.

Resnlts and Discnssion: The treated vines had slightly heavier bunches (average of 40 g heavier per bunch) and slightly higher yields per vine. There was no significant difference, in the number of berries on bunches on treated and control vines. However, treated vines had significantly larger and heavier berries and thus heavier bunches. The treated vines had a lower Brix reading indicating that the bunches were not as mature as those on control vines though the Brix readings still met market standards.

50

It appears that the application of a Combine®/GA solution by hand spray to Menindee Seedless does appear to lead to an increase in berry size and bunch weight although maturity is delayed. However, this increase in size and weight may not be great enough to make an economic difference.

While the application of the treatment by hand spray is much more efficient than by dipping individual bunches, applications need to be even more efficient. It is proposed that if this treatment is to be applied efficiently and to be cost effective further work needs to be conducted to evaluate the effectiveness of the chemical when applied by an airblast spray applicator.

The effect the application of a Combine®/GA solution has on the ability of Menindee Seedless to produce a crop in the following season also needs to be evaluated.

*****

TABLE GRAPE CULTIVAR EVALUATION IN KATHERINE

Project Officers: M Hoult, S McAlister, G Foord, J Bright and D Jaensch

Objective: The aim of this trial is to screen various table grape cultivars to determine which ones are suitable to the tropical environment of the Katherine region and to identify suitable management strategies.

Materials and Method: Various table grape cultivars, such as Ruby Seedless, Flame Seedless, Shtur Angur, Kali Sahebi, Muscat Hamburg, Perlette, Cardinal, Ribier, Queen, Carolina Black Rose, Sultana H5, and Hussiene were planted on their own roots at KRS in July and August 1994.

Other varieties such as Centennial Seedless, Menindee Seedless, and Maroo Seedless were planted in 1995, on Schwarzman rootstock, Teleki 5A rootstock and own roots respectively.

Vines were pruned in late May 1996 with an application of Dormex® (4%) applied within 24 hours of pruning. Powdery mildew and black spot levels were monitored through the season and sprayed accordingly.

Irrigations were scheduled according to soil moisture levels monitored using tensiometers.

Vine yields at 19-19.8 °Brix were recorded for each variety in the 1996 season.

Results and Discussion: Muscat Hamburg, Queen, Ribier and Cardinal vines cropped reasonably well, with Queen producing the highest yield. Carolina Black Rose vines produced a smaller crop with a large proportion of the bunches being umnarketable due to berry drop and bunch shrivel. Similarly all bunches produced on Perlette vines were unmarketable due to their extremely small size.

Harvest of Carolina Black Rose started on 9 September, Cardinal, Queen and Muscat Hamburg on 20 October and Ribier on 3 October 1996. Management practices and disease control needs to be improved in order to achieve the higher yields required to meet the high production costs.

Vines of Ruby Seedless, Flame Seedless, Shtur Angur, Kali Sahebi, Sultana, Hussiene, Centennial Seedless, Menindee Seedless, and Maroo Seedless vines failed to produce fruit in the 1996 season. The vine vigour and yields will be monitored for these varieties during the 1997 season.

Vines have been either cane pruned or spur pruned according to their fruitfulness in June 1997. Cultivars that were fruitful at the start of the canes were spur pruned, where as those cultivars that showed fruitfulness in proximal buds were cane-pruned. Many vines were cut back in 1997 at the top of the trunk in order to regain the vine structure. This is expected to greatly reduce the yields achieved in 1997.

*****

51

PROMOTION OF TABLE GRAPE INDUSTRY

Project Officers: G Kenna and J Mansfield

Objective: The aim is to assist the table grape industry in Central Australia to realise its full potential by the production of quality fruit for domestic and export markets.

The potential for the development of a table grape industry in Central Australia was originally identified when trial plantings were established at the Arid Zone Research Institute, Alice Springs, approximately twenty five years ago.

The quality and early maturity of the fruit were identified as a major marketing advantage. In addition vine growth was excellent and there was a minimal incidence of vine pests and diseases. This resulted in the first commercial planting of table grapes in Central Australia being made by Mr Ian Dahlenburg at Ti Tree, 180 kilometres north of Alice Springs in the early 1970s. The total area planted to table grapes has now reached 172 hectares with approximately 51 hectares of this being planted in the last two years. This is expected to increase significantly with plantings planned for the next two years.

The need to work cooperatively to solve problems during the production cycle is becoming increasingly evident to all involved in this industry. In April 1997, table grape growers in the region met with staff of the Department to discuss past research and to determine future research and development priorities. It is intended that these meetings will be conducted on a regular basis.

Table grape growers in the region were visited on regular basis during the year. Fruit fly traps were checked regularly to maintain area freedom status and plant health certificates issued for interstate market access. In addition, soil sampling was conducted on all properties in the region to generate base information on the nutritional status of the soils.

Limited leaf tissue analysis was also conducted and this is expected to be increased to cover all properties in the future. Some farms have also been sampled for nematodes and in future the remaining farms will be sampled. Assistance has been provided to growers with the provision of tensiometers for more efficient irrigation scheduling and with the interpretation of the readings.

*****

ASSESSMENT OF VARIOUS PRUNING METHODS FOR RED GLOBE TABLE GRAPES IN THE KATHERINE REGION

Project Officers: M Hoult, S McAlister, M Smith, G Foord, J Bright and D Jaensch

Objective: Red Globe table grapes remain one of the most popular grape cultivars for both the domestic and Asian market. Although seeded, consumers are attracted to its very large size and good eating qualities.

This project aims to find if Red Globe grapes can be successfully produced in the Katherine region and also the optimum pruning method for this cultivar in a tropical environment. Materials and Method: Six pruning methods were applied to 6 single vine replications in a randomised complete block design. Red Globe vines were grafted to Ramsey rootstocks and planted in the field in 1992. Dormex® (4%) was applied to the vines within 24 hours of pruning to promote even budburst.

Vines were harvested early October, and yield data was collected for both marketable fruit and unmarketable fruit in 1995 and 1996.

Results and Discussion: In 1995 there was a general trend of an increase in yield with an increase in the number of buds left on the vine at pruning. For this reason the pruning treatment leaving the lowest number of buds (2 bud spurs) was removed from the treatments and replaced with a cane pruning treatment to maximise the number of buds per vine. In

52

1996, the overall yields achieved were less than the yields in 1995. This reduction in yield for Red Globe was also observed in the southern grape producing areas of Australia for the 1996/97 season. In addition, the general trend of 'an increase in yield with an increase in bud number' was not as obvious in 1996 as it was in 1995. However the cane pruning treatment still produced the highest yield for 1996. In June 1997, all the pruning treatments were converted to cane pruning and yields will be monitored in the next season.

In 1995 and 1996 a large proportion of the crop was considered to be unmarketable with berry damage caused by sunburn, very tight bunches and 'hen and chicken'. Management systems will need to be greatly improved in order to increase the amount of marketable fruit produced per vine.

*****

USING CHEMICAL TREATMENTS TO BREAK GRAPEVINE DORMANCY

Project Officers:

Background:

G Kenna, J Mansfield, KYoung, N Isgro, C Ellis, S Miller (DPIF); N Dokoozlian (University of California); D Luvisi (University of California Co-operative Extension Farm Adviser)

Although grapevines do not require long cold winters for dormancy and budburst to occur, problems can occur in years when the winter months are quite, mild. In these years, the vines tend to drop all or most of their leaves but, as temperatures increase in late winter, the budburst may be reduced, prolonged or irregular. This can result in uneven vine vigour and may delay maturity of bunches on shoots which have delayed budburst. This can present management problems such as timing the application of sprays such as giberellicacid which is essential for the production of quality fruit. Market returns may also be reduced when early maturity is a key marketing advantage.

A compound known as hydrogen cyanamide was found to break dormancy in grapevines and alleviate many of the problems associated with uneven budburst. This chemical has been manufactured and marketed as Dormex® (active ingredient = 50% hydrogen cyanamide). It has been used in grape production areas throughout the world where climatic conditions are unlikely to be conducive to a satisfactory budburst or where early maturity creates a marketing advantage.

There are however a number of disadvantages associated with the use of this chemical. The user hazard is high and requires stringent adherence to the safety precautions and directions for use. The cost of the chemical is high especially when the higher recommended application rates are required, or very large areas of vines require treatment. In addition where vineyards are located in intensive horticultural areas where other fruit crops are grown a very small amount of drift associated with the application of Dormex® can cause considerable damage to non target crops. Such is the case in California where vineyards are located close to citrus plantings and damage to this crop may result from drift after a Dormex® application to vines.

It was for these reasons that the Californian grape growers requested researchers to look for alternatives to the use of Dormex®. Trials conducted in California in 1994-1995 indicated that liquid calcium ammonium nitrate (CAN-17) was an effective dormancy breaking agent when applied in conjunction with another chemical known as Armobreak®.

Field trials were established in Central Australia in 1995 to assess dormancy breaking treatments. The trials were a co-operative effort between Dr Nick Dokoozlian (Dept of Viticulture and Enology, University of California, Davis), Mr Donald Luvisi (University of California Extension, Kern County) and DPIF staff in the Alice Springs region.

In 1996 it was decided to conduct a follow up trial to further assess the potential of some of the combinations of chemicals which did show some promise as effective dormancy agents when trials were conducted at Territory Grape Farm in the previous season.

Objective: Field trials were established to examine if the efficacy of a lower than normal rate of Dormex® mixed with several surfactants or calcium ammonium nitrate (CAN -17) and the surfactant Chemwet® were similar to the standard dormancy agent Dormex® at its recommended rate of 4% (volume/volume).

53

Materials and Method: The experiment was conducted in a commercial table grape planting of Vitis vinifera cultivar Red Globe located at Territory Grape Farm, approximately 200 km north of Alice Springs. All cultural practices are as for this cultivar in this region.

The experiment was organised in a randomised complete block design. Treatments were applied to the cordons and spurs of the vines using a hand held spray wand at the rate of 1,000 litres of solution per hectare on the 1617197. The buds on the numbered spurs were monitored twice weekly from the 2818 to assess bud emergence and shoot growth.

Treatments were as follows; 1. Control, 2. Dormex® at the rate of 4% (referred to in the text as "Dormex®"), 3. Dormex® at the rate of 2% with the surfactant Agral® at the rate of 2% (referred to in the text as "Dormex®1 Agral®"), 4. Dormex® at the rate of 2% with the surfactant Chemwet® at the rate of 2% (referred to in the text as "Dormex®IChemwet®") and 5. CAN -17 at the rate of 40% with the surfactant Chemwet® at the rate of 2% (referred to in the text as "CAN/Chemwet®").

Results and Discussion: "Dormex®" was the most effective treatment for breaking dormancy with 70% of the vines reaching budbreak 51 days after the chemical was applied. "Dormex®IChemwet®" also had a satisfactory budbreak rate with 70% of the buds breaking 56 days after treatment. Vines treated with "Dormex®/Agral®" took 72 days to reach 70% budbreak: which was considerably slower than "Dormex®IChemwet®".

While those treated with "CAN/Chemwet®" were similar in performance to the control vines. They did not reach 10% budburst until 62 days after the spray application and only 59.5% of buds had burst when the experiment was completed on the 26/9.

The control vines did not reach 10% budburst until 64 days after the treatments were applied and had only reached 60.5% when the experiment was completed.

*****

EVALUATION OF NATIVE SPECIES ENDEMIC TO CENTRAL AUSTRALIA FOR SUITABILITY AS CUT FLOWERS

Project Officers: G Kenna and J Mansfield

Objective: The aim is to discover native species of Central Australian wildflowers which may have commercial potential.

Method: This project is jointly funded by DPIF and RIRDC. The first stage of the project was the completion of a literature review of previous research which identified the potential of various Central Australian native species as cut flowers and their ease or otherwise of propagation. The second stage of the project involves field work to collect native species for assessment of vase life, further propagation work and a preliminary assessment of the potential of selected species for commercial production.

Results: Rainfall in Central Australia has been sparse in the past few years with the incidence of significant falls only occurring in some areas during summer. Rainfall at this time is not conducive to the growth of wildflowers. Rain during late winter and spring is essential to enable growth to occur and the second stage of the project to be implemented.

*****

54

EVALUATION OF NEW HYBRID SELECTIONS OF KANGAROO PAW AND GERALDTON WAX TO ASSESS THEIR SillTABILITY FOR CUT FLOWER PRODUCTION IN CENTRAL AUSTRALIA

Project Officers: G Kenna, J Mansfield and S Marte

Objective: This project has the aim of assisting the development of kangaroo paw and Geraldton wax for cut flowers in Central Australia.

Method: Plantings of a range of new hybrid selections of Geraldton Wax have been made at the Ti Tree Research Farm.

Results: Growth of most selections has been satisfactory although some plants have been badly damaged by kangaroos during the drought which has prevailed in the area in recent times. Assessment of the flowers has not been continued as growers have scaled down production due to a lack of profitability. The production of kangaroo paw for cut flowers has also been reduced due to the high costs of export to Japanese markets which has resulted in marginal returns.

*****

ASSIST THE DEVELOPMENT OF THE CENTRAL AUSTRALIAN CUT FLOWER GROWERS GROUP

Project Officers: G Kenna, J Mansfield and KYoung

Objective: This group was formed to share information on the production of cut flowers and to enable the cooperative marketing of cut flowers on domestic and export markets. The main market for cut flowers produced in Central Australia has been Japan. The quality of cut flowers produced by group members has been very high however due to the high cost of export of the product to the main market which is Japan returns to growers have been marginal. Many of the activities of the group have been curtailed however assistance continues to be provided by the provision of inspection services for the export of the product.

*****

EXTENSION SERVICES TO HORTICULTURE INDUSTRY (AUSTRALIAN NATIVES)

Project Officers: G Kenna, J Mansfield and KYoung

The provision of extension services to growers producing Australian native cut flowers has been by servicing ad hoc enquires on various aspects of management and marketing and the provision of an inspection service.

***** HELICONIA AND GINGER CULTIV AR ASSESSMENTS

Project Officers: D Nielson, W Clape, J Powell and M Hoult

Objective: The aim of the project is the assessment of introductions of heliconia and ornamental ginger for commercial planting in the Territory. Cut flower production for the Top End of the NT is estimated at $2 million annually of which heliconias and gingers dominate. As the industry develops there is increasing demand for more profitable and unique cultivars.

The unfortunate introduction of Fusarium oxysporum f cubenses Race 3 has also reduced the number of cultivars available for commercial production do to susceptibility to this pathogen. Consequently, continued species/cultivar introduction and assessment is a priority, as it was in the formative stages of the industry. Suitability for the nursery trade, as well as cut flower production, is also assessed with any new introduction.

55

Materials and Method: In most instances a minimum of one or two rhizomes per cultivar andlor species are established at BARC -ornamental block. Assessments are carried out for a minimum of two cropping years, where possible, on total yield, vase-life and overall appearance. The following cultivars were assessed for the reported period Heliconia bihai - Manoa Sunrise; Etlingera elatior "Torch ginger" - Arafura, Ironstone, Thai white, Song, Penang and Tropicus light pink; Etlingera hemispherica - seedlings; Costus barbatus - seedlings; Costus sp. ex Thailand 1; Costus sp. ex Thailand 2; Costus woodsiana ? - French Kiss; Zingiber spectabilis - Lemon, Orange, Common green, Cameroon Highlands and Syzgium; Zingiber otensii and Calathea lutea.

Resnlts and Discnssion: Manoa Sunrise is a very tall, clumping heliconia vis. 3.5 to 4 m, seasonal from October to March, with large, maroon, green or yellow lipped bracts growing well in full sun. It is showing no outward symptoms of Fusarium to date. Of the torch gingers Arafura, Thai white and Song look promising due to vase-life and lor yield. Thai white with its good vase-life (vis. 10-14 days) will hopefully provide a valuable gene pool for developing hybrids with long vase-life, a lack of which has been a hindrance to the commercial development of torch gingers in the past. Costus French Kiss; Zingiber Orange, Lemon, Common green and Zingiber otensii all showed promise and have been released to industry.

*****

THE EFFECT OF CYTOKININS ON YffiLD OF ALPINIA PURPURATA

Project Officers: J Powell, P Albano and D Nielson

Alpinia purpurata is a popular cut-flower iIi the tropics with significant production in Florida and Hawaii. Production is increasing in the tropics of Australia notably far northern Queensland and the Top End of the N T. A small number of promising hybrids with varying shades of light to dark pink colours have been developed by NTDPlF. While these cultivars have outstanding bract colours generally the yield has been lower than some of the original parents. Cytokinins have been used to increase the number of sprouting shoots from rhizomes. This study was initiated to see if production could be increased by increasing the number of shoots and consequently, the number of terminal flowers.

Materials and Method: Rhizomes of the cultivar Darwin Lady were established in the field under 50% shade. The following treatments were applied: Cytolin @ 250 ppm, 500 ppm, 1000 ppm and gibberellic acid (GA,) @ 500 ppm and 1000 ppm at intervals of one month, two months and four months, respectively, for a twelve month period. Data was collected on yield, stem length, stem calliper and flower size.

Resnlts and Discnssion: No treatment increased yield and quality over the control. All growth regulant treatments resulted in distortion of flower bracts and increased shoot height. Selection of high yielding cultivars from breeding programs would be a more sustainable approach to improving the yield and quality of Alpinia purpurata.

*****

ORCHID RESEARCH

Project Officers: D Neilson, J Powell, W Clape and M Hoult

Objective: Orchid research for the reported period was minimal with some preliminary cultivar screening of locally available Yanda cultivars for suitability to commercial production.

Materials and Method: The following cultivars were assessed (number of plants) : Makara Sayan yellow (10), Aranda Chark Kuan Pride pink (10), Vanda MervL Velthuis xV. Lilliana (4) and Makara Mak Chin On pink (5). Yield, flower quality and bud-drop data was collected.

56

Results and Discussion: The best yielding of the Vanda cultivars was Aranda Chark Kuan Pride (average of 4.1 flower spikes/plantJyear) and Mokara Mak Chin On (average of 3 flower spikes/plantJyear). Yields were half to a third of commercial levels from overseas. There is a need to source virus-free, high yielding clones of the best commercial cultivars and undertake a more thorough evaluation under Top End conditions.

*****

ORNAMENTAL PLANT INTRODUCTIONS

Project Officers: D Neilson, J Powell and M Hoult

The objective of this project is plant accession and evaluation. It is an ongoing component of the Ornamental Program. Several valuable species and/or cultivars have been released to the local industry over the last decade, as cut-flower and/or ornamental plants

Materials and Method: All over-seas accessions go through a rigorous quarantine phase. On release, most material is evaluated at the ornamental block, BARC. Any outstanding lines are then released to industry for further evaluation. In most instances stock plants are held at BARC for a minimum of three years after release to industry.

Results and Discussion: The following species/cultivars are being evaluated: Zingiber sp.?-Buddah Bud; Alpinia sp. -Pendant Pearls; Zingiber longipendula; Zingiber gracile; Zingiber graminera; Zingiber macrodenia; Alpinia sp. -white cone; Etlingera sp.-Sth. Thailand; Zingiber spectabilis-bright yellow; Lagerstroemia sp.lhybrids - Sioux; Lipan; Zuni; Biloxi; Byers Wonderful white; Miami; Hopi; Acoma; Yuma and Osage. Approximately 20 species and cultivars of Curcuma are currently being sourced along with a number of new Grevillea and Hibiscus hybrids. Some of the more ornamental Arnhemland escarpment flora is also being evaluated.

*****

SPECTABILIS AND TORCH GINGER BREEDING PROGRAM

Project Officers: D Nielsen and M Hoult

Objective: Collectively, the ginger group of plants offer great scope for the development of a large range of ornamental and cut-flower types. A previous NTDPIF hybrid program with Alpinia purpurata, generated some promising hybrids out of a very small, Fl population of only 40 odd seedlings. Within open-pollinated seedling populations of Zingiber spectabilis and Etlingera elatiora sufficient variation in a number of desirable traits exists to warrant intensive selection and the instigation of a hybridising program. Alpinia purpurata, Zingiber spectabilis and Etlingera elatiora have been identified as species worthy of development. In the future, Curcumas and other Etlingera and Zingiber species will also be incorporated, as suitable genetic material is accessed.

Materials and Method: Selected material and a number of open-pollinated seedlings were established at BARC Ornamental block. Over a number of years several suitable parents have been identified and incorporated into the program. Studies on pollen viabilities, receptivity and pollination mechanisms have also been undertaken to ensure maximum seed generation from hybridising. All new material being generated is established at CPRS Ornamental block.

Results and Discussion: A number of crosses of Zingiber spectabilis were undertake using three parents vis. yellow x yellow, yellow x green, orange x yellow and orange x green. Limited number of seed were generated from these crosses and germinated then established in the field for evaluation. Percentage germination for the respective crosses were as follows: yellow x yellow = 35 %; yellow x green = 12 %; orange x yellow = 30 % and orange x green = 26 %. Some investigation into the low % germination and possible seed treatments is warranted, so as to increase the number of hybrid seedlings being established. Around 150 hybrids from the various Zingiber spectabilis crosses have been field established.

*****

57

EVALUATION OF A RANGE OF STONE FRUIT TYPES AND VARIETIES ON PEACH-ALMOND HYBRID ROOTSTOCK IN CENTRAL AUSTRALIA

Project Officers: G Kenna, N Isgro and C Ellis

Objective: At present there are no commercial plantings of stone fruit in the Alice Springs region. Although it is unlikely that stone fruit could be produced as early as the coastal areas of Northern NSW, this would not matter as there appears to be good market potential for Central Australian stone fruit in markets such as Adelaide, and the major Northern Territory cities - Alice Springs, Katherine and Darwin. In addition there may be some export potential into South East Asia.

Research plantings to assess the potential for dessert stone fruit production in Central Australia have been established in this area in the past. Most of these initially grew well and produced heavy crops but then became unthrifty and only had a short life span. This was mainly due to the unsuitability of the rootstock available at the time for Central Australian conditions.

Supplies of a new rootstock cultivar named Titan (a peach/almond hybrid also known as Bright's Hybrid) which was introduced from the USA have become available. This rootstock is reputed to have a tolerance to high soil temperatures, high pH and nematodes, the problems identified as having caused the demise of the earlier plantings. The aim of this study is to examine this cultivar as a rootstock for a variety of other cultivars.

Materials and Method: A planting of this rootstock has been established at AZRI and some have already been budded with selections of peach and nectarine including Flordagold, Flordaglo, Desert Red, 6-3 and 84-16. These trees are growing well and the rootstock appears to be able to handle the growing conditions. In the near future more trees will be budded with selections of peach, nectarine and plum. A majority of the cultivars are low chill selections bred by Professor Wayne Sherman in the USA.

Results and Discnssion: The trees which were initially budded with the low chill selections have grown satisfactorily. Vigour is not excessive and with summer pruning good tree shape has been achieved. Nutrient status of the trees appears to be adequate at this time with no visual symptoms of deficiencies evident. The tree nutrition program at this time comprises regular applications of nitrogen through the irrigation system and foliar applications of zinc. It is intended that a selection of patented medium chill varieties be included in the planting. Attempts to source planting material of these varieties from the relevant nurseries are being made at this time.

*****

ASSIST THE DEVELOPMENT OF A COMMERCIAL FIG INDUSTRY

Project Officers: G Kenna and J Mansfield

Objective: A small commercial fig industry is established in Central Australia with a planting located in the Ti Tree area and another south of Alice Springs. Supplies of fresh fruit are sent to domestic markets including Adelaide, Melbourne and Sydney when supplies of this fruit are not available from the southern production areas.

Second grade fruit is either dried or frozen and sent for processing as jams etc in the southern states. Assistance is provided to growers by the provision of Plant Health Certificates to enable fruit access to interstate markets, the provision of information on various aspects of fig production sourced from overseas literature or the provision of ad hoc extension services to solve various problems including the monitoring and control of carpophilus beetle.

*****

58

ESTABLISHMENT OF STONE FRUIT GERMPLASM

Project Officer: M Hoult

Objective: Over the last few decades, plant breeders have made significant advance in developing cultivars of traditionally cool season crops, that are adapted to warmer climates. These efforts, particularly with stone fruit in Florida, mean that it is now feasible to grow some tree crops in regions previously considered quite unsuitable. There are stone fruit cultivars now available that require limited chilling in order to induce flowering. Whilst some may find it fanciful to contemplate stone fruit growing at Katherine, the development of new cultivars and opportunities to manipulate crop phenology make it worthy of at least a preliminary study. This study examines the possibility.

Materials and Method: Six peach cultivars (Florda prince, Newbelle, Rayon, Flordaglo, Tropic sweet, and Desert red) five nectarine cultivars (Sundowner, Sunwright, 81-6N, Sunblaze and 9-11N), and 23 plum cultivars (Gulfruby, 8-lpollinator, 87-4,87-7,86-6, 85-lpollinator, 86-2, 86-9, 86-1, Gulfgold, 86-3, 86-4, 86-7, 86-8, 86-9, 87-1, 87-2, 87-3, 87-6,87-8,87-9,87-10 and 87-11) were budded onto nine month old Okinawa seedling rootstocks in the nursery at KRS in February 1997. Seedling Okinawa trees were also planted into the field in July 1996 ready for field working.

Resnlts and Discussion All cultivars established well in the nursery, with the exception of Rayon, Tropic Sweet and 87-9 which will need to be sourced again. Okinawa stocks in the field have also grown particularly well and initiated flower buds in the 1997 dry season.

Future work will see all cultivars transferred to the field where assessments of flower initiation and possible fruiting can be made. It is anticipated that only a few years will be required in order to decide whether stone fruit are likely to be a commercial proposition in the Katherine region.

*****

RAMBUTAN PHENOLOGY AND NUTRITION - RAMBUTAN CROP NUTRIENT REQUIREMENTS

Project Officers: TK Lim, L Luders, Y Diczbalis and M Poffley

The four year study of the rambutan crop nutrient requirements and fertiliser management have been completed and is reported in DPIF Technical Bulletin No. 261.

*****

RAMBUTAN FRUIT PHENOLOGY AND HARVESTING INDEX

Project Officers: M Landrigan and TK Lim

Objective: To rationalise the harvesting index for rarnbutan and to establish fruit quality assurance standards for commercial packing, data were collected from tagged fruits harvested at various colour stages. This was carried out on the commercial cultivars Jillee, Binjai, Rongrien and R 134 at Erindale Orchard and at CPHRF.

Resnlts: The best stage of harvesting was found to be from stages 5 and 6. At stage 7 quality was reduced and the incidence of 'puffy' fruit increased. Further work is required to verify these results and consider any seasonal differences before a fruit quality packing poster can be finalised.

*****

59

ENVIRONMENTAL FACTORS INFLUENCING THE GROWTH AND YIELD OF RAMBUTAN AND CUPUACU

Project Officer: Y Diczbalis

Objective: The aim of the project was to study the influence of environmental factors on the growth and yield of rambutan and cupuacu.

Results - Rambutan: Rambutan (Nephelium Zappaceum) a relative of lychee is native to the wet tropics of SE Asia. The crop was introduced into Australia in the 1970s and has been grown commercially in the NT since the early 1980s. In the NT rambutans are distinctly seasonal with flowering occurring in June/July and harvesting occurring from November to January with the peak harvest in early December. Following harvest and a light tip pruning, there are four major vegetative flushes until the onset of cooler nights in mid May.

Detailed investigation of leaf net CO2 assimilation in response to differing irrigation regimes in potted plants and nil irrigation in mature trees showed that there is a rapid decline in leaf water potential ('Pd and CO2

assimilation (A) following the cessation of irrigation.

Root distribution sampling on mature trees showed that 80 % of the root system is in the top 15 cm of the soil surface and within the dripline of the tree. This has major implications for irrigation and perhaps fertiliser management of trees which are grown in a wet/dry tropical environment. Controlled environment temperature studies revealed that rambutan vegetative growth ceases under cool day/night conditions with nights below 22°C likely to reduce growth even when day temperatures are high. The tropical adaptation of this species has been confirmed.

The response of leaf gas exchange to vapour pressure deficit (VPD) indicates that the tree can assimilate CO2

over a wide range of humidity. This is surprising considering the tree's origin in the wet tropics. But, it does explain why the trees have grown well in the wet/dry tropics of the NT where low humidity is experienced during the dry season. Pre-flowering drought is reported to trigger flowering in the rambutan's native environment. In the NT the onset of cool nights appears to be the dominant flowering trigger. Work on the effect of pre-flowering drought suggests that it can help synchronise flowering but, does not induce flowering, to occur earlier than is possible when trees are irrigated.

This study allowed the water requirements of rambutan to be assessed at various growth stages. Water use is highest during fruit filling and lowest in the pre-flowering vegetative phase. A practical irrigation guide has been designed for growers which calculates water requirements based on tree canopy cover and evaporation replacement factors for the various growth phases. The wet/dry tropics of northern Australia are more extreme then than the plant's native environment. With the aid of careful irrigation management and limiting the range of production to areas with minimal periods of low temperature, rambutan production can occur successfully.

Results • Cupuacu: Cupuacu is a relative of cocoa and is commonly used in Brazil for the production of juice, nectar and jams from the considerable mass of pulp found around the seeds. The fruits, commonly called pods, are generally larger than those of cocoa and rounder in shape. A number of publications, from Brazil, suggest that the seeds can be used to make a chocolate like product called "cupulate".

The cupulate product is low in caffeine and theobromine, two stimulants which are found in chocolate, and hence may be useful for creating a "health food" product. Cupuacu also lends itself to mechanical harvesting as the pods drop to the ground when ripe, unlike cOCOa which needs to be harvested by hand. The combination of novel product possibility and applicability of mechanical harvesting suggests that cupuacu may have potential as a new crop for the tropical north of Australia.

Seed of cupuacu were introduced into the NT in 1991. Tree growth, phenology and yield were monitored in conjunction with environmental parameters. The aim of the study was to determine whether cupuacu would grow and yield in the wet/dry tropics of the Northern Territory. Cupuacu established and grew well under irrigation. Its performance was difficult to compare with other plantings as there is no publicly available data on growth and yield of cupuacu in its native or any other environment.

60

The dry bean yield of four year old trees was 430 kglha. This yield is low when compared to similar aged cocoa trees where the dry bean yields are reported as high as 1,400 kg/ha. The low yields are thought to be partly due to the low bean recovery rate (10 %), compared to 31.5-46 % for cocoa. The direct comparison of cupuacu and cocoa yield data may not be appropriate as observations suggest that cocoa growth rates are appreciably higher than cupuacu.

The commercial potential of cupuacu needs to be thoroughly evaluated prior to further agronomic studies being undertaken. The current planting should be used for further yield monitoring and trial fermentation of seed so that the cupulate product can be evaluated by commercial chocolate manufactures. Ideally this work should be carried out in conjunction with a commercial partner. Evaluation of the pulp as a flavouring in nectars and juices may increase the economic viability of the crop if the "cupulate" is found to be commercially acceptable.

*****

RAMBUTAN ROOTSTOCK/SCION INTERACTIONS AND CROP WATER USE

Project Officers: Y Diczbalis and TK Lim

Objective: A trial was planned in 1995 in which the main aim was to ascertain whether rambutan rootstocks affected scion growth and productivity. The secondary aim of the project was to provide a planting in which further irrigation studies could be carried out.

Materials and Method: Eight rootstocks were selected for their potential dwarfing properties. Following discussions with growers and other research staff the rootstocks selected were; Bogor, Gula Batu, Jitlee, Rapiah, Rongrien, R9, R37, RI56 (red). The two scions selected, Jitlee and R134, are well regarded commercial varieties.

A considerable delay occurred during the budding process as some of the seedling material supplied to the commercial propagator was not ideal and then seasonal changes made successful budding difficult. In late 1996 approximately half of the planned budded material was returned to the Department.

Planting occurred in February 1997 during a break in the monsoonal weather experienced at the time. Further heavy rain flooded the trial area and approximately half of the trees died due to water logging.

Results: There are insufficient surviving trees of the various rootstock/scion combinations for the trial to remain viable. A number of options are being considered for the future of the trial.

*****

DURIAN INTRODUCTION AND VARIETAL TRIAL

Project Officers: T K Lim and L Luders

Objective: One of the ways to boost durian productivity is to introduce more adaptable, high-yielding and compatible clones. There is an urgent need to bring in authentic high yielding, compatible clones and Durio species from Southeast Asia as the difficulties in obtaining germplasm are increasing. Many of the named durian clones introduced into northern Australia were erroneously identified and may not represent the authentic clones from their original sources in southeast Asia. The confusion of cultivars can have a serious impact on the durian industry, extending across the whole spectrum from research to production to marketing. Marketing the wrong clones will damage the industry and cause its premature demise. This study seeks to clarify the identification of clones and introduce further clones for use in the Territory.

Results: From the overseas trips to Sarawak and Peninsular Malaysia a total of 440 plants and seeds of 45 plant species were brought back besides durian cultivars and Durio species. On the whole the plant collection trip to Sarawak

61

was extremely fruitful. Besides achieving our objectives, the trip served as the catalyst and springboard for the establishment of collaborative research and exchange of germplasm with the Department of Agriculture, Sarawak. Another spin-off from our efforts was that we helped establish contacts between growers and the Sarawak Department of Agriculture officials and private growers in Sarawak.

We found that a much higher success level was obtained by bringing in scionwood and budding them onto rootstocks in the quarantine screen-house than by introducing bare-rooted grafted durian seedlings. Many of the cultivars already introduced into Australia have different characteristics from their namesakes in their sources of origin. The misidentification and erroneous labelling of cultivars and individual durian trees are not only rampant here in Australia but also in other countries in southeast Asia. The confusion created by the wrong identification of cultivars can have a serious impact on the durian industry.

As a prelude to correct identification, detailed information was collated on recognised cultivars from south east Asian countries gleaned from various sources and the principal investigator's personal notes and a novel method called polygonal graph analysis developed to correctly characterise and identify cultivars based on leaf parameters. Polygonal graph analysis of leaf characters can be used to differentiate among durian cultivars instead of using reproductive characters which entails a long waiting period of 10-\2 years for seedling trees and 6-8 years for grafted trees. This technique rectified II cases of misidentification and confirmed similarities in identity between samples from different localities, regions and countries. Fifty samples from 32 designated durian cultivars were reduced to 21 cultivars. Similar polygonal graph profiles can be done for fruit characteristics or a combination of leaf and fruit characteristics as identification aids that can be conveniently and accurately developed and used by growers without the employment of sophisticated expensive instrumentation. This technique offers a good alternative to differentiate among cultivars in the absence of a determinative DNA finger printing test for durian and other tropical fruits.

Additionally a mUltiple linear regression model was developed to estimate leaf area in durian based on non­destructive measurements of leaf length and mid width. The model A= -52.1 + 2.67 L + 13.3 Wm had a high coefficient of determination R2 = 0.967 and lowest error mean square. The model was found to be highly predictable, precise and rapid. Leaf area, leaf length, width and dry weight are common leaf parameters employed as indices of growth and development in crop physiological studies and in horticulture.

*****

DURIAN PRECOCITY TRIAL

Project Officers: T K Lim and L Luders

Objective: Durian has a long gestation period. For seedling trees a juvenile period of 10-\2 years is not uncommon. Whilst for vegetatively propagated trees 6-8 years period is the norm. The long gestation period is a major deterrent to potential growers because of the lengthy lag time for realisation of returns to investment and the accompanying risk factors involved in production. There are many ways to obviate the long juvenile period and enhance precocity such as by using chemical growth hormones or by cultural manipulation using various forms of grafting onto precocious or dwarfing rootstocks, interstocks and multiple rootstocks. The aim of this study is to attempt to reduce the juvenile period using various precocious rootstock-scion combinations and propagation techniques with introduced Durio species and clones.

Method: In our study we compared double rootstocks and single rootstock topworked with mature scion-wood against seedling trees for growth and precocity performance. This is part of the integral durian project which was partially funded by RIRDC entitled Boosting Durian Productivity No DNT 13 A, from July 1993 to July 1996.

Results: Results from such studies are only achievable after several years. Top-working the rootstocks during the wet in 1994 with scion-wood from bearing Gumpun and D 24 trees gave 95% success. Also we found no difference in success rate between Fokert budding and cleft grafting. Multiple rootstock can produce faster growth and advance maturity by its more extensive, and better root system which facilitates greater uptake of nutrients and water. The better and stronger root system can result in better anchorage and support making the tree less prone to wind-throw by strong winds. Also multiple rootstocks can be used as an important component in an integrated

62

disease management strategy if all or one of the rootstock is tolerant or resistant to soil borne disease such as that caused by Phytophthora palmivora, the most devastating pathogen of durian.

*****

DURIAN FLOWERING, POLLINATION AND NUTRITIONAL MANAGEMENT

Project Officers: T K Lim and L Luders

Objective: The aim of these studies is to improve our understanding of the crop phenology and reproductive biology of durian with regards to pollination so as to rationalise cultural practices such as assisted pollination and fertilisation; and improve fruit yield, size, quality and uniformity by practical cultural measures. This is a part of an integral study RIRDC Project No. DNT -13 A, entitled Boosting Durian Productivity which was partially funded by Rural Industries Research Development Corporation. The funding ended in July 1996.

Materials and Method: Crop phenology: Durian vegetative and flowering phenology were monitored on durian trees at Berrimah Farm in Darwin and two growers' orchards at Lambell's Lagoon 55 Ian away from 1992-1996. Simultaneously meteorological monitoring of temperature, rainfall, relative humidity, evaporation and sunshine hours were carried out in the nearby Coastal Plain Research Station near Lambell's Lagoon. Floral initials were monitored and their development measured at weekly intervals from the first appearance of pimple protuberance through to anthesis and through fruit development to harvest drop at Berrimah Farm.

Vegetative flushing was assessed by measurement of shoot growth extension and visually. Ten shootterminals on each oftwo trees were tagged in one property in Lambell's Lagoon and fortnightly measurements were taken on shoot growth extension from May/ April 1993- May 1994.

Pollination studies: After tltinning of flower clusters the remaining flowers were tagged and emasculated before pollination and bagged. Subsequent pollinations were emasculated without bagging which was found unnecessary. Flowers were pollinated at anthesis and after from 1630 - 2230, the late night pollinations were done with the help of growers. Pollination was effected manually using a fine-hair brush. Deposition of pollen on the stigma was checked with a hand lens. Pollen viability was also determined using Alexander's stain (Lim and Luders, 1996). Successful fruit set was recorded at 2, 4, and 6 weeks after pollination and at harvest. Fruits were evaluated for all fruit and seed characteristics including:- fruit weight, shape, colour, size; peduncle length and thickoess; spine shape and length; rind thickoess and weight; aril number; flesh colour, thickoess, weight, texture, Brix, firmness, taste, and flavour; seed shape, size, weight and number.

Crop and soil nutrient monitoring studies: Two durian orchards on yellow-brown earths (Kandosols) in Lambells Lagoon were sampled for plant analysis and soil analysis every two months for more than three years, Lemcke's orchard with seven year old trees from March 1992 to May 1996 and Siah's orchard with 5 year old trees from March 1993 to May 1996. Four trees of mixed clones were selected and tagged for nutrient sampling in each orchard. The sampling procedure was standardised by randomly taking the 5th and 6th leaf from the fully expanded tip leaf of the latest mature flush from 4 quadrats of the tree. For soil analysis four soil cores, 15-20 em deep were taken from around the tree close to the canopy drip line and bulked. More than 180 leaf and soil samples were taken and analysed for nutrient levels.

Results and Discussion: Crop phenology: Durian crop phenology in the Darwin area was found to be governed closely by changes in the local weather conditions. Generally, vegetative flushing is extensive and more pronounced in February to late April and less so in September/October which coincides with fruit development, and in December. Vegetative growth is slow during the dry, cool months from June to August. Floral initials appear as small, pimple, grape­like protuberances on the branches in May to July. It takes about 6-8 week for the floral protuberances to develop into flower buds and thence to flower anthesis. Anthesis usually occurs from late afternoon, 15:30 to early evening, 18:00 hour. At this stage the stigma is mature and receptive. The durian flower is protogynous ie. the stigma matures before the anther dehisces but the flowering phenology provides ample opportunity for autogamous and geitonomous pollination. Autogamy and geitonomy are common in monoecious and hermaphroditic fruit like the durian. The former refers to the transfer of pollens from the stamen to the stigma of

63

the same flower. The latter to the transfer of pollens from one flower to the stigma of another flower on the same tree. Anther dehiscence follows stigma maturation by a lag time of 1-3 hours but the stigma still remains receptive for 12-18 hours after anthesis coinciding with the maturation and transfer of the pollens, ie. it is also homogamous thus still facilitating self-pollination. Flowering usually occurs in consecutive overlapping cycles, giving rise to an extended flowering period for 2-3 months and it takes 110 to 130 days from anthesis to fruit ripening. Fruit set generally occurs from August through October. Fruit development stretches from September through to fruit harvest in December/January or in some years as early as late October or as late as early February depending on the extent of the cool "Dry" which affects flower opening and fruit set.

Pollination studies: In the pollination and incompatibility studies, it was found that selfing resulted in lower yields and poorer fruit qUality. The selfed fruits were ruis-shapened and distorted with a fresh weight reduction of 33-50% and a lower flesh recovery of 20% compared to >30% flesh recovery with assisted cross-pollinated fruits. Selfed fruits had heavier rind that is of uneven thickness, lower number of arils 2 (1-4 range) per fruit, lower seed number, lower total seed weight, more shrunken, dysfunctional seeds and comparatively poorer flesh quality. Selfing also resulted in more fruit drop. Assisted cross-pollination resulted in higher fruit set, producing higher yields and better quality fruit. Manually assisted cross-pollination gave significantly higher fruit set of 31 % in contrast to <10% for selfing.

The studies also revealed that there was variability in the magnitude of self-incompatibility among durian clones. Durian clones can be totally self-incompatible, or partially self-incompatible, or self-compatible as was the case observed with some seedling trees. Ovule shrinkage or abortion after fertilisation but with well-developed aril was common in both well formed and deformed fruit but with a higher incidence in deformed fruit. This indicates that both pre- and post-zygotic self-incompatibility are operative in durian. The data also indicate that the self-incompatibility (SI) system operating in durian is gametophytically controlled. The assisted pollination studies also showed that there was variability in fruit harvest maturity period ie. from anthesis to harvest drop among the female parent and pollenizer source. The maternal parent was found to influence the following fruit traits:- flesh colour, taste, flavour, basic fruit shape and spine length. The data indicate that the pollenizer source had a greater influence on the fruit traits and exerted differing influence over the maternal fruit tissues. The pollen had a metaxenia effect on fruit weight, size (length), rind weight, number of locules with fertilised ovules, number of well-formed arils per lacule, number of arils per fruit, percent flesh recovery and sweetness (Brix). The pollen also exhibited xenia effects on seed shape, total seed weight and number of seed formed.

Crop and soil nutrient monitoring studies: Nutrient concentrations for all the micro- and macro-elements changed in accordance with seasonal fluctuations in durian crop phenology which in turn appeared to be governed by the prevailing meteorological patterns as described above. This emphasised the need to consider the most appropriate time for leaf sampling to estimate the nutrient status of the durian tree. We developed a standardised sampling technique by taking the 5th and 6th leaf from the shoot tip. We suggest that leaf sampling should be done in November as the variability for the nutrients were comparatively the least. Also another advantage is that result could be obtained on the leaf nutrient status just before a large fertiliser application is carried out at the tail end of harvest in January or February.

The 3-4 year monitoring study also allowed the setting up of tentative durian leaf nutrient sufficiency range norms for Australia based on nutrient status in the leaf in November. A comparison of tentative Australian standards with published Malaysian standards revealed that our standards have narrower ranges and are higher for Ca and Mg but marginally lower for K and Zn and lower for Mn. All the leaf macroelements and the ruicroelements Zn and B declined or were lower during fruit set and development. Generally, N, P and Ca were more liruiting during fruit development after September till harvest in January. K became limiting during the latter part of fruit development through harvest and remained limiting till July. Leaf N was also lower during periods of active vegetative flushing. Soil N, P and the bases - K, Ca and Mg also exhibited similar trends -lower during fruit development in October-November and during active leaf flushing from March to May.

The traditional method of leaf nutrient interpretations using critical nutrient concentrations (critical values) or sufficiency range (as described above) do not account for the dynamic nature of foliar nutrient composition influenced by the physiological stage of crop growth, nutrient interactions and interactions between nutrients, dry matter accumulation and metabolic activities. To overcome such limitations a modified Diagnosis and Recommendation Integrated System (m-DRIS) method was used to establish m-DRIS norms for durian.

Our results showed that the m-DRIS norms were able to detect more liruiting nutrients than the sufficiency range approach. There was closer agreement with the Australian than with Malaysian sufficiency range norms. For

64

durian m-DRIS norms defined seasonally or yearly is preferable because of seasonal and yearly variations. Highest nutrient imbalance periods were observed during flowering especially in July 1993 in both orchards as indicated by the higher Nutrient Imbalance Index (NIl) values. There is a need to develop more m-DRIS norms for the other elements as well.

The study of plant, plant-soil, and soil nutrients relationships can enhance our understanding of crop nutrient requirement and nutrient application. The significant low to moderate correlation and regression relationships among leaf nutrients, soil nutrients and between leaf and soil nutrients indicate that interactions between nutrients are more complex and dynamic and involve multiple interactions rather than two factor interactions.

Also the significant but weak relationships (R= 0.2-0.4) between foliar and soil nutrients suggest that the utility of soil tests to predict leaf nutrient status in durian was rather limited.

Fertiliser scheduling should be made in accordance to the crop phenology and the crop nutrient requirement fluctuations. Diagnosis of crop nutrient demand should be assessed from leaf and soil sampling done in November using the tentative standards drawn up for northern Australia. For instance from our studies, it is evident that most fertilisers should be applied in Febrnary/March after the crop harvest and at the incipient stages of major vegetative flushing, another smaller application just before the Dry during the time in late April/May and another round in late August/September to coincide with the early stages of fruit development.

The quantity of fertilisers used should be adjusted yearly according to the results of leaf sampling as well as the crop load (yield) removed. Application of micronutrients as foliar spray should be done during flushing in March and another application in May.

*****

CARAMBOLA FRIDT DEFORMITY -NUTRITIONAL AND POLLINATION PROBLEMS­SEASONAL FLUCTUATIONS IN CROP NUTRIENT LEAF LEVELS

Project Officers: T K Lim and L Luders

Objective: Fruit deformity in carambola could be attributable to nutritional and pollination problems. For satisfactory fruit production it is necessary to plant a mixture of two different morphs in close proximity or as is practised to graft a morph onto the branch of the desired clone to act as the compatible polliniser source.

Earlier preliminary studies carried out showed that spraying with boron had no effect in increasing the percentage of well-shaped fruits nor increasing fruit yield. The crop nutrient requirement is not known and leaf level standards for carambola in Australia are not available. This trial studies the effects of nutrition and pollination on fruit deformity in carambola.

Materials and Method: Leaf and soil samples were collected from Carambola trees at CPHRF every two months from March 1992 to March 1997. Four trees were tagged for foliar and soil sampling. Leaf samples were standardised by taking the middle pair of leaflets from the median, mature leaf on terminal shoots. About 40 leaflets were collected! sampled because of the small size of the leaflets.

Results and Discussion Generally, it appears that the Nand K levels are lower from January through March and higher from May through November. This could be due to the greater competition for both elements from the higher yield realised in the Wet from November to April and the more active leaf flushing during this period.

Yields of carambola during the Dry are much lower especially from June to August and leaf flushing is also less active. Ca and Mg levels are also lower during the periods of higher yield. Among the micronutrients, Zn and Fe are lower from September to January probably resuiting from dilution effect of the active leaf flushes and growth. Levels of Bo are high through the year indicating that Bo may not be the limiting factor involved in fruit set and development. However, more detailed studies are needed to investigate the effects of Bo, Zn and Ca in fruit deformity.

*****

65

TRELLISED VERSUS SINGLE TREE CARAMBOLA

Project Officers: TK Lim and L Luders

Objective: Studies on field cultural management requirement for various trellis types and single tree carambola planting and their impact on productivity were established at CPHRF to examine the differences between the two systems.

Metbod: Trees were fertilised every two months with a basal dressing and sprayed with a complete foliar fertiliser every month. Trees were rained and pruned as necessary every 3-4 months and yield records taken throughout the year.

Results: Owing to the prolonged water-logging in the block this year which lasted for more than two months, growth and tree development was affected and one free standing tree died and will be replaced. This has impacted negatively on the productivity this year and the trees are still being revitalised for productivity observations and measurements.

*****

MANGOSTEEN PRECOCITY AND PHENOLOGY - HARVESTING STAGE FOR MANGOSTEEN

Project Officers: M Landrigan, TK Lim, L Luders and Y Dizcbalis

Objective: Although mangosteen is considered the 'queen' of tropical fruit little is known about maturity indices and postharvest quality for the fruit grown in Australia. This is an important part of the phenological studies of the fruit. Due to our ongoing collaboration with north Queensland growers we had the opportunity to examine fruit quality of a range of harvesting stages of mangosteen and come up with some suggestions for time of picking for optimal fruit quality. The fruit were supplied to us by John McCormack, an exotic fruit grower near Cairns.

Materials aud Method: John sent us a 2x2.5 kg boxes of freshly harvested mangosteens which were divided into groups based on colour. The following parameters were measured: fruit weight, diameter, segment number, total soluble solids (TSS), pH and titratable acidity (TA).

The incidence of translucent flesh (an internal disorder) in fruits was also recorded. Mineral nutrient analyses were also undertaken for the rind (skin), normal and translucent flesh and seed.

Results and Discussion: Six distinct colour groups were observed. The best stage to harvest fruit appeared to be at colour stage 3-5. At any of these stages fruit have both a high TSS and TA giving a fully flavour fruit. These were the main parameters as well as a softening of the fruit which showed differences among the colour stages as well as a reduction in sappiness with maturity. Fruit at the black colour stage were also more susceptible to bruise and insect damage.

We noticed the translucent flesh occurred only in the black colour group of fruit ie the over ripe. This flesh had lower TSS and TA and poorer texture (flesh became hard) and overall flavour.

There were also differences in some elements for the mineral analysis. Ca, Mg and Na were all slightly lower in the translucent flesh. This is interesting as it suggests some electrolyte imbalance causing cell leakage and loss of white opaqueness. Other differences were lower Fe and higher B in the translucent flesh.

Further work is thus required to look at a larger sample size and the interaction of days from fruit set with storage life on postharvest quality.

*****

66

ESTABLISHMENT OF CHENIT SEEDLINGS

Project Officers: M Smith, J Bright and S McAlister

Objective: Chenit, Melicoccus bijugatus (also known as Spanish lime, mamoncillo, and various other names) is one of the few edible Sapindaceae that will flower and fruit in the lowland tropics in addition to being tolerant of low humidity and soil moisture stress. It is also reported to be tolerant of alkaline soil conditions.

These factors make it worthy of consideration for regions such as Katherine that experience extreme climatic conditions. To date, there has been limited work with this fruit in Australia.

Efforts were made to introduce more genetic material, while at the same time assessing techniques to speed-up seed germination.

Materials and Method: Fruit in the markets and street stalls of Trinidad, West Indies, were sampled in an attempt to find superior material. Once identified, de-fleshed seeds were dispatched to KRS where they were planted on 3 January 1997. Half of the seeds (21) were de-shelled prior to planting, with the remainder planted with the shell intact.

The emergence date of each seedling was recorded. On 30 June 1997, the height of each seedling was measured.

Resnlts and Discussion: Shelling the seed clearly increased the rate of germination. Seedlings from shelled seeds were near significantly (p;0.08) larger at 4 months after planting than those seedlings from unshelled seed (190 mm and 161 mm respectively).

Given that the shell is relatively easy to remove from the seed, it is recommended that seed of this fruit be de­shelled prior to planting.

A small number of the seedlings will be distributed for planting, whilst the remainder will hopefully be retained for graft compatibility testing with other Sapindaceae crops.

*****

RAMBUTAN PRUNING TRIAL - RAMBUTAN PRUNING TRIAL SUMMARY 1995-1996.

Project Officers: Y Diczbalis and C Wicks

Objective: In 1995 the Horticulture Division was invited to collaborate in a national project on Sapindaceae tree size control. Rambutan is a member of the Sapindaceae family along with lychee and longan. The three year trial funded by RIRDC is being conducted by QDPI, CSIRO and DPIP. The project aims to gather information on canopy management in the three species, but the bulk of the project funding aimed at lychee due to the importance of the industry in Queensland. In the NT the DPIP is carrying out work on rambutan with the assistance of Erindale Tropical Produce (Kerry and Diane Dysart).

Pruning of rambutans is important to maintain tree size, particularly as growers are utilising high density plantings (200 treestha) and netting to protect fruit from winged vertebrate pests. The aim of our work is to examine the relationship between time of pruning, vegetative growth, flowering and yield.

Material and Method: In 1995 we examined the effects of three pruning treatments on two varieties (Jitlee and RI67). Tree age at the time was 6-7 years depending on site and variety. The pruning treatments were;

PO - Minimal tip pruning at harvest (December 1994) PI - Removal of two to three flushes (February 1995) P2 - Removal oftwo to three flushes (April 1995)

67

Three trees of each variety were pruned at the above times and eight terminals per tree tagged and measured once per week. The measurements made were flush status and length, leaf number, flowering and harvest date.

In 1996 we changed the treatments slightly so that the treatments included some structural pruning which was necessary due to the constraints of the fixed netting and were as follows;

PO - Minimal tip pruning at and harvest (December-January 1995196) PI - Structural pruning in February followed by a tip prune (15-20 cm) in early June P2 - Structural pruning in February

Results: 1995: Measurement of flush number and length indicated that pruning treatments did affect growth and that the response was variety dependent.

Generally the results show that for RI67 the later we pruned the more the tree flushed. In Jitlee pruning time had little effect on flush number but later pruning resulted in shorter flushes.

Flowering was also affected by pruning treatment and variety. An average of 6.5 of the 8 shoots tagged per tree flowered in the PO treatment. This dropped to an average of 2 and I flowering shoot per 8 tagged panicles for the PI and P2 treatments respectively. Therefore pruning appeared to greatly reduce the flowering potential of the tree. In the PI treatment there was a clear variety difference in response with Jitlee and RI67 producing an average of 3.5 and 1.5 flowering panicles respectively.

Late pruning in April (P3) delayed the onset of flowering and February pruning (PI) delayed flowering in the variety RI67 relative to the PO treatment. Total tree yield were not recorded as this initial trial was carried out to indicate where more concentrated research should be carried out.

1996: For the 1996 season flush numbers and lengths, flowering times and whole tree yields were recorded.

Flush number and length: The data suggested that flush number and length were unaffected by pruning treatments.

Earliness of flowering and harvest synchrony: Pruning delayed the onset of harvest but tended to concentrate or synchronise the harvest period. Pruning treatment and variety influenced the start of harvest, intensity of harvest (2/3 harvested) and the last harvest date.

The pruning treatment which resulted in the most synchronous harvest was the structural prune in February followed by a tip prune in June (PI).

Yields: Tree yield was influenced by pruning treatment and variety. The PO treatment resulted in the highest yields for both varieties with an average yield of 73 kg per tree. The P I and P2 treatments resulted in a final yield of 44 and 37 kgltree respectively. The variety RI67 was the highest yielding variety for all pruning treatments except the P2 (February) structural prune.

Yield per unit canopy area: When we expressed yield in terms of remaining canopy area the PI and P2 treatments give similar results. Indicating that the structural plus tip prune treatment was as productive per unit area as the minimal pruning treatment. Structural pruning alone (P3) decreased the yield potential.

Fruit size: Fruit size data showed that the average fruit size from the structural plus tip pruning treatment was approximately 9.0 g smaller than fruit from the other treatments. This suggests that although the P2 treatment was able to maintain its productivity per unit area of canopy it did so with increased fruit numbers at the expense of fruit size.

Pruning does appear to reduce the subsequent season's yield potential, however, it appears that well managed pruning can be used to alter the onset of fruit set and the intensity of harvest thereby spreading the work load. Since regular structural pruning will be a required practise in netted orchards, the frequency and timing of the pruning will be an important feature of management. The June tip pruning treatment appears to improve the yield potential following major structural pruning. This treatment needs to be further investigated as a means of altering the timing of harvest and the synchrony of harvest.

68

The variability of results between varieties is a concern as it suggests that pruning practices may have to be examined for the major commercial varieties. In the mean time the trial is continuing this year (1997) with the same treatments as last year to see if the effects are consistent across years.

The results of the trial were shared with the NT rambutan industry at a rambutan growers workshop held in conjunction with the NTHA on March the 24. Grower interest is strong as pruning management is seen as a relatively unknown area.

*****

AVOCADO CULTIV AR EVALUATION

Project Officers: M Smith and M Hoult

Objective: A low-land tropical environment. such as Katherine, presents considerable problems in terms of avocado production. Most importantly, many cultivars recognised by the market and consumers simply fail to flower under the warm conditions. It is only cultivars from the West Indian avocado race, or hybrids derived from them, that are considered to possess the ability to fruit under conditions at Katherine.

This work seeks to identify a cultivar suitable for small scale commercial production.

Materials and Method: Trees of the cultivars Semil 34, Hall, Choquette, Peterson, Pollock, Waldin, Tower 2, Vitoria, Booth 8, Dr Dupius 2, Kimberly and T6 were propagated at KRS onto Zutano seedling rootstocks and planted in the field in October 1995.

Results and Discussion: All trees have established well, and were around 1.5 m tall by mid 1997. Although the market opportunities for this crop are considered limited, these trees will be monitored until they commence fruiting.

*****

MANAGEMENT TECHNIQUES FOR ANNONACEAE SPECIES

Project Officers: M Hoult, M Smith and S McAlister

Objective: Custard apple types are recognised as a crop with considerable market opportunities, and for which the Katherine regio~ may prove a suitable production area. However it is also recognised that much research effort will be required if this opportunity is to be captured in the medium to long term. Cultivar introduction, screening, and possibly development, together with the development of management techniques, are seen as the four critical areas for research attention.

Materials and Method: Pinks mammoth, Gefner, African pride and Bradly trees (on atemoya seedling rootstock) were field planted at KRS in October 1995. Two seedlings of Annona reticulata, and one of A. muricata were also planted at the same time.

In July 1997, the trees were cut-back to leave branches no more than l.5m in length. The trees were defoliated by hand at the same time.

Results and Discussion: All trees have established well, and some fruit was picked from Gefner early in 1997.

The effects of pruning and defoliation on flowering and fruiting will be reported as results become available.

69

Early in 1997, the Department received a generous offer from a private plant breeder in Florida to evaluate some of the early selections from his breeding program. One introduction has already taken place, and more will occur in the next few years. Such access to superior genetic material is considered essential to the accurate assessment of commercial opportunities for the crop in northern Australia.

*****

ESTABLISHMENT OF LYCHEE

Project Officers: M Smith and M Hoult

Objective: Lychee trees have been growing in the Katherine region for many years but they seldom fruit. It is felt that this is a consequence of the high night time temperatures during the floral initiation phase. Opportunities for crop phenology manipulation, and the identification of cultivars better suited to the environment, are two areas where some research is justified.

Materials and Method: Marcotts of Tai-so and Kwai may-pink were planted at KRS in 1995.

A commercial planting of over 100 Kwai may trees were also made by a commercial farmer in March 1993.

Results and Discussion: Trees at both sites have established well and should be suitable for some phenology manipulation work in the coming season.

An inspection of a lychee collection in Florida revealed a cultivar that may be suitable for the warm conditions at Katherine. This cultivar, Amboina, is available in Australia and is currently being sourced.

*****

70

71

AGRICUL TURE DIVISION

OVERVIEW

A record wet season across the Top End was abruptly terminated in mid March with only scattered storms after that.

The continuous overcast weather, high water tables, waterlogging and rapid depletion of soil water in March/April combined to reduce improved pasture dry matter and seed yields. Despite the reduced yields, hay production in the Top End will exceed the 20,000 tonnes produced in 1996, mainly in response to the cubing plants which have been set up this year. Pasture seed production should exceed 50 tonnes this year. The majority of seed harvested was Cavalcade.

While new areas of a range of introduced cultivars have been sown, a number of producers had to carry stocks of seed over to next wet season when it became too wet and stayed too wet to sow.

Two new pasture cultivars were released by the Department through the Northern Territory Herbage Plant Liaison Committee during the year, Centrosema brasilianum cv 001100 and Digitaria swynnertonii cv Arnhem. There should be small quantities of Arnhem seed available for producers to tty next wet season.

AGROFORESTRY

AGROFORESTRY PROJECT

Project Officers: Project Location:

Objective:

D Reilly, D Zuill, C Hazel BARC,DDRF

To conduct species evaluation trials on various sites which address a number of criteria to meet industry requirements for both long and short rotation crops.

Materials and Method: Trial plantings of tropical hardwood species were initiated in August 1995 at Berrimah Farm when Agroforestty Section was being developed by DPIF. The initial planting was of 7 species replicated 5 times in rows of 10 at 3 m x 3 m spacing with 3 m buffer rows surrounding in total 656 stems; (3 m x 3 m spacing = 1100/ha). Growth rates are measured annually.

Subsequently a number of trials have been implemented to evaluate production levels on various soil types of already trialled species and further introductions under differing regimes. The success of establishment, persistence and growth rate are being monitored. The sites at both DDRF and BARC can be utilised for both research and demonstration purposes with details of results made available.

In December 1996, the BARC tree trial was expanded to include another 12 species and some of their provenances. These species were planted at varying spacings in 3 replications.

The spacings were: 2.0mx2.0m 3.0mx 1.5m 3.0m x 2.5 m 3.0mx3.0m

The list of species include Gmelina schelecteri, Eucalyptis maculata, Swietenia humilis (chol), Swietenia humilis (coma), Samanea saman, Enterolobium cyclocarpum, Acacia aulaucocarpa, 17867 & 19301, Acacia auriculiformis, 18102 & 19253, Acacia mangium, 17868 & 18994, Swietenia macrophylla, Castanospermum australe and Flindersia brayleana. All plantings received supplementary irrigation from May through to November.

72

T bl 1 a e : BARe . I I dA tnaL plante ugust 1995 (all' . Irngate d I , st measurement A 6 ugust 199 ) Species Survival % Average height (em) Blepharcarya involucrigera 46 177 Cedrela odorata 96 273.8 Eucalyptus pellita 80 233 Flindersia australia 90 202 Pleiginium timorense 100 267 Syzygium nervosum 92 149 Syzygium Jorte 100 158.6

Table 2: Timber SpecIes - DDRF tn I planted December 1995, 2n 'al I d measurement 6/5/97.

Species Treatment Survival % Average height Flindersia australis irrigated 68% 1730

dryland 1% 922.5 Eucalyptus pellita irrigated 64% 1251

drvland 43% 1067 Sysygium Jorte irrigated 73% 1022

dryland 60% 878 Pleioginium timorense irrigated 83% 1186

dryland 60% 990 Syzygium nervosum irrigated 65% 758

dryland nla nla Castanospermum australe irrigated 13.3% 602

dryland 0 0 Toana australis irrigated 43% 1904

drviand 0 0 Cedrela odorata irrigated 86% 2607

dryland 0 0

T bl 3 a e : MI' u Itpurpose trees, DDRF . I I tna. plante dD b 1996 2 d ecem er , n measurement at 6/5/97 Species Treatment Survival Average Height Maranthes corumbosum Irrigated 58 1372

Drvland 12 1040 Bauninia Irrigated 79 1280

Dryland 8 1230 Pterocarpus indicus Irrigated 54 2093

Dryland 37 1709 Khaya senegalensis Irrigated 70.6 2108

Dryland 12.3 1457 Tamarindus indica Irrigated 96 1245

Drvland 41 912 Brachychiton diversifolius Irrigated 75 1016

Dryland 70 1040 Terminalia microcarpa Irrigated 79 1679

Dryland 8 1565 Peltophorum pterocarpum Irrigated 79.3 1821

Drvland 41.6 1675 Albizia lebek Irrigated 100 2531

Drvland 91.6 1735 Cupaniopsis anacandoides Irrigated 92 1397

Dryland 29 973

*****

73

ANIMAL PRODUCTION

TENDERBUFF MARKET SUPPLY AND DEVELOPMENT

Project Period: 1993 - 1998 Project Officers: B Lemcke, E Cox, S Cross, P GrahamJL Huth

Objective: To supply and foster a quality assured TenderBuff product for local and interstate markets.

Background: The philosophy behind the Tender-Buff program is to maximise the returns per head from those buffalo males available from the limited numbers remaining in farm breeding herds. TenderBuff offers a serious substitute for the traditional feral fillet market which has fallen to very small volumes in recent years.

The DPIF in conjunction with the Buffalo Industry Council runs a quality assurance program to enable wholesalers and butchers to purchase with confidence. A grid pricing system and a carcase strip brand are important components of the program. DPIF monitors throughput and checks compliance with specifications.

Litchfield Abattoir is capable of processing 30 head per day (4 days per week) so the local and interstate markets can now be catered for regularly. The health benefits of lower fat and cholesterol than beef are positive factors in marketing TenderBuff. There appears to be good demand interstate from the restaurant trade and demand during the tourist season in Darwin is brisk. Current low beef prices are putting demand pressures on the buffalo market such that demand has dropped slightly during 1996 and 1997. Despite this, the return to producers has been maintained at $3.10 per kg dressed weight.

During 1995/96, the problem in supplying interstate was the lack of supply of sufficient suitable stock numbers, even to cover local market demand during 2 critical months. In 1996/97, supplies were able to be maintained due to the availability of good condition females from the CPRS destock, but still only sufficient to supply the local NT market.

Method: The DPIF is supplying 2 year old male buffalo bulls and heifers for this market to supplement that supplied from industry sources. DPIF is also supplying the manpower for the Quality Assurance processing which involves monitoring abattoir kills and assessment (after overnight chilling) prior to delivery to wholesalers. A strip brand is applied to complying carcasses.

Current specifications: 150-220 kg Hot Standard Carcase Wt. 3-12 mm fat on rump P8 site. No permanent teeth erupted. Electrically stimulated carcase. Ultimate muscle pH (24 hrs) of less than 5.8.

The producer pays the kill fee of $55.00 per head and receives $3.10 per kg HSCW provided all specifications are met. The wholesaler also pays the BIC a IOc/kg carcase levy to help with supply and marketing promotion. Discounts apply for every specification not met and are compounded if multiple specifications are not complied with.

Results: Due to the beef price slump which is continuing, the demand for TenderBuff has decreased as the TenderBuff price has not been lowered.

Tourist numbers in Darwin during 1997 did not create the expected dry season demand. Consequently the quantity of TenderBuff has decreased but the quality parameters have iroproved with the latest average price per head increasing to over $600. Substitution with cattle bull meat is a major problem in southern markets.

No feedlots were run during 1996/97 as there were sufficient animals available from pasture. The major breakthrough on the TenderBuff scene is however the processing of the first batch of Riverine crossbred male

74

progeny which outclassed the straight swamp types in all facets of production. This is not apparent from the following table because cross bred numbers were too small to influence the picture except in eye muscle measurement, in which parameter the crossbred is markedly superior.

Carcase Parameters of Slaughter Buffalo January-June 1996 June-December 1996

Total Number 107 70 Mean HSCW 177 kg 198 kg Mean Eye Muscle 50cm2 52cm2

Area Mean pH 5.60 5.71 Mean Carcase 99.6cm 101.8 cm Length Mean Gross $ 550.50 577.61 Mean Grid $/kg 3.14 2.97 Meanp8 fat 3.0mm 5.1mm Dressing % 47.0%

Parameters in which crossbred buffalo were superior to Swamp buffalo were: Growth rates - up to 40% improvement. Eye muscle area - increased by 24% Time to turn off reduced from 30 months to 18 months. Improved dressing % - 2% increase Improved carcase yield - 2% increase Improved tenderness due to lower age at slaughter

January-June 1997 47 197.5 kg 55 cm2

5.66 101.3 cm

603.31 3.06 5.9 mm 47.8%

The feedback from the wholesalers and retailers was extremely positive and the industry is very keen to adopt this new technology as soon as possible.

This will be achieved with the distribution of high grade Riverine buffalo bulls from crossbreeding and purebred programs over the next 2-5 years.

*****

BUFFALO BREEDING PROGRAM AT COASTAL PLAINS RESEARCH STATION

Project Period: Project Officers: Project Location:

Objectives:

1986-1997 B Lemcke, E Cox, S Cross, CPRS Staff CPRS

Select for increased productivity of the Australian Swamp Buffalo. To determine the merits of Crossbreeding Riverine with Swamp for meat production in the Top End. To produce superior offspring for use by Industry for grading up the quality of commercial herds. To demonstrate the economic and productive value of a buffalo herd run on improved pastures with good management.

Background: The CPRS Buffalo Breeding Herd originated from feral stock in 1970 and was run as a comparison unit with Brahman cross cattle. Heifers were drawn from many different locations. Further introductions from feral herds occurred during 1981 - 1983 to build herd size, along with gradual improvements in the quality and quantity of improved pastures on the station.

In 1986, as a result of the measured superiority of buffalo over cattle, an increased research effort was put into buffalo to determine whether further advances could be achieved through a selection program. The herd target was 300 breeders, with the objective being to provide selected bulls and heifers to industry over the long term.

Two Riverine type buffalo bulls were imported from the US in 1994 and a third younger bull (plus 2 private heifers) by the BIC in 1995. The two larger bulls were used to mate with two groups of cows (in the CPRS herd)

75

during the 1995 and 1996 wet seasons in order to compare the growth of crossbred calves with that of contemporary pure swamp calves to 2 years of age (i.e. TenderBuff).

Ten single sire mating groups were formed during February 1996 and the bulls introduced to the groups on 23rd February. No fertility or semen tests were performed on the mating bulls. Bulls were left with the same groups from 23/2 to 221711996. In the meantime an outbreak of tuberculosis in the cull cow group from 1995 killed in March 1996 revealed large numbers of the original BBHl group were TB infected. Some other members of the group in Victoria also turned out to be positive for TB. Spread had also occurred to 1994 and 1995 progeny. It was hoped that no contact with BBH groups 1-7 would yield no disease and the 1996 progeny would have been able to be saved. BBH 1-7 plus all the bulls were meat worked in November 1996 and yielded 1 cow with a single infected lesion, which necessitated a total destock.

Results for 1996-1997

During the 1996 mating period, 10 single sire mated groups gave the following pregnancy results on meaiworks post mortems of breeders.

1995 Bull NO's Total Breeder Deaths Pregl Preg Non Non %Prcg Group Cows and Wet {Dry Preg PregDry

Mated TB Reactors Wet Deaths Reactors

BBH1 Hillary 31 3 0 0 0 19 9 0* BBH2 Bill 32 1 4 1 3 18 5 13* BBH3 4757 31 2 3 4 6 6 0 69 BBH4 4776 32 3 2 7 4 8 8 38 BBH5 4803 31 0 1 15 8 3 4 74 BBH6 4730 31 3 2 15 7 1 3 79 BBH7 4744 31 2 3 15 5 4 2 69 BBH8 4753 31 0 2 11 6 10 2 55 BBH9 O.J 43 0 3 2 41 5* BBHlO 4745 32 0 5 25 7 78

TOTAL 326 14 25 88 64 71 81 48 **

* Riverine bulls in for period of 23/2-4/4/96 only for BBH1, 2, 9. ** 66% after 3 Riverine bull groups ignored.

Recorded Deaths: (July 1996 - June 1997)

Total Deaths Causes Bulls 0 Breeders 6 Water deprivation (damaged fence) Yearlings 3 1 trauma, 1 unknown, 1 genetic defect 2 year olds 3 1 trampled, 2 unknown Weaners 6 late calverslearly weaning

Discussion: The Breeding Herd work over 10 years has all been in vain because of the TB outbreak. All the breeder herd was slaughtered at the abattoir, with a single lesion in a non spreading site being the only problem in saving all the 1996 progeny.

These are now to go to TenderBuff. Approximately \4 of these are Riverine crossbreds. Their numbers will help provide further information on the superiority of the crossbred progeny.

Pregnancy results were skewed this year due to the removal of Riverine Bulls early (at 6 weeks) from 3 groups at the TB outbreak time. Of the groups where bulls stayed in for 5 months, 66% of breeders became pregnant. This was disappointing due to the two month longer mating season, however, this year, there was no group changeover of the bull mid-mating which has helped to raise percentages in recent years.

76

There may be a possibility of saving gains made by selection through the RIRDC supported AIlET studies being done in conjunction with Victorian Department of AgricuiturelMonash University, by saving sperm and eggs at the abattoir from the 1996 progeny as they go through the TenderBuff program.

*****

PASTURES

EVALUATION OF YIELD AND NITRATE RESPONSE OF BUFFEL GRASS (Cenchrus ciliarls) WHEN SIX COMPANION PASTURE LEGUME SPECIES ARE INTRODUCED TO THE PASTURE

Project Period: Project Officer: Location:

Objective:

1996 to 2000 K Thiagalingam, P Shotton, R Parker Douglas Daly Research Farm

To monitor the value of different companion legume species to the buffel grass in terms of nitrogen availability, buffel grass quality and total biomass yield.

Background: Buffel grass is a commonly used improved pasture species in the Top End south of Tipperary. As established buffel grass pastures tend to grow in "clumps" another favourable companion species would be beneficial to help utilise the area between the buffel plants and ideally provide nitrogen to the grass plants and produce higher quality and higher yielding pastures.

Materials and Methods: The six pasture legume species were: Cavalcade Centro (Centroserna pascuorum) Amiga Stylo (Stylosanthes hamata) Wynn Cassia (Chamaechrista rotundifolia) Maldonado (Macroptiliurn gracile) Oolloo (Centroserna brasilianurn) Milgarra (Clitoria ternatea)

These legumes were planted into an established buffel grass pasture together with a control plot (Buffel grass only) and an applied nitrogen plot using 30 units applied as urea. All plots supplied with 111 kg.lha triple super + T. E. and 100 kg. Iha muriate of potash. The eight treatments were replicated three times. Leaf tips were harvested from each plot in February and again in May and samples were analysed for N, P, K. Soil samples also taken and analysed for pH, K, Ca, Mg, P, S, TKN, OC, Zn, Cu. Future measurements will include yield estimates using cut quadrats.

Progress Report: All legumes established and grew well with the Buffel grass throughout the 1996/97 Wet season. Plant and soil analysis will be compared when completed.

*****

EVALUATION OF NEW PASTURES UNDER GRAZING FOR THE DOUGLAS DALY AREA

Project Period: Project Officers: Project Location:

Objective:

Continuing D Zuill, B Lemcke, D Reilly, and DDRF staff. DDRF

To evaluate pasture species under continuous grazing at DDRF to determine their persistence, productivity and contribution to cattle performance.

Background: Promising pasture introductions are evaluated under grazing at DDRF to determine their potential in the Douglas Daly environment.

77

Method: The pastures are grazed in 4 ha paddocks by Brahman weaner steers at 1 headlha year round. Steers are allotted to paddocks in June (post weaning) and replaced the following June.

Paddocks have been fertilised with 100 kg of superphosphate plus tracelha in December along with various weed control measures during the wet season, depending on the condition of the pasture.

Animals are supplemented with ad-lib Uramol® blocks during the dry season and Phosrite® during the wet season and consumption measured.

Cattle were weighed monthly with blood and faecal samples taken for nutritive values and parasite burden.

Results: Pasture composition and dry matter content were estimated at the beginning of the dry season 28/5/97 using Botanal®. The animals commenced grazing 12/6/97.

A breakdown of pasture composition is summarised below.

Pasture Composition Pdk Pasture Type % Grass % Legume % Est. Yield No. Weed kglha 43 Silk sorghumlMaldonado 71.6 12.2 16.2 5560 44 Leucaena/Pangola 96.1 1.1 * 2.8 4680 45 Pangola 91.3 4.9 3.8 2240 46 Sabi 96.8 2.9 0.3 2880 47 Jarra 95.6 1.1 3.3 4793 49 BuffellBlue Pea 95.1 4.9 0.0 7926 51 Wynn/Stylo 50.1 37.2 12.7 3933 52 Digitaria swynnertonii 54.3 31.7 14.0 5870 531 Centrosema brasilianum 532 Leucaena \4 rowslbuffel & Sabi 95.2 1.6* 3.2 4275 533 Buffel/Sabi 95.3 2.6 2.2 3625 534 Wynn CassialBuffellSabi 54.4 41 4.5 6937

Leucaena Y2 rows 84.5 5.4* 10 4760

* Legume content does not include leucaena component.

Cattle Cumulative Weight Gains (kglhead) PdkNo. 18/9/96 13112/96 14/3/97 16/6/97

Dry Season Wet Season End of Wet End of Grazing 43 32 80.3 148 197.5 44 14.5 60.5 142.3 197.3 45 -7.8 16.5 89.8 120.3 46 10.5 61.3 130.8 169.3 47 19 76 142.5 190 49 25 62.4 137.4 190.3 51 32 61.3 136.8 176.0 52 29.8 70.5 141 198.5 531 20.8 55.5 130.5 167 532 22 57.1 139.5 193 533 12.8 57.5 136.3 171.3 534 32 80.5 149 213.8

78

Pasture Establishment Of the 12 paddocks shown above, 2 have been grazed for the first time since establishment in the 95196 wet season.

Pdk 51 - 3 lines of Chamaechrista rotundifolia including cpr 86172, 86178 and the cultivar Wynn.

Pdk 52 - Digitaria swynnertonii (Arnhem) and Centroserna brasilianum (Oolloo).

*****

COMPARISON OF PASTURE SPECIES FOR MIMOSA AREA REHABILITATION ON THE MARY RIVER FLOODPLAIN

Project Period: Project Officers: Project Location:

Objective:

Oct 94 - Oct 96 B Beumer, G Schultz, B Lemcke, F O'Gara, A Cameron Sampan Creek - Melaleuca Station

To assess various native and improved pasture species for fe-vegetation of mimosa infestation areas after chemical treatment.

Background: Once chemical treatment of mimosa has been carried out, a competitive pasture is required to help control further germination and regrowth from previously fallen mimosa seed. The more successful an establisInnent achieved by a competitive grass, the lower will be the cost of follow-up chemical treatment and the greater the animal productivity of the land post mimosa.

Method: Single row plots 50 metres long x 1 metre wide were established on the western side of Sampan Creek approximately 4-5 kms north of Shady Camp barrage.

The following species were used:

1. Wild Rice (seed) 2. Olive hymenachne (seed) 3. Vigna trilobata (seed) 4. Pelleted Olive Hymenachne (seed) 5. Para grass (seed) 6. Kazungula setaria (seed) 7. Pelleted para grass (seed) 8. Native hymenachne (seed) 9. Aleman grass (runners) 10. Leersia hexandra (runners) 11. Para grass (runners)

The western half of all the rows was fertilised with superphosphate. Planting was carried out on 12/12/94 and the plot was flooded by up to 1.5 metres of water for a significant period of the wet season.

Results: The plot was assessed on 22/5195. Most seedlings seemed to have established post flooding. The most productive plots were the Olive hymenachne, para grass and Kazungula setaria.

The only species which failed in the first year were Wild Rice (0 plants) and Vigna trilobata (1 plant only). All others had some established plants and will need to be observed over the next 2 wet seasons to see whether they survive and multiply.

During the 1995196 wet season, the most productive grasses were para grass, aleman grass and kazungula. Para grass and aleman grass showed good vegetative spread, while Kazungula and para grass had some new plants established from seed. Olive hymenachne had good survival and some spread by seed, but is not suited on these

79

shallow flood plains. Leersia hexandra was surviving, but perfonning only fairly. Native hymenachne had only 1 plant surviving. Some wild rice plants established during the wet season, but grew only fairly. The Vigna trilobata died out.

The plots were assessed on 25/6/97. The most productive grasses following the big wet this year were Aleman grass, para grass and olive. The Aleman grass and para grass had excellent spread and survival. Both were still green and suitable for grazing. The olive hays off too quickly at the start of the dry season at this site. The Kazungula has lost some of the large original plants. They died this wet season. There was some new growth in some of the tussocks and some seedlings present. Kazungula definitely suffered this wet season. The Leersia hexandra was still present but perfonning poorly. The wild rice and native hymenachne have disappeared.

*****

COMPARISON OF LEGUME INTRODUCTIONS UNDER GRAZING AT COASTAL PLAINS RESEARCH STATION

Project Period: December 1991 - July 1997 Project Officers: B Lemcke, E Cox, S Cross, B Beumer, E Pickering, A Cameron,

FO'Gara Project Location: CPRS

Objectives: To assess the performance of promising new legume introductions in continuously grazed pastures in the Top End coastal region. To compare the performance of these new introductions with currently recommended adapted pasture cultivars.

Background: A number of pasture legumes have performed well in observation and cutting trials. These legumes need to be evaluated under grazing to determine their value for animal production before they can be released as new pasture cultivars.

Nine pasture legumes were evaluated under grazing and compared with the commercial cultivars Glenn, Wynn, Bundey, Cavalcade and Maldonado. It was expected that up to 5 of the legumes would be released as new pasture cultivars.

Method: Four hectare paddocks of 13 legumes were sown at CPRS with Kazungula setaria as a companion grass in December 1991. The legumes sown are listed below.

Aeschynomene americana cv Glenn A .. histrix 93636 A.. paniculata 93635 Chamaechrista rotundifolia cv Wynn, 85836,86172,86178 Centrosema brasilianum

Early maturity mix (40067/92409) Mid maturity mix (55696/55698) Late maturity mix (58587/87987/94315)

c.. pascuorum mix cv B undey/Cavalcade c.. pubescens 58575 Macroptilium gracile cv Maldonado

Paddock 13 Paddock 12 Paddock 11 Paddocks 2,3,4,1

Paddock 7 Paddock 5 Paddock 6 Paddock 9 Paddock 8 Paddock 10

In 1992 the establishment of the Kazungula was good. The establishment of the legumes was fair to good, except for C. pubescens which was poor and Maldonado which was excellent. Establishment was good considering the low and patchy rainfall experienced during the wet season.

Re-establishment in the next wet season of Glenn was poor. There was little legume present in January 1993. The paddock was slashed and oversown with more Glenn seed.

80

These paddocks except Glenn have been grazed from February 1992 at a stocking rate of 1 beast/l.3 ha. (3 head per 4 ha paddock) by Brahman cross and Droughtmaster yearling steers ex VRRS. These stock were replaced by a new batch of yearlings on 30 June 1994 and again in June 1995. The last batch was introduced on the 26th August 1996. The C. pubescens paddock (8) was resown to Lee Joint Vetch and the Bundey/Cavalcade to Cavalcade in January 1994, however, the establishment was light.

Results: 1996-97 was the final year of trial grazing for these paddocks due to the closure of CPRS. The paddocks were not sampled for dry matter because it was too wet during the record wet season experienced this year. There was little sown legume in any of the paddocks in April, apart from the four Chamaechrista rotundifolia paddocks where the legume yield was fair to good. Grass yield was good in all of the paddocks.

Liveweight Gains of cattle Paddock No Dry season Wet Season Post-Wet L WG Total P8 Fat

LW Gains kg LW Gains kg 23/4-1Sn LWG per Depth 2S18-23110/96 23/10-23/4/97 head kg ISnl97

96/97 (nun) C. rot 86178 I + 2.0 +145 +19 +166 9.3 C. rotWynn 2 - 2.8 +147 +12 +156 6.8 C. rot 85836 3 - 0.3 +159 +21 +179 8.0 C. rot 86172 4 + 0.8 +159 +21 +181 7.3 Centrosema brasilianum 5 - 6.5 +147 +20 +161 8.0 (M) 6 - 1.8 +148 +29 +176 8.5 Centrosema brasilianum 8} - 4.5 +151 + 6 +156 6.3 (L) 9} - 1.0 +145 + 16 +150 6.0 Lee Joint vetch 10 Cavalcade } + 0.3 +157 + 16 +173 9.3 Maldonado 11 - 6.8 +138 + 18 +155 8.5 A. paniculata 12 A. histrix -10.4 +122 +24 +147 5.6 Centrosema brasilianum 7} (E) 13 Glenn 1 Mean -3.5 +146.4 +18.4 I +164.8 7.5

In 1996-97, two paddocks (7 & 10) were used as resting areas for other paddocks where the grazing pressure appeared to be excessive.

Continuously grazed paddocks for the 'full year were 1, 2, 3, 4, 5, 6, 11, 12. Paddocks 7, 8, 9, 10, and 13 were grazed variously throughout the year by 3 groups. Two groups on paddocks 8, 9 and 10 and one group of 5 head used paddocks 7 and 13.

All continuously grazed paddocks were stocked with 4 head of Brahman and Brahman cross weaners (mixed 5 & 6 year brands) (1 head/ba). Paddocks 8, 9 and 10 were stocked with 8 head (0.75 head/ba) and paddocks 7 and 13 with 5 head (0.63 head/ba).

The Kazungula setaria was still reasonably well represented in all the paddocks after 6 years of grazing.

No maintenance phosphorus fertilisers were applied this year due to CPRS funding cuts and closure plans. Maintenance weed control was also not practiced as in previous years, plus the record wet season produced siguificant waterlogging for a period of three months.

Liveweight gains in stock were lower (by 11 kg) this year probably due to the absence of maintenance fertiliser, and the poorer dry season performance this year.

Fat levels were slightly lower, probably due to the slightly lower liveweights. There were no great changes in performance between the species compared with previous years.

Those varieties which performed well were Chamaechrista rotundifolia 86172 and 85386, A. panicu/ata and the late maturity mix of Centrosema brasilianum.

The chamaechrista paddocks were the only ones which showed an increase in the legume content of the swards over a period of time. Most other legumes remained at low levels in the paslrues over the long term, particularly the

81

more palatable types. It can be seen that there is little difference in wet season performance of the mixtures, more appears to depend upon dry season performance that the species can offer which determines the better performances.

The legume cultivar OoUoo was released this year, based partly on its performance in this trial as a component of the C. brasilianum mid maturity mix ..

Three other lines are currently on pre-release with the Queensland Herbage Plant Liaison Committee CA. histrix 93636, C. rotundifolia 85836,86172).

*****

EVALUATING OF NEW PASTURE INTRODUCTIONS AT OPIUM CREEK AND MIDDLE CREEK STATION

Project Period: Project Officers: Project Location:

Objective:

December 1988 - December 1996 A Cameron, B Beumer, F O'Gara Opium Creek StationlMiddle Creek Station

To monitor the adaptation of new pasture introductions to the coastal upland environment and to a non-cropping yellow earth site in the Douglas Daly area.

Background: A range of pasture introductions which have the potential to provide new pasture cultivars for the Top End of the Northern Territory are being grown in observation plots to determine their suitability for and adaptation to the coastal upland environment and further inland.

The coastal properties have good dry season pastures where aninta1s graze the flood plains as they dry out. The upland native pastures are poor for dry season grazing and the use of improved pastures will allow producers to carry more stock during the wet season to help match dry season carrying capacity.

In the Douglas Daly many of the better cropping soils may be unusable for grazing in the wet season due to crop or forage production.

Method: Fifteen pasture introductions were sown at two sites on Opium Creek Station in December 1988. The sites sown were on upland yellow earth and a flood plain fringe site.

Twenty-one introductions were sown on another upland yellow earth site in January 1992 adjacent to a fertiliser trial site. Ten of these introductions are repeats of the previous sowing.

Two introductions which did not establish in 1992 and one other introduction were sown during the 1992193 wet season. One further introduction was planted during 1993/94 wet season.

Nineteen pasture introductions were sown on the Middle Creek site in 1991/92 wet season and later sown in 1993/94. Basal fertiliser was replied this year.

Results: Opium Creek Plots Those plots of the 1988 serving still showing some survival in 1997 are: 1. Aeschynomene paniculata 93635 2. A.americana 105906, Glenn 3. A.brasiliana 93592 4. A.histrix 93636 5. Centrosema brasilianum 55696 55698, 87987 6. Andropogon gayanus 43156

82

Texfern Plots Some plots are still perlorming well. 1. Aeschynomene paniculata 93635 2. Aeschynomene histrix 93636 3. Chamaecrista rotundifolia 86172, Wynn 4. Amiga Caribbean s!ylo 5. Centrosema brasilianum 55698 6. Digitaria milanjiana 40700 (Strickland) 7. Hyparrhenia TUfa 58656 8. Stylosanthes sp. aff scOOra 110361 9. Maldonado 10. Digitaria swynnertonii 59749 (Arnbem)

*****

EVALUATION OF THE RESIDUAL VALUE FOR PASTURE LEGUMES OF A NEW PHOSPHORUS AND SULPHUR FERTILISER

Project Period: Project Officers: Project Location:

Objective:

December 1991 - August 1998 A Caroeron, B Beumer, F O'Oara, S Cross Opium Creek Stationfrexfern Station

To evaluate a newly released fertiliser SR 13 which has 50% of its phosphorus and SUlphur as slow release components which are resistant to leaching losses.

Backgronnd: SR 13 is a new phosphorus and sulphur fertiliser developed specifically for top dressing pastures in the high rainfall districts of Victoria and South Australia where soils are acid and sandy. On these soils, fertilisers are quickly leached from the top soil.

SR 13 contains 50% of its phosphorus as slow-release reactive rock phosphate and 50% of its sulphur as elemental sulphur. These slow release components resist leaching and provide a constant supply of nutrients during the growing season.

The analysis of this product is 9.3% P and 13.3% S, which is similar to the analysis of superphosphate at 9% P and 10% S. This fertiliser has the potential to reduce the costs of fertiliser applications to pastures by reducing the aroount of fertiliser applied or the frequency of application.

Method: The trial consists of four replications in a randomised block design at two sites, one being on a Yellow earth soil at Texfern (Middle Creek Station, Douglas Daly), the other site is a Yellow earth soil on the coastal upland area at Opium Creek Station.

The test plant is verano (Stylosanthes hamata). Plots are 4m x 2m with 2m laneways between plots.

The fertiliser treatments are superphosphate and SR 13 each applied as listed below.

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

100kglha 100kglha 200kglha 200kglha 200kglha 200kglha 400kglha 400kglha 400kglha Control

applied annually applied biennially applied annually applied biennially applied triennially applied year 1 only applied biennially applied triennially applied year 1 only

83

Gypsum (18% S) is applied with the superphosphate treatments to equalise the rate of sulphur application to that of the SR 13 fertiliser.

There are a total of76 plots at each site.

Basal fertiliser of zinc chloride (46% Zn) will be applied at 10 kglha in the first, third and fifth years of the trial.

Verano was sown at a rate of 10 kg pods/ha on 16112/91 at Texfern and 811192 at Opium Creek and 24 March 1994 (Texfern).

Results: The Texfern Station site could not be harvested this year, and has been abandoned. The site was too wet initially.

When the site could be accessed, the plants in many of the plots had dropped a variable proportion of their leaf. This meant that yields and nutrient contents of samples would not be comparable, so the site was not harvested. This is the last year of this trial. The Opium Creek trial was tenninated in 1995-96.

*****

PRELIMINARY DEMONSTRATION OF SELECTED PASTURE SPECmS UNDER DRY SEASON IRRIGATION

Project Period: Project Officers: Project Location:

Objective:

1994/95 - October 1996. F O'Gara, B Beumer, C Ham, A Cameron. DDRF

To determine whether it is agronomically and economically feasible to produce high quality fodder from a selection of tropical pastures under irrigation in the dry season. To determine the relative quantity and quality of fodder produced from each species under irrigation.

Background: There is increasing interest in dry season irrigation of pastures for both fodder conservation and grazing. Producers on both large and small holdings are becoming increasingly aware of maximising production throughout the year especiaIly where the potential for irrigation exists.

There is some knowledge on the performance of temperate legumes like lucernes but very little exists on the performance of tropicaIly adapted species under dry season irrigation. The quality of fodder produced can be equal to that of temperate legumes but little knowledge is available on dry matter production. If producers can sow a wet season pasture and then carry it through all or part of the dry season then production from that unit of land is maximised.

Many producers already have irrigation in place and are looking for options on what can be used to produce dry season fodder. At the present time there is little information available to present feasible options.

Method: Pasture species were sown on 18 January 1995 into well prepared plots. Seed and fertiliser was hand broadcast and lightly harrowed.

A basal application ofNPK comprising 50,18 and 36 units respectively was applied.

Establishment conditions were ideal with intennittent rain falling throughout January. All pastures established well, except for the three lucernes cultivars which failed completely.

First harvest was taken on 4 April 1995.

Biomass measurements were taken from all plots on the 1st harvest, but only plots with sufficient dry matter were subsequently harvested. Nutrient content and digestibility will be determined from all samples. Most of the species which were sown in January 1995 were carried through the first dry season and following wet season.

84

Vigna trilabata was the only species which was omitted as it proved unsuitable for this system of production and soil type.

All plots which produced sufficient dry-matter through the dry season were harvested on an eight (8) weekly cycle. All plots received maintenance fertiliser plus trace elements (TE) after each harvest. Grasses received NPK + S + TE and legumes received PKS and TE.

Highwotth lab lab, Arafura cowpea and Leichhardt soybean were included in this season's observations to compare yields and quality as interest has been shown in these crops for fodder or green manure uses.

Results: 1994/95 Forage sorghum (c.v. Sugar graze) was the highest yielding species at 15.5 t1ha followed by Signal (7.53 t1ha), Guinea grass (6.33 t1ha), and Jarra (5.80 t1ha) after the first post wet season harvest. Cavalcade and Bundey were the highest yielding legumes with 4.8 and 4.3 t1ha respectively.

After the first harvest (4/4/95), most of the legumes did not to respond to irrigation and produced little dry matter. Blue Pea (elitaria ternatea) and Maldonado (Macraptilium gracile) responded and produced 3.6 and 2.6 t1ha respectively at the second harvest. 30/5195.

Blue Pea was the only legume species to produce significant amounts of dry matter through the first dry season with yields of 3.0 to 3.5 t1ha.

Results: 1995/96 Grasses All grasses performed sufficiently well through the dry season to produce some harvestable yield. Dry season yields were on average 25% lower than wet season yields across species. Forage sorghum was the highest yielding grass forage followed by Guinea, gamba, signal, Jarra and pangola.

Individual dry season harvests were significantly lower than wet season harvests, but, by irrigating through the dry season and harvesting on an 8 weekly cycle, up to 194% more dry matter was produced.

Forage sorghum, Guinea, Jarra and pangola produced 92%, 103%, 194% and 89% more dry matter respectively under a dry season irrigated system compared to a single wet season production.

Cool temperatures, irrigation scheduling and nutrition have a significant impact on dry matter production during the dry season

There are a number of grass species which appear suited to a dry season irrigated system at Douglas Daly including forage sorghum, Guinea, Jarra, pangola, signal and gamba.

Legumes Lablab and soybean were slow to establish and exhibited symptoms of severe nutrient deficiency in the initial stages. Lablab grew out of the symptoms and produced a moderate yield of 3.3 t1ha. The soybean failed to produce any significant yield and remained severely stunted. Cowpea produced vigorous growth throughout the season and produced a dry matter yield of 4.8 t1ha. After harvest, lablab failed to re-grow, however, cowpea displayed vigorous re-growth.

Blue pea was the only legume to produce harvestable yields throughout the dry season, with an average of 3.46 t1ha. Despite Blue pea looking excellent, much leaf-drop occurs lower in the canopy reducing overall yield and quality.

Wet season yields of Cavalcade and Bundey have been low compared to reported commercial yields. Cavalcade and Bundey have averaged 5.25 and 5.01 respectively over 2 wet season harvests. An early wet season harvest followed by an end of season harvest produced 78% and 62% more biomass respectively in Bundey and Cavalcade over a single end of season harvest. Other species did not perform well under this regime achieving higher production with a single harvest.

85

From observations in this trial, it seems evident that none of these legumes are suited to a fully irrigated dry season production. Blue pea responds well after cutting but yields are relatively low. Other legumes appear less tolerant to frequent cutting.

Cavalcade and Bundey appear to be the most suitable species for wet season and possibly early dry season production. Two harvests, one in the early wet, followed by an end of season harvest may prove to be a method of optimising production from these two legumes. Weed control is a significant issue in these legume plots and will prove a major hurdle in commercial legume fodder production systems.

Results: 1996/97 The grasses continued to yield well during the third wet season. These results have not been collated yet, and will be reported later. All of the legume plots were badly invaded by weeds, and were sprayed out during the wet season.

*****

AN INVESTIGATION lNTO THE ESTABLISHMENT OF IMPROVED PASTURES ON THE FLOOD PLAlNS OF THE NORTHERN TERRiTORY

Project Period: Project Officers: Project Location:

Objective:

Continuing F O'Gara, B Sawyer, B Lemcke, K Levey and CPRS staff Coastal Plains Research Station

Develop effective and reliable techniques for establishing commercial areas of flood plain pastures and assess the suitability of these techniques for various species.

Background: Flood plain pastures have potential to dramatically increase livestock production on many pastoral properties. The gains made through grazing flood plains in the dry season are very significant. The effective management of flood plains through the dry season with improved pastures will enable many properties in the NT to fatten stock all year round.

The benefits for NT producers and the live shipping trade should be significant. Despite many properties having some areas of improVed flood plain pastures there is little data available on the most efficient and reliable methods for establishment. Many of the previously used methods are slow and labour intensive. Many methods are hit and miss or high risk. There needs to be some preliminary investigation to assess more efficient methods of establishing pastures on a commercial scale.

Method: 1995/96 Wet Season A number of establishment techniques were evaluated in the 1995196 season at Coastal Plains Research Station in a newly constructed pond in Lagoon Paddock, as a follow on from the 1994/95 evaluations.

The evaluations included: a) Crocodile planter following knockdown herbicide b) Crocodile planter and ploughing c) Bulk para grass runner planting with three point linkage multiple disc planter following knockdown

herbicide d) Runner establishment and basal fertiliser application e) Grass species - 15 including 6 native species t) Time of planting of para grass and aleman grass runners. g) Bulk harvesting and planting of para grass runners h) Para grass seed sown with disc drill i) Legume species - 5 j) Bulk harvesting and planting of aleman grass runners k) Jarra finger grass sown by disc drill following spraying 1) Bundey centro sown by disc drill following spraying

86

Ponding The new pond has held water through until late August at least. The 1995/96 sowings and plantings will not be fully evaluated until towards the end ofthis dry season.

Seed establishment A crocodile planter is essentially a heavy duty drum seeder fitted with angled plates or shovels which scollop or pit the ground as it moves forward. Seed falls into these pits and is covered by subsequent rainfall. In the 1995/96 season the crocodile was evaluated for its potential in sowing exotic pasture species on Coastal Plains Research Station.

The crocodile planter performed satisfactorily on the Coastal heavy clay soils when the surface was dry or slightly moist. Moderately deep pits were formed (15 cm) with seed falling on the wall of the pits. Exposed seed was covered after rainfall. On wet soil the crocodile planter completely blocked with mud preventing the shovels from performing their task and preventing seed exiting the drum.

Little establishment was evident as a result of seeding with this planter as water levels rose too quickly to permit accurate assessment.

Crocodile and other "pitter" type planters have limited application on the flood plain as they tend to block up once the soil surface becomes moist. One possible application is early season sowing of pasture species to allow establishment prior to intense storms and before water levels rise.

On an area of the pond which did not flood as early as the area where the crocodile planter was used, there was good establishment of para grass from seed sown with a disc drill following early ploughing and pre-sowing spray to control weeds.

Runner Establishment Para grass (Brachiaria mutica) runners were planted with a home made multiple disc planter to evaluate the role of herbicides and basal fertiliser in establishing floodplain grasses.

It was found that glyphosate at 2.0-2.5 l/ha was a useful tool in suppressing vegetation and allowing runners to be planted and establish without prior cultivation. This permits planting to be carried out over a wider range of soil moistures and reduces the need for heavy cultivating machinery.

Basal NPK andN alone improved visual appearance and early growth of para grass runners over the control in the 1995/96 season. Despite a visual response it is uncertain as to the economic benefit of applied fertiliser to floodplain pastures at establishment. This question requires much more work before it can be answered with any accuracy.

Except for the earliest planting of aleman and para grass runners into dry soil, the runner plantings were all successful.

1996/97 The pond was fully flooded in late December and stayed that way for the remainder of the wet season. At one stage, the floodwaters from the Adelaide River were over the top of the bank.

The grasses planted in the lagoon have flourished and shown excellent spread during the wet season.

Areas of weeds (Senna, blady grass etc) were drowned during the wet season.

Preliminary Conclusions Broad scale establishment of exotic pasture on seasonally flooded coastal areas presents many logistic problems.

Without control of water, establishment of pasture by seed is risky, but can be successful provided the area does not flood soon after sowing.

87

Runner planting is still the most reliable method despite its labour intensive nature. With the use of knockdown herbicides. disc planters and mechanised runner harvesting techniques the efficiency of planting runners and the areas planted in one wet season can be increased.

*****

EVALUATION OF NEW PASTURE LINES

Project Period: Ongoing. Project Officers: Project Location:

A Cameron, B Beumer, F O'Gara Paddock 9, Berrimah Farm

Objective: To evaluate new lines in a confined non-grazed environment and to bulk-up seed from promising lines for further evaluation.

Method: During the 1994/95 wet season, a number of new lines were germinated in the shade house and transplanted to the paddock to assess their performance. The species include Vigna trilobata, Paspalum alratum, P. regnelli, P. guenoarum, Aeschynomene falcata, A. histrix, and some Arachis species. Observations and measurements will be taken during the season to determine survival, persistence, dry matter production and qUality.

Results: Paspalum spp continued to grow well. Aeschynomene histri}: also performed well and seed was collected from CPI 63599 An established plot of Arachis glabrala CPI 29986 and four new lines of Arachis glabrala CPI 12121,93483,22762 and 93469 were monitored throughout the wet season.

Staff shortages this year have reduced the amount of time available for seed harvesting.

*****

CROPS

SEED TESTING

Project Officer: Project Location:

A Simonato BARC

During the year 167 lots or consignments were submitted to the Seed Testing Laboratory for examination. This was a drop from the previous year which can be attributed to less producers farming in the NT and less seed harvested in 1996.

The laboratory is no longer an accredited laboratory with the International Seed Testing Association as the accreditation was allowed to lapse.

The following tests were carried out on the submitted lots:

Certification Purity Germination Bulk Search Seed Mass Moisture Content Identification Quarantine Inspection & Identification

Total

No. oftests

1 37 144 42 5 2 5 363

699

*****

88

GRAIN SORGHUM VARIETIES FOR THE DOUGLAS· DALY DISTRICT

Project Period: Project Officers: Project Location:

Objective:

1992 to ongoing. T Price, P Sholton, R Parker Douglas Daly Research Farm

To grow and trial new and commercially available grain sorghum varieties at the Douglas Daly Research Farm using zero till practices and evaluating which varieties are suitable for the Douglas / Daly district.

Backgronnd: Over the past five years replicated sorghum variety trials have been undertaken at the Douglas Daly Research Farm. The Sorghum seed is donated by four major seed companies who supply new and commercially available seed for the project. Varieties which have shown good characteristics in previous years are also re-examined. Trial results will provide information for Top End Sorghum producers on commercially available sorghum seed varieties suitable for local conditions, and results for the seed companies benefit as well.

Progress Report: The 1996/97 season had 17 sorghum varieties sown at the Douglas Daly Research Farm. Data recorded were hand harvest yield, plant populations, days to flowering, days to maturity, rating of leaf disease, resistance to lodging, head exertion, head type and height.

The varieties yielded between 2.3 tlha and 5.0 tJha. The varieties grown in 1996/97 season were:

Variety Yield (kglba) Success 42 3942 Rocket 3254 Titan 25 2576 Bronco 4010 BoomerMR 3210 8527 3080 S81 3649 New Tullock MR 3219 SX554 3448 Graze N Sile XS658 4072 Pac 2359 4994 Success 40W 4533 Warrier MR Buster 3210 GH2096 4057 MR42 2388 FeedN Grain 3296

*****

EVALUATE THE EFFECTS OF NO·TILLAGE AND CONVENTIONAL TILLAGE ON THE YIELD OF CAVALCADE HAY AND ITS LONG TERM EFFECTS ON SOIL PROPERTIES

Project period: Project Officers: Project Location:

Background:

1984 - ongoing K Thiagalingarn, P Sholton, R Parker Douglas Daly Research Farm

The project was started in the 1984-85 wet season with a maize/soybean rotation and tillage treatment with the original objectives completed in 1988. Long term soil changes were evaluated in 1992 and all the bays were cultivated in 1993. In the 1994-95 season a mungbeanlsorghum rotation under the two tillage systems were

89

grown. In the 1996-97 wet season Centrosema pascuorum cv Cavalcade was planted and harvested as a hay crop.

Materials and Method:

Total trial area Tillage plot size Fertiliserfor 1996/97 season Weed control

2Ha 0.33 Ha none Spinnaker Sertin Glyphosate

Cut, raked and baled each tillage treatment and weighed the total hay produced from each treatment.

Progress Report: Hay production yield results for 1996/97 season as follows: Area of each Tillage treatment 0.3 ha.

Bay Tillage Hay weight

1 Conventional 250 kg 2 No Till 1073 kg 3 No Till 1050 kg 4 Conventional 476 kg 5 No Till 1050 kg 6 Conventional 584 kg

Soil samples were taken from each bay at 0 to 5, 5 to 15 and 15 to 30 em deep and analysed for pH, K, Ca, Mg, P, S, TKN, OC, Zn, Cu. Plant samples were also taken from each bay and analysed for N, P, K, Ca, Mg, S, Zn, Cu.

*****

EVALUATION OF HAY PRODUCTION ON BLAIN SOILS AND THE EFFECTS OF SOIL NUTRITION OVER TIME

Project Period: Project Officer: Project Location:

Objective:

1996 to 2000 K Thiagalingam, P Shotton, R Parker Douglas Daly Research Farm - Paddock lOA

To monitor the changes of soil and fodder quality with the yearly removal of plant material.

Background: In recent years there has been an increasing demand for quality hay production to provide fodder, particularly for the live export cattle trade. The removal of vast quantities of fodder from paddocks throughout the Top End will have an effect on soil fertility and quality particularly on areas constantly cut for fodder production.

Materials and Method: Trial area 10.3 ha, divided into 3 phases, each 3.4 ha.

Year 1

Year 2

Year 3

all phases planted to cavalcade and cut for hay.

phases 2 and 3 cut as cavalcade hay . Phase 1 plant to sorghum, harvest as grain and the sorghum stubble also cut and removed. phases 1 and 3 cut as cavalcade hay. Phase 2 grown under sorghum and harvest as grain and the sorghum stubble also cut and removed.

Soil and plant samples to be taken to monitor soil and plant nutrient analysis.

90

Weeds will be controlled as required with selective herbicides.

Progress Report: The 10 haarea was planted to cavalcade in December 1996 and supplied with 170 kglha ofN, P, K, S with trace elements (0-11-20-6, 0.5 Cu, 0.5 Zn and 0.0015 Mo). In June, the area was cut and baled for hay production and 58.5 tonnes of Cavalcade hay was removed from the area. Soil samples were taken in November 1996 and again after hay production in June 1997.

*****

INTERACTION BETWEEN WEED AND CROP YIELD AND HERBICIDES FOR WEED CONTROL IN CAVALCADE

Project Period: Project Officers: Project Location:

Objective:

1996-1998 R Eastick, N Hartley, M Kahl, C Martin KRS

To investigate the interaction between weed and cavalcade yield. To determine the effect of various herbicide treatments on cavalcade as a sown pasture legume.

Background: Previous projects under this program examined the interaction between weed growth and sorghum yield. It was concluded that the effect of weed biomass on crop biomass was negatively linear. Herbicides including atrazine, dicamba, propachlor, metalochlor and fluroxypur had been examined. These were assessed for weed control in sorghum, where regenerating cavalcade was considered as a weed. The trial this season (1996-97) examined cavalcade as a crop. This is due to decreased emphasis on grain cropping, and increased interest in pasture legumes for both grazing and hay production. Weed control is a major concern, so a number of herbicides were assessed. Spinnaker® is the current recommended herbicide (but not registered as yet). Basagran® has also been used on cavalcade but appears to have a limited weed control spectrum. Broadstrike® appeared promising in last season's screening work. Flame® has been documented to be promising in pasture legumes, so will also

be included. There is also the need to quantify the effect of weed infestation on yield loss in a pasture situation. This has not yet been done in the NT.

Materials and Method: Experimental Design Randomised complete block with 11 treatments replicated 4 times. Cavalcade Treatments: Crop only

Weed only Unweeded (Crop & Weed) Weeded for 14 days after sowing Weeded for 28 days after sowing

Herbicide Treatments: Spinnaker® Spinnaker® Basagran@ Flame® Fusilade® & Sertin®

Land preparation. sowing and herbicide agplication

pre-emergent (300 mllha) post-emergent (300 mVha) post-emergent (2 Llha) pre-emergent (50 glha) post-emergent (IL and lLlha)

2 sites were originally prepared, but establishment was poor at DDRF so that site was abandoned. The KRS site was mulched. Approx 2 weeks later, regrowth was sprayed with Round-up® (4 Llha), sown with the trashculti drill, and the pre-emergent herbicides applied. Post-emergent herbicides were applied @ 2 weeks after sowing. Herbicides were applied with an Agmurr® hand held sprayer.

Measurements Biomass harvests were taken 1 month and 3 months after sowing. Weights for cavalcade, broadleaf weed, and grass weed were recorded. Visual ratings were also done.

91

Data Analysis and Progress: Data was analysed using ANOV A on Statistix ®. Spinnaker ®, both pre- and post-emergent, gave the highest cavalcade yields at 3 months for the herbicide treatments. Flame ® significantly reduced cavalcade yield at the first month harvest, but the yield had compensated to a large extent by the 3 month harvest. Broadstrike ® and Basagran ® did not result in a significant increase in cavalcade yield compared to the Crop and Weed treatment. Spinnaker ® and Flame ® gave the best overall weed control (Pigweeds and Summer grasses).

Results from this trial will be used to aid in a submission for registration of Spinnaker® in the NT. Flame ® and Spinnaker ® will be assessed in a trial plot on a producer's property next season to gain further information concerning the weed control spectrum.

*****

SCREENING OF HERBICIDES FOR USE ON PASTURE LEGUMES

Project Period: Project Officers: Project Location:

Objective:

Ongoing R Eastick, N Hartley, C Martin, M Kahl BARC

To screen herbicides (Milgarra Blue Pea).

for suitability of use on Centroserna pascuorum (Cavalcade) and Clitoria ternatea

Background: This herbicide screening project initially assessed pre- and post-emergence herbicides on Bundey, Verano, Wynn cassia and Maldonado at Berrimah Farm in 1992. Mungbean and sesame were subsequently included.

Increased demand for high quality legume hay has increased demand for herbicides to control weeds in legume based crops. The 1996/97 season saw this project designed as a pot trial, assessing pre-emergent and post-emergent herbicides on Cavalcade and Blue Pea. Spinnaker® (imazethypyr) had already shown potential in off-label field application, so was included to gain additional information to support application for use of this herbicide in the NT. Other herbicides included were those used on temperate pasture legumes, to assess their potential for use on tropical legumes.

Materials and Method: Experimental Design: This was a randomised complete block pot trial. Treatments were: Plant Treatments: 2 pasture legumes, Centroserna pascuorurn (cavalcade) and Clitoria ternatea (Blue pea),

were subject to all herbicide treatments.

Herbicide Treatments:

2 weeds Pennisetum pedicellatum and Senna obtusifolia were assessed for response to Spinnaker® and Flame® treatments only (pre and post emergent).

Common or Trade Name AC299,263 Basagran® Brodal® Flame® Igran Flowable® Jaguar® Spinnaker® Stomp® Tigrex®

Active Ingredient

imazamox bentazone diflufenican imazameth terbutryn bromoxynil and diflufenican imazethapyr pendimethalin MCPA and diflufenican

When Applied

pre and post post pre and post pre and post post post pre and post pre pre

Each herbicide treatment was put on at 2 rates - low (the recommended rate), and high (twice the recommended rate).

92

Pot Preparation. Planting and Herbicide Application 8 inch pots were filled with commercially available potting mix. 35 seeds of either cavalcade or blue pea were planted in each pot. Germination tests had previously been conducted - cavalcade was 55%, blue pea was 80%.

Pre-emergent herbicides were applied immediately after the seeds were planted. Irrigation was applied regularly by overhead sprinklers.

Measurements Seedling emergent counts were done on all pots I week after sowing. The post-emergent treattnent pots were thinned to 5 plants/pot. Pre-emergent treattnents were harvested for biomass at 3 weeks after planting. The post­emergent herbicides were applied at 3 weeks after planting using the Ag-murf® hand spray unit. Plants were at the 3-5 leaf stage. The final harvest of all post-emergent treattnents plus the senna and P. pedicellatum was done at 36 days after sowing.

Data Analysis and Progress: Data is currently being analysed by ANOV A using Statistica®. Visual observations indicate that Spinnaker®, Flarne®, and AC299,263 gave the best cavalcade and blue pea biomass, and that Flarne® post-emergent had the best effect on both grass and broadleaf weed.

*****

WEED MANAGEMENT STRATEGY DEMONSTRATION SITE

Project Period: Project Officers: Project Location:

Objective:

1996-1999 R Eastick, N Hartley, M Kahl, C Martin Bay 11, Tippera Block, DDRF

To demonstrate a 'best bet' weed management strategy for a weed infested legume based pasture.

Backgronnd: Weed invasion in legume based pastures is a major problem leading to reduced productivity. Bay 11 at DDRF had been a cavalcade pasture for a number of years, but was predominantly weeds by 1996. The site was chosen to represent a weedy legume pasture, with the main weeds being hyptis, senna, Pennisetum pedicellatum and Sida spp. There needs to be more emphasis toward strategic weed management rather than reactive weed control, and this project aims to demonstrate a weed management plan involving a 5 year crop/pasture rotation sequence.

Materials and Method: Experimental Design An unreplicated demonstration site.

Treatments: 1996/97 The area was slashed early in the season due to the height of the weeds. The regrowth was sprayed with knockdown herbicide, and forage sorghum (Jumbo) was sown immediately no-till. Atrazine was applied both pre- and post-emergent. No nitrogen fertiliser was applied due to adequate contribution from the previous cavalcade crop. The area was mown and baled for hay.

199711998 The area will be sown to a grass pasture (Sabi) to allow for further control of broadleaf weeds before cavalcade can be resown in the future.

Measurements: The area had 3 fixed transects, which will be used for the duration of the project. Species presence was assessed using Botanal® at strategic times, including before spraying with herbicide, after spraying, and after baling. This will enable assessment of the change in desirable to undesirable species over the duration of the project. Video recordings were also taken.

93

Progress: The first year was successful in reducing weeds, and high forage sorghum yields were attained. The change in species composition is still being analysed. It is intended that cattle will graze the stubble over the dry season.

***** THE USE OF EARLY LEAF GROWTH TO ASSESS THE NEED FOR WEED CONTROL.

Project Period: 1993-1997 Project Officers: Project Location:

C Martin, N Hartley, R Eastick KRS

Objective: To determine if early leaf area can be measured accurately and rapidly photographically. To determine if crop yield losses are related to differences in early growth between crop and weed leaf area.

Background: This was the final season of this project. Signal grass was sown at various densities into a no-till sesame crop last season to imitate the weed component. This resulted in variable establishment and no significant weed treatment differences, so this season, mungbeans were sown to represent the weed component.

Materials and Methods: Experimental Design A randomised complete block with 4 treatments replicated 4 times.

Treatments: Crop only Crop and Weed Low Crop and Weed Medium Crop and Weed High

(Mungbeans at 9.5 kg/ha @100,000 seeds/hal (Mungbeans at 19 kg/ha @ 200,000 seeds/hal

(Mungbeans at 38 kg/ha @ 400,000 seeds/hal

Land Preparation. sowing and herbicide application The area was mulched. The regrowth was sprayed (4L/ha Roundup® ) and sesame sown no-till (3.4 kglha var. Edith) with the trash-culti drill. Mungbean was broadcast over the surface with a hand-held spreader. The area was irrigated.

Photography and Harvesting The plots were photographed and the sesame and weed biomass harvested at 9, 11, 13, 17, 19 and 21 DAS. Leaf areas were estimated for a harvest @6 weeks after sowing. The final harvest was taken 3 months after sowing.

Progress: All biomass weights have been recorded, but assessment of the relative growth rates of crop and weed has not yet been done. This was an externally funded (RIRDC) project, and the final report has been submitted and accepted.

*****

PHYTOTOXICITY AND MOVEMENT OF ATRAZINE UNDER CONVENTIONAL AND NO-TILL SORGHUM

Project Period: 1995-1997 Project Officers: R Eastick, N Hartley, G Patch Project Location: DDRF, Paddock 19 of the Ley Systems Trial

Objective: To determine differences in Dual® (metalochlor) and atrazine activity and movement in the soil between no-till and conventional till sorghum.

Background: This trial intended to provide additional infonnation on last season's trial which aimed to determine toxic levels of atrazine on sorghum in Blain soils, and how this differed between conventional till and no-till sorghum. It had

94

been suggested that treating sorghum seed with the seed safener Concep® may prevent phytotoxic effects from atrazine (as it does for Dual® ). This was assessed. The efficacy of atrazine on Pennisetum pedicel/atum has appeared variable over previous seasons. The difference in control of this weed between Dual® and atrazine

was also assessed.

Soil samples were taken to assess movement of atrazine laterally on the soil surface and down the soil profile.

Materials and Method: Experimental Design A split plot design with 3 replicates 2 main treatments: no-till and conventional till sorghum 7 sub-treatments: Control (no herbicide)

Atrazine (3Llha and 6Llha at 500g/kg aj.) Atrazine plus Concep@® (3Llha and 6Llha) Dual® (2L1ha) plus Concep® Dual® (2Llha) plus atrazine (3Llha) plus Concep®

Measurements and Sampling Sorghum biomass was taken @ 35 DAS. Visual ratings for weed damage were taken. Soil samples were taken only for the 3Llha and 6Llha atrazine treatments and the control. These were sampled in the planter row and the interrow at 0-5 em and 5-10 em at 2 times after application.

Progress: There appeared to be no significant differences in sorghum biomass between the treatments, but initial sorghum establishment was variable. Weed control was best in the Duallarazine/Concep treatment for both tillage treatments, although the conventional till was the better. Soil samples are still being analysed.

*****

COTTON INDUSTRY DEVELOPMENT

Project period: Project Officers: Project Location:

Project Objectives:

1994 to 1997 C Martin, M Kahl, and N Hartley KRS,DDRF

To identify, in terms of yield, quality and maturity, the most appropriate cotton plant types or varieties for dry season production. To develop a sustainable, agronomic package for dry season production based on Ingard varieties to control Lepidopteran pests. To develop suitable irrigation systems and scheduling for light and heavy soils. To ensure that the acquired knowledge of varieties, physiology, agronomy, and pest management will hasten cotton industry development through its integration into a technological package for irrigated, dry season cotton production. To identify suitable soils and regions for cotton production and motivate politicians to hasten land release for

agricultural development.

The specific aims of the 1996/97 experimental work were to: i) sow a large area (1 hal of Ingard cotton (L 23i) to observe its effectiveness in reducing the

number of sprays required for Helicoverpa control. ii) measure N uptake and yield of cotton under different N fertilisation regimens. iii) test some promising varieties identified from previous seasons.

Background: DPIF is collaborating with Western Australian Department of Agriculture and CSIRO in a project to investigate the possibility of, and establish guidelines for, the development of a cotton industry in northern Australia. The proposed industry will be based on irrigated cotton grown in the dry season to minimise the insect problems that caused the failure of a cotton industry at Kununurra in the 1970s. A possible drawback to cotton grown in the dry season is a reduction in quality since this is markedly reduced by low temperatures. Preliminary experiments

95

at Kununurra and Katherine indicate that high yields of good quality cotton, with reduced insect pressure, can be grown in the dry. This work has elicited favourable reports from industry leaders (scientists, farmers and manufacturers) from NSW and Qld. A major problem in the NT is the availability of suitable land. Most cotton in Australia is grown with flood irrigation on heavy soils. The distribution of these soils needs to be mapped in conjunction with irrigation possibilities, and winter temperatures.

Materials and Method: The total area comprised 1.2 ha of cotton at KRS under drip irrigation with T-tape. The bulk cotton was sown on 27 March 1997 with L23i, and the N and varietal trials were sown on 26 March 1997.

N trial. This comprised continuous strips (90 m) of 5 N regimens replicated 4 times. The treatments were a factorial combination of 2 times of application (all the N applied 130, or 100 days after sowing), and 2 N rates (125 and 250 kglha), plus a zero N rate to give a total of 5 treatments.

Variety experiment. Fourteen varieties, replicated 4 times, were used: CS50, CS50i, Siokra L23, Siokra L23i, 90209-158, 88208-214,90003-118, Siokra 1-4, DP5690, CS34, CS189, VI6 91203-163, Nucot 37, CS189.

Irrigation scheduling. All cotton was irrigated twice a week (Monday and Thurs.day using crop factors of: 0.4 to squaring, 0.7 to first flower, 1.1 to 10% open bolls, and 0.7 to harvest.

Measurements: Agronomic data recorded in 1997 for cotton at KRS. Table I

Measurement Trial (N or variety) Crop establishment all Main stem node both number (NN) Plant height (H) both Date & position of both first square Date & position of both first flower Fruit counts both Nodes above last both white flower (NA WF) Date of first open boll both Boll period; both.

Rate of boll opening both

Seed cotton yield both Lint quality both Plant maps both

Plant analysis N trial

Progress Report:

Method Date at 80% final emergence. Weekly, 5 plants/plot.

Weekly, 5 plants/plot. Date when 50% of 10 plants/plot have I square. Position; Node number with just unfolded leaf. - date and node number when I flower/m.

Count at same time as NN & H; use 1.1 m row length. From first flower, record weekly average of 5 plants.

-I boWm. Tag: open, + & - 1 day flowers, 30/plot at: early (node 9), mid (node 12), & late (4 NAWF) flowering. Note date & position. For each replicate, pool lint collected at a date. Compare the number tagged with the number harvested. Record % open bolls at 2 to 3 day intervals until harvest. From 7.5 m' Subsample I kg from each plot. Harvest 10 plants/plot & record: boll position, internode lenliths on main stem & branches. N + other elements, fortnightly

Results for yield and quality from the 1995/96 season are shown in Table 2. The water applied was scheduled according to open pan evaporation data (780 mm), 25% less than this (580 mm), and 25% more (970 mm). It is apparent that yield and quality of cotton was optimum when irrigation was scheduled according to open pan evaporation values. These results represent a significant advance in our knowledge since irrigation is expensive, and there is no data on how much water to apply to cotton at Katherine to achieve high yield and qUality.

96

The 1996/97 cotton is growing well with very few sprays, showing the effectiveness ofIngard cotton in reducing the number of sprays required for Helicoverpa control. Relevant scientific data such as fertiliser requirements will be meagre since the 1 ha of cotton was designed to demonstrate to industry and other interested parties that relatively large areas of cotton could be grown successfully at Katherine.

T bl 2 C a e . Id d r otton Yle an I qua ltv as aff db f r d ecte by vo ume 0 applIe water at K h . at erme Res earch station in 1996. Water applied (mm) 780 580 970

Yield (bales/ha) 13.1 A 11.2 B 12.6 A Fibre length (inches) 1.1 A 1.08 A 1.08 A Fibre strength (g/tex) 27.4 A 27.3 A 26.7 A Values in a row followed bv the same letter are not significantlv different @ P<0.05

*****

LEY FARMING SYSTEMS PROJECT

Project Period: Continuing Project Officers: Project Location:

B Lemcke, R Eastick, D Reilly, P. Shotton, DDRF Farm Staff DDRF

Objective: To evaluate the sustainable production of an agricultural system which integrates a pasture phase grown in rotation with a cereal crop phase and incorporates cattle production.

Background: The Ley Systems Trial was initiated in the 1994-95 Wet Season, with the establishment of Phase 1 (paddocks 1-6) as either a cavalcade only pasture or a mixed pasture of sabi and cavalcade. This phase was sown no-till to sorghum this season (1996-97) after two years of pasture. This was the completion of the first full 3 year rotation. Phase 2 (paddocks 7-12) was sown in 1995-96 to the pasture treatments and was left as a second year pasture this season. Phase 3 (paddocks 13-19) was sown to sorghum in 1995-96 and then to the pasture treatments this season. All phases of the trial are now established, and the crop/pasture rotation and cattle grazing treatments can now be fully implemented.

Cattle production was recorded for the 1996 Dry Season at 3 stocking rates - 1,2 or 3 head per hectare, on either Cavalcade only pasture, Cavalcade / sabi mixed pasture or sorghum stubble. The rotation is based on a pasture phase for two years, followed by the cereal crop phase for one year. There is one paddock under continuous sorghum for comparison. The paddocks were stocked in August with weaners averaging @150 kg/hd. Ideally cattIe should be introduced as weaners coming off their mothers around June.

The dynamics of the pasture populations - the change in the proportions of grass, legume and weeds is assessed at the beginning and the end of the wet season each year, using Botanal®. Vegetation monitoring is necessary to examine the effect cattle grazing and crop rotation has on plant population dynamics of the paddocks. Grazing manipulation is a vital tool in management of the amount of biomass necessary for desirable mulch levels for the no-till cropping phase.

Method: Phase 1. The paddocks were fertilised with @230 kg/ha of 0-11-20-6. Glyphosate was applied as a knockdown herbicide and sorghum (Feed 'N' Grain® at 7.3 kglha) was sown no-till with the Buffalo planter. Dual® and atrazine were applied post-planting pre-emergence. Nitrogen treatments (0, 30, 60 and 120 units of N) were randomly applied within each paddock. Paddock 19: This paddock was resown no-till to sorghum as the continuous crop treatment. An area of conventional till sorghum was also sown.

97

Measurements: Sorghum leaves (second youngest true leaf) were sampled for nitrogen and phosphorus analysis. Sorghum was both mechanically harvested and hand-harvested for determination of grain yield under different pasture, and nitrogen, treatroents. Soil samples were taken in May at 3 depths (0-5 cm, 5-15 cm, and 15-30 cm) for soil nutrient analysis. Sampling for estimation of biomass and Botanal® was conducted in November and May.

Phase 2. All paddocks were fertilised with @200 kglha of 0-11-20-6. All paddocks had a high incidence of broadleaf weeds, particularly hyptis. To reduce weed numbers, the mixed paddocks were sprayed with 2,4-D. The Cavalcade only paddocks were slashed, the regrowth sprayed with glyphosate and resown no-till (Cavalcade at 7.8 kglha). Spinnaker® was then applied post-planting pre-emergence (400 ml/ha). chlorpyrifos (IL/ha) was also applied due to high hopper numbers. Sertin® and Basagran® were subsequently applied post-emergence. All paddocks were crash-grazed at some stage in an effort to reduce the amount of vegetative matter, particularly Ptmnisetum pedicellatum. Grazing only had a minimal effect in the mixed pasture treatroents, so the herbicide roller (glyphosate) was also used.

Measurements: Soil samples were taken in May at 3 depths (0-5 cm, 5-15 cm, and 15-30 cm) for soil nutrient analysis. Sampling for estimation of biomass and Botanal ® was conducted in November and May.

Phase 3. All paddocks were fertilised with @200 kglha of 0-11-20-6. All paddocks were slashed, then subsequently ploughed, due to high levels of vegetative matter before sowing of the pasture treatroents could occur. The mixed pasture treatroents were sown with the trash-culti drill (10 kglha Cavalcade and 4.2 kg/ha Sabi). Basagran ® (2 L/ha) was applied post-emergence. The Cavalcade only paddocks were sown with the Mason 8-row planter (7.8 kg/ha). Spinnaker ® (400 ml) was applied pre-emergence and Sertin® (lL/ha) applied post-emergence. Some hand-roguing of the paddocks was conducted due to introduction of senna, sesbania and phasey bean seed with the purchased Cavalcade seed. Measurements: Soil samples were taken in May at 3 depths (0-5 cm, 5-15 cm, and 15-30 cm) for soil nutrient analysis. Sampling for estimation of biomass and Botanal ® was conducted in November and May.

Results: Vegetation monitoring: Phase 1. There were problems with sorghum establishment due to planter and insect problems. There was also considerable bird damage. Pennisetum pedicellatum was the major weed in these paddocks, particularly where the sorghum population was low. The level of pennisetum in the mixed pasture treatroents inhibited harvesting, so mechanical grain yields were not obtained. The level of pennisetum in the Cavalcade only paddocks was lower, so grain yields were possible (@30 tonnes total for paddocks 4, 5, and 6). Less grass weed may be attributable to the use of selective grass herbicides in the previous season.

Phase 2. The pasture treatroents going into their second year of production had high levels of broadleaf weed, particularly hyptis. The Cavalcade only paddocks were resown with good re-establishment of Cavalcade. The mixed pasture paddocks were treated with herbicide, with resultant good kills of broadleaf weeds, but this also reduced the proportion of Cavalcade into the dry season grazing.

Phase 3. The pasture treatroents sown in the 1996-97 wet season have established well, but P.pedicellatum was again an invasive weed. Strategic grazing of these paddocks over the wet season may aid in reducing future seed set of this grass weed.

Progress: The sorghum paddocks were harvested in mid-late April. Regeneration of pasture species as the understorey in these stubble paddocks was good for the Cavalcade but poor for the sabi. Weaner steers averaging 185 kg per head were introduced into the Systems Trial paddocks in early June, 1997. Weights are currently being measured monthly.

98

Cattle Production Cattle were introduced into the Ley Systems paddocks in mid-August. The table below summarises the cattle weight gains from that time to when they were removed from the trial paddocks in November, (@90 days) for the first and second year pasture, and the sorghum stubble paddocks. There is an obvious stocking rate effect. The sorghum stubble produced the best weight gains overall.

Paddock Paddock Weight Gain Weight Gain Stocking No. DescriEtion (kglha) (kglhd) Rate (hdlha) I Sabi/Cav 2nd yr 59.3 29.6 2 2 Sabi/Cav 2nd yr 36.8 36.8 I 3 Sabi/Cav 2nd yr 70.3 23.4 3 4 Cay only 2nd yr 19.1 19.1 I 5 Cay only 2nd yr 26.5 8.8 3 6 Cay only 2nd yr 36.8 18.4 2 7 Sabi/Cav 1st yr 50.5 25.3 2 8 Sabi/Cav 1st yr 32.8 32.8 I 9 Sabi/Cav 1st yr 42.4 14.1 3 10 Cay only 1st yr 14.4 14.4 I 11 Cay only 1st yr 60.9 20.3 3 12 Cay only 1st yr 43.1 21.6 2 13 Sorghum 40.2 40.2 I 14 Sorghum 62.6 31.3 2 IS Sorghum 47.0 15.7 3 16 Sorghum 49.9 24.9 2 17 Sorghum 83.5 27.8 3 18 Sorghum 29.5 29.5 I 19 Sorghum 39.9 39.9 I

*****

99

PASTORAL DIVISIONS

KATHERINE PASTORAL DIVISION

Introduction:

The major breeder genotype comparison at Victoria River Research Station (VRRS), highlighted in the 1995/96 report has weaned its first batch of home-bred weaners. These weaners are now in the growing (feeder production) phase project at Douglas Daly Research Farm (DDRF). The fIrst of these cattle will reach live export feeder weight-specifIcations by the end of 1997. These cattle will then be placed in the feedlot being built at Katherine Research Station. They will be fed to two levels of fatness prior to slaughter and their weights at these fatness levels recorded.

This integrated program of work will include the collection of pre-weaning and post-weaning data from commercial cattle on native pasture in the VRD/Gulf. It will provide information of crucial importance to an evaluation of an economic rationale for the development in the NT of a two stage beef industry with a northwards focus. This would mimic and compete with the two stage beef industry that already exists between the Barkly and Queensland.

In conjunction with the planting of 150 000 ha or so of improved pasture in the Daly Basin, such a development could result in a doubling of the number of NT bred store weaners available each year in the northern half of the NT. This would cover the anticipated shortfall in young cattle from Queensland, imported for growing out in the NT. This shortfall is thought likely to occur as pasture and grain supplies in Queensland and northern NSW improve and US competition in the NE Asian market for feedlot beef, wanes.

During 1996/97 a detailed proposal was prepared and submitted to the Meat Research Corporation (MRC) for $1.1 M funding for this project. This proposal was well received. However a restructure of the Commonwealth's statutory arrangements for funding research and development in Australia's meat and livestock industry will probably restrict external funding from this source to a quarter of that requested.

During the year a comprehensive and well presented collation and preliminary evaluation of data from the work at Mt Sanford was prepared and distributed to industry. While this project has enjoyed a particularly good run of seasons which have effectively masked much of the anticipated stocking rate effects, the very high levels of breeding herd efficiency recorded have surprised most if not all observers.

In the fIeld of sustainable pasture utilisation, funding was secured from MRC during 1996/97, for a major expansion of this activity in the Katherine Region. This fIve year program of activity, starting in 1996/97, will enable earlier small scale plot work at the 1-10 ha scale to be tested at a commercial paddock and landscape scale (30 - 100 sq km). Paired similar paddocks on each collaborating property will enable pasture and animal production to be compared between the 'normal' and the 'new' grazing management regimes. The animal production data will form part of the information collected for the live export project outlined at the beginning of this Introduction. The MRC has committed $0.5 m over the next fIve years to this sustainable rangeland production activity.

In addition to these three main areas of activity, other significant work undertaken by the Division is reported below.

*****

100

FEEDER STEER PRODUCTION SYSTEM - FARMLET PHASE

Project Period: Project Staff: Project Location:

Objective:

1992/93 to 1995/96 P Ridley, D La Fontaine, R Muirhead, P Price Douglas Daly Research Farm (DDRF)

To measure the live weight gain (kg/ha/yr) of first weaning round steer weaners from a number of herds in the VRD/Gulf, when grazing buffel pasture in the northern Daly Basin for the first twelve months after weaning.

Background: This project provides part of the mosaic of information required for a rigorous assessment of an economic rationale for a two-stage beef industry with a northern focus, in the northern half to two thirds of the NT. Such a development would mimic the well established two-stage industry with a south eastern focus that has existed for several decades between the Barkly and Queensland and where, in recent years, breeding has been concentrated on native pastures and the feeder (growing) phase has been largely conducted on improved pastures.

The farmlet phase of this project:

• adapted the pasture in the experimental area to the pattern and level of utilisation, characteristic of the production system (prior to the component research phase),

• provided an essential preliminary assessment of sustainable carrying capacity for weaners (relevant to subsequent experimental design),

• enabled an evaluation of property of origin effects on the performance of first weaning round pastoral/area Brahman steer weaners (13 commercial properties were sampled over the 4 years, and 30-40 Droughtmaster steer weaners from Victoria River Research Station were used each year),

• enabled a robust assessment of the impact of weaner initial-weight on live weight gain (kglha/yr) and the proportion each year that failed to reach the market minimum live weight specification of 280 kg.

Method: The project reported here was based on improved pasture of buffel, (Cenchrus ciliaris cv. Gayndah) established from virgin bush in 1988 on Blain soil (a red sandy loam). Annual dressings of 75 kg super phosphate were used, with trace elements (Cu, Mo, Zn) included every four years.

Weaners were drenched (lvomectin®) vaccinated (bivalent botulism, 5 in 1 ) dehorned and castrated on arrival at DDRF and provided with ad libitum access to uramol in the Dry and phosrite in the Wet.

In 1994/95 and 1995/96 it was decided to impose an initial-weight treatment. A target initial-weight range (140 - 180 kg) was calculated by deducting expected weight gain (140 kglhd) from the market weight specification (280 - 320 kg). The control group had a weight range (100 - 260 kg) and average (180 kg) typical of first weaning round weaners in herds using the Victoria River Research Station (VRRS) best bet system in the Victoria River District (VRD).

When the farmlet was divided in to two equal halves in 1994/95, to facilitate the comparison of the two initial­weight groups, the same initial weight of weaner was placed on each new farmlet. This resulted in 60 weaners in the c. 180 kg average weight group (control) and 67 weaners in the c. 160 kg average weight group (treatroent) in 1994/95 and 1995/96. The control and treatment sets were located in each new farmlet on alternate years, providing an unreplicated Latin Square design.

Steers were 'sold' off the 100 ha farmlet area whenever the heaviest 15% or more (15% of the original number) averaged at least 300 kg. This resulted in three or four drafts from the farmlet each year, including the final draft when remaining animals were all removed (in May/June) before restocking with new season's first weaning round weaners.

Results: 1992/93 to 1995/96 Detailed results will appear in a Technote which is being prepared, together with an economic evaluation of their wider implications. The draft abstract from this Technote is provided below, as a guide to the findings from the

101

farmlet phase of this project. These findings are based on data from 475 steers, with only four deaths over a four year period, using weaners from 14 properties in the VRD/Gulf.

An important consequence of the 'selling' system was that a feed bank of 3.5 - 4.5 tonnes/ha or more built up in the second half of the Wet, as stocking rate declined. This feed bank enabled new season's weaners to consistently achieve moderate weight gains (+ 10-20 kg) through the Dry.

A rule of thumb derived from the data was that 3-5 tonnes of dry matter per ha at the start of the Dry enabled 210-230 kg of weaner to be grazed through the Dry on a better than maintenance plane of nutrition. This level of feed on offer also appeared to minimise the germination of weeds in the Wet, an important issue in the northern Daly Basin.

Post weaning gain of pastoral weaners was increased by 26% (from 139 kg/ha/yr to 176 kglha/yr or +37 kglha [P<.OOI]) by altering the initial-weight range and average.

Data collected in 1994/95 and 1995/96 suggests that this production system has the capacity to: enable all pastoral area steer weaners to meet a 280 kg target by May in the year after weaning,

- achieve up to 238 kg gain/ha/yr using a target initial-weight range of 120-160 kg.

Other consequences of using this target initial-weight range (140 - 180 kg) were: a small delay in average turnoff date (+ 17 days,[P<.OOI]), a more compact turnoff pattern,

- a large increase in steer grazing days/ha (+20%, 55 days [P<.OOI]), a small decrease in residual feed on offer (310 kglha,NS),

- elimination of the 1.5 % failure to meet minimum market weight.

Other conclusions derived from the data include: - property of origin of commercial Brahman weaners had no effect on growth rate, - Droughtmasters from VRRS grew as fast as commercial Bralunans (0.84 kgld vs 0.86 kg/d), - weight gain to turnoff (y) was strongly negatively correlated with initial weight (Xl):

y = -0.75xl + 259 r2 == 0.81

P<.OOl r.s.d. = 12.6 kg

- days grazing (y) was strongly negatively correlated with initial weight (Xl):

y = -0.95 Xl + 399 r" = 0.65

P<.OOl r.s.d. = 28.1 days

- by including day of year on which grazing started (x,) the accuracy of the prediction of days grazing could be greatly improved:

y = -0.94xl -0.66 X, + 530 r' = 0.85

P<.OOl f.s.d. = 18.4 days

*****

FEEDER STEER PRODUCTION SYSTEM - STOCKING RATE (4) X GENOTYPE (2)

Project Period: Project Staff Project Location:

Objective:

June 1996 - June 1997 P Ridley, D La Fontaine, R Muirhead, P Price, C Hazel Douglas Daly Research Farm (DDRF)

To measure the effect of four stocking rates on live weight gain (kglha/yr) in first weaning round Brahman and 1M Charolais steer weaners. when grazing buffel pasture in the northern Daly Basin for the first twelve months after weaning.

102

Background: This project utilised the pasture described in the previous trial after the two farmlets were each divided into eight 6.1 ha plots. The cattle were derived from the breeder genotype comparison at Victoria River Research Station (VRRS) described in the 'Improving Breeding Herd Efficiency' section of this divisional annual report. The Brahmans and \4 Charolais were conceived prior to the purchase of their mothers for the breeder genotype comparison.

Because the calving patterns of the darns of the two genotypes were not a consequence of the management system and the environment of the genotype comparison, the weaning weights were not a reflection of genotype differences.

Method: The experimental design was a replicated (2) factorial involving stocking rate (4) and genotype (2) with the replicates confounded with two target turnoff weights (320 kg or 340 kg). Stocking rate differences were effected by varying the number of steers per plot. The larger genotype (\4 Charolais) was run at 5, 6, 7 or 8 weaners per plot and the Bralnnans were run at 6, 7 8 or 9 steers per plot. This provided three identical stocking rates for each genotype and a range of initial grazing pressures (kg of weaner per hal that were similar for the two genotypes (see Table I).

Weaners were drenched (Ivomectin®), vaccinated (bivalent botulism, 5 in I), dehorned and castrated on arrival at DDRF, and provided with ad libitum access to Urarnol® in the Dry and Phosrite® in the Wet.

Results: The data has not yet been analysed because the last steers were not turned off until mid May 1997. Treatment means clearly indicate that there was no major effect of stocking rate or genotype on individual animal performance. As a consequence, stocking rate showed a strong positive linear relationship with live weight gain per hectare per year as shown in Table I.

Table 1: Treatmeut means (kg gain/ha/yr) Steers per ha Bralnnan

Rep. I Rep. 2 (320) (340)

0.82 0.98 133 146 1.15 161 178 1.31 178 207 1.48 211 205

Average 171 184

\4 Charolais Rep. I (320) 103 121 140 169

133

Rep. 2 (340) 112 136 162 206

154

Average

134 160 190

The apparent moderate genotype effect in Table 1 reflects the 20 kg lower initial weight of the Brahman steers, and the apparent replicate difference reflects the 20 kg difference in target turnoff weights (shown in brackets in Table I). The replicates were in effect, a secondary treatment.

These results will be discussed in next year's report after the data has been analysed. *****

FEEDER STEER PRODUCTION SYSTEM - GENOTYPE (3) X SEX (3)

Project Period: Project Staff: Project Location:

Objective:

1997/98 - 1999/2000 P Ridley, 0 La Fontaine, P Price Douglas Daly Research farm (DDRF)

To measure the effect of three genotypes and three sex alternatives on the annual live weight gain (kg/ha/yr) of first weaning round weaners from the VRD, when grazing buffel pasture in the northern Daly Basin for the first twelve months after weaning.

103

Background: This project utilises the same pastures described in the previous trial but started one year later. The weaners are also derived from the Victoria River Research Station (VRRS) genotype comparison breeding project. All weaners are the result of planned matings at VRRS and all three available genotypes (Brahman, \4 Charolais and Droughtmaster) are being used.

Initial weights of the weaners are still more a function of calving patterns established prior to the purchase of their mothers, than a reflection of genotype differences.

Method: Three experimental designs are being used. The fIrst (involving bulls and steers) is a replicated (3), sex (2) by genotype (2) factorial with seven weaners per cell. The second design (involving only steers) is a replicated (3) genotype (3) comparison with seven weaners per cell. The third (which only uses heifers) is a replicated (3) genotype (3) comparison with seven weaners per cell.

All three designs will operate for three successive annual cycles of production.

Alternative phosphorus (Phosrite®) and nitrogen (Uramol®) supplementation regimes are confounded with the replicates in all three designs described above. This supplementation experiment is described below (Responses to Dry Season and Wet Season Supplements).

Weaners were drenched (Ivomectin®), vaccinated (botulism, 5 in I) dehorned and castrated on arrival at DDRF in June 1997.

As soon as ten of the males in any sex x genotype set average 300 kg, they will be turned off and transported to a research feedlot at Katherine for the next phase of the production system. The transfer target-weight for heifers is 250 kg group-average, for the heaviest ten heifers in each genotype set.

The remaining animals will continue to graze their experimental areas until they are removed in May 1998, when their fInal grazing phase weights will be recorded.

Results: Since the first weaners entered this experiment in June 1997, no results are yet available.

*****

FEEDER STEER PRODUCTION SYSTEM - RESPONSES TO DRY AND WET SEASON SUPPLEMENTATION

Project Period: Project Staff: Project Location:

Objective:

1997/98 to 1998/99 P Ridley, D La Fontaine, P Price Douglas Daly Research Farm (DDRF)

To measure the seasonal (kglhd) and annual growth (kg/ha/yr) response to dry and wet season supplementation in weaners from the VRD, when grazing buffel pasture in the northern Daly Basin for the fIrst twelve months after weaning.

Background: Insufficient information is currently available to provide an economic rationale for dry season and wet season nitrogen and phosphorus supplementation of growing cattle grazing improVed grass-only pastures in the Daly Basin. This project will measure the response in fIrst weaning round weaners from the breeding herd genotype comparison at Victoria River Research Station. The Blain soil at DDRF, on which the predominantly buffel (Cenchrus ciliaris cv. Gayndah) grass-only pasture is growing, has a soil P content less then 5 parts per million, and receives an annual dressing of 75 kg of superphosphate.

Method: The three experimental designs are all replicated (5) and contain the alternative supplementation regimes shown below. The animal numbers shown represent two annual cycles of production.

Experiment Design Experiment n 1 90

90 90

2 20 20 20

3 20

n U P

= = =

20 20

number of weaners Uramol® Phosrite®

104

Dry Season Wet Season U p

U P

U P P

U P U

The husbandry and management of the cattle in this experiment have already been described elsewhere in this report (Genotype 3 x Sex 3).

Results: Since the first batch of weaners only entered this project in June 1997, no results are yet available.

*****

FEEDER STEER PRODUCTION SYSTEM· TRANSPORT WEIGHT LOSS TO THE WHARF

Project Period: 1995/96 Project Staff: P Ridley, R Muirhead Project Location: Douglas Daly Research Farm (DDRF)

Objective: To measure the effect of alternative pre loading regimes (3) on live weight losses between yarding at the property of origin and arrival at the live export loading facility.

Background: No data was available on weight losses likely to be experienced in live export feeder steers in the second half of the wet season, between the time they were mustered and the time they arrived in Darwin prior to weighing and loading for export. This information has a bearing on the meeting of live export market specifications when payment is based on weight at the Darwin weighbridge.

The feeder steer project provided a source of suitable cattle and a dummy trip of 500 km on bituminised roads was used to simulate the stress and duration of the trip from say the Victoria River District to the Darwin wharf. The trips began at 9 am or thereabouts in March at DDRF and ended approximately eight hours later, also at DDRF.

Method: The three treatments were: Mustered on day 1 (Feb 2S) at 3pm, weighed, held over night with access to water only, weighed at Sam, loaded and transported for 500 km, unloaded and immediately weighed.

Mustered on day 1 at 3pm, weighed and turned out to graze. Mustered on day 2, weighed at Sam, loaded and transported for 500 km (with treatment 2), unloaded and immediately weighed.

As in treatment 1 but provided with ad lib pangola hay over night before the Sam weighing.

These treatments were repeated in late March, with the steers in treatments 2 and 3 being changed over to provide an unreplicated Latin Square design. Each treatment comprised six steers of 325 kg average weight on Feb 2S.

105

Another group of 54 steers (average full weight 295 kg) was transported with the 18 original steers, in late March. Their pre-loading regime was the same as treatment 1.

Results: There was a statistically significant difference in the weight loss between treatment 1 and treatments 2 and 3 (-18 kg vs -34 kg and -31 kg, P<.OOI), with no advantage to the group fed pangola hay over night. The transport weight loss of the 54 steers in late March (-5.6%) was identical to that of the 6 steers from the same treatment in the original group of 18.

A week before their 500 km road trip these 54 steers had lost 7.1 % (21 kg) of their full weight after 24 hours without feed, 16 hours without water. They were mustered for weighing at 8am, walked approximately 3 km to the yards and had been grazing plentiful green buffel (approximately 4 tJha dry matter).

*****

THE EFFECT OF VACCINATION FOR BOVINE EPHEMERAL FEVER (BEF) ON LIVEWEIGHT GAIN IN WEANER STEERS AND HEIFERS

Project Period: 1995 - 1998 Project Officers: D La Fontaine, L Melville Project Location: Douglas Daly Research Farm (DDRF)

Objective: To measure the frequency of infection, growth rate response and economic benefit arising out of vaccination against BEF in pastoral area weaners moved from the Victoria River District (VRD) to the Daly Basin.

Background: With the growth of the live export trade there has been a large increase in the practice of holding steers on pasture close to Darwin whilst health protocols and other shipping details are finalised (depoting). There has also been an increase in interest from producers in the Victoria River District (VRD) and Gulf in the pre-positioning of stock in areas closer to the port with all weather access allowing wet season sales and a reduced effect of transport weight loss on stock sold. As the practice of depoting has grown so have reports of losses of stock due to BEF. Anecdotal evidence suggested that stock from areas such as the VRD, Gulf and Barldy were more susceptible to infection as drier climates limit the level of background infection and insect vectors. Individual animals showing erratic growth rates and short term debilitation within the feeder steer project at DDRF, and lack of local information on the impact of BEF vaccination on growth rate and mortality rates in pastoral area weaners transferred to the Daly Basin gave rise to the need for this project.

Method: The project utilises weaners brought from the VRD to DDRF for other experiments. On arrival at DDRF blood samples from all weaners are screened for evidence of exposure to BEF . Those animals which test negative are randomly allocated to either a treatment or control group. Treatment consists of a 2 m1 sub-cutaneous injection of commercial vaccine with a repeat vaccination four weeks after the first.

Results: Table 1 shows the results for the first two years of work. The weight gain was measured over a 300 day grazing period in 1995 - 6 and 313 day period in 1996 -7. In both years all animals vaccinated showed rapid rises in antibody titre in the month after the second vaccination.

Year Expt. Breed Age No. Response (kgs) % control sera- % Positive No. Class to treatment convn. on Arrival

1995 - 6 1 Brahman Wnr 94 - 8.5 (NS) 43% 0

2 Drou2;htmaster Wnr 32 6.8 (NS) 69% 0 1996 -7 3 Brahman Wnr 32 15.7 (p<.05) 64% 17%

4 1/4 Charolais Wnr 12 -2.3 (NS) 80% 29% 5 Droughtmaster Yrl. 21 19.4 (p<.05) 90% 9%

Discussion: In 1996-7 a high level BEF activity was confirmed in both sentinel and commercial herds right across the Northern Territory including clinical cases south of Alice Springs. The 1996-7 results suggest that there may be

106

a weight gain advantage from vaccination against BEF in years when the disease is highly active. Once the field work is complete a thorough evaluation of the cost -benefits of vaccination for BEF will be undertaken.

*****

SURPLUS WEANER HEIFER UTILISATION - FARMLET PHASE

Project Period: Project Staff: Project Location:

Objective:

Farmlet phase 1996/97 - 1997/98 P Ridley, D La Fontaine, R Muirhead, P Price Douglas Daly Research Farm (DDRF)

To measure the growth rate of first and second weaning round cull heifers to the end of their first post weaning wet season, when grazing buffel pasture in the northern Daly Basin.

Background: The Katherine Pastoral Division strategic planning document, "A Scenario for the Northern NT Beef Industry' predicts an ultimate annual production of up to 50,000 heifers per year surplus to replacement requirements in the VRD/Gulf.

These heifers could make up nearly 30% of the young cattle available from this area, for the live feeder export trade to SE Asia. Alternatively they provide a resource base for additional weight gains and conversion to carcasses which meet the specifications of the Darwin chilled beef market. The Darwin chilled beef market has the capacity to utilise more than 20,000 x 200 kg carcasses a year.

Data from Victoria River Research Station suggests that these surplus heifers can be effectively identified early in the production process by drafting off all female calves between 100 - 160 kg when they are mustered for weaning.

These heifers could then be managed for meat production on improved pastures where small paddock size and good fencing facilitate the effective exclusion of bulls. This process could be part of the evolution of a two-stage beef industry in the northern half of the NT.

Method: Experimental heifers were grazed on a predominantly buffel pasture (Cenchrus ciliaris cv. Gayndah) receiving annual dressings of 100 kg superphosphate. Weaners were drenched (Ivomectin® vaccinated (bivalent botulism, 5 in I) and dehorned within a week of their arrival and set stocked in the respective locations until the early Dry of 1997.

Results: The data means, which appear in Tables I and 2, have not yet been subjected to statistical analysis. The two main items of interest in the 1996/97 results are:

In Table I, first weaning round Brahman heifer weaners (location I) grew 25% (29 kg) more than their second weaning round counterparts (location 2), by the end of their first post-weaning Wet. However more than half of this difference (16 kg) occurred before the second weaning round, during the Dry.

The grazing pressure of these two groups was similar at the beginning of the Wet (247 kg/ha and 266 kglha respectively).

In Table I the first weaning round y.; Charolais heifers grew 12% (15 kg) more than the first weaning round Brahman heifers (144 kg vs 129 kg) during the wet season. Their growth in the Dry was almost identical (17 kg vs 16 kg respectively).

The y.; Charolais started the Wet at a slightly lower grazing pressure (228 kglha vs 247 kglha). However it is unlikely that this limited the relative growth of the Brahman heifers because abundant feed (>3 tonneslha) was available in both paddocks throughout the Wet.

107

T bl I L a e : ocatlOn, mba :speCl catIOns an I .. IS 'fi dG thR row ates 0 u el ers In ee fCllH'£ . Thr F arm ets at DDRF Location Breed/Age No. Weaning June 27 Oct 24 May 6 Wet Season Gain

ronnd kg kg kg 1 Brahman 35 1 139 (16) 155 284 129

Weaner + 145 2 Brahman 29 2 - 164 280 116

Weaner

DM 6 189 306 117 Weaner

3 DM 23 1 292 (11) 303 435 132 Yearling +143 Y-\ 20 1 156 (17) 173 317 144 Charolais +161 Weaner Brahman 4 1 169 (18) 187 324 137 Weaner +155

DM = Droughtmaster Y-\ Charolais = Y-\ Charolais '4 Brahman

Figures in brackets show dry season weight gains. The second row of figures in the column headed May 6 are total weight gains (wet season + dry season).

*****

THE EFFECT OF SEX (2) AND AGE (2) ON WEIGHT AT TARGET FATNESS (2)

Project Period: Project Staff: Project Location:

Objective:

June 1997 - November 1997 P Ridley, J Wheeler, G McBride, D LaFontaine Katherine Research Station (KRS)

To measure the effect on live weight and carcass weight of twelve months difference in age in Brahman steers and heifers, when they are slaughtered at approximately 6 mm or approximately 12 mm of fat depth at the P8 site.

Backgronnd: One of the objectives of the feedlot phase of the genotype comparison is to provide data to describe the weight x age x fatness interrelationship in young bulls, steers and heifers from the breeding herds in the Victoria River Research Station (VRRS) breeder genotype comparison.

This project provides the first information to meet this objective and utilises tail end first weaning round steers and heifers weaned in 1996 and 1997, from the Brahman herd at VRRS.

Method: Tail end first weaning round Brahman steers and heifers from the 1996 and 1997 weanings at VRRS were placed in a temporary unshaded feedlot at Katherine Research Station in late June 1997.

The animals were adapted to a high grain content diet over a three week period by allowing them ad libitum access to two self feeders. The feed in these self feeders was progressively altered from 20% grain 80% hay to 80% grain 20% hay over these three weeks. The main grain was sorghum with mungbean providing 4% of the ration throughout. Cavalcade (Centrosema pascuorum cv. Cavalcade) hay was used throughout.

The grain was rolled and contained 5-9% uncracked grain. The hay was hammermilled through a 25 mm screen and mixed with the hay. The two age groups were fed separately. Both groups had ad libitum access to phosrite lick blocks.

108

At the start of the experiment five animals in each age x sex set were allocated for slaughter at a group average of 6 mm fat depth at the P8 site (group average, estimated ultrasonically). The other five in each group were to be slaughtered at 12 mm. Carcass measurements (hot weight and cold fat depth at the P8 site and the 12113 rib quartered surface) were to be taken when experimental animals were slaughtered three days after their last full weight.

Results: No results are available in this report since the experiment only began at the end of June 1997.

*****

BEST BET BREEDER HERD

Project Period: Project Officer: Project Location:

Objectives:

Ongoing since 1990 M Cobiac Victoria River Research Station (VRRS)

To act as a long running demonstration of an integrated package of the Department's current management recommendations for breeder herds in the semi-arid region, and to act as a benchmark of the level of productivity achievable with cost-effective mineral supplementation.

Background: Up to 1990, the Droughtmaster herd on VRRS were engaged in lengthy trials on the effects of weaning on breeders and progeny. Even with weaning and control of botulism, breeder mortality between 1985-1990 averaged 12% and the weaning rate averaged only 51 %.

In 1990, the Best Bet system was implemented, consisting of: • Mustering and weaning twice annually (April and September) • Calves weaned to 100 kg onto spelled native pasture • AIl stock supplemented year round with urea-based licks in the dry season and phosphorus-based

supplements during wet • Cows culled 10-11 years of age, orfor injury, temperament of poor reproductive performance • Heifers selected at 2 years of age on liveweight, conformation and temperament • Heifers control mated and run separately until they have weaned their first calf • Bulls ratio 5%, continuously mated. Annual vaccination for vibriosis and culling for injury, temperament,

age (8-9 years) or poor fertility • All stock vaccinated annually for botulism strains C & D • Fire used to manage pastures

The result of the introduction of the Best Bet System is seen in Table 1. Average cow mortality has been cut to less than 3%, and average weaning rate has increased to above 75%. Average cow weight also increased by 40 kg. The main aspect is the year round supplementation. Over 5 years, the cost of this averaged $16.75lhead/year.

Table 1:Performance of VRRS Breeder Herd 1985-95 Year Weaning rate % Mortality rate % Supplement $/cow

1985-1990 Average 51 12.0

1990-91 52 4.5 19.00

1991-92 85 2.5 17.00

1992-93 68 3.7 18.00

1993-94 80 2.2 14.00

1994-95 78 2.2 15.70

109

Developments in 1996-97: The VRRS Droughtmaster breeder herd was reduced to 130 animals in 1995 and incorporated into the genotype comparison. Each of the herds in the genotype comparison is run under the Best Bet breeder management recommendations. While animal performance is still being measured as part of the genotype comparison, a new emphasis on the stability of native pastures under such a system has lead to the setting up of a number of pasture monitoring points throughout the paddock in which the Droughtmasters are grazing. These points are on clay and earth soils, and at a range of distances from watering points. Pasture yield and composition, ground cover, and grazing level are measured twice annually at each point. Monitoring will continue for an indefinite period.

The full data analysis of the 1990-95 results has progressed somewhat slower than originally anticipated. It is, however, under way and should be completed in 1997-98.

Discussion: With the Best Bet System resulting in an increase in breeder liveweight, increased weaning rate and hence more lactating cows, and increased weaner liveweight, grazing pressure on the paddock has increased by about 40%. It is as yet unclear how this will impact on the long-term sustainability of the pastures on which the cattle graze. Pasture monitoring, and utilising technologies such as pasture growth modeling and satellite imagery will help interpret the results obtained, and some assessment of the impact of the Best Bet system on native pasture communities will be made. As monitoring is ongoing, conclusions will be continually refined as more data is collected

Cattle management and reporting will continue as part of the genotype comparison. Statistical analysis of the 1990-95 data is expected to be completed in 1997-98 and draft scientific papers prepared. It is also planned to publish the results of the Best Bet System in book form in conjunction with other recent herd studies across Northern Australia.

*****

PRODUCTIVITY OF VARIOUS BREEDER GENOTYPES

Project Period: Project Officer: Project Location:

Objectives:

1995 - 2000 MCobiac Victoria River Research Station (VRRS)

To compare the ability of four breeder genotypes to improve breeding herd efficiency (kgs of calf weaned per 100 kg of cow mated) under current Best Bet breeder management practices. To provide weaners of different sex (3) and genotype (3) for an evaluation elsewhere of their post weaning performance in the grazing and feedlot phases of production.

Background: Breeder herd productivity at VRRS has been increased dramatically over the past 5 years due to the implementation of the 'Best Bet Breeder Herd Management Package'. Weaning rates have been increased from 50% to over 75% and breeder mortality has fallen from 12% to less than 3% (Sullivan, unpubl. data) (See Figure 1). Average breeder liveweight also increased by 40 kg. This represents ajump in kgs of calf weaned per 100 kgs of cow mated of 14 kgs (ie. from 23.4 kgs to 37.5 kgs) (Sullivan, unpubl. data).

Further increases in breeding herd efficiency may be achieved through: • increasing the remating conception rate of heifers suckling their first calf, andlor • hybrid vigour in the areas of growth, fertility and maternal traits achieved by crossbreeding with breeds which

complement each other.

A pivotal point in the development of this project was a workshop at VRRS involving producers, an Asian importer, researchers from several organisations, and extension officers.

Method: The breed types being compared represent a range of genotypes available in north Australia, likely to be adapted to the environment. The Charolais was chosen as an example of the large late maturing breeds of Bos taurus available in Australia. The pure Brahman herd represents the current breeding objective of the majority of regional herds.

110

The Droughtmaster herd provides a link to past research and is a benchmark for performance in the region. It also represents a simple option for district managers in that it is a stabilised 2 breed composite, selected for performance in the region. It combines the attributes of the Bra1mum and British Shorthorn breed.

The herd using Brahman bulls over FJ (CharolaislBrahman) cows was chosen for the following reasons:

• The inclusion of genes from a large European (Bas taurus) breed has the potential to produce larger mature size offspring. This should result in heavier yearlings, and fewer weaners requiring two post weaning wet seasons to reach live export feeder weight specifications. It should also reduce overfalness problems in SE Asian feedlots supplying the wet market sector.

• FJ females would be generated in a Brahman herd using large, late maturing Bas taurus bulls. Such cows have a larger dose of unadapted (Bos taurus) genes than the 33% level which arises in a criss cross crossbreeding system using FJ and Brahman bulls, planned for VRRS in the future. This herd will test the adaptation of 50% Charolais females.

• The herd is a source of 14 Charolais progeny required in the development of the criss cross herd.

The treatment consisting of CharolaislBrahman FJ bulls over Brahman cows aIIows the maintenance of a highly adapted cow herd but introducing Bas taurus genes in the FJ bull, thus producing offspring genetically similar to the third herd. This treatment represents the most likely path taken by a producer starting a crossbreeding program, because purebred Bos taurus bulls may not function well or last long in the stressful environment of the VRD/Gulf Districts.

Discussion: In 1996, the first calves of the trial were conceived. A hot dry spell in early 1996 appears to have delayed the remating conceptions of those cattle which were pregnant on arrival. The three herds of purchased cows seemed to be more affected by tltis than the resident Droughtmasters, quite probably due to the recent arrivals still settling in to both the location and the breeding cycle. In May 1997, when the first trial calves were weaned, the number of younger calves left on their mothers reflected this. Table I shows some figures from the muster in May 1997. These figures do not represent a full production year's data. What is apparent is that all groups of breeders seem to be doing well under the Best Bet breeder management system. The wet season of 1996-97 was ideal for pasture growth, and good animal performance figures are expected for the year when the second round of weaning is completed in October. Conception rates at the May muster were improved on the previous year, more in line with long term patterns.

Table I, VRRS Genotype Herds and their performance in May 1997 Herd Bull Cow CowWt Calf Weaner % of Calves weaned

(May) Wt(May) in May (>100Im) 1 D'master D'master 424 kg D'master 176 kg 94% (Ill from 118) 2 Brahman Bra1mum 430 kg Brahman 156 kg 86% (89 from 103) 3 y,char,Y213r Bra1mum 442 kg 14Char,'AB 160 kg 82% (84 from 102)

r 4 Brahman Y,Char,Y213r 475 kg 14Char,'AB 169 kg 87% (95 from 109)

r

The use of newly developed NIRS (Near InfraRed Reflectance Spectroscopy) technology has been adopted for the purpose of quantifying the diet quality of each breeder herd. Monthly samples are collected for analysis to determine animal intake and nutritional and digestive properties. Indicator steers are also present in each breeder paddock for the purpose of estimating the relative nutritional stains of the four breeding herd grazing areas.

*****

111

EFFECT OF YEAR-ROUND SUPPLEMENTATION

Project Period: Project Officer: Project Location:

Objectives:

1993-1997 NMacDonald Paddock Demonstration Site, Mt Sanford Station, VRD

To record how the viability of supplying mineral supplements to cattle is affected by stocking rate. To quantify and demonstrate the impact on the pasture of providing supplementation to the cattle.

Background: This project was included as part of the Mt Sanford stocking rate trial in 1993 to answer a question posed by a major producer group on whether a property that reduces its stocking rates sufficiently could avoid having to supplement their cattle. Two additional paddocks were therefore added to the stocking rate trial, duplicating the trial's lowest two stocking rates (5 and 7.5 per sq km) without supplementation. This project is sponsored by the MRC under their Producer Demonstration Site program. This project also acts as the basis oLthe research into methods of diagnosing the phosphorus status of breeders, reported in the project comparing techniques for assessment of nutrient deficiencies. The project has always been run as part of the Mt Sanford stocking rate trial.

Developments in 1996-97: 1996-97 constituted the fourth year of steer data and the third year of breeder data from the project. Completion of the 1996-97 breeder data is waiting for the results of the second round muster in October 1997.

Results from the different years of the project have been very consistent. Supplementation has shown no benefit to weaning rate, but the liveweight of the supplemented cows has increased relative to the unsupplemented ones -so they are now an average of 31 kg heavier.

1n terms of steer growth, supplementation has shown a major benefit - 15 kg/head this year and 17 kg/head on average over the last 4 years. Almost all of the advantage has been in the wet season.

Table I:Average performance of supplemented and nnsupplemented cattle on Mt Sanford project Supplemented Unsupplemented 96-97 Average to date 96-97 Average to date

Weaning % 90 88 90 90 Cow liveweight (kg) 458 435 427 416 Steer growth dry (kg) 33 26 35 25 Steer growth wet (kg) 164 140 148 124 Steer growth total (kg) 197 166 182 149

This project was reported in two major reports on the Mt Sanford project, during the year.

Supplement costs (including transport) have averaged $17 per breeder per year over the last 4 years. As the steers and breeders are in the same paddocks, it is not possible to determine how much steers consume compared to breeders. It is assumed that their supplement consumption is in line with their nominal pasture consumption -about 0.6 of a breeder or $10.20 per head per year. At $1.20 per kg, this results in 100% return on capital invested.

These results were tested statistically. In the long run, we can be 97.5% sure that the supplement will result in an extra 9 kg/head/year (thus paying for itself) and 61 % confident that this will apply in any particular year.

Discussion: All stocking rate effects, and the effect of the supplementation on the pastures, are masked by the run of excellent seasons experienced since 1993. So far the trial suggests that supplementation of breeders in this environment is not worthwhile, while it is worthwhile for steers. The reason why the weaning rate has not responded to supplementation is suggested to be that the nutritional status of even the unsupplemented breeders has been good enough for the weaning rate to be maximised, because of the moderate stocking rates and excellent seasons. Since they cannot have more than one calf a year, the supplemented cows have been putting on liveweight. Possibly in a run of poorer years, supplementation of breeders would come into its own.

113

reviewed by a committee of local pastoralists in October 1996. They concluded that the demonstration should continue in its present form for another 4 years with the addition of further studies. Larger paddocks, flexible stocking rates, and more input from producers were seen by producers as important project issues. As a fIrst stage, a management group of producers now meets twice a year. The aim is to continue the project into a second phase until 2001, and applications for further external funding have been lodged.

Discussion: The performance of the cattle in this project is among the best ever recorded in the NT. For this excellent run of seasons, there have been few differences attributable to stocking rate. There has been a minor difference in weaning rates, but no difference in average weaner weight or steer growth.

The major conclusions are that stable perennial pastures are able to withstand much heavier utilisation than mixed pastures and that short term animal production is by itself a poor guide to appropriate stocking rates. Many stations use comparable stocking rates to this project without getting as good results. The most likely explanation is that the cattle on this project have less distance to go for water. Provision of more water points is probably the best available means of improving sustainable pastoral production.

*****

TECHNIQUES FOR ASSESSMENT OF NUTRIENT DEFICIENCIES

Project Period: Project Officer: Project Location:

Objectives:

1993-1996 NMacDonaid Mt Sanford, Katherine Research Station, commercial stations in Katherine Region

To examine existing techniques for determining nutrient deficiencies in cattle, identifying any worthy of further application. To train extension officers in the techniques found to be of practical use. To further develop new diagnostic techniques in cooperation with researchers elsewhere.

Background: This project has so far been concerned with fluorine, phosphorus and protein. In 1993-94 it investigated teeth and bone abnormalities in cattle that had been fed phosphorus supplements containing high fluorine levels. Widespread and significant teeth damage was found, associated with lower levels of bone fluorine. Based on this and other evidence, the feeding of MAP as a source of phosphorus is no longer recommended.

The diagnosis of phosphorus status of cattle has been investigated in a series of joint projects without much success. The present project involves testing plasma inorganic phosphorus in conjunction with faecal nitrogen from lactating and dry cows, with and without supplementation. The technique depends on there being no other over-riding deficiency, so they are taken at a time of year when protein is thought to be adequate. At Mt Sanford, samples were taken each May 1994-96 and each February 1995-96. Testing also took place in Auvergne in May 95. Results showed P on the Mt Sanford site to be marginally deficient, which agrees with soil tests and cattle performance, but satisfactory on Auvergne which is totally at odds with existing data.

In 1995-96, a University of Queensland student, Robert Young, studied the supply of protein to grazing lactating cows over the course of a wet season at Katherine Research Station, measuring rumen ammonia, plasma urea nitrogen, and faecal nitrogen, and compared cows receiving no nitrogen supplement, receiving urea, and cotton seed meal. He also took samples at VRRS, Mt Sanford and Newcastle Waters.

Developments in 1996-97: The only activity under this project in 1996-97 was the write-up of Robert Young's N-diagnosis project, and planning of a follow-up project. He concluded that nitrogen does become limiting by mid-February and that urea is more effective at correcting this deficiency than true protein. The MRC has agreed to sponsor a student over the 1997-98 wet season, and this student will try to confirm this finding and investigate the efficacy of near­infrared reflectance spectroscopy (NIRS) as a rapid and cost-effective method of assessing the protein available to animals. The life of this project is being extended until 1999.

*****

SPIKE FEEDING FIRST CALF HEIFERS

Project Period: Project Officer:

1994-1997 NMacDonald

114

Project Location: Victoria River Research Station (VRRS)

Objectives: To assess whether spike feeding (a short pre-partum nutritional boost) significantly reduces lactation anoestrus in first calf heifers and to assess the cost effectiveness of this treatment.

Background: Spike feeding is the feeding of a high energy supplement for about 50 days in the late dry season to cows in their last trimester of pregnancy. This appears to stimulate reproductive hormone production before the stress of lactation begins, thus aiding early re-conception.

Expected benefits are extra calves in the subsequent year and reduced out of season calving. Although spike feeding could have an effect on cows of all ages, this trial focuses on first calf heifers as their usual re­conception rate is much lower than mature cows, so there is more chance of the treatment being profitable.

At VRRS, heifers are seasonally mated. Bulls are introduced into the segregated heifer paddock in January, and the heifers are pregnancy tested in June. For this trial, one hundred pregnant Droughtmaster heifers were selected and drafted on weight and expected calving date into two groups in different paddocks. For 50 days in September and October, one group is fed 1.5 kg/hd/day of a mixture of crushed sorghum and meat meal, while the other is not. Paddocks are rotated half way through the feeding period and the heifers weighed at the beginning middle and end of the feeding period.

A increase in re-conception rate of 17% would be required to cover the $30 per head cost of the treatment. This was easily achieved in 1994-95, when the re-conception rate of the spike-fed heifers was 74%, compared to 42% in the unfed ones. However in 1995-96, the reconception rate of both groups was similar and very low (27% fed, 26% unfed). It was assumed that the cause of this was an extended dry spell in the middle of the wet season.

Developments in 1996-97: In 1996-97, the reconception rate of both was similar and high (both 68%). It would seem that seasonal conditions were good enough to make the supplement unnecessary.

Discussion: It would seem that a favourable return from spike feeding depends on there being particular middle range wet season afterwards - neither so bad that neither group reconceive, nor so good that they all do. Although the treatment showed a net return of nearly 100% in 1995, spike feeding is clearly a risky investment, and it is unlikely to be widely used unless the cost is greatly reduced. It may be worth pursuing using urea and molasses from the Ord.

With a success rate of only one year out of three, no further work on spike feeding is planned at VRRS at present.

*****

SUSTAINABLE RANGELAND PRODUCTION

A BOOKLET FOR BETTER LAND MANAGEMENT OF NATIVE PASTURE COMMUNITIES IN THEVRD

Project Period: Project Officer: Project Location:

Objectives:

1997-2001 MCobiac KatherineNRD

To produce a booklet that ensures the majority of pastoral land managers gain an increased understanding and knowledge of local pasture communities and basic grazing ecology and management.

115

Background: The aim of this sUb-project is to utilise research information gained throughout the first phase of NTA 022 to produce a booklet directed at graziers throughout the VRD, Katherine and Sturt Plateau areas. This booklet will provide description of the basic characteristics of the major pasture communities and outline the likely impact of land management practices in a state and transition model framework. Collaboration with the Resource Capability Assessment section within the NT Dept. of Lands, planning and Environment will be sought.

Results: A total of twenty three SWIFTSYND sites were established in NAP2 to calibrate and validate GRASP pasture growth models for a range of pasture types and land conditions throughout the VRD. Completed models will enable the description of seasonal variability effects on pasture production. From these sites a detailed data set of pasture, soil and climate relationships exists.

Fire management research at VRRS and the Mount Sanford stocking rate demonstration has also yielded valuable pasture and animal production data.

Detailed analysis of pasture, soil and climate data is underway. Input from pastoralists, other government agencies and other researchers will be sought. The format and content of the booklet will be determined by December 1997. A draft outline is expected by June 1998.

*****

ECONOMIC ASSESSMENT OF GRAZING MANAGEMENT OPTIONS

Project Period: Project Officer: Project Location:

Objectives:

1997-2001 RDyer KatherineNRDISturt Plateau

To ensure that 50% of pastoral managers have investigated the economic viability of a range of sustainable grazing management options using a range of Decision Support Systems (DSS) in a whole-property framework

Background: The economic analysis of development, management and marketing options is essential to assess the potential financial risk and impact of management decisions. It is also necessary to promote the increased adoption of sustainable grazing management options.

In cooperation with individual pastoralists. the economic impact of various climatic and management scenarios is being investigated throughout the Sturt Plateau and VRD. On-property case studies will utilise Herd Econ, GRASP, Breedcow Dynama and RAlNMAN decision support systems. Input data for each enterprise will be provided from producer records and knowledge, and available production and economic data.

Results: During June and July 1997, Rosemary Buxton, from CSIRO Wildlife and Ecology in Alice Springs demonstrated the use of the Herd Econ and undertook, in conjunction with DPIF, case studies on five individual properties in the Sturt Plateau and VRD. This has provided an excellent start to this sub-project, and will be continued for other properties throughout the project. Individual property reports are provided to each pastoralist. Major regional issues will be summarised in regional reports.

Four of the five properties were located on the Sturt Plateau. This is a unique biogeogrphic region characterised by the ongoing subdivision of large extensive leases (2000 km') Grazing management issues in this region are unique.

Properties are in the early stages of development. Current herd sizes are generally small but increasing. Grazing is totally reliant on native pastures however there is potential for improved pastures and opportunity cropping enterprises.

Herd size is currently restricted by limited fenced country, the availability of capital to purchase livestock, fencing and water infrastructure, the natural rate of herd increase and the supply and cost of labour. Trading in

116

cattle, providing land for agistment and short term 'depoting' of cattle on route to the live export markets in Asia provides important additional income and cash flow for enterprises in this region.

Regional and property stocking rates are generally very low, but there is potential for localised overgrazing with the confinement of cattle to available fenced paddocks during herd development. There are currently no objective assessments of carrying capacity for the various pasture communities within the region.

Property case studies investigate herd and property development options that maximise cash flow while maintaining stocking rates at sustainable levels. Case studies will include stocking strategies (conservative, flexible) the influence of seasonal variation, herd management options, purchasing and marketing options, sensitivity analysis of reproduction and market performance, burning management and the possible future impact of increasing woody plants.

*****

ASSESSMENT OF STOCKING RATES AND CARRYING CAPACITY FOR PASTORAL PROPERTIES

Project Period: Project Officer: Project Location:

Objectives:

1996-2001 RDyer KatherineNRD/Sturt Plateau

To ensure 60% of pastoral properties have documented current paddock and property stocking rates and developed individual estimates of sustainable livestock carrying capacity.

Background: There are few objective estimates of safe stocking rates for pasture communities throughout the VRD and Sturt Plateau. Current recommendations are based on subjective estimates over the years. Disagreement regarding 'safe' stocking rates exists between government agencies and pastoralists.

This project will gather current stocking rate information and utilise grazing research results, pasture growth models, producer knowledge and GIS to estimate safe levels of stocking on a pasture community (land unit), paddock and property basis. The methodologies outlined by Scanlan et al1994 and Johnston et al 1996 will be utilised.

Results: Preliminary estimates of safe levels of utilisation and stocking have been made for Mitchell grass from data collected at the Mount Sanford Stocking Rate demonstration. In the Mount Sanford trial area, most of the stocking rate treatment paddocks would be considered to be in "good" condition.

The pastures are characterised by a dominance of perennial tussock grasses, mainly Mitchell grass species, complimented with a range of annual grasses and forbs in inter-tussock spaces. Since 1994 the proportion of perennial grass across the sites has increased, while annual grasses have generally decreased. The proportion of legumes and forbs has remained steady. This is a result of an exceptional run of above average seasons.

Safe levels of utilisation of Mitchell grass pastures in good condition appear to be between 20% - 25%. Although a stocking rate of 15 head/km2 would be appropriate for recent seasons, long term stocking at this level would result in an average utilisation rates of greater than 40%. At these levels reduced animal production and pasture degradation would be likely. Stocking rates between 7.5-10 headlkm2 provide average utilisation rates between 21.4% - 28.5% respectively. Likewise average stocking rates can be calculated for a desired level of utilisation. A stocking rate of 9.4 head/km2 will utilise on average 22% of annual pasture production.

*****

117

PRACTICAL BURNING GUIDELINES TO MANAGE PASTURE COMMUNITIES AND WOODY PLANT POPULATIONS

Project Period: 1997-2001 Project Officer: R Dyer and L Cafe Project Location: Victoria River District (VRD)

Objectives: That 70% of producers are aware of the principles and best practice of controlled burning by providing a relevant and practical fire management manual and presenting information at on-property workshops, field days and shows.

Background: Fire management is of particular importance for the sustainable use of pastoral lands in northern Australia. There is considerable uncertainty and difference of opinion regarding the potential benefits and cost associated with the prescribed use of fire.

The aim of this sub-project is to further develop burning gnidelines and provide land managers with a booklet that details the expected benefits and impacts of using fire. The booklet will be directed at land managers and provide answers to frequently asked questions such as the reasons for burning. when, where, how often, what types of country and how much to burn for a range of climatic zones and pasture communities. It will also serve to outline practical operational procedures involved in sustainable use of fire. Information will be collated from available fire ecology research undertaken in the VRD and across northern Australia and involve input from experienced pastoralists, other researchers and other agencies such as the NT Bushfire Council and Bureau of Meteorology.

Results: The effects of fire on pasture condition and woody plant structure have been examined on black and red soil pasture communities in the VRD. Results are summarised in the MRC final report for NT A 022. The longer-term influences of fire season (early dry and late dry season) and frequency (0,2,4,6 years) are being investigated in continuing research. Successful late and early dry season burns were carried out in October 1996 and June 1997 respectively. Early results indicate that regular fire is essential to manage native woody tree and shrub structure. Plant mortality following fires over a range of fire frequencies, intensities and seasons is very low. Woody plants are well adapted to regular fire. There is little impact of fire on the yield, cover and species composition of perennial grass pastures in 'good' condition. Preliminary recommendations have been made regarding fIre frequency, season, intensity and fuel load required for effective management. Relationships have been identified that allow the prediction of fire impact on woody vegetation from fuel (yield and cover) and average woody plant height inputs. Investigations have identified that fire should not be used as part of land management on pastures in poor condition. Where annual forbs and grasses are recolonising heavily utilised areas, fire can cause significant reductions in yield and cover.

THE IMPACT OF WOODY VEGETATION

Project Period: Project Officer: Project Location:

Objectives:

1997-2001 LCafe KatherineNRD

*****

To ensure the maJonty of land managers and administrators are aware of the increase, cause, impact and potential cost of unchecked woody plants.

Background: Anecdotal and scientific evidence suggests that the size and density of native and shrub species are increasing throughout the VRD. The influence of the tree and shrub layer on pastures in northern Australia is poorly understood.

118

Four experimental sites have been established in the Victoria River and Katherine districts to determine overstorey and understorey relationships in densely treed and cleared areas. The aim of this trial is to: Quantify the effects of tree density on soil moisture and pasture production at two locations with distinctly different rainfall; Provide sufficient data to calibrate and validate tree effects within the GRASP pasture growth model for the communities sampled and; Utilise GRASP to extrapolate tree effects across a range of climate, soil and vegetation systems.

Results: Early results indicate that tree effects may be suppressing pasture growth but this response may well be a result of competition for nutrients, particularly nitrogen, rather than for soil moisture alone. Nitrogen, which is tied up in the woody overstorey root system is released from roots upon clearing, enabling enhanced pasture growth. Continued measurements over time will investigate the trend in plant yield and nutrient content.

Initial calibration of tree effects in GRASP has been undertaken by Jillian Heywood, (University of Queensland student), in cooperation with Greg McKeon. These early results also indicate the role of nitrogen. A complete data set over a two-year period will be utilised for more complete calibration and validation by December 1997.

*****

SUSTAINABLE GRAZING PRACTICES PRODUCER DEMONSTRATION SITES

Project Period: Project Officer: Project Location:

Objectives:

1997-2001 ROyer KatherineNRDfSturt Plateau

To ensure that 50% of pastoral leases have developed or implemented strategic grazing management plans as a result of active participation in whole paddock demonstrations of sustainable grazing management options.

Background: In cooperation with pastoralists, sustainable grazing management demonstration paddocks will be established on several properties throughout the region. A process of local producer group input and consensus will identify a range of management objectives and options, which will be implemented over a period of four years. Ongoing feedback and input will be sought from producers. In regions where fire management is a critical issue a coordinated effort will be undertaken will the NT Bushflfes Council.

The impact of implemented grazing and land management practices across the paddock will be monitored twice yearly throughout the project. Of particular interest is the interaction between the imposed grazing management practices (eg. stocking rates, burning and spelling) and influences such as seasonal variation, pasture community, pasture condition, distance to water, previous grazing history have on land condition and grazing pressure in a spatial context. A measure of animal performance (eg. weaning rates, growth rates etc) will be undertaken where possible.

Results: The impact of rotational burning and flexible stocking on pasture condition and animal performance is underway in a small paddock (approx 500 hal within the Mount Sanford stocking rate demonstration trial area. Annual stocking rates are determined using desired levels of utilisation for separate pasture types and available standing pasture in April. The paddock is currently stocked with 120 large weanerS (approx. 230 kg). An area of 45 ha will be burnt in August to provide nutritious green leaf during the following wet season and to manipulate grazing pressure around the paddock. Paddock pasture types and topography are described using available land unit maps and ground-truthed with GPS. Grazing impacts, grazing pressure and pasture condition will be sampled on a stratified basis throughout the paddock and geo-referenced with GPS. Spatial analysis of grazing impacts will be undertaken using GIS, while statistical differences of grazing pressure and land condition between soil/pasture type, distance from water, grazing history, land condition and burning will be undertaken. This paddock will act as a pilot study for larger study sites. The location and initial measurements of other demonstration properties and paddocks will be finalised and carried out before 1998.

119

The primary outcome of these demonstrations is to establish the practicality and impact of a range of sustainable grazing management practices at an extensive paddock scale. It will establish and demonstrate a methodology for developing grazing management plans. It will also involve producers throughout the trial, to record and monitor their inputs and perceptions in regard to grazing management.

*****

SPA TIAL VALIDATION OF GRASP PASTURE PRODUCTION MODELS AND NOAA FIRE SCAR IMAGES IN TIlE TOP END, NT AND KIMBERLEY, WA

Project Period: Project Officer: Project Location:

Objectives:

1997-1999 ROyer KatherineNRD/Sturt Plateau

Complete calibration and validation of NT GRASP models from SWIFTSYND sites throughout the Victoria River and Katherine regions. Collect an independent spatial validation data set for associated pasture communities throughout the Top End of the NT and the Kimberley, W A. Coordinate with QDNR to carry out validation of spatial models of NT GRASP sites throughout the northern NT and the Kimberley. Ground truth fire scar maps generated from remotely sensed NOAA imagery. Provide updated spatial data for modelling inputs of property carrying capacity, levels of utilisation and property rainfall.

Background: The LWRRDC funded project "Development of a National Drought Alert Strategic Information System" (NDASIS) partially developed a national environmental modeling grid. NDASIS produced a national spatial model of grass growth and utilisation by grazing animals. Model outputs can be absolute or values relative to any season since 1957. The model can be run in forecast mode into the future using ensembles of analogue years selected by the current phase of the SOL This system is run on an ad hoc basis on the QDNR Cary supercomputer in Brisbane for Queensland however the prototype is unproven in other states, particularly northern Australia. The second phase project, "Aussie Grass" arises from an all states and NT analysis of the NDASIS prototype and is scheduled to evolve into a operational national system with locally relevant products at the end of the project. The NT is undertaking one of eight sub-projects within Aussie Grass.

Results: Past work funded by the MRC has established 22 SWIFTSYND/GRASP sites across a range of pasture communities, rainfall zones and land conditions in the Victoria River and Katherine regions. Initial calibration for these sites has been completed. Final calibration of GRASP models for these sites will be carried out in coordination with Ken Day and Greg McKeon.

Spatial field observations of TSDM will be made between April and May 1998 for pasture commumlles represented by SWIFTSYND sites throughout the VRD and Katherine regions. This will ensure measurement of peak yield prior to significant impacts from grazing. During the second year of sampling similar pasture communities will be sampled in locations throughout the Kimberley and Top End of the NT representing a greater range of seasonal conditions. A sampling methodology similar to that used in NDASIS I will be utilised. Preliminary testing of GPS and field/attribute collection devices has been carried out.

Field observations of TSDM will be used for the spatial calibration and validation of GRASP for northern NT and W A pasture communities. Significant coordination between Carter et al will be required to ensure an appropriate methodology is utilised. Of particular concern is the low density and accuracy of rainfall records throughout the region. A combination of BoM and property records could be utilised.

The use of NOAA fire scar images provides a means of resetting standing yield in areas burnt by fire back to zero. The accuracy of these images has not been calculated.

In coordination with the Northern Territory Bushfires Council it is intended to ground truth NOAA fire scar images following controlled and uncontrolled burning activities throughout the Top End in 1995 and 1999. A

120

methodology has been developed at a practical fire management workshop at in June 1997 (Jeremy Russell Smith).

A combination of ground and aerial survey will collect geo-referenced data sets recording presence and patchiness of burning. Estimation of error will be calculated by comparing observed data sets with interpreted fire scar locations from both NOAA and LANDSAT imagery sources. Sampling will be carried out at several times during the year representing different burning seasons and intensities as well as interference from cloud cover. Fire in a range of pasture and soil types will also be measured.

*****

TENNANT CREEK PASTORAL DIVISION

REMOTE MONITORING OF WATER POINTS

Project Period: Project Officers: Project Location:

Objective:

1992 - 1997 M Adams (from March 1996) and J Peart (until January 1996)

Tennant Creek station

Successfully and reliably monitor remote water points using a telemetry system. Field test the reliability of a telemetry system to monitor, record and transmit data relating to a remote stock water supply. Reduce the number of necessary bore runs for water supervision by at least half.

Backgronnd: Funding and support for the project was proposed under the Meat Research Corporation's NAP 2 initiative of reducing the cost of beef production.

One of the major costs to the beef industry in central and northern Australia is associated with the supervision of watering points. Remote monitoring of water points, using telemetry equipment, offers the opportunity to reduce the number of bore runs required for supervision, allow selective visits to start pumps or motors, as well as facilitate immediate recognition of supply problems.

In Central Australia a typical property would have 25 watering points (predominantly bores). A bore run would involve 550 km of travel (on some places the distance can be twice this figure). Taking into account labour at $70.00 a day and vehicle costs at 35 cents per kilometre, a typical bore run over 1.5 days would cost $297.50. Allowing for two bore runs a week, the annual cost for bore supervision is $30,940. If remote sensing could replace one in two bore runs, an annual saving of $15,470 could be achieved.

Method: In July 1995 the Tennant Creek DPIP office was set up as the homestead for this project. Three remote bore sites were selected on "Tennant Creek" station, south west of the town. The bores are 29, 39 and approximately 60 km from the base. The two closest bores "Limestone" and "Bluebush" were each equipped with a remote telemetry unit (RTU) in early August 1995. Initially, transmission of information was unreliable particularly from Bluebush, the distance stretching the limits of UHF transmission. Raising the receiver antenna at the base increased signal reliability to a certain extent.

In April 1996 communications between the remotes failed. A consultant David Bone (formerly of Navcom Electronics) was sub-contracted to visit Tennant Creek to service the system and provide tutorials to familiarise staff with the system, components and software. The Elpro software package "Focus", is not, in David's opinion or mine user-friendly. Communication failures were found at both remotes, due to signal fade, during the hottest periods of most days. It was decided to test the output I transmitting power of the installed units. All units were designed to operate at 1.0 watt power output (standard telemetry output). Power output was recorded well below this in the two remote units as well as the base unit.

David suggested that we send all units including the third remote (yet to be installed) back to Navcom to be serviced. He also suggested that we apply to the Spectrum Management Agency (SMA) for a licence to operate

121

the system on 5.0 watt power output to gain extra coverage and reduce signal fade. The units were returned to Navcom, who in turn, sent them back to Elpro Electronics for service and upgrading.

While the units were away the base station antenna was upgraded and increased in height. Permission from SMA to operate the system on 5.0 watt output power was also granted. Late October 1996 the original two remotes and base were reinstalled. Communication between these two remotes and the base station have been excellent, giving complete coverage 24 hours a day.

In March 1997 in consultation with Shane Blakeley (MRC - NAP Program Coordinator) it was decided not to install the proposed third RTU. The existing system had sufficiently met the objectives to field test and evaluate a telemetry system for monitoring remote water points.

Discussion: Work to date has demonstrated that the system offers reliability of information and that bores at significant distances from the homestead can be monitored. The units themselves and sensory equipment have demonstrated durability in harsh environmental conditions. The equipment will be continually monitored in following years for performance. The Elpro units used are a base model or standard unit. Now that reliable communication between remote units and base station has been established other applications and sensory equipment could be added onto the system with minimal cost. Other applications could include; recording climatic data, monitor water supplementation dispensers, record cattle numbers, turn pumps on or off and monitor power to electric fences. The practicality of these applications will rely on the initial cost of the telemetry unit installed.

Earlier reference in the project background stated an annual cost of supervisory bore runs at $30,940 (assuming a single bore run round trip of 550 km). If the number of bore runs required could be halved an annual saving of $15,470 would be achieved. The associated costs of installing the Tennant Creek system was approximately $15,000 (Section 2.4.4). A bore run to service the two bores equipped with the RTU's on Tennant Creek station is 102 km, with an estimated annual cost of $5600. As a result from this trial, reducing the number of supervisory bore runs to the two RTU equipped bores, results in an annual saving of $2,800. The time period to recoup costs for the telemetry equipment will be approximately five and a half years.

Industry reaction to the concept and development has been positive to date. The northern pastoral industry foresees the potential in remote monitoring to significantly reduce operating costs, and if the availability of lower cost units proves a reality, then acceptance will be increased.

SEASONAL CALVING STUDY

Project Period: Project Officers: Project Location:

Objective:

1996-1999 M Adams and D Savage Barkly Tablelands

*****

With minimal interference to normal station management and operations, monitor and record reproductive performance of "1996" replacement heifers for a minimum period of three years. Without increasing the breeder herd, increase reproductive performance to improve turnoff.

Background: The need for a seasonal calving study on the Barkly Tablelands stems from varied opinions on achievable reproductive goals, and the practicality of controlled, seasonal and uncontrolled mating programs. Documented studies on optimal mating periods and critical mating weights for the Barkly Tablelands are scarce. Research into postpartum anoestrous and calving interval in relation to joining age, liveweight and body condition score is also limited.

Prior to changing any management practices, current levels of productivity should be assessed to determine if, when or where improvements may be made. This project will record the current fertility status of replacement heifers taking into account Barkly seasonal conditions. It will establish benchmark parameters from an analysis of reproductive performance in relation to calving date, heifer joining age, weight, and body condition.

122

Results: In early April 1996, approximately 800 No.4 replacement heifers were mustered and yarded. Standard husbandry practices and selection criteria for replacements were applied. Under extensive pastoral conditions heifer segregation is hard to achieve and especially difficult to maintain Over the wet season. Heifers that came into the yards with a calf at foot were excluded from the project group; heifers that were dry, but diagnosed as being pregnant were retained and will be monitored as a subgroup (of early joiners) for analysis on reproductive performance. All heifers were individually identified by coloured and numbered ear tags. Liveweight, body condition score and pregnancy diagnosis was recorded. A total of 615 No.4 heifers were selected for the project. A total of 419 No.5 heifers were also selected and added for the project group. Three year old bulls were introduced on the 15th April, 1996,43 in total.

*****

DEVELOPMENT OF COW/CALF SEPARATORS

Project Period: Project Officers: Project Location:

Objectives:

1994-1997 M Adams and D Savage Harkly Region

To design and construct a separator unit capable of removing weaners and late season calves with minimal disturbance to the breeder herd.

To reduce mustering and labour costs associated with conventional musters.

Background: The development of cow/calf separators originated in Queensland in the late 1980s. Interest in the Territory for similar "automatic" cattle handling equipment stems from producers that utilise trap yards as part of normal station management. The intended prototype is different from the Queensland model. The original concept for the Territory model was designed by a local station manager, Peter McNeven of Alroy Downs.

The separators are useful where stock can be trapped onto water. Ideally the separator will be used to replace the conventional second round muster for the removal of weaners and out of season calves.

Results: Two prototypes have been tested in the region. The original "Alroy" based design was trialed on three stations. As a result, one station has now taIren on board the concept and incorporated it into usual husbandry practices. The second and more sophisticated prototype based on an "off-set" walk-through was also trialed. This was abandoned with project officers deciding to concentrate on further improvements to the "Alroy" design.

Cattle educated to a trap yard system whereby the inward spear and outgoing spear are at separated locations require little education to adapt to the separator. Placing the unit on the outward spear eliminates the chances of perishing livestock especially during the introductory stage.

The prototype has been finalised. The designs are with a professional draughtsman to be drawn up and sketched for publication in an Agnote.

*****

DEVELOPMENT OF SOLUBLE NUTRIENT DISPENSERS FOR LIVESTOCK

Project Period: Project Officers: Project Location:

Objectives:

1996-1998 M Adams and D Savage Harkly Region

To develop a safe, reliable and cost effective soluble nutrient dispenser for livestock. To demonstrate the benefits of delivering soluble nutrients as a management option for mineral supplementation of livestock.

123

Background: Delivering soluble nutrients in water supplies for livestock is perceived as a very efficient and cost effective method of supplementation, provided access to drinking water is restricted to supplemented troughs. The advantage over a traditional supplementary system using loose mix or lick blocks is that soluble mineral supplements in drinking water deliver a compulsory intake of nutrient at a pre-determined concentration. The cost, in cents per gram of nutrient delivered, is also considerably cheaper compared to other methods.

Over the past 10 to 15 years numerous water supplement dispensers have been tried. Most have fallen short in providing a reliable and safe system to administer nutrients. In 1990 Jack Peart (District Animal Production Officer, Alice Springs) developed the "Norprim" in-line nutrient dispenser. The unit consists of an electronic device which measures water flow via a small paddlewheel type flow sensor. Water flow rate information is transmitted to a control unit which records and displays actual water flow. When a preset volume of water passes through the paddlewheel sensor, a diaphragm pump is initiated and injects a measured amount of nutrient into the water line.

Norprim units have achieved moderate success in the Alice Springs and Barkly regions. Lack of sensitivity to small water flow rates however have reduce the efficiency of the system. A unit installed further north at Mt Sanford in the VRD region experienced problems with condensation interfering with the circuit board. Other problems such as a nutrient pump not switching off and an incident where syphoning of the nutrient tank occurred had caused some major safety concerns within the Territory. Consequently developments and improvements came to a stand still in the following years.

In 1995 persistent pastoral interest from Central Australia and continued support from DPIP in Alice Springs lead to a breakthrough in the dispensing system. A safety "cut-out" mechanism (lock out relay) was incorporated into the control unit which is initiated if the pump runs continuously for more than 12 seconds. The design of the control box itself was improved and sealed which eliminated problems associated with moisture accumulation. The paddlewheel flow sensor is housed in a smaller diameter pipe to increase sensitivity to flow rate. The syphoning effect has been eliminated by incorporating a breather into the nutrient delivery line.

Results: N ornrim unit at Brunette Downs The Norprim unit installed at Brunette Downs (1992) was upgraded with the new control unit containing the safety "cut out" mechanism in August 1996. At the same time the original SO mm galvanised tee piece (SO to 25 mm), which houses the paddle wheel flow sensor was further reduced to a 40mm galvanised tee piece (40 to 25 mm). The flow sensor slides into a brass bush, which in turn screws into the 25mm nipple socket on the galvanised tee piece.

In November 1996 a breather mechanism to break the syphoning effect was incorporated into the system. The breather mechanism is facilitated by a brass "Giacomini" RSS/1 3/S" automatic air vent mounted on a 25 mm poly tee piece and fittings. The nutrient tank was filled with water only. The system was then turned on and monitored over the wet season by station staff when practical. Up until the end of December the unit was functioning satisfactorily.

In March 1997, after a better than average wet season on the Barkly the unit was inspected by DPIP staff. Unfortunately, cattle had gained access to the turkey nest compound and kicked the dispenser unit. Repairs are currently being made to the system.

Nororim unit on Hayfield station In October 1996 the new commercially available Norprim nutrient dispenser was installed on Hayfield Station. The breather mechanism was incorporated into the system which was complimented by a 2000 litre low profile poly tank. The existing SO mm galvanised pipe line was reduced to a 40 mm galvanised pipe section to increase the sensitivity of the paddle wheel flow sensor. The nutrient tank was filled with water only and monitored for two months. The dispenser unit and system operated satisfactorily. The sensitivity of the paddlewheel sensor to measure low volumes of flow rate was acceptable but remains a focus point for further fine tuning. The system was again turned on and monitored over the wet season.

A better than average wet season was also received at Hayfield. The nutrient dispenser system came through the wet season with promising potential. In March 1997 the system had shut down and we were called to investigate the problem. Upon inspection we found a new chink in systems armoury. A dingo had chewed the reinforced

124

hose that housed the wiring to the paddle wheel flow sensor. It was found that the system was close to bird, mice and rat proof but obviously not dingo proof. We are currently in the process eliminating future problems in that area.

L-78 Tennant Creek Field Day. April 1997 The commercially available Norprim unit and breather system was installed at the homestead yards on Alroy for the L-78 field day. The existing water line that fed the yard troughs was 50 mm poly pipe. Instead of using a conventional 40 to 25 mm galvanised tee piece to accommodate the flow sensor it was decided to fabricate one using 50 mm thick walled poly pipe. The inside diameter of which was 40 mm. The flow sensor was then screwed into a 25 mm poly saddle and nipple attached to the thick poly pipe insert. After receiving further advice from the manufacturer of the flow sensor (Manu Electronics), additional lengths of 40 mm pipe were incorporated each side 25 mm nipple and saddle. The extra length (or distance) of the same diameter pipe, either side of the flow sensor reduced turbulence and increased sensitivity.

The installed system worked satisfactorily. Pastoral interest on the day was encouraging. Confidence in the system is increasing but remains a hurdle to be demonstrated before further adoption and application in the Barldy.

*****

SEASONAL PRODUCTIVITY OF NATIVE PASTURES IN THE BARKLY REGION

Project Period: Project Officer: Project Location:

Objective:

1994 - 2000 F Anderson Helen Springs Station

To record the productivity of several Barldy pasture associations in different seasons. The correlation between pasture productivity and seasonal variation will be assessed whilst considering management of the area. To achieve this, pasture composition and yield will be assessed against available climatic data.

Background: The Barldy region consists of pastures that are extremely variable in productivity and composition. All respond variably to external influences such as climate, fire, grazing and human intervention. The efficiency of the pastoral industry depends upon the condition of the grazed pastures.

A pasture monitoring program referred to as the Range Condition Assessment (RCA) program was developed to monitor and assess changes in pastures over time. This current project uses the main principles from the RCA program with the addition of measuring seasonal variations and noting management of the assessed areas.

Twelve grazed sites and one exclosure constitute this experiment. The exc1osure. referred to as the Jingerah bore exclosure, was established in 1974. These sites will be assessed over an initial period of three years to consider the influence of season and management on pasture composition and yield.

Results: In the past yield assessments have not been performed at a uniform time after completion of the wet season. For this reason it is difficult to compare results, particularly those results collected from the sites outside the exclosure. It is noticeable that yield decreases by approximately 600% in some years as the distance from the bore becomes greater (Table 1). This result is unexpected and can be attributed to the close proximity of another paddock fence, where cattle seem to congregate, and to paddock heterogeneity.

After a sequence of dry wet seasons followed by an average rainfall year the yield seems to decrease then increases following another average rainfall the next year. There seems to be little variation between yields inside and outside the exclosure each year.

125

Table I. Pasture ields from inside and outside the exclosure, includin~ distance from the bore (kg /ha) Inside Outside

kmfrom bore 0.8 1.6 3.2 3.6 0.8 1.6 3.2 3.6 April 1994 1899 2106 1768 - 1956 2204 1908 -July 1995 828 766 504 446 745 817 307 306 Sent. 1996 1713 1240 293 425 1747 1237 210 296

The percentage of annual grasses increases both inside and outside the exclosure as the distance from the bore increases. The percentage of perennial grasses in pasture seems to vary at certain distances from the bore with most sites maintaining similar compositions from year to year.

A comparison of the data collected in the 1970s, 1980s and 1990s will be conducted to detect any major changes in dominate pasture species. This data will be useful from an ecological viewpoint as it will give a historical perspective of the last 24 years.

This project has highlighted the importance of exclosures being erected to include a large enough area to allow replicated paired sites of similar vegetation types.

It is also necessary for assessments to take place at similar intervals from the last main rain event each year to account for seasonal variation.

This project will be finalised due to difficulties in comparing grazed and ungrazed sites. Due to unforeseen circumstances ungrazed sites have been either stocked or baled for hay at various stages since the late 1980s.

*****

WATER PONDING ON RED COUNTRY

Project Period: Project Officer: Project Location:

Objective:

1996 - 1999 FAnderson Murray Downs Station

To demonstrate native and introduced pasture species suited to pasture establishment behind ponding banks. To promote spelling as an effective management tool whilst allowing pasture regeneration behind ponding banks.

Background: On the red soils of the Barkly region stock rely heavily upon the native pastures in "floodout" areas - areas where intermittent creeks spill out and flood the low-lying surrounds. The thin, sandy A-horizon of the red soils in these floodouts may be removed by water or wind erosion.

On Murray Downs station large areas between floodouts have been affected by this scalding process with various reclamation methods having limited success. The principle behind using ponding banks as a reclamation technique is to slow the flow of water across the scalds which will allow a greater volume of water to infiltrate. As a result of the increased infiltration it is expected that pasture productivity will increase whilst alleviating the scalding problem.

Results: All introduced and native grass and legume species established successfully, however sabi grass (Urochloa mosambicensis), native millet (Panicum decompositum) and verano stylo (Stylosanthes hamata) were most successful (Table 1).

It is interesting to note that the legume species were able to establish in the banks that held more water whereas the drier banks were favoured by the grasses. Cavalcade (Centrosema pascuorum) was a reliable species, with plants recorded in every bank.

126

Table 1. Establishment counts at each bank recorded late in May 1997. Bank Control Sabi Birdwood USA buffel Native Wynn Verano Cavalcade

orass !ITass !ITass millet cassia stvlo I 76 54 54 38 64 18 65 29 2 10 39 48 12 57 15 54 24 3 14 0 3 3 2 I 0 4 4 40 I 3 0 0 46 70 27 5 16 0 0 0 5 I 26 10 6 28 2 11 5 25 28 107 31 7 38 8 3 30 0 0 30 10 8 56 158 55 53 36 55 40 13 TotaV 40m2 278 262 177 141 189 164 392 148

The control treatments were also influenced by the amount of water held in each bank. Although there were a number of forb species that established in each bank a proportion of these were poisonous, belonging to the genus Indigo/era, Crotalaria or Ipomoea. Annual grasses, such as Australian dropseed grass (Sporobolus australasicus), were recorded in abundance in the 'control treatment, however no perennial grass species were recorded apart from the foreign seeds that travelled with water flowing from other sown treatments (Table 2).

Table 2. Breakdown of the botanical com osition in the control (unsown) treatment. Bank I 2 3 4 5 6 7 8 Average % forbs 50 20 50 30 75 25 18 14 35% % annual 45 20 25 70 6 75 76 80 50% grass % perennial 0 0 0 0 0 0 0 0 0% grass % foreign 5 0 25 0 0 0 3 6 5% seed % sedge 0 60 0 0 19 0 3 0 10%

*****

THE CONTROL OF WOODY PERENNIALS - PART ONE: BLADE PLOUGHING

Project Period: Project Officer: Project Location:

Objective:

1994 - 1999 F Anderson Phillip Creek Station

To assess blade ploughing as a means of controlling dense stands of woody perennial shrubs on the red soils of the Baddy region.

Backgrouud: Since the early 1970s populations of woody weeds, particularly Acacia species have increased on the red soil types in central Australia. One contributing factor to the woody weed problem may be the exclusion of flre from management practices. A strategy to control and manage the adult woody shrubs may involve blade-ploughing. Blade-ploughing kills adult woody weeds by severing their tap roots 20 - 30 cm below the soil surface. Once the trees and shrubs have died, native pasture species can colonise the bare areas. However, native pastures are not well adapted to heavy grazing so those paddocks that are subjected to a high degree of grazing pressure should be sown to pasture species that are more tolerant of heavy grazing.

On a cattle station near Tennant Creek dense stands of woody weeds interfered with mustering in two holding paddocks. The woody shrubs were so thick that grasses were unable to persist, providing insufflcient dry matter to support cattle or flre. These two paddocks were blade-ploughed and sown with Cenchrus ciliaris cv USA (USA buffel grass) and Stylosanthes scabra cv Seca (Seca stylo) in 1994.

127

Results: In the Eastern Holding Paddock (EHP) woody weed seedlings have increased from 4216 seedlings per hectare in 1995 to 20319 seedlings per hectare in 1996, with over 50 percent of the species being turpentine (Acacia lysiphloia). Other problem shrubs are scrubby wattle (A. stipuligera) and Petalostylis cassioides.

There had been an insignificant change in the number of seedlings per hectare in the Western Holding Paddock (WHP) from 1995 to 1996. This paddock had a seedling density of 5882 seedlings per hectare in 1996. In the WHP 78 percent of the young plants were turpentine, with the other seedlings being dogwood (A. coriacea) and soapy wattle (A. holosericea).

The fact that the WHP had fewer seedlings than the EHP could be attributed to the presence of an established stand of buffel grass in the WHP prior to blade-ploughing and a marginally different soil type. After blade­ploughing the WHP buffel grass quickly re-established and provided competition for the woody seedlings.

A burn was planned for 1997 that was expected to reduce the number of seedlings. However due to problems with data collection and paddock management the burn was postponed. The Department's biometrician has advised that the results collected to date be analysed and relevant information be reported in order to finalise this project.

*****

THE CONTROL OF WOODY PERENNIALS - PART TWO: THE EVALUATION OF IMPROVED PASTURE SPECIES

Project Period: Project Officer: Project Location:

Objective:

1994 - 1999 F Anderson Phillip Creek Station

To determine those introduced and native pasture grasses and legumes suited to specific pasture improvement programs. on the red soils of the Barkly region.

Backgronnd: There is very little information available regarding introduced pasture species suited to the Barkly region. Introduced pasture species have been, and will continue to be, sown in small areas in the Barkly for specific purposes. Pasture species that suit the red soils of the Barkly can be recommended to producers for rejuvenating small areas where pastures are degraded or heavily grazed.

Two holding paddocks that were densely populated by woody shrubs on a station near Tennant Creek were blade-ploughed. The blade-ploughed strips provided an opportunity to test several introduced and native pasture species on red sandy soils in the semi-arid tropics.

Resnlts: Presently, only plant establishment data from 1995 is available. The 1996 plant density data has yet to be collated. From the 1995 establishment data, Aeschynomene brasiliana CPI 92519 has shown to be the most successful.

Other successful legume species includes Stylosanthes spp. and Aeschynomene histrix CPI 93636. Sabi grass (Urochloa mosambicensis) was the most successful grass species. Most of the 14 species sown were represented by some established plants, with the exception of saltbush (Atriplex nummularia) and Indian bluegrass (Bothriochloa pertusa).

The Department's biometrician has advised that this project be finalised. More extensive work of a sintilar nature is included in the 'Waterponding on red country' project. A poster has been prepared on the initial findings of this project.

*****

128

NUTRITIONAL VALUE OF NATIVE PASTURES/SEASONAL PRODUCTIVITY OF NATIVE PASTURES - PART ONE

Project Period: Project Officer: Project Location:

Objective:

1995 - 1998 FAnderson A von Downs Station

From laboratory and field data, estimate the levels of nitrogen, phosphorus and metabolisable energy supplied to grazing animals by native pasture at the beginning and end of the dry season. This will provide a data set of the nutritional value of native pastures on the Barkly Tableland.

Investigate and increase the existing knowledge base on the influence of seasonal variation on native pasture yield, botanical composition and ground cover.

Background: Station managers in the Barkly region have approached Tennant Creek Pastoral staff regarding the nutritional value of native pastures and the improvement in breeder perfonnance by supplementing. Previous projects defined a process for estimating the nutritional quality of the highly variable, native pastures. The current project will streamline that process.

Limited ecological information is available on the native plant species that dominate the Barkly rangelands. From year to year it is observed that the pasture composition changes remarkably from dominant Mitchell grass to dominant flinders grass and annual sorghum a few years later. An automatic weather station is installed to monitor climatic conditions at intervals throughout the day. The seasonal variation in this semi-arid environment is believed to be a factor influencing the change in dominant species. This research aims to increase our understanding of how seasonal variation affects the pasture. This in turn will assist managers to predict and apply sustainable grazing strategies whilst considering the past seasonal conditions.

The project involves collecting data on pasture yield, botanical composition, plant cover, amount of bare ground and includes the actual collection of plant samples to be analysed for nitrogen, phosphorus, metabolisable energy and digestibility.

Results: It is interesting to note that the low yielding sites are not limited in species biodiversity (Table 1). Comparisons of the early dry and late dry season will consider the rainfall received over the previous wet season. The 1995/96 wet season received 243 mm (below average) of rain with the 1996/97 wet season receiving 479 mm (above average).

Minimum and average monthly air and soil temperatures as at the end of May 1997 have been up to 4°C lower in 1996 compared to the temperatures recorded in 1997. Temperature extremes in July 1996 ranged from -1.47°C to 38.81 °C. The warmest air temperature month during 1996 was November with 49.42°C, and soil temperature reaching 44.39°C in January of 1997. It will be interesting to see if the air and soil temperature has a measurable impact on pasture yield and composition. These are the first climatic data sets and over time they will form a base for the seasonal comparisons.

Following the wet season of 1996/97, unpalatable perennial grasses, such as Aristida, increased excepting the site where it was aheady present in 1996. At all sites, excepting Site 1, the percentage of forbs decreased following the above average wet season. Annual grasses were much more abundant early in the dry season of 1997 with their presence making up 31% in 1997 compared to 0.7% in 1996. The percentage of palatable perennial grasses (PPG) in 1996 and 1997 was variable. The sites dominated by PPG remained constant and the sites with a low to medium level ofPPG had either an increase or decrease in the percentage of PPG.

T bl 1 y' Id k /h a e . Ie Kgl a an d b f num er 0 speCIes o d d h recor e at eac assessment SIte. Site 1 2 3 4 5 Oct. 1996 1427 (19) 45 (30) 479 (29) 193 (33) 650 (24) May 1997 2847 (46) 1546 (30) 1936 (43) 1715 (50) 2647 (37)

*****

129

NUTRITIONAL VALUE OF NATIVE PASTURES/SEASONAL PRODUCTIVITY OF NATIVE PASTURES - PART TWO

Project Period: Project Officer: Project Location:

Objective:

1997 - 2000 F Anderson Alexandria Station

From laboratory and field data, estimate the levels of nitrogen, phosphorus and metabolisable energy supplied to grazing animals by native pasture at the beginning and end of the dry season. This will provide a data set of the nutritional value of native pastures on the Barldy Tableland.

Investigate and increase the existing knowledge base on the influence of seasonal variation on native pasture yield, botanical composition and ground cover.

Background: This project is similar to the 'Nutritional value of native pastures/seasonal productivity of native pastures - part one' project excepting that additional data sets are collected. This in depth study includes an extensive number of pasture associations and a detailed collection of water, soil and vegetation resources.

Station managers in the Barkly region have approached Tennant Creek Pastoral staff regarding the nutritional value of native pastures and the improvement in breeder performance by supplementing.

Previous projects defined a process for estimating the nutritional quality of the highly variable, native pastures. The current project will streamline that process.

Limited ecological information is available on the native plant species that dominate the Barkly rangelands. From year to year it is observed that the pasture composition changes remarkably from dominant mitchell grass to dominant flinders grass and annual sorghum a few years later. Automatic weather stations are installed across the trial area to monitor climatic conditions throughout the day.

The seasonal variation in this semi-arid environment is believed to be a factor influencing the change in dominant species. This research aims to increase our understanding of how seasonal variation effects the pasture. This, in turm, will assist managers to predict and apply sustainable grazing strategies whilst considering the past seasonal conditions.

The project involves collecting data on pasture yield, botanical composition, plant cover, amount of bare ground and includes the actual collection of plant, water, soil and faecal samples to be laboratory analysed.

Results: The nutritional value data of the various species and the overall paddock nitrogen and phosphorus summary is still being collated.

The seasonal productivity data (Table 1 and Table 2) will be collected twice yearly to detect year to year changes and variations at the beginning and end of the dry season.

The botanical composition data (Table 2) will be monitoring the type of species that are growing each year to determine how rainfall and temperature influences their abundance. This initial data was collected in the early to mid dry season. The number of species recorded acts as an indicator for biodiversity. The lower yielding sites are not limited in the number of species that occur with some of these sites having the highest level of biodiversity. With a higher site yield it is more likely that there will be a lower number of plant species recorded.

Table 1. Yield (kg/ha) and the number of different s ecies recorded at each site for June 1997. Site 1 2 3 4 5 6 7 8 9 10 II Yield 268 3026 3408 2707 2760 238 258 2977 1897 4344 1653 (kglha) 5 3 1 No.of 49 32 21 44 47 34 37 44 40 29 36 species

130

T bl 2 B a e . I otamca compost ono f 81 es assesse d' J 10 une 1997 Site I 2 3 4 5 6 7 8 9 10 11 % Forbs 5 5 25 10 6 2 2 I 2 2 32 % Annual grass 14 17 66 30 32 85 24 30 43 22 8 % Perennial grass 75 78 8 35 18 13 62 56 30 76 9 % Unpalatable 5 0 0 25 46 0 12 13 25 0 50 grass % Sedge 0 0 0.6 0.2 0.1 0 0 0.1 0 0 0.2 No. of trees 0 0 0 I 0 0 0 0 I 0 4

*****

ESTABLISHMENT AND PERSISTENCE OF SOWN NATIVE GRASSES AFTER THE MECHANICAL CONTROL OF RUBBERBUSH

Project Period: Project Officer: Project Location:

Objectives:

1996 - 1998 F Anderson Powell Creek Station

To determine the effect of grazing and mechanical disturbance of soil on the establishment of sown Astrebla pectinata (barley mitchell grass). To determine the impact of grazing and soil disturbance on the rehabilitation of a degraded black soil area. To increase producer awareness of spelling and reseeding through the collation and distribution of a 'demonstration' package.

Background: The work commenced in association with the local Weeds Officers who are hoping to determine if grasses can provide competition for weed seedlings that emerge after mechanical control. This project will assess the establishment of sown mitchell grass in an area where there is grazing, no grazing, soil disturbance and no soil disturbance.

A fence was erected around an area that contained disturbed and undisturbed land. This exclosure site will demonstrate the benefits of spelling degraded land to assist with revegetation.

Observations will include the regeneration from the existing soil seed bank and from reseeding.

Results: The disturbed-ungrazed reseeded treatment established most successfully (Table1). This means that a combination of soil disturbance and stock exclusion, on black cracking clay soil, increases the establishment of sown barley mitchell grass.

T bilE bl" h a e sta IS ment 0 f sown b I . h 11 2 ar ey mIte e I ,grass per m . Treatment Astrebla peetinatalm2

disturbed-ungrazed 2.27 undisturbed-ungrazed 0.53 disturbed-grazed 0.6 undisturbed-grazed 0.93

Barley mitchell grass can be used in reseeding programs to assist in the rehabilitation of areas affected by high grazing pressures and areas that have had severe weed infestation.

Cattle exclusion is necessary for perennial grass re-establishment (Table 2). When soil disturbance is avoided and grazing is eliminated the number of forbs, palatable perennial grasses and palatable annual grasses able to establish is enhanced. Grazing restricts the establishment of palatable perennial grasses.

131

h Table 2. Comparison of the unsown treatments S owmg natura regeneration 0 f d·ff 1 erent plant species. Treatment Numbe of forbs/15m2 Number of palatable Number of palatable annual

perennial grasses/15m2 grassesl15m2

disturbed-grazed 454 38 87 disturbed-ungrazed 410 65 346 undisturbed-grazed 507 11 422 undisturbed-ungrazed 687 80 511

The low level of newly established palatable annual grasses in the disturbed-grazed treatment could be attributed to those plants that germinated providing 'richer' feed due to the soil disturbance factor. These plants are also more likely to be pulled out of the ground when grazed because the soil structure has been loosened by the action of the cutterbar.

*****

ALICE SPRINGS PASTORAL DIVISION

EXCLOSURES

Project Period: Project Officer: Project Location:

Objectives:

1958 - 1996 A White Alice Springs District

Maintain as long term reference areas, secure and accessible portions of country which are representative of the broad, pastorally productive land types in the district. Demonstrate and document the effects of grazing by direct comparison of grazed and ungrazed portions of the same land type. Demonstrate and document the relative responses to pasture improvement practices on grazed and ungrazed treatments.

Background: The project currently monitors 9 long term exclosures and 3 short term exclosures. The short term exclosures are focused on comparing pasture improvement practices in grazed and ungrazed areas. The long term exclosures have been used to study seasonal responses and grazing impact on the vegetation. The exclosures range in age from 6 to 30 years.

Current work focuses on the second of the three objectives stated above.

Results: A final report was prepared in 1996, with recommendations made for each exclosure.

This project has been terminated. Some of the exclosures used by the project have now been grazed. At other locations, no impact of grazing has been detected, and yet others proved unsuitable for their intended purpose. Some instances of probable grazing impact were identified and as appropriate these will be subject to more intensive study in other projects to clarify the magnitude of the treatment effect.

An inspection of the exclosure at Spinifex Bore on Mt Riddock Station was carried out in early 1997. Similar results were again recorded to those already reported in previous years.

*****

RANGE CONDmON ASSESSMENT (RCA)

Project Period: Project Officer: Project Location:

Objectives:

1976 - 1996 RDance Alice Springs District

132

Record, interpret and provide timely feedback to producers about changes in grazed rangeland which are attributable to seasonal and management factors. In particular to: Monitor rangeland responses to season, management practices and other appropriate phenomena. Derive relationships between management practices, season and the value of rangeland as a grazing resource. Provide advice to pastoralists and government agencies on the productive utilisation of the area's resources.

Background: RCA activities have focused on fixed, 10 hectare sites, but have related the site specific details to the wider area. Sites were established on high productivity land systems or those areas likely to be sensitive to seasonal and management influences.

The sites were reassessed at intervals of one to ten years using procedures outlined by Bastin(1989). Principally, sites were photographed and detailed information collected on soils, herbage, shrubs and trees. Site inspections and discussions with landholders provided information on rainfall, fire and grazing histories. This project was conducted on a lease by lease basis and operated within a framework of goodwill, professional advice and encouragement

Results: Formal data collection and reporting for this project ceased some years ago. At the request of one landholder, a detailed reassessment of the pasture state at each monitoring site on this property was undertaken in early 1997.

While some other requests for similar reassessment have been made from time to time, it is considered unlikely that a great deal of future benefit will be obtained from this type of work. It has been a study which by its nature has asked more questions than it has answered.

More specific projects are now undertaken to address these issues.

The data collected over the duration of the projects is to be collated, but this has not yet commenced.

*****

GREEN COVER REPORTING

Project Period: Project Officer: Project Location:

Objective:

1989 - 1996 RDance Alice Springs

To develop and verify seasonal indices of rangeland pasture growth in Central Australia.

Background: The most significant cause of variation in the productivity of the grazing industry, both in space and in time, is recognised as being due to variation in the suitability of climatic conditions for plant growth. Any action which people may take to enhance the utility of rangelands for livestock is secondary to unpredictable, unreliable and uncontrollable weather influences. It follows that to make any intelligent interpretation of the effects of management, quantification of seasonal conditions is essential. There is currently no altogether satisfactory means of doing this. The available information is either qualitative, spatially sparse, or lacks an adequate interpretation model.

The use of satellite based indices of plant growth provides an opportunity to record production on a regional scale at the "grass roots" stage. Although technical problems persist, this project has already demonstrated the potential of this approach for Central Australia. Other states, and the Commonwealth, have also developed expertise in this area, for their own purposes.

133

Results: Fortnightly data continues to be acquired from the W A Department of Land Administration. It is used qualitatively within the Department from time to time to clarify the extent of seasonal responses. Some field data has been collected in an attempt to refine the calibration of the imagery to observed field conditions, but its worth has not been adequately tested.

*****

ECONOMICS OF TREE AND SHRUB CONTROL

Project Period: Project Officer: Project Location:

Objective:

1987 -1997 A White, G Bohning. Alice Springs District

Continue to evaluate and report on the costs and returns of the use of herbicides and mechanical methods for the control of excess woody vegetation in the Alice Springs area.

Backgronnd: Increase in unpalatable native woody vegetation is a continuing issue within some sections of the pastoral community, particularly to the north of Alice Springs. The dense vegetation competes with native pasture for moisture and nutrients, rendering the affected areas less productive. Mechanical methods of control such as chaining and blade ploughing are recommended as is the use of fire, however limited data has been available in the past on the costs and benefits of these control methods. Granular herbicides have been advocated as another option to the mechanical methods. They have the advantage of being very fast to apply and achieving a high level of control. This method does not require expensive application equipment, nor is there any need to lock country up for extended periods to accumulate fuel for burning.

Trials using the herbicide Graslan® commenced at Alcoota station during 1987 on target species mulga (Acacia aneura) and ironwood (A. estrophiolata) and on Stirling station in 1989 on ironwood and witchetry bush (A. kempeana.) The results achieved on the juvenile ironwood were very encouraging and it become apparent that the control of ironwoods could be achieved at low rates (below 5 kg/ha). Additional plots were thus established on Alcoota and Stirling stations to determine the lowest and most economical rate of Graslan® necessary to achieve satisfactory control of the juvenile ironwood.

The mechanical treatments being considered are those that pastoralists have already applied in an attempt to maintain grassland productivity. These include chaining and blade ploughing. They have been applied to various plant communities dominated by

1. Gidyea (Acacia georginae and A. cambagei) 2. Witchetty bush 3. Ironwood 4. Mulga 5. Turkey bush (Eremophila gilesii)

In the medium term both chaining and blade ploughing have proved to be effective methods of controlling woody weeds in the Alice Springs district. A high mortality has occurred immediately following treatment with most of the target trees and shrubs removed. After 7 years control has been achieved on 75% of the chained sites. Removal of the woody weed has allowed pasture yield to increase in all instances. A link between increased shrub densities and a loss of production has been confirmed in this study. The trial has demonstrated that observed densities of between 1460 - 5400 trees/ha have been responsible for losses in pastoral production.

Results: Incomplete data is not yet available for the season 1996 - 1997, see Technical Annual Report 1995 - 1996 for previous results.

Blade ploughed ( mixed mulga over Triodia sp & mixed mulga with Eremophila gilesii) The 4 blade ploughed sites have continued to show a positive response to the removal of the target species when compared to their respective controls. The mean increase in pasture yield attributed to blade ploughing was 720 kg/ha.

Table 1 Yields and of Target Species SITE LOCATION

906c * Mt Caroline 905t* Mt Caroline 912c Horsepdk 911 t Horsepdk 908c Gimcrack pdk 907t Gimcrack pdk 910c Gimcrack pdk 909t Gimcrack pdk

* c - control sIte t - blade ploughed site nla - not assessed

TARGET SPECIES

mulga/turkey bush mulga/turkey bush mulga mulga spinifex spinifex spinifeximulga spinifeximulga

134

YIELDS 1997 kg/ha

664 1131 550 1224 150 875 100 1114

SPECIES COMPOSITION % annual perennial forbs grass grass

84 15 1 60 29 11 64 23 13 80 17 3 nla nla nla 43 35 22 nla nla nla 24 72 4

The pasture plant buffel grass (Cenchrus ciliaris) was sown in the same operation as the blade ploughing and in all cases significant germination and establishment occurred. A run down affect has recently become apparent on the buffel grass pasture. As a consequence of this, the pastures on the blade ploughed areas are becoming more akin to the native pastures in species composition and frequency.

NEEDLEBUSH RABBIT CONTROL

Project Period: Project Officer: Project Location:

Objective:

1991 - 2000 G Bohning Alice Springs

*****

To undertake an evaluation of the effect of rabbit eradication on vegetation in the CLMA Needlebush Rabbit Eradication Project.

Background: The Centralian Land Management Association (CLMA) has established a 300 km2 rabbit eradication area on Erldunda, Lyndavale and Mt Ebenezer stations. The overall objective of the CLMA program is to show, by establishing a demonstration at the extensive scale, the ecological and economic benefits of combined rabbit eradication and associated grass planting in an area of low and unpredictable rainfall. The role the Department plays is to measure the vegetation responses over the project period following the removal of the rabbits and to calculate the costs and benefits of the control operation.

Results: Through 1994, 1995, 1996, and 1997 rabbit numbers have remained low in all areas. They have continued to remain higher in the untreated area when compared to the numbers sighted on the treated (eradication area) transects. During this period the untreated area has recorded a mean of 1.67 rabbits sighted per linear kilometre. On the treated areas the mean rabbit numbers have remained around 0.257 to 0.616 rabbits sighted per linear kilometre during the same period. The difference attributed to the exercise remains low, while conditions continue to be unfavourable for rabbit breeding and survival. During September 1996 evidence of Rabbit Calici Virus infecting the project was apparent and has further decreased rabbit numbers.

Trends in pasture yields of both the eradication and the untreated areas remained similar. After 6 years of measurements it is difficult to quantify the effect the removal of rabbits has had on the pasture yield. Seasonal conditions, not rabbit damage, appear to have been the overriding factor. With the continued low numbers of rabbits, pasture measurements have ceased and will only be resumed if justified by a large increase in the population of rabbits.

*****

135

ESTABLISHMENT OF REGIONAL TREE AND SHRUB MONITORING

Project Period: Project Officer:

Project Location:

Objectives:

1994-1996 A White from Febrary 1996 R Dance from October 1996 Alice Springs and Barldy Tableland

Establish baseline regional tree and shrub cover data against which future change can be estimated. Establish a network of fixed recording sites to monitor the dual issues of excess woody vegetation ("woody weeds"), and dintinished tree and shrub populations (often attributed to rabbits). This will provide estimates of regional impact and enable the development of a regional strategy.

Background: Excess growth of endemic trees and shrubs can lead to a significant decline in the productivity of pastoral land. Shrub invasion is a serious problem in south-west Queensland and western NSW. The main problem with high tree and shrub densities are reduced pasture growth, increased mustering costs and lower reproductive rates. Conversely, diminished tree and shrub populations, especially in Acacia dominated woodlands can result in reduced soil stability leading to increased soil erosion, less shade for stock and the loss of valuable drought reserve top feed.

Recording of tree and shrub data began in 1981 at fixed recording sites previously established to monitor pasture change. These sites have given an indication of tree and shrub density and cover changes but do not provide valid regional statistics for planning. The current project aims to address this problem using methods previously developed.

Results: The final report of the project is being prepared.

DOCUMENTING SEASONAL CONDITIONS

Project Period: Project Officer: Project Location:

Objectives :

1995 - 1996 A Wilkie and G O'Reilly Alice Springs District

*****

To determine the broad vegetation response to season whilst establishing a procedure which can regularly be undertaken to improve knowledge of pastoral conditions. To draft a brief manual which provides standard procedures suitable for regular seasonal condition surveys. To improve rainfall records for remote areas of the Alice Springs region and to investigate the use of plant/water balance models for the interpretation of rainfall data

1l Plant Growth Modelling

Background: The CSIRO developed ARlDGROW model as an ecosystem model designed for the rangelands of central Australia. ARlDGROW is a simple model that uses the inputs of rainfall and potential evaporation to model daily soil moisture and plant growth in central Australia. It does this by combining three smaller component models; a soil moisture model, a plant growth model and a plant decay model. The objective of this experiment is to validate the ARlDGROW model for a range of pasture communities in the Alice Springs pastoral district. The collection of soil moisture, pasture growth, rainfall and evaporation data will allow a comparison to be made with the ARIDGROW modelled data.

Method: Initially five sites were selected based on geographical location and relative pastoral importance. Two of these sites were later abandoned due to lack of rainfall. All three sites were set up in existing exc\osures located within a 200 km radius of Alice Springs. At each site adjacent pasture and soil plots were established. Rainfall, pasture growth and soil moisture measurements were carried out regularly during the growing season.

136

Results: Calculation of site specific constants used in the soil moisture and plant growth models are currently underway to allow the models to be run and compared to the actual collected site data.

2) Rapid Vehicle Method

Background: To estimate seasonal conditions as they affect pastoral production in Central Australia we need information at the regional scale that can be collected efficiently.

A technique based on the field validation for Queenslands National Drought Alert Strategic Information System was developed for trial in Central Australia as a way of measuring seasonal conditions over a large area in a short time. Pasture yields are estimated from a moving vehicle. Estimates are verified by a calibration procedure.

Results: The technique was used by several field tearns in March 1997. An excellent coverage of the region was achieved with data being recorded on public roads and station tracks through fifty leases in the disttict. After spatial averaging, there were over 600 records to import into a GIS for presentation overlying a regional base map.

The results quantified the 1997 season, and presented this information in a visually effective manner.

Significant progress has been made in the processing and support technology used for this work, allowing for even more efficient data collection and better, more "meaningful", data presentation.

A technical manual of field and data processing procedures is in draft form.

*****

PRODUCTION OF PHOTOSTANDARDS

Project Period: Project Officer : Project Location:

Objectives:

1996-1997 A. Wilkie Alice Springs District

To develop a standardised method of producing photostandards capable of being used for quadrat based pasture yield and cover estimates. To produce a manual detailing the method and equipment used in producing photostandards.

Background: Photographic standards (photostandards) are widely used by NT DPIF staff in central Australia to estimate pasture yield in field assessments. The set of photostandards used was found to be limited in the range of yields and types of plant communities covered. The photostandards were also unsuitable for estimating aerial plant cover as no truly vertical photographs were included in the original procedure.

Results: Over twenty new photostandards have been produced showing a range of pasture species, biomass yields and levels of plant cover. A manual detailing the equipment and methods used in the production of these photostandards is in the draft stage. This manual will be used when producing photostandards in the future.

*****

137

LAND RESOURCE MANAGEMENT DIVISION

WEED STRATEGIES

WEED MANAGEMENT PLANS - KATHERINE AND VICTORIA RIVER

Project Officer: Project Location:

Objective:

M. Ashley Katherine Region

Laodholder consultation and approval of a weed management plan.

Background: The development of regional weed maoagement plans is a mechaoism to implement weed management. A large cross section of the community is directly or indirectly involved in weed maoagement aod the production of a regional weed management plan provides a mechanism to coordinate the variety of activities to ensure maximum community benefit.

Results: For the Katherine district, a draft plan was prepared in 1995196 and returned to the community for comment. Ground mapping and Geographic Information Systems will be utilised to prepare weed distribution maps and quantify the rates of spread.

In the Victoria River District, a second draft document has been prepared and made available for public comment. Final document preparation will incorporate mapping aod distribution aoalysis. This document will be completed in 1998 in accordance with the completion of the National Landcare project.

*****

WEED SURVEY AND CONTROL

ERADICATION OF CLASS A NOXIOUS WEEDS IN THE DARWIN REGION

Project Officers:

Project Location:

Objective:

G. Schultz, O. Sutter, B. Stapleton, T. Randall, G. Hore, B. O'Haolon, E. Conway, G. Flanagan, A. Wilson Darwin Region

To eradicate infestations of all Class A noxious weeds in the region.

Results: The Territory's first infestation of Cabomba caroliniana was discovered at Marlow Lagoon in Palmerston. It was declared a Class A noxious weed and all aquarium retailers and their suppliers have been advised of its status. A joint project to eradicate it from the lagoon by draining aod dredging will commence in September 1997.

Several reports of Salvinia molesta (salvinia) at Shady Camp and Corroboree Billabong on the Mary River proved to be false.

Cutch tree (Acacia catechu), a Class A noxious weed, was planted in the Darwin Botanic Gardens in the 1880s. In the early 1980s, a major operation cleared an infestation of this Class A noxious weed from the hill towards Salonika Street. Unfortunately, plants still occur and on-going control is required. It does not occur anywhere else in the Territory.

*****

138

ERADICATION OF CLASS A NOXIOUS WEEDS IN THE KATHERINE REGION

Project Officers: Project Location:

Objective:

M. Ashley, L. Johns, S. Martin Katherine Region

Eradication of parthenium weed (Parthenium hysterophorus) and other Class A noxious weeds as they occur.

Background: Following the discovery of parthenium weed (Parthenium hysterophorus) in Elsey Creek in 1977, a combination of aerial and ground based herbicide application methods were used to control this infestation.

In 1995, parthenium was found on private property at Collins Road, Katherine. Hand-pulling of emerging seedlings has been used to manage this small infestation. A small parthenium infestation was also discovered in Chardon Street in 1996. It is suspected the seed was imported during road construction.

Results: Ground surveys continued along Elsey Creek, but no plants were found. Eradication will be assumed in 1999 if no plants are found in the meantime.

Hand-pulling of parthenium continued at the Collin's Road infestation. The Chardon Street parthenium infestation was surveyed several times this year and no plants were discovered. Eradication will be assumed in 2001 if no plants are found.

The Katherine Weeds Branch continued the active management of the Class A noxious weeds mimosa (Mimosa pigra) and prickly acacia (Acacia nilotica). Mimosa control continued at two sites and was successful in containing the spread of this species. Control of prickly acacia continued this year. Following aerial surveys all known prickly acacia plants were treated.

Approximately six hundred and fifty hectares of Devil's claw (Martynia annua) were aerially sprayed on Willeroo Station. Strategic control of chinee apple (Ziziphus mauritiana) continued along the Katherine River.

*****

ERADICATION OF CLASS A NOXIOUS WEEDS IN THE TENNANT CREEK REGION

Project Officers: Project Location:

Objective:

A. Gracie, J. McMahon Tennant Creek Region

Eradication of prickly acacia (Acacia nilotica), devil's claw (Martynia annual and parthenium (Parthenium hysterophorus) as they occur.

Results: A two metre high prickly acacia plant was discovered beside a road on Anthony's Lagoon. Seed pods were removed and the plant was destroyed.

Juvenile plants of Devil's claw continue to be detected in two locations on McArthur River Station. One of these areas was treated with residual herbicide while the other area was treated with foliar­translocated spray because of its proximity to native species.

No parthenium plants have been found this year at the only known outbreak of parthenium in the Barkly/Gulf region.

*****

139

ERADICATION OF CLASS A NOXIOUS WEEDS IN THE SOUTHERN REGION

Project Officer: M. Fuller Project Location: Alice Springs Region

Objective: Eradication of Class A weeds as they occur.

Results: Control of the Class A noxious weed Paterson's curse (Echium plantagineum) was maintained in the Alice Springs township and along roadsides in the region.

*****

SURVEY AND CONTROL OF THE CLASS B NOXIOUS WEED, MIMOSA, IN THE DARWIN REGION

Project Officers:

Project Location:

Objective:

G. Schultz, G. Flanagan, O. Sutter, H. Stapleton, G. Hore, T. Randall, B. O'Hanlon, F. Maurer, E. Conway. Darwin Region

To protect NT industries and the environment from the effects of Mimosa pigra.

Results: Field teams continue to provide a range of extension services to landholders, both private and government, while their on-ground work has returned to infestations that can be eradicated and to upper catchment infestations.

The mimosa control assistance scheme supported this objective by providing a subsidy to 22 pastoralists. The Scheme is being reviewed in order to provide a financial incentive for an integrated approach to mimosa management.

The adverse environmental effects of mimosa are being controlled along Sampan Creek in the lower Mary River System. A corridor is being cleared along the banks and both native and introduced grass species sown in its place. Salt water intrusion is stopping the downstream expansion of this infestation. However, the use of barrages to reduce the effect of salt water may lead to a rapid expansion of mimosa.

*****

SURVEY AND CONTROL OF MIMOSA ON ABORIGINAL LAND

Project Officers:

Project Location:

Objective:

G. Schultz, G. Flanagan, T. Randall, G. Hore, F. Maurer, O. Sutter, E. Conway Oenpelli, Arafura Swamp, Wagait Land Trust, Daly RiverlPort Keats Land Trust

To manage mimosa (Mimosa pigra) on Aboriginal land.

Results: Seeding was prevented at all infestations at Murgenella, Mt Borradaile and in the Arafura Swamp where two new infestations were found. A combination of ground and aerial application occurred over the entire Oenpelli floodplain. Some seeding occurred on the floodplain where native and introduced floodplain flora continue to flourish, however, isolated mimosa seedlings and juvenile plants also continue to be found across the floodplain. An aerial survey of floodplains between the Arafura Swamp and Gove failed to locate any mimosa in these areas. Miroosa infestations threatening culturally significant sites and neighbouring properties were treated on the Wagait Land Trust, as were the

140

southern most infestations in the Daly RiverlPort Keats Land Trust. These infestations present the greatest danger of further spread to the south-west.

*****

SURVEY AND CONTROL OF CLASS B NOXIOUS WEEDS IN THE KATHERINE REGION

Project Officers: Project Location:

Objective:

M. Ashley, L. Johns, S. Martin Katherine Region

Improved weed management and awareness.

Background: The program involves the effective management of strategic Class B noxious weed infestations. Strategic infestations are infestations that are isolated and lintited in their current range, but have the potential to spread throughout entire catchment areas.

The management of lantana (Lantana camara) and parkinsonia (Parkinsonia aculeata) continued at strategic sites throughout the Roper River catchment area. Noogoora burr (Xanthium occidentale) management continued along the Katherine River, and lion's tail (Leonotis nepetifolia) control continued in the Victoria River catchment area, with assistance from the Yarralin Aboriginal Community.

The management of these weeds involves aerial and ground based surveys, mapping and monitoring infestations, extensive liaison with appropriate land managers and the release of various biological control agents.

Results: Only previously mentioned Class B infestations were visited this year. The Katherine Weeds Branch is placing a greater emphasis on the management of Class A noxious weeds, because control of these species will provide the greatest economic and environmental benefit to community members.

Roadsides were treated throughout the Katherine Region this year. Unfortunately due to delays in the funding from the Department of Transport and Warks, some areas were not treated at optimal times.

*****

SURVEY AND CONTROL OF CLASS B NOXIOUS WEEDS IN THE TENNANT CREEK REGION

Project Officers: Project Location:

Objective:

A. Gracie, J. McMahon Tennant Creek Region

To manage the impact and spread of noxious weeds.

Results: Khaki weed (Altemanthera pungens) continues to be the most problematic of the region's community weeds. Control was carried out at Renner Springs Roadhouse, Tennant Creek Caravan Park and around Tennant Creek town area.

Rubber bush (Calotropis procera) represents an increasing land management problem on the western Barkly Tablelands. Over 1600 litres of Arsenal mix was applied at Ferguson bore, Powell Creek Station. In addition, 13 hectares of plants were ploughed around the bore using a cutter bar fitted to a D7 bulldozer. Plants were also treated on five other western Barkly properties.

Extensive areas of hyptis (Hyptis suaveolens) were treated along the Borroloola-Wollogorang roadside and along the Calvert Hills road. Other small, isolated outbreaks were also treated in the region.

141

Bellyache bush (Jatropha gossipifolia) has not shown a propensity to invade in lower rainfall areas such as on the black soil plains. However, control work has been active around Borroloola, and at McArthur River and Balbarini stations. New outbreaks were discovered at two areas on Greenbank station this year.

Occasional plants of lion's tail (Leonotis nepetifolia) continue to be hand-pulled at the only known outbreak: in the region, along the McArthur River.

Parkinsonia (Parkinsonia aculeata) remains the major weed of the Barkly Tablelands and was shown in a recent survey conducted by the Department of Lands, Planning and Environment to be the weed of greatest concern amongst the pastoral community in its potential to degrade pastures. Over 1,800 kg of tebuthiuron pellets were applied to large thicket areas across the Tablelands with smaller areas being controlled using mechanical or alternative chemical methods. The seed-eating bioagent Penthobruchus germaini was distributed both in the Gulf and on the Barkly Tablelands.

Mesquite (Prosopis limensis) continues to be a concern on the heavier, clay soils of the region because of its increased incidence. Bulldozing larger plants remains the only effective control method.

Spinyhead sida (Sida acuta) is widespread in the Gulf region. Little chemical control was carried out this year, but Cal/igrapha beetles were released on Kiana Station.

Caltrop (Tribulus terrestris) received similar control efforts to kbaki weed because both species exploit the same environmental niches. Consequently, caltrop is often controlled at the same time as kbaki weed using the same herbicide.

Annual spraying programs for Noogoora burr (Xanthium pungens), following the wet season, focussed on Crown Land areas on Helen Springs Station, and on leasehold land on Epenarra and Alexandria stations. This year, Crown Land infestations on Helen Springs station were aerially sprayed for the first time since 1988.

*****

SURVEY AND CONTROL OF CLASS B NOXIOUS WEEDS IN THE SOUTHERN REGION

Project Officer: M. Fuller Project Location: Alice Springs Region

Objective: hnproved weeds awareness and management.

Results: Survey and control activities were undertaken throughout the Alice Springs region. Emphasis was placed on control of Athel pine on the Finke River and at several other infested sites. Eradication of Athel pine is imminent at several of these minor infestations, including the Ross River.

However, massive seedling germination on the Finke River occurred during 1995 and again in 1996, and this infestation continues to expand. Blade ploughing is now being integrated with chemical control methods for control of Athel pine.

Other priority weeds in the Alice Springs region include Bathurst burr, Mexican poppy, parkinsonia, rubber bush and saffron thistle. Mexican poppy continues to spread out of control down several river systems and control is only possible in key areas such as the Todd River and at Jessie Gap.

*****

142

WEEDS RESEARCH

BIOLOGICAL CONTROL OF MIMOSA

Project Period: Project Officers:

Project Location:

Objective:

1979 - 2001 C. Wilson, G. Flanagan, B. Hennecke, A. Wilson, M. Paskins, B. Hitchins, L. Burrell, B. Luckitsh, in collaboration with CSIRO Division of Entomology Darwin

To reduce the competitiveness, reproductive potential, rate of spread and hence the impact on primary industry and the enviromnent of mimosa through the introduction and establishment of host-specific natural enemies.

Background: Mimosa pigra is one of Australia's most significant environmental weeds, and is a major hindrance to pastoral activities, tourism and public amenity in the monsoonal regions of the Northern Territory. It has the potential to invade. and devastate wetlands in coastal regions across all of Australia's tropics and sub-tropics.

An investigation into the biological control of mimosa commenced in 1979 involving both DPIP and CSIRO.

During 1980-81 the search for natural enemies of mimosa was centred on Brazil, with brief sorties to Mexico, southern USA and Venezuela. Since 1984, the search has concentrated on Mexico, with visits to Costa Rica, Honduras, Venezuela and Brazil.

Progress Report: To date, 8 species of insects and 2 species of fungal pathogen have been imported from Mexico and/or Brazil and released in the Northern Territory as biological control agents of mimosa.

Two species of seed beetle, Acanthoscelides puniceus and A. quadridentatus, are widespread but destroy less than 1 % of the seed. The beetles are reported to be much more effective in Thailand. A colony of A. quadridentatus, originating in Thailand, was released along the Adelaide River in case the difference in perfonnance has a genetic rather than environmental basis.

The leaf beetle Chlamisus mimosae has been established sparsely along the Finniss River for many years, but has occasional population explosions where noticeable damage is caused to mimosa plants. The 1995/96 wet season saw one such flare-up.

The tip-boring moth Neurostrota gunniella spread rapidly from release sites and is now established throughout the range of mimosa in the Northern Territory. It is having an effect on seed production and is also linked with a naturally-occurring stem-dieback fungus, Botryodiplodia theobromae. Field experiments have shown that it concentrates at the edge of mimosa thickets, which is where most seed production occurs.

The stem-boring moth Carmenta mimosa has spread over an area of some 200 km2 from release sites along the Finniss River and up to 10 km from release sites on the Adelaide River. Redistribution of larvae and pupae has been made from established populations to new sites along the Reynolds and Daly Rivers using the artificial diet as a transport medium. Where it is most abundant along parts of the Finniss River, this agent is causing a visible change in the architecture of mimosa infestations. Mature plants in dense thickets are being "pruned" of their top 1m of stems, but the greatest effect is to regrowth following fire or mechanical clearing, and to seedling establishment along thicket edges. Mimosa in these areas remains sparse and stunted under the impact of repeated stem-borer attack. Two landholders have independently reported a thinning of mimosa on their Finniss River properties.

143

Field-collected larvae of C. mimosa were sent to CSIRO Division of Entomology in Brisbane for quarantine clearance before being exported to Indonesia, Malaysia and Vietnam as biological control agents against mimosa.

Two species of bud-feeding weevils, Coelocephalapion aculeatum and C. pigrae, are established along the Adelaide and Finniss Rivers. C. pigrae in particular has reached high population levels and has spread rapidly and widely. It has spread to the Reynolds River and to the southern side of the Daly River some 80 kms from the nearest release site.

Experiments to improve the efficiency of culturing and establishing the fungal pathogen Phloeospora mimosae-pigrae have been successful and resulted in the first aerial application of large volumes of spore solution by helicopter during the 1996/97 wet season.

Releases of the new mimosa rust fungus Diabole cubensis continued at sites along the Finniss River although culturing has proved difficult in Darwin. This pathogen, in contrast with P. mimosae-pigrae, is most active during the dry season. Experiments to increase the efficiency of both culturing the pathogen and establishing it widely in the field, continue.

Releases of the weevil Chalcodermus serripes, which feeds within mature, green mimosa seeds, have continued at sites along the Finniss and Adelaide Rivers.

A weevil that feeds on tiny, immature mimosa seeds, Sibinia jastigiata, has been approved for release from quarantine.

*****

BIOLOGICAL CONTROL OF SIDA SPP.

Project Period: Project Officers:

Project Location:

Objective:

1984 - 2001 G. Flanagan, A. Wilson, L. Burrell, in collaboration with CSIRO Division of Entomology Berrimah Agricultural Research Centre and Katherine Research Station

To reduce the competitiveness, reproductive potential, rate of spread and hence the impact on primary industry and the environment of weedy sida species through the introduction and establishment of host­specific natural enemies.

Background: Spinyhead sida (Sida acuta) is a perennial weed of improved pastures, disturbed areas and roadsides in the Northern Territory. It is a small, erect shrub with a woody, fibrous stem and a deep tap root. It can dominate areas that are heavily grazed, leading to a loss of pastures and a reduction in biodiversity. Flannel weed (Sida cordifolia), spiny sida (Sida spinosa) and Paddy's lucerne (Sida rhombifolia) are other related weeds that can cause similar problems to landholders and the environment.

These sida species are all native to tropical America and have been in Australia for at least 100 years. They are widespread in the monsoonal regions of the Northern Territory.

In 1984, a biological control program for weedy sida species was commenced with the establishment of an exploratory station in Mexico funded jointly by DPlF and CSIRO Division of Entomology. The aim was to search the Americas for damaging natural enemies of the sidas and to introduce into Australia those that passed stringent host-specificity tests.

The sida leaf beetle Calligrapha pantherina was first released onto spinyhead sida in September 1989 at Finniss River Station, and subsequently at several hundred sites in the Northern Territory. The beetle established readily near Darwin. A field study, using insecticides to maintain some spinyhead sida plants insect-free, has shown that Calligrapha beetles can reduce seed production by over 90%, leading to an annual reduction in plant density of more than one third.

144

Dry-season survival can be a problem and so landholders have been encouraged to irrigate an area of sida to maintain beetle populations through the limiting season. However, it has still proved impossible to permanently establish Cal/igrapha in the drier climate of the Katherine region. A stem-boring weevil, Eutinobothrus sp., was introduced in 1994 in an attempt to extend control into drier inland areas.

Progress Report: The second stem-boring weevil, Eutinobothrus pilosellus, was released at several sites around Katherine and Darwin.

During the 1996/97 wet season the Calligrapha beetle was recovered at several sites in the Katherine region for the first time since initial releases in 1989.

*****

BIOLOGICAL CONTROL OF PARKINSONIA

Project Period: Project Officers:

Project Location:

Objective:

1982 - 1997 G. Flanagan, M. Ashley, in collaboration with Roper River Landcare Group and Northern Territory Parks and Wildlife Commission. Roper River Catchment

To promote a coordinated approach to land management in the Roper River catchment, to achieve an improvement in the quality of riparian habitat, and reduce the threat to the pastoral and tourist industries and traditional aboriginal lifestyles through containment and reduction of parkinsonia populations.

Background: Parkinsonia (Parkinsonia aculeata) is a woody, thorny shrub or small tree that can form dense thickets, making areas of land inaccessible for both people and animals. It is native to southern USA, Mexico and Central America, but has become one of the most troublesome weeds in the Northern Territory, especially on the Barkly Tablelands and in the Roper and Victoria River districts.

In 1982 the DPIF, WA Department of Agriculture and the Queensland Department of Natural Resources (formerly Department of Lands) entered into a joint biological control program against parkinsonia. In 1989 a tiny sap-sucking bug (Rhinacloa callicrates) was released in the Northern Territory, but has probably failed to establish. Two species of seed-feeding beetles (Mimosestes ulkei and Penthobruchus germaini) were subsequently processed through quarantine in Brisbane and cleared for release in Australia, but the Department made insufficient resources available to pursue their rearing and release.

The Roper River Landcare Group is a community-based organisation with representation from all pastoralists in the catchment, the Djilkminggan aboriginal community, the Northern Territory Parks and Wildlife Commission, DPIF and other stakeholders. The Landcare Group obtained three years of Federal funding, commencing in November 1994, for a project to achieve an improvement in the quality of riparian habitat along the Roper River through containment and reduction of parkinsonia infestations.

Progress Report: Releases of the seed feeding beetles at numerous sites continued in the catchment. Both species have established though P. germaini is by far the most abundant. P. germaini has been released on the Victoria River and the BarkJy Tablelands and a rearing colony was established at Helen Springs Station. Reports from Queensland indicate that up to 95% of the seed bank is destroyed by these beetles.

*****

145

BIOLOGICAL CONTROL OF SIAM WEED IN INDONESIA AND THE PHILIPPINES

Project Period: Project Officers:

Project Location:

Objective:

1993 - 1999 C. Wilson, in collaboration with Queensland Department of Natural Resources and Nusa Cendana University, Kupang, Timor Darwin, Kupang, Marihat (northern Sumatra), eastern Indonesia

To assist in the management of Siam weed in eastern Indonesia and reduce the threat of Siam weed to northern Australia by establishing biological control agents throughout eastern Indonesia.

Background: Siam weed (Chromolaena odorata), originally from the West Indies, has become one of the world's worst weeds in the tropics of Africa and Asia. It has spread southwards through Indonesia in recent years and now occurs in Timor, Irian Jaya and Papua New Guinea. Until recently it was not known to occur in Australia, but an infestation was discovered on the Tully River in north Queensland, probably originating with contaminated pasture seed from Brazil. An attempt is being made to eradicate it using herbicides.

If Siam weed was to occur in the Territory, it would be one of the most serious threats to agriculture, the environment and property in the Top End through its ability to smother all other vegetation and carry fierce fires.

The successful biological control of Siam weed in eastern Iudonesia may prevent or delay its arrival in the Northern Territory, and the technology and expertise developed on the project will be invaluable should the weed ever become established here.

DPIF collaborated with the Queensland Department of Natural Resources (formerly Department of Lands) in 1993 on a project, funded by the Australian Centre for International Agricultural Research, to achieve biological control of Siam weed in Indonesia and the Philippines.

DPIF was responsible for facilitating this work in eastern Indonesia, and a partnership was formed with scientists in the Faculty of Agriculture at Nusa Cendana University in Kupang, Timor.

Progress Report: The first biological control agent for Siam weed to be available for release in Indonesia was the moth Pareuchaetes pseudoinsulata. A colony was established at Nusa Cendana University and releases of adults and larvae made at several sites. There is no evidence of successful establishment on Timor yet, but the moth is providing good control in northern Sumatra and continued efforts will be made to establish it on Timor.

The second agent, the gall-fly Procecidochares connexa. It is already effective in northern Sumatra causing wide spread dieback. A small number of field-collected galls from Sumatra were carried to Timor and released directly into the field. Establishment has occurred at Pariti and insects have been redistributed to Soe.

A third agent, the butterfly Actinote anteas, is in quarantine at Marihat in northern Sumatra prior to approval being sought for its release.

The project was originally funded for the calendar years 1993-1995 but a favourable independent review has seen a further extension of the project for the calendar years 1997-1999, including Papua New Guinea and with a greater emphasis on eastern Iudonesia. The second phase of this project is being carried out by the Parks and Wildlife Commission of the NT.

*****

146

WEEDS DATA BASE AND GIS DEVELOPMENT

Project Officer: J. Pitt Project Location: Northern Territory

Objective: Establishment of a total system for recording, retrieving and disseminating weeds data.

Backgronnd: The Northern Territory Weed Management Strategy 1996-2001 identified the need to learn more about weeds and to incorporate weed management with other land management practices. Monitoring the distribution of weeds in the Northern Territory is essential for developing sustainable land management practices. Weed distribution data is required by land managers to assist in the development of property management plans and weed control strategies. The development of a weeds recording, data base and mapping system which incorporates Geographic Information System (GIS) and Global Positioning System (GPS) technology will enable improved recording, retrieval and distribution of weeds data at a range of scales.

Progress: During the last three months of the 1996/97 financial year, substantial progress was made towards the development and implementation of a Northern Territory weeds recording system. A full-time professional officer was appointed to manage the staged development of the system, including the assessment and purchase of appropriate hardware and software items, and to consult with potential user groups.

*****

FAART FOLIAR APPLmD ATIffiL PINE RESEARCH TRIAL AND COST EFFECTIVENESS OF BLADE PLOUGHING AND FOLIAR TREATMENTS.

Project Officer: Project location:

Objective:

M. Fuller, J. Pitt Alice Springs Region

Improved Athel pine control

Results: Foutteen foliar herbicides were trialed. Much of the trial was destroyed by flooding and results are not comprehensive. Indications are that irnazypyr at 2% plus glyphosate at 2% and fluroxypyr at 1 % plus Uptake® give the best control.

Chemical control is more cost-effective than mechanical control in lightly infested areas, however, mechanical control in dense infestations provides good control of most trees and access for follow-up chemical treatments of regrowth.

*****

WEEDS EDUCATION & EXTENSION

Project Officers: Project Location:

Objective:

All Weeds Branch staff Throughout the N.T.

To create public awareness of the impact of weeds and their management.

Backgronnd: Effective weed management requires an understanding of the impact of weeds, enhanced skills and commitment by landholders to manage them. Therefore public awareness and education is a high priority under the NT Weeds Management Strategy.

147

Results: Extension inquiries were received from a wide section of the community, including pastoral properties, small block owners, Aboriginal communities, home gardeners, students, other government departments and media representatives.

Extension activities included presentations on weeds at a field day at Alroy Downs, weed management workshops at various centres, displays at shows and property visits. Articles were provided to newspapers throughout the Territory. The annual weeds calendar was produced and distributed to pastoral properties, roadhouses, Aboriginal communities, military organisations and schools. Weeds awareness advertisements were placed in magazines.

Three externally funded Landcare programs were coordinated by the Katherine staff and involved extensive liaison and community education. The Katherine District Farmers Association Landcare program incorporated a Weed Management Field Day which was attended by 47 community members.

Weed Management Workshops were conducted for clients, NT Rural College students, Local Government employees, and Northern Territory Parks and Wildlife Commission staff. A weed identification and control workshop was held for Aboriginal horticulture students from the Mabjunji Resource Centre in Borroloola.

148

RESOURCE PROTECTION DIVISION

PLANT PATHOLOGY

CROP DISEASE SURVEYS - MANGOES

Project Period: Project Officers: Project Location:

Objective:

1994-1998 B Conde, R Pitkethley, M Connelly, L Ulyatt Darwin-Katherine

The aim of this study is to monitor the presences and extent of diseases of mango.

Results: The mango orchards at Berrimah Farm were surveyed in July 1996 to see the distribution of possible carry over sites for post-harvest diseases such as anthracnose (Colletotrichum gloeosporioides) and stem end rot (mainly Botryodiplodia theobromae). Twigs with lesions were collected but yielded only secondary fungi such as Pestalotiopsis sp. and Curvularia sp.

Another survey of the Berrimah orchards on 26 March 1997 showed plentiful symptoms of mango scab caused by Elsino!! mangiferae (see Investigations, below). This was the first time the disease had been seen in the Berrimah orchard. Scab disease appears to have spread to a greater extent in the Darwin area following the gusty wet season rains (including cyclone Rachel). Information gained in this survey supported previous observations of susceptibility of young flush growth and the effect of gusty rains on spread of mango scab within an orchard.

Orchards at Virginia and Acacia Hills were surveyed in April 1997. One had some scab symptoms. Another property at Humpty Doo had mango seedlings in bags declining and dying. Some leaves had marginal lesions of mango scab.

A mango orchard in the Howard Springs area was surveyed in June after the grower reported successful control of mango scab (Elsino!! mangiferae) with a copper spray program. There was no evidence of phytotoxicity even though spray had been applied during flowering and early fruit development. The same grower had reported very heavy losses from scab in the 1996-97 season. The information gained from this survey including that on timing and formulation of copper fungicide will be invaluable in developing recommendations for integrated scab and anthracnose control for the industry.

*****

CROP DISEASE SURVEYS - ASPARAGUS

Project Period: Project Officers: Project Location:

1996-1998 B Conde, R Pitkethley, M Connelly, L Ulyatt and J Duff Darwin-Katherine

On 19 December 1996 following a request from Horticulture Division, Barry Conde visited two asparagus growers at Katherine to investigate reported disease problems. Examination of the crops revealed the presence of two diseases already known to occur in the area, stem anthracnose caused by Colletotrichum gloeosporioides and crown rot caused by Fusarium sp. The visit was mutually beneficial, Barry was able to identify and explain the nature of the diseases to the growers and at the same time was able to gather knowledge that should help in the development of management strategies for the diseases.

On 7 March 1997 Rex Pitkethley and Barry Conde visited Katherine and inspected experimental asparagus at KRS as well as a commercial crop. Damage caused by anthracnose and any other diseases was assessed. Incidence of anthracnose was high because of the effect of the extreme wet season on the disease and the inability of the grower to get onto the crop to spray in the wet conditions.

*****

149

DISEASE SURVEYS - DIEBACKS OF NATIVE VEGETATION

Project Period: Project Officers: Project Location:

Objective:

1996-1998 B Conde, R Pitketh1ey, M Connelly, L Ulyatt, S Smith and J Duff Darwin-Katherine

Examine reports of disease in native vegetation.

Yu1ara and Kata Tjuta (the Olgas) At the request Mr Jake Gillen of ANCA (later Environment Australia) Rex Pitkethley and Stuart Smith (Entomology) visited the Yulara and Kata Tju!a (the Olgas) areas on 8-9 October to examine death of trees in a stand of river red gum (Eucalyptus camaldulensis) and desert oaks (Allocasuarina decaisneana). There were fears that the diebacks might spread. Initial impressions were that (moisture) stress played the major part in the syndrome. Bark and insects collected from affected trees are being examined and a report will be prepared.

Iovestigations of samples collected continued in Darwin. Fungi were isolated from bark samples collected from some of the affected trees. Identification was attempted. The isolates were consistent with described pathogens that are known to be associated with stressed Eucalypts. A report was completed in January 1997 (see publications)

Mr Jake Gillen of ANCA at Yulara reported on 24 March that the trees are improving since recent rains in the area. This fits in with the diagnosis of prolonged drought stress.

Mangarre rainforest Liaison was established with Environment Australia (formerly ANCA) regarding dieback-like symptoms at Mangarre rainforest near Cahills Crossing on the East Alligator River in Kakadu National Park. The area was visited in May 1997 by Rex Pitkethley in the company of Dr Frank Podger (dieback expert and consultant of Western Australia). The mutual conclusion was that the deterioration of the rainforest was the result of earlier fire damage which had killed many of the trees and destroyed the canopy, exposing and stressing the understorey plants which lost their ability to compete and the area then became subject to weed invasion.

Pine Creek Mine rehabilitation assessment Rex Pitkethley visited Pine Creek on 18-19 December 1996 to make a plant health assessment of rehabilitation areas at Pine Creek Goldfields. The plant health assessment was done on a consultancy basis for ERA Environmental Services Pty Ltd which is doing an overall assessment for Fawcett Rehabilitation Services.

A report was prepared for ERA Environmental Services (see publications).

*****

DISEASE INVESTIGATIONS - MANGO DISEASES

Project Period: Project Officers: Project Location:

Post-harvest diseases

ongoing B. Conde, R Pitkethley, L Ulyatt, M Connelly Darwin

Investigations continued into the aetiology and epidemiology of anthracnose and stem end rots in Darwin conditions. Samples from the Berrimah orchard yielded a number of fungi, confirming that dead twigs remaining on the tree can be sources of inoculum of post-harvest diseases. Fungi isolated included Cladosporium sp., Pestalotiopsis sp., Botryodiplodia theobromae, Colletotrichum gloeosporioides, Curvularia sp. and Alternaria sp.

Mango scab In recent years an unfamiliar spotting disease had been observed affecting leaves and fruit on a number of properties. The disease caused increasing concern and initial attempts to determine the cause were unsuccessful.

150

An intensive study of the disease from about September 1996 resulted in the identification of the disease as mango scab caused by the fungus Elsino!! mangiferae (Bitancourt & Jenkins). This was achieved when a very slow growing fungns was isolated from lesions. The appearance of the fungus in culture and the mycelial growth directly observed on lesion surfaces was consistent with E. mangiferae. An experiment to establish pathogenicity of the suspect fungal isolate by inoculation of mango seedlings (fulfilment of Koch's postulates) was successful. In December typical lesions were observed on the seedlings.

Cultures of the fungus and symptomatic fruit and leaves were sent to Dr Mary Palm, an Elsino!! specialist in USA. She confirmed mango scab caused by Elsino!! mangiferae.

Preliminary recommendations for control were gathered and made available to growers as an insert in an agnate.

*****

INDEX ARACHIS INTRODUCTIONS FOR PEANUT MOTTLE VIRUS FREEDOM

Project Period: Project Officers: Project Location:

1995-ongoing B Conde, M Connelly Darwin

New peanut lines imported from USA were screened visually in post-entry quarantine and in addition all plants were indexed onto Phaseolus vulgaris navy bean cv Spearfelt, to satisfy NT peanut mottle virus (PMV) freedom requirements. The peanut lines Georgia Green and Georgia Runner tested so far have been negative for PMV.

FUSARIUM WILT IN HELICONIAS

Project Period: Project Officers: Project Location:

Objective:

1995-1997 (review) J Duff, M Connelly Darwin

*****

Continue investigation into heliconia wilt (caused by Fusarium oxysporum f.sp cubense (Foc) Race 3). Work done previously showed that two Heliconia cultivars exhibited typical symptoms 17 weeks after inoculation: cv. Sexy Pink and cv. Extra Sexy Pink. Fusarium was consistently isolated from these two cultivars.

It was indicated that future work should look at 20 additional Heliconia cultivars commonly grown for cut flowers and also at closely related hosts such as gingers and cannas.

Method: Setting up of the extended cultivar trial in 1996-97 was completed in September 1996 and the plants were allowed to grow before inoculation. Plants were inoculated on 23 May 1997 using infected H. psittacorum rhizomes at a rate of 4/pot buried approximately 15 cm deep. The plants are being monitored for symptom expression.

Another small trial is looking at the effects of two oil-based products, at the request of the local manufacturer, to test the efficacy of these in controlling Fusarium wilt in heliconias.

There was also a demand from growers for these products to be tested. Twenty pots of cv. Sexy Pink were inoculated on 30 May 1997 using infected H. psittacorum rhizomes at a rate of 3/pot buried approximately 15 cm deep.

A small experiment was done to test hot water treatment for disinfestation of heliconia rhizomes. Unfortunately the disease was not controlled even after heating at 50°C for 60 minutes.

*****

151

ASPARAGUS ANTHRACNOSE DffiEASE

Project Period: Project Officers: Project Location:

1996-1998 (review) B Conde, M Connelly, L Ulyatt, R Pitkethley Katherine, Darwin

Stem anthracnose caused by a strain of Colletotrichum gloeosporioides continued to affect asparagus crops in the Katherine area. In order to get some idea of varietal susceptibility or resistance a preliminary glasshouse trial was set up in conjunction with Horticulture Katherine. A fresh isolate of the fungus was obtained from newly collected material from Katherine. Asparagus seedlings of a number of cultivars were inoculated with the fungus.

The data show that no cultivars have any strong resistance or tolerance although in some cases the number of plants was insufficient to get adequate results. Plant Pathology has put forward a proposal that a "disease nursery" be set up at Katherine Research Station to get more realistic data on resistance/tolerance and to trial management practices.

*****

DISEASE DIAGNOSTIC AND INFORMATION SERVICE

DISEASE DIAGNOSTIC SERVICE

Project Period: Project Officers: Project Location:

Ongoing B Conde, R Pitkethley, J Duff, L Ulyatt, M Connelly Darwin

The plant disease diagnostic service is the core function of Plant Pathology Branch which handled 710 diagnostic cases for the year 1996/97. Some of the more interesting diagnoses were:

Mangoes

• Large numbers of mango samples were received. Leaf and stem anthracnose was identified on a number of samples from January to April 1997. Several mango shoots with symptoms of mango scab were identified in February. Katherine samples showed no anthracnose or scab.

Other fruits

• Rambutan dieback: A property at Howard Springs was re-visited in September 1996 following a report of another occurrence of dieback affecting one tree. It was noticed that a number of trees had lesions or cankers towards the base where water from the sprinklers constantly hit them. Affected bark was collected from two rambutan trees and the fungus Botryodiplodia theobromae was subsequently isolated from both samples. This phenomenon, where bark subjected to repeated sprinkler action becomes vulnerable to fungus invasion, may explain similar symptoms seen on other hosts in the past (Barry Conde and Rex Pitkethley).

• Grape vine wilt/death at a Ti-Tree vineyard. Suspected Verticillium sp. (V. dahliae?) fungus was isolated from roots of affected vines.

• Fiji apple (Spondias cytheria) with scab-like lesions, determination in progress.

• Grape vine samples from Katherine with anthracnose caused by Elsinoe ampelina in December 1996.

• Banana samples in December 1996: root rot associated with root knot nematode (Meloidogyne sp.) infestation and in another case dark leaf streaks of unknown cause. Samples of the latter were tested in Brisbane found to be negative for banana streak virus.

• Cashew trees with lower trunk rot caused by Botryodplodia theobromae invasion encouraged by moist conditions created by mulch piled up around the trunk in December 1996.

152

• Citrus Dieback: A citrus dieback at KRS associated with cicada oviposition is being studied for any fungal association.

• Passionfruit: fruit rot identified as anthracnose caused by Colletotrichum gloeosporioides.

• Citrus scab on lemon leaves and twigs from Manton Dam area, caused by Sphaceloma (Elsinoif)jawcetii var scabiosa.

• Banana root and pseudostem disease at a commercial plantation, investigation started in June 1997.

Vegetables

• Capsicum with post-harvest rot due to soft rot bacteria.

• Neptunia oleracea, a water vegetable with discoloured "floats" due to fresh water diatoms.

• Button squash not developing due to excess nitrogen because the farmer changed from urea nitrogen to nitrate nitrogen.

• Root kuot nematode (Meloidogyne sp.) - severe case on snake bean in April 1997.

Ornamentals

• Costus (an ornamental in the ginger family) with bacterial wilt caused by Ralstonia (Pseudomonas) solanacearum.

• Celosia leaf blight caused by Pseudomonas cichorii.

• Gerbera stem rot caused by Pseudomonas cichorii (on same commercial property as above).

• Pythiurn base rot of heliconia, cv J aquinii.

• Wilt of heliconia at a commercial property at Berrimah, caused by Fusarium oxysporum f. sp. cubense Race 3.

• Turf problem: Patchy death of lawn at Rockhampton Downs via Tennant Creek - Curvularia leafspot associated with undetermined stress.

• Ornamental bromeliads with centre rot - Rhizoctonia and Ceratocystis, associated with wet conditions.

Field crops and pastures

• Sorghum with zonate leaf spot (Gloeocercospora sorghi) in January 1997.

• Arachis glabrata with patch death during wet season (January 1997), cause undetermined.

• Blue pea (ClitoTia ternatea) with crown rot caused by Fusarium sp.

• Soybean seed ex Katherine. Had failed to emerge, the mould Aspergillus flavus was present.

• Flower bud death of Mimosa pigra weed with associated mould growth. This was occurring in experimental plants, it had not been observed before. The mould was identified as Cladosporium sp., which is usually a secondary fungus. Original cause of bud death not known, may be insect attack.

• Weed Euphorbia heterophylla with scab-like lesions, determination in progress.

153

Forestry trees

• Trees (several species) in Berrimah Agroforestry plot, sudden death in March 1997. Diagnosed as root rot and lower stem fungal invasion (Macrophomina phaseolina) following extreme wet conditions.

*****

PLANT DISEASE REFERENCE COLLECTION

Project Period: Project Officers: Project Location:

Ongoing R Pitkethley, L Ulyatt, B Conde, J Duff Darwin

Approximately 80 accessions were added to the collection during the year. These were recorded in an accession book as well as the computer data base. Packaging and labelling of dried specimens continued (Lois Ulyatt).

The reference database was utilised for diagnostic work and to provide disease listings in response to requests. The Australian Quarantine Inspection Service and Bureau of Resource Sciences sought information to support negotiations for overseas market access and for the purpose of disease risk assessments.

*****

MANAGEMENT PRACTICES FOR DISEASE CONTROL IN ASIAN VEGETABLES

Project Period: Project Officers: Project Location:

1995-1998 (review) B Conde, R Pitkethley, M Connelly Darwin

The aim is to accumulate data on diseases of Asian vegetables grown locally and control recommendations for them. This is seen as a move toward development of an integrated management regime for these crops. A major problem in snake bean and some other Asian vegetables has been root knot nematode (Meloidogyne sp.). Integrated control is being sought and approaches include use of trap crops such as Crotalaria spp. and cultural practices.

Problems have been encountered in basil, including yellowing and dying in the field as a result of over watering, and root knot nematode (Meloidogyne sp.) on basil at Humpty Doo. A new problem in several plantings was investigated: stem rot and leaf blight symptoms yielded a Fusarium sp. and a possible Colletotrichum sp. Based on symptoms the Fusarium is thought to be F. oxysporum f.sp. basilici which has been reported elsewhere. This will need to be confirmed by host studies or by vegetative compatibility group (VCG) or other analyses. The Fusarium is believed to be the primary pathogen in this case.

*****

ENTOMOLOGY

FACTORS AFFECTING SCALD DAMAGE IN HOT WATER TREATED MANGOES

Project Period: 1993 - 1996 Project Officers: ESC Smith, M J Neal, H Wallace Project Location: BARC; Katherine Research Station; Growers' properties

Objective: To determine the pre- and post-harvest conditions which can predispose mango fruit to suffer scald damage when exposed to an on-farm hot water treatment effective against fruit flies and post-harvest rots.

Background: A Hot Water Dipping (HWD) system for mangoes has been developed over the past 7-8 years. The treatment will:

154

• satisfy quarantine security for fruit flies • significantly reduce the incidence of post-harvest rots • eliminate the use of post-harvest chemicals • accelerate ripening • give other advantages over the currently accepted methods of marketing mangoes for interstate trade.

The main drawback to general acceptance of the technique by NT growers has been the possibility of fruit suffering heat scald. In the past, this damage has been severe enough to prevent marketing of the fruit. Previous work had shown that scald damage was strongly associated with pre-harvest rainfall and that the damaging effects could be ameliorated by field irrigation practices. Post-harvest conditioning by holding for 24 hours (or longer if harvested after rain) or heating the fruit will also decrease the risk of scalding. Work during the 1996 season was aimed at developing a practical preconditioning method to carry out the HWD practice on the farm or at the packing shed.

Results: Several areas of work were conducted during the 1996 season.

1. Conditioning fruit prior to HWD treatment. The previous season showed that even with rain affected fruit, holding at ambient temperatures for 48 hours eliminated the scald problem. In the 1996 season, we tested the effect of preconditioning fruit at 38-40°C prior to treatment. Mangoes were harvested and held overnight at that temperature before immersion in 47°C water within 24 h of harvest. Preconditioning under these conditions shortened the ripening time; increased the appearance and marketability of fruit and decreased the lenticel score when compared with fruit held for 24 h at ambient temperatures before HWD. There was no scald or disease recorded in preconditioned and HWD fruit. Preconditioning without HWD appeared to improve the appearance and marketability of the fruit, decrease lenticel enlargement and, of course, eliminate the chance of scald compared with those fruit held overnight at ambient temperature and then HWD.

2. Determination of heat tolerance in immature stages of fruit fly pest species. A collaborative project between QDPI, Agriculture W A and DPIF will determine the heat tolerance for a range of pest fruit fly species. This work is aimed at identifying the most heat tolerant stage of the most tolerant species of fly to facilitate international trade The Entomology Branch has undertaken to provide data on B. aquilonis. The project commenced in November 1996 and will be completed in 1997.

3. Heating profile of mango fruit - comparison of temperatures at 10 mm below the skin and at the seed surface. In early 1996, an NT organic grower queried why core temperatures are specified for heat treatments while the chemical treatment is thought to penetrate only a short distance beneath the skin. Subsequently, the Interstate Plant Health Regulation Working Group requested that the NT provide experimental data on the heating profile of fruit which compares temperatures at 10 mm below the surface with those at the seed surface. The propensity to produce heat damage in mangoes during disinfestation treatment is dependent on the interaction between time of exposure and the temperature.

A series of experiments were comnducted and temperature profiles were similar and remarkably consistent for all trials. When mangoes preconditioned to a temperature of >36°C were heated in 47°C water, sufficient heat penetrated through the skin to a depth of 10 mm to raise the flesh temperature to 46°C within 36 minutes. To attain the same temperature at the seed surface in all the fruit tested required exposure for an additional 23 minutes. The major factors affecting the heating times were the initial fruit temperature and the water circulation within the dip tanks. Size of fruit had little effect on heating times.

A heating treatment which raises the flesh temperature 10 mm below the skin of mangoes to 46°C and maintains it at that temperature for 10 minutes would significantly reduce the risk of heat damage to the produce.

Work currently in progress (point 3 above) will produce data on the tolerance of immature fruit fly stages to heat exposure. If interstate quarantine authorities are prepared to accept this schedule as a reliable fruit fly disinfestation treatment, the core temperature of preconditioned mangoes should have reached a minimum of 45.5°C.

155

4. Repeat of 1994 and 1995 experiment on fruit from different rootstocks. During 1994, differences were apparent in a Katherine planting but significant differences were not revealed by statistical analysis. The block was originally established to test the effect of rootstock on fruit production and other factors in Kensington Pride mangoes. In the 1995 season, statistical differences in the HWD scalding of fruit from various rootstocks were shown. With little rain during the 1996 season, no differences were apparent. These findings will be assessed by the Horticulture staff at Katherine in relation to other tree and fruit parameters.

*****

ARTHROPOD PROBLEMS ON MANGOES

Project Period: Project Officers: Project Location:

Objective:

1995-1998 ESC Smith, H Wallace, D Chin Top End properties

To identify potential arthropod problems in mangoes.

Background: Mangoes are the most important horticultural crop in the NT and receive a proportionate amount of the Entomology Branch's resources. New problems appear each year as this relatively new crop continues to expand in area and value and new growers enter the production phase. Horticultural officers, commercial mango growers and urban backyard producers frequently refer previously unobserved or assumed pest situations to the Branch for advice or comment and these situations may detect a new or potentially damaging pest problem.

Results: During the year, several arthropod species were identified as new or potentially damaging to mango trees in the Top End.

The two species of fluted scales, lcerya aegyptiaca (Douglas) and I. seychellarum (Westwood) (Homoptera: Margarodidae) previously mentioned (Technical Anual Report 1995/96) continued to expand in distribution and numbers in mango blocks. As described in the next section, the commercially available predatory beetle Cryptolaemus montrouzeri Mulsant (Coleoptera: CoccinelIidae) has given good control of these pests.

Several reports of large aggregations of chrysomelid beetles on leaves and fruit from both the Katherine and Darwin rural regions were received. On one property, ? Agetinus sp. (Coleoptera: Chrysomelidae) defoliated new flush tissue while elsewhere, two species of Aphthona (Coleoptera: Chrysomelidae) were present but no damage was noted.

Melon aphid Aphis gossypii Glover (Hemiptera: Aphidae) was recorded from mango flush in the Katherine area. This is a wide spread species with many hosts throughout the NT. A predatory fly Leucopsis formosana Hennig (Diptera : Chamaemyiidae) was collected feeding on the aphid colonies.

As growers examined their trees more thoroughly, more requests for information on thrips were received. During the last year, Frankliniella schultzei Trybom (Thysanoptera: Thripidae), Thrips hawaiiensis Morgan (Thysanoptera: Thripidae), T. imaginis Bagnall (Thysanoptera: Thripidae), ? T. coloratus Schmutz (Thysanoptera: Thripidae) and Haplothrips sp. (Thysanoptera: Phlaeo-thripidae) have all been collected from flowers. Only the T. hawaiiensis and ? T. coloratus detections represented new records for mangoes in the NT. Redbanded thrips, Selenothrips rubrocinctus (Giard) (Thysanoptera: Thripidae) was recorded from a second commercial property in the Katherine region.

In addition, more detailed investigations involving several other arthropods on mangoes were conducted. The main investigations were:

Investigations on the insect involvement in mango scab disease and the lenticel blowout syndrome In collaboration with the Plant Pathology Branch, The Principal Entomologist was heavily involved in investigations to rule out the involvement of insects in these two disorders. In particular, damage by mango scab appeared superficially similar to that of thrips which may feed on very young developing fruitlets.

156

Fruit fly infestation in mangoes within open trays inside a packing shed The Interstate Plant Health Regulation Working Group requested that the NT conduct trials to determine whether flies could oviposit in fruit left on benches or in open boxes in packing sheds following heat disinfestation treatments.

Initial observations of flies on fruit stored in plastic picking crates within a packing shed and subsequent experiments on placing fruit for exposure at various locations in the shed clearly indicated that B. jarvisi could infest fruit in those situations. It is very likely that the 1995 infestations detected by interstate quarantine inspectors occurred in NT mangoes after hot water disinfestation treatments had been applied and during storage of packed fruit as cartons were placed to build a pallet.

Further investigations on flower caterpillars Following work conducted previously (TAR 1989/90; 1990/91) a series of emerging flower panicles on several properties were tagged and numbered at emergence. These were then examined at weekly intervals (at least) for at least 6 weeks to determine the incidence of flower caterpillar infestation, the abundance of natural enemies and the fate of fruitlets which set on these panicles.

Although infestation was very patchy due to the uneven spread of flowering during the season, the information collected again indicated that fruit set was probably not affected by flower caterpillars during this period; that caterpillar levels of 2-3 per panicle could be sustained without yield loss; but that superficial damage to the fruit (enough to cause downgrading at harvest) could be produced when old inflorescences and larval webbing remained on the panicle long after the caterpillars had pupated.

There was also ample evidence that where growers followed the current recommendations of Bacillus thuringiensis formulations at a high volume of carrier, wetting agent and high pump pressures, very good control was achieved.

*****

PRODUCE INSPECTION AND CERTIFICATION SERVICE

Project Period: Project Officers: Project Location:

Objective:

1994-ongoing ELCrowson Top End annual vegetables, cutflower and nursery properties

To provide an inspection and certification service to growers of annual vegetables, cutflowers and ornamental plants to enable produce to be marketed interstate.

Background: In 1991, NT producers and exporters of annual vegetables, cutflowers and ornamental plants suffered very considerably due to the detection of melon thrips (Thrips palmi Karny (Thysanoptera : Thripidae) on Top End properties. All interstate markets severely restricted access of NT produce until negotiations with interstate quarantine authorities allowed access under declared area freedom or property freedom status.

Over the next few years, the situation eased with other interstate growing areas infested by the pest and the development of disinfestation techniques acceptable for quarantine security. The current situation is that producers exporting to W A, SA and Tasmania require certification of T. palmi freedom for each shipment of produce. This entails visual inspection following physical disinfestation on produce grown in infested areas or maintenance of a trapping program for declaration of area freedom.

In addition, the Entomology Branch maintains a trapping grid for declaration of freedom from poinsettia whitefly (Bemisia tabaci (Gennadius) Homoptera : Aleyradidae biotype B) and surveillance for western flower thrips (Frankliniella Gccidentalis Pergande Thysanoptera : Thripidae).

Results: More than 630 shipments were provided with inspection certificates against melon thrips and some Northern Territory growing areas were regularly monitored to allow certification through area freedom decIarations.

*****

157

INTEGRATED PEST MANAGEMENT IN TROPICAL TREE CROPS

Project Period: 1994/1997 Project Officers: D Chin, ESC Smith Project Location: Top End commercial fruit growing properties

Objective: To demonstrate and encourage the practice of Integrated Pest Management (!PM) on commercial properties.

Background: Through a series of extension exercises, commercial growers were supplied with information to enhance control of artbropod pests in tree crops, particularly mango, abiu, citrus, and rambutan orchards.

Recommendations emphasised an integrated approach using a combination of cultural and biological methods or, when necessary, the application of non-disruptive pesticides. The main pests targeted were fluted scales, mealybugs, thrips, mites and sucking bugs.

Results: The Branch has continued to work toward reduced insecticidal use and further grower acceptance of IPM principles in NT mango plantations. Investigations included the control of Redbanded thrips using soaps and petroleum oils; collecting further data on flower caterpillars and the use of commercially avaliable predators against mealybugs and fluted scales. For example, observation trials were conducted on the introduction of predatory ladybirds to commercial properties for the control of mealybugs and fluted scales on flush tissue. The technique appeared quite successful and further onbservations will be made in the coming season to assess the effect of these predators on mango scales.

Demonstrations of effective IPM practices for arthropod pests in fruit trees have continued. In conjunction with the use of cultural methods and non-disruptive pesticides including biological formulations, mineral oils and high concentration potassium soaps, innundative releases of commercially available biological control agents have been very effective in on-property trials on rambutan and mango trees.

There has been a noticible swing away from acceptance of the more toxic chemicals in favour of less disruptive and "softer" pesticides by many tree crop growers.

!PM trials in mangoes included the application of potassium soaps for control of red banded thrips, and the introduction of Cryptolaemus montouzieri Mulsant (Coleoptera: Chrysomelidae) to establish natural control of fluted scales in a fruit orchard with mangoes, rambutans and abius. Laboratory trials showed that Cryptolaemus was also effective in controlling mango scale, Aulncaspis tubercularis Newstead, (Hemiptera: Diaspididae) and soft green scale Coccus hesperidum L. (Hemiptera: Coccidae).

The green lacewing larvae Mallada signata (Schneider) (Neuroptera: Chrysopidae) was effective in controlling redbanded thrips Selenothrips rubrocinctus (Giard) (Thysanoptera: Thripidae) on mango leaves in laboratory trials. This predator will be tested in the field and may prove to be an important natural control agent for redbanded thrips, mealybugs, fluted scales, twospotted mites and small caterpillars.

A large coloured poster on IPM in mangoes has been finished and submitted for printing. This has been designed to be used in conjunction with DPIP Agnotes.

*****

MANAGEMENT AND CONTROL OF MASTOTERMES IN NORTHERN AUSTRALIA

Project Period: Project Officers: Project Location:

Objective:

1995/1997 L Miller, (CSIRO) MJ Neal, M Hoschke (CSIRO) Darwin, Gunn Point, Wildman area

To develop effective control methods against Mastotermes darwiniensis in horticultural crops that are environmentally sustainable and can be applied by growers or other persons non-expert in termite biology and

158

control. Studies of the biology of the species are being carried out in conjunction with development and testing of control methods so that their effectiveness can be fully assessed.

Background: Mastatermes darwiniensis Froggatt (Isoptera: Mastotermitidae) is the most destructive species of termite in tropical Australia. In Northern Australia this species accounts for about one million dollars in annual production losses within horticultural tree crops and also is responsible for losses in vegetable and agricultural crops.

Mastotermes can also cause major damage to buildings, wooden structures, electrical cables and a variety of other materials.

The main chemical registered for use in horticulture against this pest is an organochlorine. With organochlorines being phased out it is necessary that other alternatives be developed.

Method: A series of plots designed to monitor Mastotermes activity on a seasonal basis were established and monitored at regular intervals.

The data gathered shows that there is a complex pattern of relationships between Mastatermes and other termite species, and between termite activity and temperature/rainfall, but that different termites respond to different environmental factors. Selected plots are being treated with a variety of bait formulations and monitoring of activity will continue until October.

Suitable aggregation techniques have been developed to deliver the current bait substrate (see below) in large quantities to Mastatermes colonies. Preliminary trials with various baits have shown that, although termite activity can be reduced using alternative toxins, quantity of bait delivered is critical.

A bait substrate has been developed which appears to overcome repellency associated with otherwise promising bait toxins. Testing of toxins has been largely confined to those proposed by various chemical companies as suitable for social insect control, but a major restraint has been the availability of such experimental chemicals.

In summary, a suitable bait substrate and delivery system has been developed, but as yet there is no commercially-available toxin to replace the currently-used organochlorine mirex.

Results: 1.Site selection and establishment of Plots

Plots have been established in uncleared areas and have been assessed every 6 weeks over the last 2 years.

Mastotermes darwiniensis Gunn Point I-25m x 5m plots with 192 staIres and 225 stakes Gunn Point 3-7 1m x 1m plots with 121 staIres Wildman River 1-4 5m x 5m plots with 121 stakes

Coptotermes acinaciformis Froggatt (Isoptera: Rhinotermitidae) There are 4 plots 1m x 1m with 121 staIres at Gunn Point Data collected from these plots is essential in assessing new control methods.

2. Biology Laboratory and field experiments are in progress to gather information on the biology of the insect ego colony size, distribution, foraging territory and behaviour.

Such information forms the basis for assessment of the effectiveness of new control methods. For example, there have been claims that termites do not generally forage deeper than about 30 cm, so that a vertical physical barrier will prevent attack. In an experiment to test this theory field studies showed that a barrier to more than twice that depth (70 cm) may be passed.

3. Bait Substrates Various bait substrates have been tested extensively in the laboratory and in field trials with promising results.

159

4. New Chemicals New chemicals have been tested over the past 2 years with some good results. Several of these are currently being tested more intensively in laboratory and field trials.

*****

ARTHROPOD IDENTIFICATION AND CONTROL SERVICE

Project Period: Project Officers: Project Location:

Objective:

1970 - 1999 D Chin, ESC Smith, H Brown Territory wide

To provide accurate advice on identification and control of agricultural and domestic arthropods to producers, government personnel, pest control operators and the general public.

Background: The Branch has provided an advisory service on entomological matters pertaining to agricultural or domestic situations for many years. Over the past few years, the demand for this service has increased dramatically as the number of horticultural producers has increased and fruit trees in suburban gardens mature.

Results: The nature of the enquiry and the recommendation provided are recorded and enquiries entered into a data base. The information recorded may be used for future planning and allocation of research.

During the 1996-1997 period, the Branch received over 1400 enquiries. The proportion of the various client group categories (and the change during the past 12 months) are summarised as follows: Government: 45.0 % (+3.9 %) Primary producers: 21.2 % (-1.5 %) Householders: 17.3 % (-5.0 %) Pest control operators: 1.5 % (-1.1 %) Others: 14.7 % (+3.7 %)

Most of the extension enquiries were associated with services provided on insect identifications and pest control for primary producers and to other officers of the Department. A large majority of the enquiries were based on pests of mangoes (commercial and backyard), mixed vegetables and ornamentals (especially palms). The main investigations on mangoes were associated with termites, redbanded thrips, flower caterpillars, fruit flies and mango seed weevils.

The practices incorporated into Integrated Pest Management systems were encouraged and promoted through trials on fruit and vegetable growing properties. A series of displays were set up in the Department and at the rural shows in addition, lengthy discussions were carried out with growers.

Diagnostic identifications were provided to all outstations of the Department and extension visits were carried out at Coastal Plains, Katherine and Douglas Daly Research Stations to cover enquiries on fruit, vegetables and crops.

*****

BIOLOGICAL CONTROL OF PALM LEAF BEETLE IN COCONUT PALMS AND RE­INTRODUCTION OF A BIOLOGICAL CONTROL AGENT IN THE DARWIN AREA

Project Period: Project Officers: Project Location:

Objective:

1993 - 1997 D Chin, H Brown Darwin area

To determine the level of infestation of Brontispa longissima (Oestro) (Coleoptera: Chrysomelidae) in coconut palms before and after the release of the biological control agent; Tetrastichus brontispae (Ferriere) (Hymenoptera: Eulophidae).

160

Background: Coconut palms in the Darwin area are subjected to heavy infestations of palm leaf beetles (PLB). The Darwin City Council has planted coconut palms extensively as amenity trees along the foreshores throughout the Darwin area. Coconut palms are commonly planted in private gardens as they are attractive palms and are fast growing. Commercially, coconuts are grown as a fruit crop as well as an ornamental in nurseries in the Top End.

Palm leaf beetle is currently controlled with repeated spray applications of carbaryl which is applied to the unopened frond. On very tall coconut palms, the new frond is too high to reach easily and is therefore difficult to spray. Chemical spraying will not eradicate the pest and continual insecticide application is necessary for good control. The use of chemical spraying is expensive, time consuming and harmful to both the environment and the operator.

To reduce the usage of chemical sprays and to control palm leaf beetles in tall coconuts, a biological control agent was introduced. This biological control agent, Tetrastichus brantispae (Ferriere), is a very small wasp that is harmless to humans but is effective as a parasite of palm leaf beetles. T. brantispae parasitises PLBs by laying eggs into the late instar larvae or early pupae. The eulophid eggs hatch and develop into larvae which feed and pupate inside the beetle pupae and then emerge as adult wasps.

T. brantispae was first introduced into Darwin and Palmerston in 1982 and survived for about five years. In 1994, the Entomology Branch of the Department of Primary Industry and Fisheries re-introduced the parasitoid as field releases into selected Darwin City Council sites along the Darwin foreshores.

Study Sites: A total of seven sites were selected from the coconut tree plantings in Darwin City Council amenities sites (Table 1). These areas included picnic sites, street plantings, experimental plantings and parks. Most of the sites were situated close to the foreshore.

Table 1. Study sites selected for monitoring the PLB infestation levels.

Site No. Location 1 Cullen Bay 2 Mindil Beach 3 East Point Reserve 4 Coconut Grove 5 Nightcliff West 6 Nightcliff East 7 near Nightcliff Pool

Method: The eulophid wasp Tetrastichus brantispae was reared in mass numbers in the laboratory and released at selected sites of coconut palms along the Darwin foreshores. T. brantispae was re-introduced to Australia and the NT and reared in mass numbers in the laboratory and released at selected sites in Darwin, commencing in October 1994.

The release sites included: site 1, Cullen Bay; 2, Mindil Beach; 4,Coconut Grove; 6, Nightcliff East and 7, near Nightcliff Pool. An extra release site was established at Berrirnah Research Farm. T. brantispae was not released at East Point Reserve (site 3) and Nightcliff West (site 5) and these two sites were used as control sites to show the effect of PLB on coconut palms in the absence of T. brantispae.

Monitoring in most of the sites commenced 12 months prior to the introduction of the parasitoid (ie about March 1993). The sites were monitored and scored at intervals of 6-8 weeks pre and post release of the parasitoid. At each site, 12 coconut palms were selected randomly for assessment. The infestation rate of the palm leaf beetles in coconut palms was assessed by scoring the % damage of the first opened leaf frond. (A new leaf spear is produced approximately every 6-8 weeks).

Releases of T. brantispae at the selected field sites were carried out at intervals of 1-3 weeks. (Releases were made every week, alternating between sites from week to week.) At the time of release, observations were made on the population numbers of PLB in the new leaf spear of the coconuts. The sites were assessed and monitored every 6 weeks, or at intervals when there was new shoot growth.

161

Results: Monitoring of PLB damage levels This involved comparison of the palm leaf beetle population in the field pre and post release of the parasitoid

The PLB damage levels of the palms were assessed from March 1993 to March 1997 (4 years) at approximately 6-8 weekly intervals (Figure 1 and Table 2).

The information in Figure 1 and Table 2 was compiled by calculating the mean score damage of 12 coconut palms from each site for each period and show the change in the PLB infestation rate pre and post introduction of the parasitoid.

Release sites There was a 20% decrease in the level of damage at three of the release sites, Cullen Bay, Mindil Beach and Nightcliff East.

Unfortunately, site 4 did not have a damage assessment before release, however, it was estimated from observations to be about 60%.

At the site near Nightcliff Pool, the PLB damage level pre-release remained the same as post-release.

Non-release sites In the sites that have not had a release of T. brontispae, (site 3, East Point and site 5, Nightcliff West, the damage levels fluctnated from 0-60% at site 3 and 1-80% at site 5.

A comparison of PLB damage levels pre-release and post release are shown in Figure 1.

Effectiveness of parasitoid establishment (success ofrecaptnre) Over 13 000 adult T. brontispae were released in the selected sites between October 1994 and April 1996. At 6-8 weekly intervals, coconut palms at the sites were inspected for parasitised PLB pupae.

Samples of pupae (healthy and parasitised) were collected and reared in the laboratory. Between January 1996 and March 1997, eulophid infested PLB pupae were recaptured from all of the release sites.

Figure 1. The infestation level of Brontispa /ongissima, pre and post introduction of Tetrastichu5 brontispae

4

" ~

.c " 3.5 ~ c 0 0 3 ~ u

0 1l. u 2.5 .. "" E " C 2 as c e ~ ~- 1.5

- >- 1 ,,-0.5 > ;;:

" " ..J C 0 2 3 4

Site number

-parasitoid = pre release of parasitoid +parasitoid = post release of parasitoid

5 6 7 1m -parasitoid

• +parasitoid

162

Table 2. Summary of the change in PLB damage to coconut palms at the study sites since the release of the eulophid parasitoid.

Site No. Level of PLB Infestation

Pre-parasitoid Post parasitoid Parasitoids Change in PLB release release released infestation level

(Yes! No) since the release of the parasitoid

1 4 3 Yes decreased 20% 2 3 2 Yes decreased 20% 3 I 2 No increased 20% 4 - 3 Yes -5 4 2 No decreased 40% 6 3 2 Yes decreased 20% 7 2 2 Yes no change

If T. brontispae survives over the 1997 dry season it may have adapted to the Top End climatic conditions. It is not known how long the parasitoid will be able to sustain its populations in the released sites. When T. brontispae was released in Darwin and Palmerston in the 1980s, it died out after five years, presumably because the strain was not adapted to the dry season.

Conclusion: The biological control of B. iongissima with T. brontispae has been more effective than using chemicals. T. brontispae has established in all five monitoring sites in the Darwin area and has reduced the PLB damage by up to 40%. The parasitoid will have a greater chance of survival, in areas that have overhead irrigation throughout the dry season. A second parasitoid such as the larval parasitoid, Asecodes sp, released in areas with T. brontispae may be more effective in controlling B. longissima over a longer term.

*****

ARTHROPOD REFERENCE COLLECTION

Project Period: Project Officers: Project Location:

Objective:

1970 - 1999 H Brown, D Chin, ESC Smith BARC

To develop, curate and maintain a reference collection of economically important arthropods of the various NT agricultural industries and to develop and maintain a suitable, retrievable data base of all specimens held in the collection.

Background: The insect reference collection was initiated in 1970 and rapidly became the main Insect Reference Collection in the NT. Over the years, the collection expanded to include economically important arthropods from agricultural and domestic situations as well as general collections. In 1992, the majority of the non-economic insect specimens were donated to the NT Museum.

Results: Duriog 1996!97 the Branch forwarded 219 specimens for species confirmation or identification. Most specimens were of economic significance.

The majority of the specimens in the collection have been sorted and some updated with name changes. Computerisation of the museum specimens onto the network (ACCESS Database) is continuing. At this stage over 12000 specimens have been recorded on the database, which is about 55% of the entire collection.

163

New Records and Specimens of Interest:

Thysanoptera: Thripidae • Chaetanaphothrips signipennis (Bagnall) ex Anthurium sp. and flower bell of Musa sp. • Thrips hawaiiensis Morgan ex Mangifera indica inflorescence (Kensington Pride and Irwin) • Frankliniella schultzei Trybom collected from Citrus grandis flowers • Selenothrips rubrocinctus (Giard) was recorded feeding on the frnit of Nephelium lappaceum • Dichromothrips corbetti (Priesner) causing damage to "vanda" orchid flowers.

Acarina: • Tyrophagus palmarum Oudemans (Acarina: Acaridae) on calyx of mangosteen fruit. This species is often

found feeding on mould and detritus and is common around all types of stored products • Damage on badly scarred mangosteen fruit forwarded for examination appeared to have been caused by

mites during the dry season. The mites causing the damage were no longer present but oribatid mites (fungus feeders) were collected and identified as Brachypylina: Poronota: Oripodoidea.

Hemiptera: • Aphis gossypii Glover (Aphididae) has been confirmed from Mangifera indica (new flush leaves) and

Gossypium hirsutum leaves. Both samples were collected from the Katherine region • Aonidiella orientalis (Newstead) (Diaspididae) ex leaves of Dendrobium rigidum • Coccus hesperidum Linnaeus (Coccidae) ex Mangifera indica seedling leaf (Glenn var.) • Maconellicoccus hirsutus (Green) (Pseudococcidae) ex asparagus plant stems • Pinnaspis strachani (Cooley) (Diaspididae) ex asparagus plant stems • Aonidiella orientalis (Newstead) (Diaspididae) ex Solanum melongena stem • Parasaissetia nigra (Nietoer) (Coccidae) ex asparagus stems.

Coleoptera: • Coccinellidae beetles swarming and aggregating in mango trees were identified as Aphthona spp.

(Chrysomelidae).

Diptera: • Larvae of the predatory fly Leucopis formosana Hennig (Chamaemyiidae) which were feeding on Aphis

gossypii Glover (Hemiptera: Aphididae), were collected from mango leaves in Katherine.

BEANFLY

Project Period: Project Officers: Project Location:

Objectives:

1995 - 1997 Young, G., Zhang, L. Darwin area

*****

To identify the wild and cultivated host plants of bean fly, Ophiomyia phaseoli (Tryon) (Diptera Agromyzidae). To identify the parasites of beanfly. To investigate methods of control of beanfly in snake bean crops.

Background: Bean seedlings must be sprayed twice with dimethoate in the week after emergence. Failure to spray can result in high mortality of the seedlings.

Data from East Africa and India suggests that a reasonable level of control is exerted by the parasitoid Opius phaseoli Fischer (Hymenoptera: Braconidae).

Before any consideration can be given to importing an exotic parasitoid such as O. phaseoli, a thorough survey of the indigenous parasitoids needs to be carried out.

Nothing is known of the wild host range of beanfly in the Northern Territory.

164

Results: Spray trials to find an alternative to dimethoate were inconclusive. The formulation trialled was imidacloprid flowable, applied as a seed dressing. The formulation proved difficult to handle and it is unlikely to find commercial use in its present form.

A range of parasitoids have been reared from beanfly puparia, none of the parasitoids belonged to the genus Opius. The parasitoids reared from beanfly puparia collected on snake beans were; Pteromalidae sp? and Tetracampidae sp?, while those from puparia collected on phasey bean were; Eurytoma sp? and Pteromalidae sp?

Cultivated host plants of beanfly identified were snake bean, Vigna unguiculata and phasey bean, Macroptilium lathyroides.

Wild hosts of beanfly are; Vigna radiata, beanfly oviposited and completed its life history. Vigna vexillata, beanfly freely oviposited and fed on the oviposition punctures, but was unable to complete its life history. Both species of Vigna are indigenous to the top end.

*****

MONITORING POINSETTIA WHITEFLY IN PROTECTED CULTIVATION

Project Period: Project Officers: Project Location:

Objective:

1995- 1996 G Young" L Zhang, NT Orchids, Berrimab

To monitor the population dynamics of the whitefly, Bemisia tabaci Type-B, and record any natural enemies.

Background: Bemisia tabaci type B was first recorded from the Northern Territory during October 1994. From the insect's pest status overseas it was predicted that it would become a serious pest in the top end.

Method: Ten potted rockmelon plants were exposed for 5 or 6 days each month from July 1996 to December 1996 in a nursery infested with whitefly. Overlapping melon crops at Berry Springs were monitored at monthly intervals from June to September 1996. One hundred plants being sampled on each occassion.

Results: Numbers of whitefly peaked during September. During the two years of the study the lowest numbers were recorded during the period January to April and numbers peaked during September/October and May. October and May were the only months when the whitefly was recovered from cucurbit crops in the field. Natural enemies recorded were: the fungus, Verticillium lecani, the nymphal parasitoids, Eretmocerus sp. (Hymenoptera: Aphelinidae), a another species of? Aphelinidae and Signiphoridae sp. While B. tabaci type B is a minor pest of protected cultivation in the Darwin area, there is no evidence to suggest that the whitefly is likely to become a pest of broadacre crops in the top end. In nurseries the main host plants are mainly ornamentals of neotropical origin, such as Duranta sp., Euphorbia spp., and some Hibiscus hybrids.

***** ROOT KNOT NEMATODE Project Period: 1997 - 1999 Project Officers: G Young,., Zhang, L., E. Crowson. Project Location: Humpty Doo

Objective: To control Root knot nematode Meloidogyne spp., by planting a completely resistant cover crop over the wet season.

165

Backgrouud: Meloidogyne spp. is apparently endemic in virgin soils around Darwin. After several crops of snake bean or cucurbits, populations of Meloidogyne spp. build up to the point where it is no longer possible to grow either of these crops. The problem is more severe on the better soils containing some clay.

Methods: A property in Humpty Doo have been selected for a trial in cultural control. The soil in the area concerned has a history of nematode infestation. Soil samples will be taken in early October 1997 to estimate the populations of Meloidogyne. The soil will be ploughed with a chisel plough, as soon as there is sufficient soil moisture, probably during October 1997.

During December, "Jumbo Hybrid" forage sorghum will be sown. Jumbo hybrid is completely resistant to Meloidogyne spp. The object is to deny the nematodes a host over the wet season. The crop will be slashed before flowering and eventually ploughed in during late March. A second estimate of Meloidogyne populations will be made in early April.

Results: Some useful results were obtained from last years experiments, but there was no indication as to whether to the forage sorghum method of nematode suspression would work in the top end environment. Pre-planting counts of nematodes were made on two of the three properties during October 1996. Sorghum was planted on one of the properties but the seed was washed out by heavy rain. The major problem with these experiments was the disinterest shown by two of the three cooperators.

*****

PARASITES OF THE COWPEA APHID AND THE MELON APHID

Project Period: Project Officers: Project Location:

Objective:

1996 - 1998 GYoung, LZhang Darwin area

To survey the parasites of the cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphididae) and the melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae).

Background: The cowpea aphid is a serious, if intermittent pest, of snake beans and some pasture legumes. The melon aphid attacks a wide range of cultivated plants including cucurbits. With the melon aphid, virus transmission may be far more important than direct damage to crops. In southern Australia, both cowpea and melon aphid are attacked by a parasitoid, Aphidius colemani (Hymenoptera: Braconidae) which appears to have been an accidental introduction from Asia Minor or India. Recently, A. colemani from Canberra was successfully introduced into Tonga, where the parasitoid established on A. gossypii.

The cowpea aphid is easily conrolled with pirmicarb, a specific aphicide which does not harm other insects and is a component of integrated pest management. The melon aphid has shown widespread resistance to insecticides in other parts of Australia, but the level of resistance in the NT is unknown. If introductions of natua! enemies are to be considered in the future as an alternative to chemical control, then it will be necessary to have some data on the natural enemies already present in the NT.

Results: Several species of parasitoid have been recovered from melon aphid, while no parasitoids were recovered from cowpea aphid. One parasitoid reared from melon aphid was identified as Aphelinus gossypii, known to be polyphagus parasitoid. Predators recorded feeding on melon aphid were; a lacewing, Chysopidae sp. and the mirid Deraeocoris sp.

A shipment of aphid mummies containing parasitoids was recieved from C.S.I.R.O. in December 1996, but none of the parasitoids reared were A. colemani. Most of the available evidence would suggest that A. colemani prefers a cooler climate than the top end.

*****

166

INSECT DAMAGE ON CONVENTIONAL AND REDUCED TILLAGE PLOTS AT DOUGLAS DALY RESEARCH FARM

Project Period: Project Officers: Project Location:

Objective:

1996 - 1998 G R Young, ESC Smith Douglas Daly Research Farm

To determine the reason for greater insect damage in no till crops by comparison with crops planted by conventional cultivation.

Background: No-till crops planted at Douglas Daly Research Farm and on commercial properties in the Douglas/Daly area have consistently suffered greater insect damage, post-germination, than crops planted by conventional cultivation. The mortality of seedlings is sufficient to threaten the acceptance of no till cropping.

Methods: An agronomic trial, tilVno-till, has been running since 1983/84 in the rotgut paddock of Douglas Daly Research Farm. There are 3 replicates of each treatment, tilVno till. Nine pitfall traps were placed overnight in each replicate and the catch sorted the next day. The invertebrates captured were sorted to Order and Family, and, in the case of ants to Genus and Species. Additional observations were made on each plot in the last week of December, one week post-emergence.

Results: Preliminary analysis of data collected suggested that there were no differences between the fauna trapped from no-till and conventional till plots. This result contrasted with information from more temperate areas where no­till plots have more predators than conventional till plots. The result at Douglas Daly Research Farm is probably due to the small differences in the organic matter content of the soils between no-till and conventional-till plots.

During the 1995/96 growing season, the percentage of insect damaged sorghum plants in no-till and conventionally tilled plots were 20.1 % and 3.8% respectively.

During the 1996/97 growing season the pasture legume Cavalcade (Centrosema pascorum) was sown in the trial. In the conventionally cultivated plots the mean emergence/establishment and the proportion of plants suffering insect damage was 16.1 plants per metre row and 5.4% respectively, while no-till plots had 12.6 per metre row and 16.4% damaged.

The results for the 1996/97 season conflrmed the previous year's observations that reduced tillage plots suffered more insect damage than the conventionally cultivated plots.

The pitfall trapping and post-emergence observations will continue for at least another year. *****

INTEGRATED PEST MANAGEMENT OF VEGETABLES WITH PARTICULAR REFERENCE TO SNAKE BEAN

Project Period: Project Officers: Project Location:

Objective:

1995/1998 G Young, L Zhang Darwin area

To control two spotted mite and other bean pests by means of natural enemies and safe pesticides.

Background: Two spotted mite (TSM), Tetranychus urticae Koch (Acarina: Tetranychidae) is the most serious pest of snake beans (vigna unguiculata) in the Darwin area usually limiting the productive life of the crop to less than 6 weeks. Two spotted mite is resistant to a greater or lesser extent to all of the available miticides.

167

A non chemical method of controlling two spotted mite is by the use of the Chilean predatory mite, Phytoseiulus persimilis, Athias-Henriot (Acarina: Phytoseiidae). The predatory mite is reared commercially in NSW and Queensland. When TSM appears on the crop predatory mites are released and the population of predators brings the TSM population under control.

Leaf feeders can be adequately controlled with either carbaryl, to which P. persimilis is resistant, or Bacillus thuringiensis.

The cowpea aphid can be controlled with pirimicarb which is only active against aphids.

Results: P. persimilis brought two spotted mite under control within 3 weeks of introduction to the crop, extending the productive life of the crop for up to 5 weeks longer than normal. Two percent petroleum spray oil or the miticides fenbutatin oxide and propargite were used to retard the rate of increase of TSM and allow the predator populations to catch up with the prey.

All of these substances are relatively non toxic to the predatory mite.

Predators of two spotted mite recorded were; mites belonging to the families, Phytoseidae, Cunaxidae and Chaetodactylidae?; Scolothrips ?sexamaculatus (Pergande) (Thysanoptera: Thripidae); Feltiella acarivora (Zehntner) (Diptera: Cecidomyiidae).

*****

MELON THRIP INTEGRATED PEST MANAGEMENT ON EGGPLANT

Project Period: Project Officers: Project Location:

Objective:

1996 - 1998 G Young, L Zhang Knuckey's Lagoon

Control of melon thrip, Thrips palmi Karny (Thysanoptera: Thripidaelon eggplant.

Background: Thrips palmi has proved resistant to a wide range of pesticides. Bioassays using potassium soaps showed a high level of activity against the nymphs and adults of Thrips palmi.

Results: Three applications of potassium soap at weekly intervals reduced the number of Thrips palmi nymphs from over 200 per leaf to 2 per leaf. The control rows remained at greater than 200 nymphs per leaf.

A study of the popUlation dynamics of T. palmi on eggplant at Knuckey's Lagoon showed that populations started to increase in late June and early July. The populations remained high until January when numbers suddenly decreased and remained low for the rest of the wet season. The reason for the decline in numbers over the wet is thought to be high pupal mortality in damp soil.

When populations of T. palmi on eggplant were suppressed with three applications of potassium soap, the pest's predators were able to keep it under control. Predators of T. palmi recorded from the Kuckey's Lagoon property were; Chrysopidae sp.; the mirid, Deraeocoris sp. and Haplothrips sp.

While !PM of T. palmi proved successful during the dry season, the eggfruit caterpillar (Seeloides cordalis, Doubleday, Lepidoptera: Pyralidae) increased in numbers in the absence of chemical controls.

Routine spraying for eggfruit caterpillar would destroy the natural enemy complex of T. palmi. More work is required on control methods for the caterpillar, particularly destruction of infested fruit and spot spraying of flowers and fruit with endosulfan or methomyl.

*****

168

CITRUS ENTOMOLOGY

Project Period: 1996-1999 Project Officers: ESC Smith, D Chin Project Location: Top End commercial citrus properties and Research Stations

Objective: To identify potential pest species and their control and to encourage the practice of Integrated Pest Management on commercial properties.

Background: The area planted to citrus in the Top End and in Central Australia is increasing annually. The Branch has frequently been requested to advise on pest situations in citrus orchards but has rarely been involved in research programs.

Recommendations have emphasised an integrated approach using a combination of cultural and biological methods or, when necessary, the application of non-disruptive pesticides. The main pests targeted were citrus leaf miner, scales, mealybugs, thrips, mites, fruit piercing moths and some leaf feeding caterpillars.

Results: Citrus leaf miner is found in most citrus growing areas of Australia but the level of control for this pest by indigenous natural enemies is generally very low. Three species of parasitic wasps, Ageniaspis citricola (Hymenoptera : Encyrtidae), Citrostichus phyllocnistoides (Hymenoptera : Eulopidae) and Cirrospilus quadristriatus (Hymenoptera: Eulopidae), were imported from China and Thailand and released into eastern and southern States of Australia during 1990 and 1991.

Over a five week period in March - April 1997, batches of these three parasitoids were introduced from S-E Queensland to citrus blocks in both the Katherine and Kununurra \W A) areas in an attempt to establish populations which could control the leaf miner. The levels of citrus leaf miner before and after release were recorded.

This trial is reported in more detail in the Horticulture Division Technical Annual Report.

Adults of a weevil, Myllocerus sp. (Coleoptera: Curculionidae) which commonly feed on flush tissue of other hosts were recorded for the first time on citrus.

Information on major and minor pest species in the NT was supplied to the authors of a book to be published by QDPI and HRDC. This book, entitled "Citrus pests and their natural enemies - Integrated pest management in Australia" will shortly be released.

*****

ASSOCIATION BETWEEN CICADA DAMAGE AND CITRUS DIEBACK

Project Period: 1996-1998 Project Officers: ESC Smith, M Hoult, B D Conde, J Grigg Project Location: Katherine and Darwin commercial citrus properties and Research Stations

Objective: To examine the role of cicada damage in the initiation of citrus dieback.

Background: Over the past few years occasional reports of elongated lesion damage to recently expanded flush shoots on young trees of several citrus varieties have been received. Reports emanated from both the Darwin and Katherine region with Clementine mandarins and super-red grapefruit particularly affected. There were frequently 3 - 4 or more lesions, each 5-6 mm long and 2-3 mm wide on a twig orientated in a line along the upper surface of the shoot and with 10-20 mm of undamaged tissue separating them. When noticed, much of the damage had calloused over, leaving a "lens-shaped" split in the bark. Under microscopic examination, the internal vascular bundles within the shoots were seen to be severed and old empty cicada egg shells were embedded amongst the "frayed" end of the bundles. Dieback and subsequent exudation of gum from the affected twigs was common on some trees. The physical damage was thought to be caused either by cicada adults laying eggs into the hardening shoots in December or by the emergence of the nymphs from the eggs and plant tissue

169

some 2-3 months later. Since the latter period would be during mid-late wet season, disease organisms could enter the damaged shoot and perhaps cause twig dieback.

During late November 1996, heavy emergence of cicadas occurred on two citrus blocks at Katherine and adult feeding and ovipositing was particularly prevalent on lemons and mandarins. Between 10-100 % of hardened flush shoots were damaged on 50 - 80 % of all trees. The damaged shoots were largely pruned off in one commercial block while on the Katherine Research Station, most damaged shoots were tagged without pruning. Specimens of cicadas were collected for specialist identification.

Results: Two species of cicada, Abricta castanea Distant and Illyra hilli (Ashton) (Hemiptera: Cicadidae) were identified as feeding and laying eggs into hardened flush tissue of citrus during early December 1996.

On the commercial property, very little dieback subsequently occurred within the citrus trees but on the Station where the affected shoots were not pruned off, many (> 50%) of the damaged shoots had developed typical "dieback"symptoms with rusty-red coloured gummy exudates when examined some 3 - 4 months later. At that time, diseased and non diseased shoots were excised and taken to Darwin for pathological testing.

The disease organism Colletotrichum gloeosporioides Penz. was consistently isolated from one sample of damaged shoots from various trees which exhibited dieback symptoms. C. gloeosporioides usually grows as an endophyte or latent infection within plant tissue and does not express itself until the tissue ages. The fungus is unlikely to be the primary cause of the dieback symptoms, but rather the fungus expresses itself on damaged or dying tissue.

DISSEMINATION OF INFORMATION

Project Period: Project Officers: Project Location:

Objective:

Ongoing All Branch Officers Territory wide

*****

To provide relevant agricultural entomological information to a range of clients.

Backgrouud: The Branch is the main provider of agricultural entomological information relevant to the Northern Territory. All primary producers and the general public may request information on a wide range of insect pest problems and this information is normally provided in the form of original or annotated Departmental Agnotes, extracts from published works or illustrated talks and lectures.

In addition, the Branch provides data on arthropod occurrence and distribution to National and International organisations and this is frequently used for pest management or trade purposes. In conjunction with the NT Parks and Wildlife Commission, all applications for the introduction into, or release from, quarantine of biological control agents used against agricultural pests, diseases and weeds are reviewed by the Branch as part of an Australia wide assessment.

Results: During the year, separate reports were provided to the Australian Quarantine and Inspection Service on host and distribution data of both quarantinable and non-quarantine organisms in the Northern Territory. These included associations of arthropods on tomatoes and minor (in the NT) ornamental crops which will assist in the negotiations for potential market exports.

Updates and comments on the complete fruit fly host list for the NT were supplied to QDPI which is co­ordinating the response for all fruit flies within Australia for HRDC and AQIS.

Information on the major and minor pest species of citrus in the NT was supplied to the authors of a book to be published by QDPI and HRDC. This book, entitled "Citrus pests and their natural enemies - Integrated pest management in Australia" will shortly be released.

170

Reports were also prepared for an assessment of the Papaya Fruit Fly Eradication Program for the Queensland Department of Primary Industry and an investigation into the decline of native vegetation in Central Australia for Parks Australia. A further 15 biological control applications were processed for AQIS and the Australian Nature Conservation

Authority.

Three reviews of entomological research on grapes, dates and citrus in the NT were also produced for inclusion in Technical Bulletins to be produced by the Horticultural Division.

Talks were presented to several visiting groups of primary and high school students and project information made available for universities in the NT and interstate. Insect display materials were also provided for students.

171

ANIMAL HEALTH DIVISION

Animal Health Division delivers programs to protect and enhance the health and marketability of commercial livestock in the Territory. A key function is providing health certification for consignments of livestock and livestock products produced in the Territory, so that they comply with the requirements of other Australian states and importing countries.

In order to provide credible health certification, the Division monitors the disease status of Territory livestock by investigating disease incidents and through planned surveillance programs. Information is collected on the incidence and distribution of bacterial and viral animal diseases, plant toxins and other toxic and deficiency states.

The Berrimah Veterinary Laboratories (BVL) play an important role in gathering objective information on disease status of Territory livestock.

The largest program of the Division is still the Brucellosis and Tuberculosis Eradication Campaign (BTEC), which is funded and driven to a significant extent by the national cattle industry. The Territory was declared free of bovine brucellosis at the end of 1989, and there have been no further confirmed cases since. Eradication of bovine tuberculosis reached Impending Freedom in 1992, with a small number of breakdown herds still being dealt with. The Northern Territory is on track to be declared a TB free area, along with the rest of Australia, at the end of 1997.

In addition to health certification for market access, disease investigation and surveillance programs, and disease control and eradication programs, the Division maintains preparedness to deal with outbreaks of animal diseases not normally found in Australia and carries out surveillance to detect these exotic diseases if and when they enter the country.

Divisional programs also help to protect the community from disease and chemical residues in animal products and from zoonoses (diseases transmitted from animals to people).

National Animal Health Information System The National Animal Health Information System (NAIDS) is managed by the Australian Animal Health Council (AAHC); and the DPIF Animal Health Division provides a quarterly report to NAIDS on animal health status, specific testing carried out at Berrimah Veterinary Laboratories and significant animal disease events. The Bureau of Resource Sciences, for the AAHC, collects and collates these reports from all the agriculture/primary industry departments, as well as information from AQIS, NAQS, the National Arbovirus Monitoring Program, the National Residue Survey, the Commonwealth Department of Family Services and Health, and various national reference laboratories. A quarterly report, Animal Health Surveillance Quarterly, is produced.

Quantitative data for the NT report is extracted from ANDI and significant disease event entries are also identified with ANDI. Animal health information systems such as ANDI and NAIDS will allow Australia to demonstrate that acceptable animal health standards are maintained, thus supporting market requirements and quarantine issues for trade both within Australia and overseas.

The quarterly publication of an animal health newsletter by the Animal Health Division started at the beginning of 1996. It is sent to all registered veterinarians in the NT (and bordering towns in WA and Queensland), stock inspectors and other interested people. The articles cover topical animal disease events, animal health surveillance news, information from Berrimah Veterinary Laboratories and other items. Articles have been received from laboratory and field staff, in southern and northern regions.

A review completed during 1997 indicated that the clients found the newsletter to be a valuable communication tool.

172

ACTIVE DISEASE SURVEILLANCE

JOHNE'S DISEASE SEROLOGY SURVEY

Project Period: Project Officers: Project Location:

Objective:

1995-1996 A J anmaat, D Pinch, B Radunz, Darwin region and Vet Lab staff Berrimah Agricultural Lanoratory

A collaborative Meat Research Corporation project involving the Queensland Department of Primary Industries, the NT Department of Primary Industry and Fisheries, and the Victorian Institute of Animal Science was conducted to determine the suitability of the JD ELISA for use in northern Australian cattle populations. The main objective was to determine the specificity of the JD ELISA in north Australian cattle.

Background : Bovine Johne's disease (JD) is an infection of the intestines and mesenteric lymph nodes by Mycobacterium paratuberculosis, which leads to weight loss, chronic scouring and death in cattle.

A major problem in the control of JD is the inability to detect sub-clinically infected animals. It was hoped that the JD ELISA, a new test developed by the Victorian Institute of Animal Science (VIAS), would improve the ability to detect infected animals, compared to the complement fixation test (CFT) that was routinely used.

There was some improvement in the ability to detect infected animals but from a north Australian perspective, the high specificity (ability to correctly detect non-infected animals) was more important as the disease is not known to occur. A test with high specificity would be ideal to demonstrate freedom from bovine JD in northern Australia, and also to minimise the number of live export animals (mainly breeders to Indonesia) rejected due to positive test results.

JD has not been diagnosed in cattle in northern Australia, except for rare occasions in animals that were brought from infected southern areas; and the Northern Territory. Queensland and Western Australia are considered free.

Method: The project included 508 mature beef cattle from the NT (293 cattle) and Kimberley (215 cattle) properties, 541 mature beef cattle from a range of north Queensland properties, and 474 mature dairy cows from the Atherton Tablelands. Blood and tissue samples were collected from the beef cattle at slaughter, and blood and faecal samples were collected from the dairy cattle. Sample collection took place between July 1995 and October 1996.

The beef cattle samples (usually 50 at a time) from the NT and Kimberley properties were collected at Tenarra abattoir, and taken to Berrimah Agricultural Laboratory, where the blood samples were tested using the JD ELISA. Inunediately after the test, tissue samples from cattle which were reactors or 'high negatives' were processed for bacteriological culture and histopathological examination. Tissue samples were collected in duplicate from six different sites. The coordination of the sample collection and laboratory testing by abattoir, field and laboratory staff was a challenge and was carried out most efficiently.

Progress Report: None of the bacteriological culture or histopathological examination results showed evidence of JD infection. The specificity of the JD ELISA determined from this study for mature beef cattle is 98.0% (95% cr' of 97.0 to 98.8%) and for mature dairy cattle is 98.3% (95% cr of 96.7 to 99.3%). This is similar to the specificity figure for the CFT, which is currently required for testing live export animals.

The JD ELISA does not appear to be more useful than the CFT or export testing or to demonstrate freedom from JD in northern Australia. Further research may address the question of why there is a difference in specificity of the JD ELISA test between northern and southern Australia where specificity is high (98.8%). * cr - confidence interval.

*****

173

PASSIVE DISEASE SURVEILLANCE

DISEASE INVESTIGATION

Project Period: Project Officers: Project Location: Backgronnd :

1946 ongoing Regional Veterinary Officers and Laboratory Officers NT

A reactive service is provided to industry to investigate disease and provide disease control advice. Loss of production is reduced by advice on cost effective practices for disease prevention. Passive monitoring provided by this reactive service provides data to maintain market access for animals and animal products. Active surveillance programs supplement passive monitoring.

Objectives: To investigate unusual disease events to exclude exotic disease. To investigate significant disease events causing loss of production including mortality. To provide advice on disease control.

Method: Disease events eg mortality, sickness, illthrift etc are reported by producers by telephone. It may be possible to offer a diagnosis or control method over the phone. Otherwise, a property visit is done to investigate the history, conduct a clinical examination of affected stock, collect samples, conduct autopsies and collect samples for laboratory examination.

Samples are examined at the veterinary laboratory in Darwin with some samples referred to other laboratories. Following assessment of the field investigation and laboratory findings, the producer is advised of the diagnosis, if any can be made, and control measures are discussed.

The aim is prevention of the disease or identification of methods to minimise the loss from disease. Data from the field and the laboratory examinations are entered on an Animal Disease Information (ANDI) database for reporting and collation.

Project Progress: Exclusion of Exotic Disease There were 9 submissions to exclude exotic disease. The possible exotic disease were screw worm fly, brucellosis, bovine spongiform encephalopathy, equine morbilli virus (exotic to the NT) and canine ehrlichiasis.

Endemic Disease Investigations of disease problems by region for the period July 1996 to June 1997 :

Darwin Bee 2 Bilby Bird 5 Buffalo 4 Camel Cattle 16 Crocodile 27 Deer 4 Dog 2 Goat 1 Horse 2 Human 1 Not applicable 3 Pig 7 Poultry 1 Rabbit Total 75

Katherine 1

1 1

28

5

1 3

1 41

Tennant Creek Alice Springs 1 I 2

3 30 13

1 3

4 8

3

25 35 59

Total 4 1 8 5 3 87 27 4 3 4 19 1 7 10 1 26 210

174

The 84 cattle investigations were done on 52 properties. There are about 250 commercial cattle properties in the Northern Tertitory and this high level of monitoring enhances the likelihood that the veterinary service will detect any incursion of exotic disease.

Diagnostic Highlights: Rabbit Calicivirus Disease Rabbit Calicivirus Disease was diagnosed from most properties south of Alice Springs during 1996. There was also release of virus in areas where the virus was not naturally occurring.

Jahne's Disease Johne's Disease was diagnosed in a dairy herd in the Northern Territory in 1994. The disease has been eradicated from this herd using a combination of accelerated culling of introduced cattle, blood and faecal testing, and on-farm management. There was an initial reactor with typical clinical symptoms. One other non­clinically infected cow was found in the first round oftesting (culture oflymph nodes).

No infected cattle were subsequently found. Spread of infection has not been detected in the infected herd, ie the two infected cows were introductions which is consistent with previous infected herds in the Northern Territory. Trace-forward investigations from this infected herd and from introduced cattle from Victoria and NSW did not detect any other infected herds.

Diagnostic Comments: Birdsville Disease Reported on a property near Alice Springs and on two properties in the Tennant Creek area.

Black Soil Blindness Neither coral bodies of the fungus nor clinical cases were not seen during the 1995, 1996 and 1997 dry season in both the southern Victoria River district and the Barkly Tablelands. The fungus has reappeared during 1997 in the East Kimberley but is not causing problems at present.

Blue-Green Alga 40/500 cows died within 10 days at one bore on a Barkly Tablelands station. Intensive investigations yielded a tentative diagnosis of blue-green algae poisoning. No more deaths occurred after treating the tank with copper sulphate, possibly confirming the diagnosis of blue-green alga poisoning.

Botulism Botulism was again confirmed on several properties in the Tennant Creek region. Losses were associated with inadequate vaccination regimes as the disease is not recognised on properties in the gulf area and the desert area south of Tennant Creek. Disease investigations and serology surveys using the ELISA blood test detected exposure to the botulism toxin in unvaccinated herds. ELISA blood test is a valuable diagnostic aid to assess exposure to the toxin and protection by vaccination. Eight properties are now vaccinating following the demonstration of exposure to the botulism toxin.

A botulism vaccine research trial is being conducted at Ucharonidge station compating CSL Bivalent Botulinum vaccine with the new Cyanamid Websters "Singvac" product. An interesting finding on the initial sampling was high levels of maternal antibody present in 5 month old weaners. Potential interference by maternal antibody with the vaccine response will be assessed during the trial, as well as vaccine effic·acy. The purpose of the trial is to provide accurate advice to NT pastoralists.

Botulism was not diagnosed in the Katherine area during the year. This is probably due to greater awareness following the disease in recent years.

Chalkbrood Chalkbrood was found in bee hives on a property ion the Darwin area and a property in the Katherine area.

Coccidiosis Outbreaks of coccidiosis or black scours were confIrmed in several herds of weaner beef cattle. Improved nutrition and medicated feed controlled the infection.

175

Ephemeral Fever Clinical cases of ephemeral fever were observed on many properties in all regions of the Northern Territory. Some significant losses have been recorded. Brahman export steers are commonly affected and last wet season up to 3% mortalities occurred in a group of steers. Some valuable stud animals died and calf losses were observed in one stud group where the dams were affected and the calves were not able to suckle during hot weather.

The disease occurs regularly in the Darwin and Katherine area every year, with yearling and two year old cattle usually being affected.

The PCR technique which identifies virus antigen has greatly increased the diagnostic capacity to confirm the disease compared to paired blood samples for serology testing.

Heart Leaf poison During numerous intensive investigations into catde losses on a property near Tennant Creek, one post-mortem showed evidence consistent with heartleaf poison (Gastrolobium grandiflorum). The plant was difficult to identify by Animal Health and Rangeland Officers as it was not flowering or seeding at this time. However, the plant was positively identified at the end of the 1997 wet season. The plant produces a monofluoroacetate poisoning similar to Georgina gidyea.

Poultry Sentinel Flock A sentinel flock of chickens has been maintained at various locations throughout the Northern Territory and bled monthly for Newcastle disease and avian influenza of poultry and flavivirus infections. Murray valley encephalitis was shown to be active in the northern half of the Northern Territory during the lat 1997 wet season. Public health warnings were provided. More details are reported in the monitoring of flavivirus and for avian influenza and Newcastle disease sections of this report.

Short head cattle "Snorter" cattle were accumulated on one VRD property and presented for investigation in association with a dingo baiting exercise. Various theories exist for the cause of this condition but it is likely to be genetic with a simple recessive mode of inheritance. The main signs seen have been under shot jaws due to maxillary shortening with other defects in the maxilla. The skulls are grossly deformed with the bones being very thin. A nasal discharge and sniffily respiratory noises are often present. Animals may be in poor condition and have other problems such as corneal oedema and joint swellings. The condition is widespread and occurs at a rate of about one case per thousand progeny. Producers are advised to cull any breeding animals observed with the condition.

Stringhalt The bovine "stringhalt" herd of 9 head has been assessed regularly for 3 years now with no apparent progression of the disease. The manifestation of the condition varies without explanation but affected cattle are able to survive in a small paddock situation and lighter condition cattle may be less affected. No cases have developed in progeny retained to 9 months of age. The herd has been culled.

Tick fever Babesia bovis disease was confirmed in imported European cattle near Katherine. Babesiosis still has not been confrrmed in locally bred stock. A case of anaplasmosis was confinued on a property near Darwin recently in a weaner introduced from a property near Top Springs presumed to be due to inadequate protection from natural exposure.

Yellow pig syndrome Yellowish discolouration of tissues in feral pigs will lead to their rejection at meat inspection on the basis of jaundice. The cases are not jaundiced and are normal except for the presence of the pigment which is thought to be a plant pigment.

A number of plants are suspect but probably the chief suspect is the fruit of the Pandanus 'palm'. In some habitats around Katherine most adult feral pigs are discoloured. Further work will take place as a low priority.

176

ZamiaPaim Properties in the endemic zamia palm area east of Borroloola and Darwin have again had cattle losses from zamia palm poisoning.

Other Diagnoses Cattle

Bird

Buffalo

Camel

Crocodile

Deer

Goat

Kangaroo

Horse

Pig

Actinomycosis Bovine Virus Diarrhoea Cooperiasis erotalaria spp toxicity Erythrophleum toxicity (ironwood) Eremophila latrobei toxicity (fuschia bush) Euphorbia eremophilia toxicity (caustic bush) Ipomoea muelleri toxicity (morning glory) Haematopinus erythema (Cattle Sucking Louse) Lead poisoning Nicotinia velutina toxicity (native tobacco) Oxalate poisoning Pinkeye Pestivirus Ringworm Urea toxicity

Coccidiosis Marek's Disease

Bronchopneumonia Dermatophilosis Trauma

Allergic Dermatitis Abscess Demodectic mange

Bubblefoot Dermatophilosis Septicaemia

Melioidosis

Haemonchosis Lice Malnutrition Mastitis Melioidosis Pneumonia Toxoplasmosis

Salmonellosis

Allergic dermatitis Dermatophilosis Fungal Granuloma Habronemiasis Onchocerciasis Sarcoid Swamp Cancer

Nil

*****

177

CATTLE TICK AND TICK FEVER CONTROL

STOCK MOVEMENTS

Project Period: Project Officers: Project Location:

Objectives:

1966 ongoing B Radunz, D Russell, K Lunn, R Baker NT

Prevent the spread of cattle tick from NT Cattle Tick Restricted Area to tick-free areas within the NT and interstate. Prevent entry of cattle tick from interstate, particularly acaricide resistant strains from Queensland.

Background: There is continual review of stock movement controls and area declarations in consultation with Queensland Department of Primary Industry (QDPI), Western Australian Department of Agriculture, industry associations and chemical companies, Mobile spray plants and chemical are provided for spraying horses for movement

Progress Report: The spread of cattle tick was prevented, There were no outbreaks of cattle tick within tick free areas, Movement of stock to Queensland, Western Australia and South Australia was facilitated (see Market Assurance Section for details),

Concurrent with proposals to move the Queensland tick boundaries adjacent to the NT border north, four properties in the eastern Barkly Tablelands were declared a Tick Free Area, A new protected area (buffer area) was established in the northern Barkly Tablelands area with the intention of moving the tick line north, It is anticipated that an additional 5 properties in the Barkly Tablelands will be declared a Tick Free Area in early 1998, This will reduce the number of inspections and treatments needed to facilitate stock movements, Advice on tick fever risk was provided to producers from tick free and tick marginal areas moving stock to export depots in the tick infected area, There were sporadic cases of tick fever in non-exposed cattle which is described in detail in the disease surveillance section,

*****

MONITORING FOR CHEMICALLY RESISTANT STRAINS OF CATTLE TICK

Project Period: Project Officers: Project Location:

Objective:

1969 ongoing B Radunz and Regional Staff NT cattle tick area

Control cattle tick with recommended, registered acaricides, Locate chemically resistant strains of cattle tick on NT properties and prevent their spread. Advise industry on correct chemical use, Advise industry on chemical control of resistant cattle tick strains.

Method: Fully engorged female cattle ticks are collected in the field and sent to CSIRO Division of Tropical Animal Production, Indooroopilly for processing and larval packet testing against a number of tickicides, Collectors and station owner/managers are given the results and appropriately advised, The program targets properties which report poor tick kill and properties on which pour-on synthetic pyrethroids are used for cattle tick or buffalo fly controL

Progress Report: There was suspicion of resistance to flumethrin at an export depot near Darwin (many stock are introduced from Qld). Tick samples were taken from four properties dealing with export steers from Queensland. A survey of 10 properties was planned with sufficient ticks for testing being found on only four properties. There was no evidence of acaricide resistance detected. The ongoing monitoring program will continue.

*****

178

MONITORING CATTLE DIP STRENGTH

Project Period: Project Officers: Project Location:

Objectives:

1969 ongoing B Radunz and Regional Staff NT cattle tick area

Ensure government and private dipping facilities are run at correct strength. Provide an advisory service on correct dip chemical usage, plunge dip management and choice of acaricide. Provide a dip analysis service.

Metbod: Provision of dip sample bottles. dip sampling sticks and an analysis service for industry and government. Dip samples are collected by station staff. veterinary officers and stock inspectors. Samples are sent to BARC Chemistry Section. Collectors. station owner/managers and Program Managers are notified and appropriate advice is given.

Progress Report: There is minimal use of acaricides except for movement treatments due to the increasing proportion of Brahman content in the breeding herd in the tick endemic areas. A total of 48 dip samples were analysed including 16 from Western Australia and 32 samples from 13 Northern Territory properties. Of these 11 samples were at correct strength, 5 samples were over-strength and 16 samples were under strength. Corrective action was advised in each case,

*****

BRUCELLOSIS AND TUBERCULOSIS ERADICATION CAMPAIGN (BTEC)

TUBERCULOSIS ERADICATION

Project Period: Project Officer: Project Location:

Objective:

1970 to 1997 B Radunz and Regional Veterinary Officers NT

It is planned that, by 1997, the Northern Territory will be declared a Free Area for TB, although monitoring will be done at abattoirs for a number of years to confirm the absence of tuberculosis.

A 5 year monitoring program to be known as the TB Freedom Assurance Program (TF AP) has been endorsed and funded for 5 years from 1998 to 2002 by the states and NT, cattle industry and Commonwealth.

Background: The Tuberculosis Impending Free declaration in November 1992 was a culmination of years of work by many pastoralists and Departmental staff and the expenditure of $188m.

BTEC is still the major program conducted by the Department. In 1996/97, 30 staff were involved with 12.8 salaries paid by the BTEC Trust Fund with a total BTEC expenditure of $5.2m during the year.

Activity: Breakdowns At the end of 1995 95% of the cattle and buffalo were TB free (Monitored Negative, Tested Negative, Confirmed Free 2 and Confirmed Free 3 status).

There were three breakdowns in the Territory in 1996/97. The three herds had the TB case found at slaughter (two were old cows and one was a bullock). No further TB has been found following destocking of the exposed group and testing of the rest of the herd.

179

During 1996 1,979 cattle were destocked to abattoir from 1 property with no TB found and 11 cases of TB were found in 382 buffalo slaughtered from one buffalo herd.

Destocking The 'Judas cow' radio tracking technique in bush areas is an essential tool in locating residual animals. The goal to achieve the completion of bush destocking in all category 2 areas was achieved at the end of 1995. There was destocking still to be completed in about 50 000 sq kms in the Category 1 areas (initial high prevalence) at the start of the year. Kakadu National Park was completed at the end of June 1997. The remaining two areas will be completed by the end of 1997.

Granuloma Submission Program CGSP) The monitoring system includes a granuloma submission program which is working satisfactorily. A pleasing aspect of the granuloma submission program is that the majority of lesions which are detected through abattoir monitoring are not tuberculosis. This increases confidence that meat inspectors are submitting granulomas which will assist the early detection of TB breakdowns. During 1996 there were 45,013 cattle and buffalo slaughtered at NT abattoirs. There were 65 granulomas detected with 5 confirmed as TB.

TB Testing 1996

Cattle Buffalo

Number Tested

163,095 3,032

No. Reactors

221 73

Note: Buffalo testing was primarily in one infected herd having 1 animal with TB.

Overall Progress

No. with TB

1 10

The TB eradication program is proceeding well, with eradication testing and bush destocking progressing to plan. There were 17 tailtag areas not TB free at the start and at the end of the year. There was good eradication progress in herds with a TB case found during 1995 and 1996 but there were new herds for eradication activity due to TB cases detected during the year. A small number of TB breakdowns are expected to occur in decreasing numbers over the next few years. The risk of further breakdowns will be diminished when all breeders exposed to TB in the late 1980s have been slaughtered at abattoirs by virtue of age culling.

*****

LABORATORY DIAGNOSTIC SERVICES

The Berrimah Veterinary Laboratories (BVL) provide an ongoing diagnostic service in the broad fields of veterinary pathology and veterinary virology. BVL also conducts research projects and participates in quality assurance programs to ensure that the quality of tests carried out at BVL meets national and international standards.

The diagnostic service is provided free of charge to the extensive (cattle and buffalo), intensive (pig, goat, poultry and dairy) and emerging (crocodile and camel) animal industries as well as to the fishing, aquaculture and pearl oyster industries.

The diagnostic service is also provided on a fee for service basis to exporters of livestock for animal health certification purposes, to private veterinarians for submissions of specimens from companion and performance animals, to NT Government (other than DPIF, eg wildlife testing for the Parks and Wildlife Commission) and Commonwealth departments (eg testing of feral animals for surra for NAQS - the North Australian Quarantine Strategy) and to private agencies such as food processing enterprises for testing to ensure adequate hygiene standards.

A total of 2,272 submissions were received and processed during the year at BVL, a decrease of 8.8% on last year. Each submission may consist of one or more specimens and each specimen may undergo one or more tests in one or more of the 12 sections of BVL.

180

The 2,272 submissions resulted in 71,676 individual tests being performed including 11,444 for export certification, 10,165 in support of field investigation of animal disease, 10,394 for fee for service and 37,901 for sentinel herd and flock monitoring, research and surveillance programs.

Laboratory submissions by region and by sl2ecies Darwin Katherine Tennant Creek Alice Springs

Cattle 261 242 154 Buffalo 50 I Banteng 2 Horse 99 11 4 Goat 22 4 Sheep 14 Deer 11 Camel 7 Pig 72 4 Poultry 65 7 3 Crocodile 44 Fish 11 Pearl Oyster 14 Prawn 5 Bee 4 I Dog 551 14 2 Cat 94 I Insect 71 15 16 Bat 50 2 I Rabbit 5 I Bird 98 6 4 Native fauna 53 2 Other 32 I Total 1635 312 184

* Figures are based on date collected

Laboratory submissions per investigation reason Diagnostic BTEC Export Sentinel Research Survey Regulatory Fee for Service Quality Assurance Other

505 294

62 240 312 55 7

762 20

~ 2272*

* Figures based on date received

DIAGNOSTIC PATHOLOGY

*****

59

7 3

4

8

1 I 2 9 8

25 2 2 3

134

Interstate 14

I

2

20 37

Total 730

51 2

121 29 14 11 11 76 83 45 11 14 5 6

570 97

111 61 31

110 57 56

2302*

Project Officers: A Janmaat, L Melville, D Pritchard, J Gilfedder,K Fomiatti, L Chambers, N. Joliffe, L Small, R Wilson, C Day, N Cox, S Aumann

Objective: Provide an accurate, efficient and reliable veterinary pathology service

The sub-program is divided into the sections of gross pathology, histopathology, bacteriology, parasitology, serology, clinical chemistry, haematology, cytology and urinalysis - the last four sections fan under the heading of clinical pathology.

181

Gross Pathology

Submissions 213 Native birds made up 27% of submissions, domestic and commercial poultry 13%, bats 21 %, crocodiles 9%, dogs 6%, fish 4% and goats 3%. The remainder varied from an axolotl to a bilby, trutles and prawn submissions. The bat submissio$ were concerned with equine morbillivirus and Australian bat Iyssavirus .surveys. Serum samples were collected at necropsy at BVL and were forwarded to the Australian Animal Health Laboratory (AAHL) at Geelong. Six bats, all black flying foxes (Pteropus alecto) had antibodies to equine morbillivirus. Australian bat Iyssavirus was isolated from a little fruit bat (P. scapulatus) found at Noonamah, in February. The bat had shown rabies-like symptoms.

*****

Histopathology

Submissions 690 The submissions led to the processing, sectioning and routine haematoxylin and eosin (H&E) staining of 5,631 tissues. Of these, 3228 pearl oyster tissues were processed for the Fisheries Division and 512 turtle tissues were processed for the Australian National University. Therefore a total of 1,891 H&E sections were examined by the BVL duty pathologists. An additional 800 "special stain" sections were also examined.

Of the total submissions, 145 were cattle (139), buffalo (5) or camel (1) submissions under BTEC either as lesions from reactors or as lesions collected at abattoirs under the National Granuloma Submission Program. One of the cattle and two of the buffalo submissions showed lesions consistent with tuberculosis. The steer came from an Alice Springs property, representing the first case of confirmed TB since 1987, in that area. One of the buffalo came from a known infected property, the second buffalo was a Judas cow from North West Arnhem Land.

*****

Bacteriology

Submissions 870 A total of 606 samples, mainly lymph nodes, were cultured for Mycobacterium bovis. A total of 359 submissions were finalised during the year and M. bovis was isolated from samples of eight of these.

A total of 1655 samples were processed in general bacteriology which resulted in 1,997 primary cultures, 574 microscopical examinations and 313 antibiotic sensitivity cultures.

The bacteriology laboratory participates in the BTEC quality assurance program for the culture and identification of M. bovis. It was the only laboratory, among the seven participating laboratories, to achieve a perfect score during the year.

*****

Parasitology

Submissions 286 Faecal egg counts and faecal oocyst counts were performed on 1,260 cattle and nine buffalo samples for monitoring purposes and on another 145 samples from cattle, pigs, buffalo, horses, camels, deer, goats, dogs, cats and various wildlife species for diagnostic purposes. Larval cultrues of selected monitoring samples revealed Cooperia sp., Oesophagostomum sp. and Haemonchus sp.

Eighty two samples were submitted for parasite identification and 115 gastro-intestinal tracts of feral cats were examined for parasites on a fee for service basis. Seventeen pig samples were examined for Trichinella sp., and blood smears from a bovine and two buffaloes were examined for Trypanasoma evansi infection (surra) at the request of NAQS - all were apparently free of the respective parasites.

Export testing consisted of seven dog sera for antigen to Dirofilaria immitis.

*****

182

Serology

Submissions 260 Export testing consisted of 3,197 cattle, 62 buffalo, 24 deer and seven camel sera by the complement fixation test (CFT) for brucellosis; 1,209 cattle, 62 buffalo and 24 deer sera by the CFT for Johne's Disease (JD) and 24 deer sera by the CFT for melioidosis.

Sentinel testing consisted of 1,643 cattle sera and 84 buffalo sera being subjected to the bluetongue ELISA. Under the auspices of NAQS, 140 chicken sera were tested in the avian influenza (Al) ELISA and 173 chicken sera were tested in the Newcastle disease (ND) ELISA.

Testing for diagnostic purposes included 13 cattle sera for brucellosis by CFT and Rose Bengal, 10 cattle buffy coats for pestivirus antigen ELISA and five cattle sera for the JD ELISA. The latex agglutination test for toxoplasmosis was applied to 12 goat, three birds and two wallaby sera.

Melioidosis testing by both CFT and indirect haemagglutination (IRA), for diagnostic purposes, was performed on 30 goat, two deer and one pig sera and for research purposes on 64 goat sera. Nine cattle, seven wallaby and two bird sera were tested in the CFT for chlamydiosis and one bilby was tested for antigen to rabbit calicivirus by ELISA.

Surveillance testing included 25 horse sera by the African horse sickness ELISA.

Three hundred and twenty eight beef cattle sera were tested with the Johne's disease ELISA as part of a Meat Research Corporation sponsored project to determine the specificity of the JD ELISA under North Australian conditions. The project found that the specificity was 98% which is allowable for export testing but not ideal for the purpose of showing freedom from infection.

The serology section successfully participated in the Australian National Quality Assurance Program (ANQAP) with the ELISAs for bluetongue, JD and caprine arthritis and encephalitis, the CFTs for JD, brucellosis and chlamydiosis, and the Rose Bengal precipitation test for brucellosis.

*****

Clinical Chemistry

Submissions 429 A total of 1740 serum or lithium-heparin samples were subjected to, usually, multiple biochemical analyses, including 979 cattle sera for research purposes and 310 cattle sera for diagnostic purposes. The cattle sera for monitoring purposes originate from Departmental surveys and research such as feeding and pasture trials. One hundred and forty three crocodile samples were tested to determine reference ranges; the results have been recorded in a scientific paper which has been accepted for publication in the Australian Veterinary Journal.

Fee for service submissions numbered 269 or 62.7% of the total. Expressed as number of animals, fee for service involved four birds, 38 horses, 39 cats and 188 dogs or 269/1740 = 15.5% of the total.

The section participates in the BIORAD international quality assurance program for clinical chemistry.

*****

Haematology

Submissions 515 A total of 671 EDTA blood samples were examined for, usually, multiple haematological variables. These included 149 cattle bloods and 199 bloods, from a wide variety of species, for diagnostic and research purposes.

There were 312 (60.6%) fee for service submissions, involving 41 cats, 82 horses and 194 dogs or 217/671 =32.3% of the total number of animals.

The section participates in the RCPA (Royal College of Pathologists of Australia) haematology quality assurance program.

*****

183

Cytology

Submissions 102 There were 83 (81.4%) submissions from private practitioners on a fee for service basis and 19 (18.6%) for diagnostic purposes from production, companion and native animals.

***** Urinalysis

Submissions 54 There were 39 (72.2%) submissions from private practitioners on a fee for service basis and 15 (27.8%) for diagnostic purposes from production animals.

*****

HERD HEALTH

HERD HEALTH ADVISORY SERVICE

Project period: Project officers: Project location:

Objective:

Continuing K de Witte, Regional Veterinary Officers and Stock Inspectors NT wide

1. Collect health and production data for cattle and identify methods to increase productivity 2. Increase adoption of recommended strategies to increase cattle productivity. 3. Develop herd health and production programs for export steer depots. 4. Provide services to the Territory Wild life Park.

Progress report: Valuable advice was given to NT cattle producers on a wide range aftopies.

Mt Riddock Project The Mt Riddock study is in the final stages. This project has been a 'pilot property study' to determine breeder cattle productivity and investigate options for imprOVed productivity. Collection of information from other Centralian Pastoral Properties is planned.

Completed pilot property field data collection and preliminary data analysis. Processing and interpretation of data is continuing. Preliminary data interpretation includes eg : preliminary interpretation of serum samples sent to W A Dept of Agriculture suggests that [Vitamin A] peaks 6 weeks after rain, and the [Vitamin E] is affected by the type of mineral supplement supplied to the cattle.

Static display for the AZRI "Breeding Better Bulls" Field Day (17/6/96). The display demonstrated the benefits of basic cattle herd recording. The results were discussed with the owners of Mt Riddock Station. Relevant results were presented to the Alice Springs Pastoral Industry Advisory Committee and a breed magazine article was prepared.

Other Projects The analysis of data from the Newcastle Waters Single Sire Herds was finalised. The project identified April/May as the most efficient conception period and a 12% loss from pregnancy testing to calving. These parameters are supported by the work done by Leith Andrews (Masters Thesis, 1976). The Newcastle Waters Bralunans exhibited a much flatter conception pattern in contrast to the work by Andrews on primarily British Breed types. A Technote will be developed.

A Gulf property reported a reduction in branding rates from 80% to 52% over a 4 year period. Pregnancy testing with foetal ageing and disease testing concluded causes to be phosphorus deficiency due to a reduced supplementation program and calving creep from a courageous 3 month joining period. A follow up pregnancy

184

test with partial budgets on two options 10 months later assisted the owner to manage the implications of low branding rates on a small herd.

Three station bovine pregnancy testing schools were held in the Tennant Creek region.

In the Katherine region significant contributions were made to the conduct of the MRC - Paddock Demonstration Site at Mt Sanford station and work at Kidman Springs Research station.

A large amount of time was spent in training veterinary and lay operators in the Willis Dropped Ovary Technique for spaying cattle. The Willis technique is a vaginal spaying method developed in the USA in the early 1980s which has largely replaced flank spaying in many areas of North America. This is because it is quicker, simpler, less invasive, and less carcase damage. The disadvantages are the inability to complete all spays (heifer too small, too pregnant, rarely ovaries too large), and the higher skill level required. The technique has major animal welfare and production advantages over other spay methods. A training manual and a lay spayer accreditation scheme are being developed.

The development of a station stock recording system in conjunction with a New Zealand co-operator was abandoned because a major client pursued their own development and external funding could not be gained. In the Darwin region advice is given to live export depots. The Territory Wildlife Park is no longer supported by the division as they have employed their own veterinarian.

*****

ANIMAL WELFARE

ANIMAL WELFARE MONITORING AND POLICY

Project period: Project Officers: Project location:

Objective:

Ongoing K de Witte, A Bryce and Pastoral staff NT

Participate in the development and implementation of appropriate national welfare standards for animals.

Progress report: The Standing Committee on Agricultural Resource Management (SCARM) has raised the profile of animal welfare by forming the Animal Welfare Committee (AWC) to report directly to SCARM to better address market and community concerns regarding animal welfare. The roles of A WC will include development of Codes of Practice and adoption of improved animal welfare practices by industry. AWC will be more pro-active in future in involving stakeholders in Code of Practice development and revision to ensure greater ownership by industry. The Codes of Practice are seen by AWC as a standard of good animal practice, neither minimum nor "gold" standard.

Of particular relevance to the NT, the codes on the 'Land Transport of Horses' and 'Camels' will be available soon. The 'Land Transport of Cattle' revision is delayed as agreement has not been reached on a 36 hour travel limit. All codes are reasonably up to date with the exception of the Land Transport Codes and the Sea Transport of Livestock Code. The "Cattle" code is currently being reviewed and there are 10 Codes being developed.

The final draft of the 6 Th edition of the "Code of Practice for the Care and of Animals for Scientific Purposes", was endorsed. Educational and research facilities have been advised. The major changes are: a new section to address the issues of capture, identification and transport of wildlife and the impact on target and non target species and the ecology of the study area, a new section that makes clearer the responsibilities of field officers using farm animals that may range from no approval for routine husbandry demonstrations to a full ethics application for other procedures and a new section that spells out the responsibilities for the use of animals in schools, the limits of animal use and the need to consider alternatives.

A draft Crocodile Code of Practice has been circulated for comment.

185

The Animal Ethics Committee reviews applications to use animals and inspects facilities to ensure that compliance is achieved. There are two committees in the NT. The section has been expanded to give more specific instructions on who qualifies for membership and how the committee will operate.

The National Consultative Committee on Animal Welfare (NCCAW) to the Federal Minister for Primary Industries and Energy met in April 1997. Two issues relevant to the NT are a Recreational Fishing Code, and Essential Provisions Of Legislation To Prevent Cruelty To Animals will provide guidance for the Territory in our own Animal Welfare Legislation review.

Concern was expressed at NCCA W that the AQIS Third Party Service Provider Program should recognise community accountability and noted that the Codes of Practice for the Welfare of Animals are not fully incorporated in Australian Live Export Standards.

It was agreed that, despite the need for further research on the electro immobiliser, the technique should not replace anaesthesia where that is required.

The NT Prevention of Cruelty to Animals Act is under review and will be replaced by the Animal Welfare Act at some time in the future. Management of this process is by the Department of Housing and Local Government with Primary Industry and Fisheries supplying advice.

The issue of cattle spaying is under review. The adoption of the Willis Dropped Ovary Technique has led to an improvement for cattle needing to be spayed. Research is continuing into non-surgical alternatives.

All NT egg farms have produced animal care statements as part of Quality Assurance for their operations. Minimum space requirements for caged layer birds are agreed to nationally and are gazetted under the NT Stock Diseases Act. All local operations comply with this standard.

All reported animal welfare incidents were successfully resolved and potential animal welfare incidents were investigated and corrected. Investigations were undertaken in respect of starving, injured and perishing stock. Dog health and traditional aboriginal hunting practices have been identified as animal welfare concerns with the matter being considered by ATSIC.

*****

EMERGING AND INTENSIVE ANIMAL INDUSTRIES

CROCODILES

Project Period: Project Officers: Project Location:

Objective:

Continuing J Millan, V Simlesa and regional staff NT (Darwin and Katherine regions)

To provide a regulatory service to crocodile farms in the Northern Territory.

Method: In order to carry out regulatory duties under the Territory Parks and Wildlife Conservation Act, on crocodile farms in the Northern Territory, two crocodile officers are appointed as Honorary Conservation Officers. In addition, the Veterinary Officer is an authorised officer under the Commonwealth Export Control Act to carry out other regulatory duties requiring a veterinary officer, such as inspection of export abattoirs.

Regulatory duties include the inspection and certification of export shipments, collation of monthly reports from all NT crocodile farms to Environment Australia through Parks and Wildlife Commission of the Northern Territory (PWCNT), regular full audits andlor inventories of all stock on NT crocodile farms to conform to the Convention on International Trade in Endangered Species (CITES) requirements, issuing of movement permits involving farmed crocodile products produced in the NT, regular inspection of NT crocodile abattoirs, and the

186

issuing of health certificates accompanying crocodile skins as required by importing countries. A disease investigation service is provided to all NT crocodile farms on request.

Results: The DPIP has taken over all regulatory duties from PWCNT that are associated with the crocodile farming industry in the NT. DPIP officers are also responsible for AQIS regulatory duties as required.

A small research project completed last year compared the effect on growth rate and frequent grading in hatchling crocodiles. The results will be published when statistical analysis is complete. The research was funded by the NT crocodile farming industry. A second project to establish reference ranges for biochemical and haematological values was also conducted and will be submitted for publication.

Externally funded research, in conjunction with other organisations, will continue in areas indicated and supported by the industry. Current research is investigating a the effects on growth rate of regularly grading hatchling crocodiles. Approved research projects with· external funding from RIRDC include a joint project with Wildlife Management International to investigate normal skin structure. Funding for transmission trials of skin diseases has also been approved by RIRDC and the project, also involving James Cook University, will commence in late July 1997.

A discussion paper on public health risks of crocodile flesh was prepared by Department officers and accepted for publication in an OlE Technical Report.

*****

HONEY BEE INDUSTRY DEVELOPMENT

Project period: Project officers: Project location:

Objective:

Continuing K de Witte, Regional Veterinary Officers and Stock Inspectors NT wide

Provide technical advice, disease investigation and regulatory services to the honey bee industry.

Background: The apiary industry in the NT declined in the 96/97 period due to a major producer returning to Queensland but the NT position as an exporter of honey continued. The current program direction has been to raise the awareness of issues amongst our own staff and the public and to protect the Territory disease free status and ability to trade.

Objectives: 1. Liaise with the local and national honey bee industry matters and produce necessary legislative support for

the industry. 2. Provide advice on hive management, diseases and regulatory matters to bee keepers. 3. Coordinate and conduct disease surveys. 4. Maintain a small apiary at KRS 1 Katherine and educate interested staff in bee keeping husbandry. 5. In conjunction with NAQS, ensure that there is a body of staff within DPIP capable of responding to exotic

bee disease threats.

Activities: Advice was provided to the NT Bee Keepers Association in relation to the development of disease response plan. This will form the basis for DPIP policy in dealing with a disease problem. The association has been working to gain a modification of the regulations governing the importation of bees and products into the NT. It is now possible to import disease free queen bees and second hand material with treatment. The association seeks further changes to allow the local industry to expand more freely. The NT is a corresponding member on the AHC National Working Party on Bee Diseases.

No disease surveys were conducted but sporadic cases of chalk brood have been confirmed in the top half of the NT. The impact on commercial bee keeping has been minimal. The epidemiology of the disease is not understood but the impact is minor.

187

The DPIF apiary at Katherine was expanded to about 10 hives. Various combinations of equipment have been tried to assess their practicality in the local situation. These variations are designed to reduce labour inputs and improve resistance to pests. The apiary assists with pollination at KRS.

Inspection and destruction of feral colonies is undertaken around Katherine and for the NAQS program. There is a major concern over the potential introduction of exotic bees and parasitic mites.

*****

MEAT INDUSTRIES

Project Period: Project Officers: Project Location:

Objectives:

Continuing J Purdie, P Barry, R Smith Northern Territory

Ensure compliance with national and international standards for all sectors of the meat industry.

Progress Report: Abattoirs Three export abattoirs were licensed, operating on a seasonal basis. The following stock were slaughtered:

cattle 50498 buffalo *

Two domestic abattoirs and five small slaughterhouses were licensed. The following stock were slaughtered: cattle 1 906 buffalo 293 pigs camel deer

* * *

Two poultry abattoirs were licensed, one only operating for 6 months; 770 125 birds were slaughtered. * Figures not given due to confidentiality (ie one abattoir only involved in these species)

Pet Meat 25 licences to slaughter and 5 licences to process were issued though several persons with slaughter licences did not operate. The following stock were slaughtered (figures incomplete) :

1770 horses 242 donkeys 189 cattle 111 buffalo

The following amounts of pet meat were processed: 24.14 tonnes horse & donkey 10.56 tonnes buffalo 9.73 tonnes

124.31 tonnes beef kangaroo

All the kangaroo meat was sourced from interstate, mainly Queensland and South Australia.

Game Meat 139 people were trained in the harvesting of wild pigs for game meat for human consumption.

Legislation The Meat Industries Act was passed by Parliament and will come into force on completion of the regulations.

*****

EXOTIC DISEASES

EXOTIC DISEASE PREPAREDNESS

Project Period: Project Officers: Project Location:

Objective:

Ongoing J Millan & Pastoral staff NT

188

To participate in contingency planning and training for exotic disease preparedness. To ensure that DPIF staff, relevant organisations and pastoralists have a continuing high level of awareness in relation to the threat of exotic diseases.

Activities : Exotic disease awareness training was included in several courses held for wild pig harvesters with funding from the Wildlife and Exotic Animal Diseases Preparedness Fund.

The NT agreed to conduct an avian influenza and Newcastle disease survey of all commercial poultry farmers, as part of a national ARC agreement. The survey (based on one already carried out in W A) will also provide an excellent extension opportunity to maintain exotic disease awareness.

The NT continues to send officers to exotic disease courses at AAHL, and virtually all field staff have now been trained in practical exotic disease recognition.

*****

MARKET ASSURANCE

MARKET ASSURANCE FOR ANIMALS AND PRODUCTS

Project Period: Project Officers: Project Location:

Objectives:

1946 ongoing Regional Stock Inspectors and Pastoral staff NT

Provide property and animal certification for export, interstate and intrastate movements. Assist the industry to satisfy export protocols by conducting required treatments if private veterinary practitioners are not available. Facilitate interstate movements from the Tick Infected and Tick Protected areas by providing a service to inspect andlor treat cattle and horses for cattle ticks and for weed seeds.

Metbod: Certifications are provided to AQIS regarding the disease status of properties and animals to satisfy export protocols.

An associated project to improve the reporting and retrieval of disease data for this purpose is the Animal Health Information System. Planned active surveillance programs complement passive disease monitoring. Some export protocols require treatment of animals prior to export. Departmental staff provide this service if authorised private veterinarians are not available.

Stock from the tick infected area require a clean treatment (clean inspection and treatment) to pass into or through the NT Tick Free area or into the Tick Free areas of other States. Treatment is by plunge dipping, except for led and tractable horses and show cattle which may be sprayed in lieu of dipping.

Progress Report: The trend to export cattle through Darwin from Queensland continued. Northern Territory live cattle exports were derived from all regions of the Northern Territory with most from the Darwin, Katherine and Tennant Creek regions with an increasing number of slaughter cattle from the Alice Springs area.

189

With this current trend of cattle heading north for export, the Elliott clearing dip has had very little use.

Tick Area Changes Concurrent with proposals to move the Queensland tick boundaries adjacent to the NT border north, four properties in the eastern Barkly Tablelands were declared a Tick Free Area.

A new protected area (buffer area) was established in the northern Barkly Tablelands area with the intention to move the free tick line north. It is anticipated that an additional 5 properties in the Barkly Tablelands will be declared a Tick Free Area in early 1998. This will reduce the number of inspections and treatments needed to facilitate stock movements.

The Katherine Trucking Yard sales were active with commercial cattle and herd bull sales. The annual Brahman bull sale was again held in April. No sales were held at Bohning Yards in Alice Springs.

Several properties in the southern parts of the Tennant Creek area and in the Alice Springs area have purchased Brahman bulls to produce cattle for the export feeder market. This is a marked change to the dominant Hereford breeding for the South Australian market and shows confidence in the long term future of the export market to make such a major change to property management. There is a marked reduction in Departmental involvement in treatments and inspections associated with the export trade following the adoption of a policy of using Third Party Providers (authorised private vets).

There was a reduction in the number of cattle inspected for movement to Queensland following the changes to the tick areas. However, certification is required for cattle moving from the tick free areas to Queensland and Western Australia and all cattle moving to Western Australia must be inspected for weeds.

Summary of activity 1996/97:

Activity Darwin Katherine Tennant Alice Total Creek Springs

Export Treatments 0 2,213 1,993 5,321 9,527

Export Inspections 0 10,166 3,541 4,175 17,882

Cattle Inspected and treated for cattle 31 11,531 54,340 0 65,902 tick Horses inspected and treated for cattle 390 403 336 0 1,129 tick Cattle inspected at saleyards 0 3,392 0 8,720 12,012

Cattle moved interstate from tick free 0 0 27,095 14,213 41,308 areas

(Note: These are export treatments and inspections carried out by Animal Health staff, not total export figures.)

*****

CHEMICAL RESIDUES IN ANIMAL PRODUCTS

Project Period: Project Officers: Project Location:

Ohjectives:

1990 ongoing B Radunz, D Russell, K Lunn, R Baker and B Tye NT

Present chemical residue free animal product to the consumer and protect and maintain the NT meat and milk markets. Provide an advisory service on chemical residue issues to industry, government and the public. Represent NT on relevant national committees.

This program has four components: (1) National Residue Survey (NRS)

190

(2) Beef organochlorines, organophosphates and synthetic pyrethroids residues (3) Hormonal Growth Promotant (HGP) (4) National Antibacterial Residues Minimisation Program (NARM)

National Residue Survey

Background: The National Residue Survey (NRS) is a random sample survey to monitor residues in Australia's agricultural food commodities. The NT animal industries do not have a chemical residue problem, however, there are ongoing programs to monitor the situation and demonstrate the absence of residues. There are no properties under quarantine.

From 1996 following the need for participation in the NRS for domestic consumption as well as the export market has created an additional cost for small industries such as the buffalo industry. The required sample size for a range of chemicals results in a significant cost for each buffalo slaughtered.

Results During 1996/97, 220 samples were collected from Northern territory stock. There were 118 cattle samples analysed with one detection greater than the maximum residue limit (MRL)/ maximum permissable concentration (MPC) from a Northern Territory property. There was no evidence of contamination of copper other than by normal environmental contamination. The MPC for copper needs to be reviewed. There were no detections of antimicrobials, organochlorines and organophosphates and hormonal growth promotants (zeranol and trenbo10ne).

During 1996/97 37 egg and 15 poultry samples were analysed with no detection of antimicrobials, organochlorines and organophosphates or traces of environmental metals. A total of 28 buffalo and 5 horse samples were analysed with no detection of antimicrobials, organochlorines or organophosphates. 17 possum samples were analysed with no detection of organochlorines or organophosphates.

Beef Organochlorines. Organophosphates and Synthetic Pyrethoids The main issue for the Northern Territory is the interval between the last treatment with cattle tick and buffalo fly treatments and slaughter to satisfy the Maximum Residue Limit (MRL) in both domestic and export markets. The Meat Research Corporation funded research to establish the Export Slaughter Interval (ESI) for the common treatments of external parasites of cattle. The ESI varies from nil to 8 weeks depending on the chemical and the formulation of the chemical.

Advice was provided to all producers in the cattle tick and buffalo fly area on the residue risk and control of cattle tick and buffalo fly.

Hormonal Growth Promotants fHGPs) Following an unsatisfactory voluntary vendor declaration system from 1989 to 1992 a revised enhanced national program was developed in 1993 which satisfied EU reviewers subject to on-going review. Legislation was activated by all state governments with the Control of Hormonal Growth Promotants (Stock Act) becoming law from April 1993. Industry (exporters, cattle council and livestock agents) decided that it was important to maintain the $80 million market to the EU.

From 1 April 1994, cattle producers must use a pink eartag or tailtag instead of a Vendor Declaration Form to declare HGP free animals. Due to the difficulty in retention of tailtags in buffalo, the Vendor Declaration was retained for buffalo. There has since been extension activity via rural news sheets and direct contact with producers.

A total of 133816 doses ofHGPs were sold by 16 registered retailers in 1996/97 (an increase of about 50% over the last two years). About 55,000 being exported directly as implants with the remaining being used for cattle being prepared for the export feeder market.

Five audits were done during the year as required under the national HGPs audit program (2 users, 1 salesyard, 1 retailer and 1 non-user).

191

National Antibacterial Residues Minimisation Program INARM) NARM is a national program to monitor antibiotic and antibacterial contaminants. The national program is now targeted to high risk areas which excludes the Northern Territory.

*****

VIROLOGY

DIAGNOSTIC VIROLOGY

Project Period: Project Officers:

Project Location:

Objective:

Ongoing L Melville, N Hunt, R Weir M Harmsen, S Walsh, L Simmington, N McNaughton, N Jolliffe. A.L. Rose Virology Laboratory, Bertimah Farm.

Provision of an accurate, efficient and reliable veterinary virology service to support diagnostic, regulatory and research programs in livestock health and production.

Background: The diagnostic virology service comprises both virus isolation and identification and serology. A number of co­operative projects on bovine ephemeral fever continued during the year with groups in Agriculture and Animal Health following increasing interest in this disease, particularly with respect to the live export trade.

Results: During the year 64 submissions were received for diagnostic virus isolation, electron microscopy or polymerase chain reaction (PCR). Viruses isolated from diagnostic cases included bovine ephemeral fever (BEF) virus and infectious bovine rhinotracheitis (IBR) virus. Viruses identified by electron microscopy included pox virus, beak and feather dystrophy and canine parvovirus. A total of 118 submissions were received for diagnostic serology, including 42 for export testing.

Export testing consisted of 6206 cattle sera for enzootic bovine leucosis (EBL), 34 horse sera for equine infectious anaemia (EIA) and 88 camel sera for akabane and bluetongue. Co-operative BEF projects generated 1192 cattle sera for BEF serology. Eighty cattle were tested for BEF by PCR with 38 of these positive. An improved BEF isolation system resulted in viruses being isolated from 5 animals.

Quality assurance tests were provided by Australian National Quality Assurance Program (ANQAP) for Agar Gel Immunodiffusion (AGID) tests for EBL, BVD, EIA, BEF, epizootic haemorrhagic disease (EHD), bluetongue, aino and caprine arthritis encephalitis (CAE). Serum neutralisation tests (SNT) were performed for bluetongue, BEF, akabane and aino.

*****

EPIDEMIOLOGY OF A BUNY AMWERA SEROGROUP VIRUS

Project Period: Project Officer: Project Location:

Objective:

July 1996 - June 1997 R Weir, M Harmsen, L Simmington. Darwin

To determine the number of species and range of distribution of a member of the Bunyarnwera serogroup recently introduced to northern Australia.

Background: Bunyamwera viruses were present on all continents with the exception of Australia and Antarctica until 1993. In 1993 five viruses (which could not be identified by conventional means) were isolated from sentinel cattle located at Coastal Plains Research Station. These viruses were shown to be members of the Bunyarnwera

192

serogroup. Several members of this serogroup do cause significant disease in domestic animals and humans in Africa, South America and the United States.

Method: A comprehensive sample of stored animal sera, paired human sera, human sera from a virus disease outbreak and human sera from patients presenting at hospital with a viral-like illness who were Ross River Virus (RRV) and Barmah Forest Virus (BFV) negative, were initially screened in a neutralisation test. Serum showing neutralising antibodies was titrated.

Results: 5530 serum samples were tested from eighteen species. 199 samples were positive with a titre of 40 or greater. Location of positive samples ranged from Darwin in the north, to Mt Riddock in the south, Fitzroy Crossing in the west and Bogyu Island in the Torres Strait to the east.

*****

NATIONAL ARBOVIRUS MONITORING PROGRAM (NAMP)

Project Period: Ongoing Project Officers McNaughton,

L Melville, N Hunt, M Harmsen, R Weir, S Walsh, L Simmington, N

G Bellis. Project Location CPRS, BARC, DDRF, KRS, VRRS, AZRI, Rockhampton Downs.

Objectives: Trade support - by providing information to meet Australian Quarantine and Inspection Service (AQIS) requirements for export protocol negotiation and certification.

Bluetongue early warning - by the dynamic surveillance of the northern bluetongue endemic area to detect any new viruses or vectors entering Australia and monitoring any southern spread.

Control of important insect-borne endemic disease - by monitoring for endemic virus activity and the insect vectors which transmit these viruses.

Background: NAMP is an integrated national program jointly funded by industry and governments to monitor the spread of economically important insect borne viruses of livestock and their insect vectors.

Method: Monitoring is achieved by using sentinel herds at various sites around the Northern Territory which are bled at regular intervals and tested for antibodies to a number of viruses. At CPRS, weekly blood collections are made and virus isolations performed. Monthly light trap collections of insects are also made at each site.

Results: (1) Sentinel Herd Serology and Virus Isolation Coastal Plains Research Station A total of 369 viruses were isolated from the following groups: Bluetongue type 1 October - March 105

EHD

BEF Untyped Ungrouped

type 20 March - May 82

type 2 typeS type 7

October October - April January - June

September - October

I 63 32

10 19 89

193

Monthly serology also indicated Akabane activity from August - April and Douglas from January - March. BEF activity was recorded from October - April and Palyam in December.

BARe Monthly serology indicated the following activity: Bluetongue type I February - April Akabane July BEF September - May Douglas October - February EHD December Palyam December

DDRF Monthly serology indicated the following activity: Bluetongue type I March - April type 20 March - April Akabane December BEF December Douglas October EHD December Palyam December

KRS Monthly serology indicated the following activity: Douglas October BEF January - March Bluetongue type I March

type 20 March EHD Palyam

November November

VRRS Monthly serology indicated the following activity:

AkabaneDecember Bluetongue

Douglas BEF EHD Palyam

Rockhampton Downs

type 16 type 21

January January October September, December October October

Bluetongue type 21 activity was detected in April and BEF in March.

AZRI BEF and Douglas activity was recorded in March.

(2) Entomology

Insect numbers were high at all sites compared to 1995-1996.

The most widespread vector, C. brevitarsis, was identified at all sites except AZRI and Rockhampton Downs. C. fulvus, the most efficient vector, was found at ePRS during September - June, BARe in March, DDRF in February and KRS in March. C. wadai was found at ePRS during September to March and BARe in March. C. actoni was found at ePRS in all months, at BARe from October to March, DDRF in February and KRS in March.

194

(3) Genotypic Analysis of Bluetongue Isolates

Sequence analysis of BLU I and BLU 20 from 1997 have confirmed the reassortant virus first identified in 1995 has continued to circulate in the environment.

*****

MONITORING FOR MURRAY VALLEY ENCEPHALITIS (MVE) AND KUNJIN VIRUSES FOR TERRITORY HEALTH SERVICES

Project Period Project Officers Project Locations

Objective:

1996 - 1997 L Melville, N Hunt, S Aumann. Darwin, Katherine, Tennant Creek, Alice Springs, Gave.

To detect flavivirus (MVE and Kunjin) activity through poultry sentinel flocks which are bled monthly and tested for antibodies to these viruses.

Background: Sentinel chickens are used to monitor flavivirus actIVIty in Australia. Currently twenty four flocks are maintained in the north of Western Australia, seven in the Northern Territory, ten in New South Wales and ten in Victoria.

The aim is to provide early warning for the potentially fatal disease in humans, Australian Encephalitis, caused by the viruses MVE and Kunjin.

Results: Sentinel flocks were located at Leanyer, Howard Springs, Coastal Plains Research Station, Katherine, Tennant Creek, Alice Springs and Gove. During April, seroconversions occurred in the flocks at Katherine, Coastal Plains Research Station, Tennant Creek and Alice Springs.

All the chickens at Tennant Creek seroconverted, four to MVE, three to MVE and Kunjin, two to Kunjin and one to flavivirus only. Seroconversions at Katherine and Coastal Plains Research Station were to both MVE and Kunjin.

Seven out of nine birds at Alice Springs seroconverted, six to MVE and one to MVE and Kunjin. Further seroconversions to MVE occurred at Katherine and Coastal Plains Research Station during May.

*****

WILDLIFE AND EXOTIC DISEASE PREPAREDNESS PROGRAM (WEDPP) " DEVELOPMENT OF FLA VIVIRAL MONITORING STRATEGIES IN NORTHERN ANIMAL ECOSYSTEMS JAPANESE ENCEPHALITIS PREPAREDNESS

Project Period: July 1996 " June 1997 Project Officers: L. Melville, S. Walsh, N. Hunt. Project Location: Darwin, Northern Region, Research Farms.

Objective: To investigate sampling strategies and develop a laboratory testing capability in northern Australian to allow monitoring of flaviviral infections of animals as preparedness for a possible incursion of Japanese Encephalitis.

Background: In 1995, clinical and serological evidence was obtained of the presence of Japanese Encephalitis (IE) in the Torres Strait Islands. IE is exotic to Australia but the vector Culex annulirostris is widely distributed. It is currently unknown if the virus would establish in Australia and how far and fast it would spread.

195

Resu[ts: Feral pig sera were obtained from feral game meat hunters, NAQS surveys and Departmental officers. Cattle sera were collected under the NAMP and other sera were obtained from NAQS surveys and Parks and Wildlife officers.

Sera were screened in a flavivirus ELISA and positive sera tested for lE, MVE and Kunjin specific antibodies by neutralisation. A total of [973 sera were tested comprising 825 porcine, 31 avian, [047 sentinel cattle, 4 macropods, 59 feral animals and 7 native rodents. 3 [4 of the pig sera were flavivirus positive. Of these, 5 gave low titres to lE. These titres are being further investigated. Flavivirus activity was detected in sentinel cattle in northern Australia each year from 1994 to [997. Antibodies were also found in birds, macropods and other feral animals.

*****

FISHERIES DIVISION

AQUACULTURE

PEARL OYSTER AQUACULTURE

Project Period: Project Officer:

199611997 C Shelley

196

Project Location: Darwin Aquaculture Centre

Objective: Maintain a viable and healthy pearl culture industry.

Backgronnd: There are currently two major research projects being undertaken on behalf of the pearl oyster industry.

The first is the Fisheries Research and Development Corporation Pearl Oyster Health Survey of Northern Australia, which includes Western Australia, Queensland and the Northern Territory. The direct benefits of the study will include a better understanding of the potential risk to pearl oyster health and identification of agents currently causing mortalities or poor performance in farmed oysters. Data collected will also assist industry and government to make informed decisions relating to movement of oysters between farms, and interstate and Northern Territory locations. The Northern Territory part of the program is operated from the Darwin Aquaculture Centre (DAC) with technical support from the Animal Health Laboratory, Berrirnah and the assistance of local pearl farmers.

The second is a Pearl Oyster Nursery Project funded by the Cooperative Research Centre for Aquaculture. The program is operated from the DAC with assistance from the local pearl oyster hatchery and farms. If successful the benefit is a more controlled and regular supply of juvenile pearl oysters. The value of the pearl industry in the Northern Territory was $45 million in 1993/94.

Results: A review of the second year's work of the Pearl Oyster Health project in Western Australia, Queensland and the Northern Territory was held in Darwin 1996 and the work plan for the following year reviewed. Preliminary results were provided to industry in Broome at the industry's annual meeting. Ao application was successfully made to the Fisheries Research and Development Corporation for funds for the production of an histological atlas of disease and normal pearl oysters. Samples for the health survey from wild grounds and farms within the Territory have been collected, processed and examined by the consultant pathologist.

For the Pearl Oyster Nursery project, trials on the nutrition and conditioning of pearl oyster broodstock have been completed and work has commenced on the examination of preferred feeds and environmental parameters for pearl oyster spat.

*****

GOLDEN SNAPPER AQUACULTURE

Project Period: Project Officer: Project Location:

Objective:

1993-1998 G Schipp Darwin Aquaculture Centre

To examine the feasibility of the commercial production of golden snapper for marine aquaculture farms.

Background: Research of the farming potential of golden snapper, Lutjanus johnii, commenced at the Darwin Aquaculture Centre in November 1993. Early research concentrated on improving the quality of spawned eggs as well as

197

overcoming the difficulties of early larval survival. In February 1996 a breakthrough in the research was achieved by the production of the first golden snapper fingerlings in Australia. This breakthrough demonstrated that the research was on the right track and that the early survival of the larvae depended on the availability of a particular type of zooplankton food in their diet. Following on from the results of February 1996, the research has continued to focus on improving the diet of the larvae.

If the development of a cost effective production system for the golden snapper can be achieved, new and existing farmers in the Northern Territory will benefit from the opportunity to diversify their production. It could be expected that the industry would develop at a similar rate to farmed barramundi production and that in five years time more than 200 tonnes per annum could be produced, predominantly for export markets.

Whilst mainly funded by the Northern Territory government, this project has also benefited from the support of the Cooperative Research Centre for Aquaculture.

Results: A number of larval trials were undertaken using various feeds and environmental conditions. The supply of the Calanoid copepod, Acartia, has proven to be the key element in the early survival of the larvae. Several successful trials produced small numbers of golden snapper fingerlings, 200-300 each time, between October 1996 and February 1997.

In May 1997 the first commercial quantity of golden snapper fingerlings were produced when 18,000 fish were harvested from a single tank. The survival rate of these fish from larvae was 30% which represents the best survival recorded for the hatchery production of this fish anywhere in the world.

This success was subsequently repeated and it is now likely that a commercial production method for golden snapper will be developed within the near future.

MUD CRAB AQUACULTURE

Project Period: Project Officer: Project Location:

Objective:

1993-1998 G Williams Darwin Aquaculture Centre

*****

To examine the feasibility of the commercial production of mud crab, Scylla serrata.

Background: If successful, this research will directly benefit coastal aquaculture in the Northern Territory, Queensland, Western Australia and New South Wales. It would provide an additional species for farming and allow either for the diversification of existing facilities, or provide a stimulus for the development of specialist mud crab farms.

This research project is being undertaken in collaboration with Queensland Department of Primary Industries, SEAFDEC and the University of the Visayas in the Philippines. Financial assistance was received from the Australian centre for International Agricultural Research (ACIAR).

Resnlts: Larval trials have compared various live feeds, water parameters and water quality control regimes in attempts to improve larval survival.

A production regime has been developed that has lead to improved survival through to the megalopa stage of more than 20%. The production of megalopal crabs is now at a commercial level. Future research will focus on overcoming problems during the nursery phase, particularly the high incidence of cannibalism.

Research efforts have benefited from the international networking of the staff within the ACIAR project. ACIAR funded a mud crab conference in Darwin in May 1997, which was attended by program partuers from the Philippines and Queensland.

*****

BARRAMUNDIAQUACULTURE

Project Period: Project Officer: Project Location:

Objective:

1996-1997 G Schipp Darwin Aquaculture Centre

198

An economically viable barramundi industry, including production of larvae by the private sector.

Background: The barramundi program in 1996-97 involved regular production of larvae, operating an extension service for industry, stocking of Manton Dam for recreational fishing and undertaking research aimed at improving farm productivity.

Results: The Darwin Aquaculture centre functioned as a semi-commercial barramundi hatchery for the 1996-97 season. Barramundi larvae were supplied to industry as required.

A total of 50,000 barramundi fingerlings were released into Manton Dam as part of a program to stock it with fish for the recreation sector.

An on-farm demonstration of the production of barramundi fingerlings in green-water ponds was undertaken at a local farm. Barramundi fingerlings were also produced in a semi-extensive tank production system at the aquaculture Centre. This is an alternative production method for farmers that do not have large earthen ponds for green water culture.

*****

FISHERY RESEARCH

BARRAMUNDI POPULATION ASSESSMENT

Project Period: 1978-1998 Project Officers: R. Griffin, G. White, P. Johnson Project Location: Northern Territory Rivers, principally the Mary River

Objectives: Provide long-term fishery independent assessment of the status of barramundi stocks in the Mary River (and other areas as resources permit) utilising a range of methods.

Assess the level of recruitment of barramundi (spawning success) from year to year and evaluate fluctuations due to seasonal factors and environmental changes.

Assess the overall status of the barramundi fishery on the basis of commercial fishermen!s returns, research information and seasonal conditions.

Background: Regular sampling, mainly using gillnets and electrofishing, is conducted at several locations in the Mary River concentrating on the billabong environment where populations are isolated and relatively stable at the end of the dry season. Numbers of migrating juvenile barramundi have been monitored at several sites, beginning with the Daly River in 1982, to assess interannual changes in abundance. Since 1989 this recruitment monitoring has concentrated on the Mary River at Shady Camp where migrating recruits are concentrated at the saline intrusion control barrage.

In response to expressions of concern from anglers at Borroloola a five day sampling of the barramundi popUlation in the McArthur River was carried out in 1992. That sampling was repeated in 1995 but was not undertaken in 1996/97.

199

Method: A major feature of this work since 1987 has been the development and application of a technique known as a Closed Area Depletion Experiment (BARRACADE). This involves virtual total sampling of a section of billabong, some 400m in length, over a period of six days. The sampling area is isolated from the rest of the billabong by small mesh, heavy gauge block nets which prevent fish from entering or leaving the area unassisted.

The fish are caught using gillnets ranging in mesh size from 75 mm to 200 mm. This range of mesh sizes effectively samples the whole population of barramundi in the billabong environment.

After measurement, scale sampling and examination, the fish are tagged and released outside the enclosed area. This technique provides an estimate of the population of the sample area and an accurate assessment of the age structure of the population. The sampling period was reduced by one day in 1996 mainly to reduce the cost of overtime and allowances.

As the floods recede migrating juvenile barramundi are captured at the Shady Camp Barrage by electrofishing and by trapping. Otoliths are taken from a sample of them to allow for accurate age determination.

Data from commercial fishermen's monthly catch returns is analysed to assess trends in the popnlation. This information, together with the research information, is used to model the way in which the population has responded to fishing in the past and to assess the likely impacts of various management scenarios in the future.

Results: BARRACADE Sampling In the 4 days of the annual BARRACADE experiment at Corroboree Billabong, 291 barramundi were captured. The size distribution was again dominated by two distinct size groups; 45-55 cm, and 75-90 em. There were no new recruits of the 1995/96 year class present.

The age distribution (Figure 1.) was dominated by one year aids from the 1994/95 year class which made up 63% of the catch. The other significant age class was 2+ (from 1993/94) which comprised about 23%. The two year aids ofthe 1993/94 year class have grown very rapidly, and at 77 em mean TL are some 11 em larger than average at that age. The one year aids, at 35.0 em TL are of average size.

Figure 1. Age distribution of barramundi - BARRACADE 96.

70

".... 60 !Ill '"" 50 ~ u 40 c OJ 30 = g 20 ... u.. 10

0+------+-o 1 2 3 4

Age (years) 5+

Several methods of estimating the population of barramundi in the enclosed area can be applied to the data from this experiment.

A good estimate is provided by the weighted maximum likelihood method of Carl and Strube (1978). This method estimates the 1996 population to be 450 (between 374 and 493 with 95% confidence), slightly less than in 1995. Barramundi populations of the enclosed experimental area for the period 1989-1996, estimated by the Carl and Strube method, are shown in Figure 2.

200

Figure 2. Estimated barramundi population of the BARRACADE experimental area 1989·1996, determined by the Carl and Strube method, and the calculated biomass of barramundi based on that estimate. Error bar = 95% confidence interval for population estimate. Error is not calculated for the biomass estimate.

1200 1400

1000 1200

-. c 1000 co

" 800 ... :;:; ~ .. 800 "' :; "' 600 .. CI. E " 600 c.. " .~

...: 400 II:I

"' 400

""' ... "' 200 _Number ... 200

-+-Biomass

0 0

'" <:> C;; N "' ". In '" co '" '" '" '" '" '" '" '" "' "' '" '" '" '" Year

Relative abundance is reasonably reflected in the catch per unit effort (CPUE - fish per 100 m of net per hour, hmh), which at 2.6 fishlhmh is 12% less than the 1995 4-day CPUE of3.2 fishlhmh (Figure 3).

Figure 3. Total catch per unit of effort (CPUE) and CPUE of legal sized barramundi in Corroboree Billabong, September 1996.

6

5 """' -= e 4 -= .... -= 3 ., -= .... 2 .... ::::) ... u

0 1993 1994

--+-CPUE ____ Legal CPUE

1995

Year

1996

Of most relevance to the recreational sector is the relative abundance of legal size barramundi in the billabong (Figure 3). The CPUE for fish greater than 55 cm was 1.0 fishlhmh this year, compared to the 0.8 fishlhmh observed in 1995.

The numbers of saratoga at the sampling site has been recorded each year since 1993. In 1996 the number of saratoga caught was, for the first time, sufficient to enable meaningful estimation oftotal population using depletion methods. Using the same method as for barramundi, the saratoga population was estimated to be 153 (± 32). In the previous three years the number of saratoga caught did not exceed 20. Reasons for this apparent 5-fold increase in the saratoga population are not immediately obvious. While very little is known of the factors which influence saratoga popUlations, it is possible that the succession of four average or above average rainfall years has resulted in high recruitment and/or survival.

Recruitment monitoring Moderate numbers of utigrating juveniles from 15-35 cm total length were captured at the Shady Camp barrage in the late wet season. Sampling was hampered for most of the season by very high flood levels and overall sampling frequency was reduced in favour of work on the wetlands project. Data from that sampling has not yet been analysed.

201

Stock assessment and modelling. Assessment of the Northern Territory barramundi fishery has shown that the catch and effort have remained quite stable while the catch per unit effort, indicating relative abundance, has maintained a slightly increasing trend. A model describing and predicting fishery behaviour in response to fishing and to seasonal factors has been completed and was subject to some development and enhancement during the visit of Professor Carl Walters in November.

*****

BARRAMUNDI POPULATION ASSESSMENT - YELLOW WATERS

Project Period: 1995-96 Project Officers: R. Griffin, G. White, P. Johnson Project Location: Yellow Waters Billabong, Kakadu National Park

Objectives: Provide long-term fishery independent assessment of the status of barramundi stocks in Yellow Waters using the closed area depletion method.

Background: In 1993 assessment of the barramundi population of Yellow Waters Billabong in Kakadu National Park was carried out using the closed area depletion method developed for use at Corroboree Billabong. That work was funded by the Australian Nature Conservation Agency. Following the success of that sampling funding was again provided for further sampling in 1995 and 1996.

Methods: See Barramundi Population assessment - Mary River.

Results: Over 3 days of sampling (two 24 hr periods) 616 barramundi were captured. The barramundi population of the study area was estimated to be approximately 1250. This represents a slight increase over 1995. Sampling was terminated at the end the second day due to staffing problems and as a consequence the population estimate was made using an inferior method and is therefore less reliable than previous estimates. Catch per unit effort (CPUE), which reflects abundance, was 8% lower than in 1995 and CPUE for legal size fish (ie. > 55 cm) was 30% lower. The estimated biomass, however, was very similar to 1995.

Overall numerical abundance of barramundi was 3 times higher at Yellow Waters than at Corroboree and numerical abundance of legal sized barramundi was 2.4 times higher.

The age distribution (Figure 4) was very similar to Corroboree Billabong, dominated by the 1994/95 year class (1 +) which constituted 62% of the total population. New recruits of the 1995/96 year class (0+) make up only 9% of the population.

Figure 4 Age distribution of barramundi in Yellow Waters Billabong - September 1996

~ 70.0

~ 60.0 ->. 50.0 V 40.0 c <J) 30.0 ::l C" 20.0 e 10.0 u.

0 1 2 3 4 5+

Age

202

The most significant difference between 1996 and previous years is that the incidence of ulcer disease was high at Yellow Waters for the first time, with some 30% of fish showing active lesions. This level is higher than at Corroboree Billabong in 1996. While little is known of the causes of ulcer disease, it is possible that the high biomass of barramundi present at Yellow Waters in the past two years has lead to shortage of prey causing loss of condition and susceptibility to disease. This could be interpreted as an indication that the biomass of barramundi in Yellow Waters is indeed as high as it could be expected to get, as was suggested in the 1995 sampling report.

*****

MARY RIVER WETLANDS PROJECT

Project Period: 1995-2000 Project Officers: R. Griffin, G. White, P. Johnson Project Location: Darwin/Coastal areas from Cape Hotham to Wildman River

Objectives: Locate, characterise and map barramundi nursery habitat areas in the coastal zone adjacent to Chambers Bay and Finke Bay.

Assess the impacts of saline intrusion on barramundi populations, including the impacts of saline intrusion control works.

Background: Saline intrusion into freshwater habitats of the Mary River has caused extensive modification of habitats and flood regimes over the past 20 years. Works to control or reverse this intrusion have considerable potential to negatively impact on barramundi nursery habitats in the coastal zone either through direct modification or through denial of access from tidal waters to seasonal freshwater swamps.

A preliminary study, funded by the Fisheries Research and Development Corporation, ofbarramundi nursery swamps in the Mary River region commenced in September 1994 and was completed in May 1995. A final report on that work was circulated in late 1995.

In October 1995 annual funding of $47,500 for a five year study of barramundi nursery swamps and the impacts of saline intrusion control works on barramundi was announced by the Northern Territory govermuent . This allocation has been supplemented by diversion of resources from other barramundi research projects and other fisheries projects.

Methods: Vatious coastal swamp habitats in areas with and without saline intrusion control bunds were sampled using a variety of methods including scoop nets, seine nets, cast nets and hide traps. Access to most areas was by helicopter or in some cases by air boat. Water temperature and dissolved oxygen were measured at all sites.

Results: Intensive field work was undertaken from November 1996 to May 1996. A limited number of selected sites were sampled during the 1996/97 wet season with early efforts focussed on areas behind new bunds built to the west of Tommycut Creek. Sampling in these areas showed very low numbers of fish before late January, possibly because dissolved oxygen levels were quite low over that period. Massive flooding radically altered those sample sites and sampling effort was diverted to more coastal areas from February.

Sampling has been concentrated on a small bunded swamp area east of Point Stuart (called Fisher's Swamp), a similar but unaltered creek nearby (Thring's Creek), and three small coastal bunds west of Tommycut (EC3, EC4 and EC5). Fish access to Fisher's Swamp is provided for via a spillway and was densely populated by barramundi, ranging in size from 15 cm to 45 cm, but mostly around 25 cm, from February to May, as it was in 1995/96. Abundance and size of these fish were monitored on a weekly basis. Approximately 300 of those fish have been tagged in an attempt to determine their fate if they leave the swamp. After May there was no water remaining in the spillway and fish are therefore no longer able to depart from the swamp. Large numbers of barramundi were known to be still resident at the end of May. The swamp at upper Thring's Creek proved to be very difficult to sample because of dense reeds, shallow water, and abundant, large crocodiles. Numbers of

203

barramundi found there were comparable to the upper parts of Fisher's Swamp away from the spillway. While data analysis so far has been only cursory it is difficult to draw any conclusions from the comparative sampling.

Sampling techniques for these situations are still being developed and considerable difficulty is being experienced in identifying methods suitable for the range of conditions and water levels prevailing at different sites and times.

Detailed photographic records have been made of seasonal conditions in coastal swamp areas. Plots on salt affected areas above and below new bunds in the Tommycut Creek area were marked ant and photographed as a prelude to assessment of changes to vegetation. However flood damage to those bunds has halted the photographic project.

MUD CRAB PROJECT

Project Period: Project Officer: Project Location:

Objectives:

1989- ongoing T.Hay Darwin

*****

Manage the Northern Territory mud crab fishery for sustainable utilisation and maximum benefit to the Northern Territory. Monitor biological aspects of mud crab growth and behaviour, and catch and effort data from commercial logbooks. Comply with legislative requirements and foster strong industry liaison. Develop a plan of management for the mud crab fishery.

Background: The mud crab, Scylla serrata, is the basis of an important fishery in the Northern Territory. This fishery fosters high recreational participation, has a commercial component with a landed value worth over $7 million in 1996 and is an important food source for traditional people.

The mud crab research program has been in place since 1989 and a substantial body of knowledge on the fishery has been gathered during that period. Positive results from this research include the increase of the size limit for female mud crabs from 130 mm to 140 mm in order to protect immature crabs and the banning of restricted bait nets in Borroloola.

A significant amount of educational and scientific material has already been prepared and the former scientist is currently finalising his doctoral thesis and will soon make available his findings.

Methods: Continue to monitor and review the literature on mud crab in the Northern Territory and relevant fisheries in other regions. Provide annual summaries of the catch and effort data from fishermen's logbooks and review logbooks as necessary. Increase the presence of the Department amongst user groups of the mud crab fishery. Undertake liaison trips to major crabbing regions. Collect biological data from 100 mud crabs from each of the three major regions on a monthly basis to monitor any change in the fishery. This data will be collected in Darwin utilising the contacts established during the course of the project. The Mud Crab Fishery Advisory Committee (MCFAC) will meet as required. Prepare a mud crab fishery project report for MCFAC. Clients will be advised of management changes and general information on the fishery. Meet legislative requirements. Disseminate information through publications including newsletters, brochures, Fishnotes and scientific papers and by providing information at public forums.

204

Participate in a workshop held by Prof Carl Walters on assessing the status of the stock of Northern Territory mud crab, state of the fishery and possible management and research options.

Results: Considerable biological information and catch and effort data has been collected and will provide an understanding of the effects of fishing on the population dynamics of the mud crab resource in the Northern Territory. It is estimated that it will require a further 12 months for the former scientist to complete his final analyses although recommendations were made to increase the size limit for female mud crabs based on findings to date.

Base level information was collected monthly in order to monitor the health of the resource and the fishery. This was in the form of monthly catch and effort data and commercial catch monitoring.

Liaison was maintained with the commercial mud crab fishermen through printed material and fields trip to major crabbing areas.

The annual project report was presented to and endorsed by the Mud Crab Fishery Advisory Committee (MCFAC).This report details results and proposed future directions.

Mud crab status reports for 1995 and 1996 and new Fishnotes were completed. Amendments to the mud crab management plan were agreed to, including an increase in the minimum size for female mud crabs and the prohibition of the use of restricted bait nets in the southern Gulf of Carpentaria. Further amendments are proposed to clarify control of the fishing operation and other administrative aspects of the fishery.

Prof Carl Walters determined that the use of trend index statistics such as CPUE was not suitable for undertaking accurate stock assessment in the mud crab fishery. He proposed a number of management and research initiatives and strongly recommended that collection of fishery independent data be made a priority. Identification of spatial habitat patterns and densities per unit habitat area are prerequisites to future stock assessment. The continued monitoring of the fishery data was also endorsed.

STOCK ASSESSMENT

Project Period: Project Officers: Project Location:

Objective:

*****

1991- ongoing R Buckworth, R Griffin, T Hay, J Lloyd, D Ramm Darwin

Improve estimates of the potential yields and optimum fishing levels for Northern Territory fisheries, identify appropriate management approaches, and increase the assessment expertise of Northern Territory staff.

Background: Identification of optimum levels for harvesting fisheries is difficult; fish and other aquatic creatures can seldom be counted directly, the behaviour of fishers is difficult to predict, and the effects of weather, technological advances and movement of prices are all difficult to forecast. Fishery scientists and managers rely on mathematical models that use biological data and information from the fishery such as age, composition of the catch, and catch and fishing effort data. Expertise with such models is a rare commodity. The Fisheries Division has sought external peer review, guidance and training in fishery assessment. To this end, collaborative work is regularly undertaken with other fisheries institutions, and a Memorandum of Agreement has been signed with the Fisheries Centre, University of British Columbia (UBC). During 1996/97, collaboration under this MOA included higher degree training for Divisional research officers (Buckworth, 1996, in press; Pitcher et aI., in press), joint research and a major review of some of the more important Northern Territory fisheries, by Prof Carl Walters, ofUBC (Ramm, 1997).

205

Method: Prof Walters was invited to Darwin for a 4 week consultancy to review stock assessment and management strategies for barramundi (Lates calcarifer), goldband snapper (Pristipomoides spp.), mud crab (Scylla ferrata), red snapper, and coastal reeffish (Lutjanus spp.).

Assessment teams consisting of scientists, managers and some visiting scientists, were led by Prof Walters. Results were reported at the end of each session. in a public forum at the end of the series of workshops and as a Departmental Fishery Report (Ramm, 1997).

Results: It was found that; there is opportunity for growth in some Northern Territory fisheries, particularly red snapper; the barramundi and mud crab fisheries are fully developed and fishers are generally harvesting stocks at biologically safe levels, the goldband snapper fishery is likely to be overfished in the future by developing fisheries in the Indonesian sector. Abundances and growth opportunities for a number of fisheries could not be assessed, due to inadequate data.

*****

NORTHERN PRAWN FISHERY MONITORING

Project Period: Project Officer: Project Location:

Objective:

1978- ongoing D Grey, R Buckworth Darwin

Maintain a watching brief on the Northern Prawn Fishery (NPF) for issues specific to the Northern Territory.

Background: The NPF is one of Australia's most valuable fisheries and contributes a large proportion of the value of commercial fishery landings from waters off the coast of the Northern Territory. The fishery is managed by the Commonwealth, with the Northern Territory contributing via its position on the fishery's management advisory committee. The role of this program is thus to provide input to the fishery, and to monitor the interactions of the NPF with other Northern Territory fisheries and communities.

Results: Although this is a watching brief and thus does not in itself provide data, it has provided a framework for bycatch and technology projects, such as the recent completed studies of bycatch reduction devices (McGilvray et al., 1996; Robins et al., 1997).

*****

TROLL FISHERY FOR SPANISH MACKEREL

Project Period: Project Officers: Project Location:

Objectives:

1991- ongoing R Buckworth, N Gill, C Bryce Darwin

Identify the sectors of the fishing industry exploiting mackerel, their target species, and fishing unit characteristics. Develop a logbook and biological monitoring system for the provision of both commercial catch and effort data, and biological data. Identify the geographic structure of stocks of the target species. Draw together all available information to develop models of the fishery which allow stock assessment and exploration of various management regimes and indicate required research.

Backgronnd: Declared as a limited entry fishery in 1991, the troll fishery for Spanish mackerel is regarded as a developing fishery. The species was taken and possibly overfished in northern Australia, by licensed foreign driftnetters

206

until the ntid-1980s. Local participation grew with prices throughout the 1980s, with annual catch peaking in 1990 at about 270 t. Growing concerns for the viability of the resource and economic performance of the fishery saw lintitation of entry and the introduction of input controls. Research into the fishery has been directed at providing information on potential sustainable exploitation rates and yields for this stock.

Information on catch and distribution of effort have, on their own, proven to be inadequate to closely define sustainable yields for this fishery. Modelling of the fishery has been conducted with expert input from Norm Hall, of the Fisheries Department of Western Australia, and more recently with the Fisheries Centre, University of British Columbia

Method: Base level biological information is collected by researchers aboard fishing vessels. Selected fishers also collect this biological information, and provide daily logbooks. Otoliths collected during the study have been examined as part of a study funded by Fisheries Research and Development Corporation to establish the age structure of the commercial Spanish mackerel catch.

Stock assessment models have been constructed which use the biological and age data, as well as logbook and literature information, in efforts to define the potential catch of the fishery and to examine possible management and research strategies.

Results: A database has been compiled of daily logbook data and biological information. Modelling of the fishery indicates that the fish population is reasonably robust to harvest, as there is significant reproduction before most fish are available to the fishery. The age structure indicates most fish in the catch are 4-6 years old with few exceeding 10 years of age, suggesting the biggest and oldest fish may also not be available to the fishery. It has not yet been possible to predict the optimum catch for the fishery.

*****

STOCK STRUCTURE OF GOLDBAND SNAPPER RESOURCES ACROSS NORTHERN AUSTRALIA

Project period: Project officer: Project location:

Objectives:

1996-1998 JLioyd

Northern Territory and Western Australia

Investigate the stock structure of goldband snapper (Pristipomoides multidens) in northern Australian waters, to assist in the development of appropriate management plans for the deepwater snapper fisheries of Northern Territory and Western Australia.

Backgrouud: This is a joint project between the Northern Territory and Western Australia, funded by Fisheries Research and Development Corporation. Over the last 5 years there has been rapid development in both states of deepwater snapper fisheries which target Pristipomoides multidens. Both Western Australia and the Northern Territory are presently formulating management plans for their respective deepwater fisheries. A key issue in formulating these plans is whether there is a single shared stock or distinct isolated stocks. This important question must be resolved before accurate estimates of sustainable yield(s) can be determined and appropriate management plans implemented.

Method: To examine the stock structure of Pristipomoides multidens between Western Australia and the Northern Territory in the most cost effective way, a step wise approach using both mitochondrial DNA and otolith nticrochentistry will be employed.

Samples for both ntitochondrial DNA as well as otolith nticrochemistry were obtained from commercial boats in 5 areas where Pristipomoides multidens is taken in commercial quantities, ie Timor Sea, Arafora Sea, Kimberley region, North West shelf and the Exmouth area. A total of 100 samples per location were collected for mitochondrial DNA analysis and 40 samples were collected for otolith nticrochentistry. Initially only 25

207

samples will be screened to determine if there is any indication of genetic differences. If these initial findings suggest that there may be genetic differences then the rest of the material will be analysed.

If no genetic differences are observed in the initial screening it is proposed to investigate for local populations of Pristipomoides multidens using otolith microchemistry. This material would be obtained at the same time as the mitochondrial DNA samples, but a second collection would also be required 6 months later to determine if there is a seasonal variation.

Results: The initial screening is almost completed, and a meeting between the Western Australian and Northern Territory researchers will take place in Darwin in July 1997 to discuss these results and coordinate the next phase of the project.

ASSESSMENT OF DEMERSAL FISH STOCKS

Project Period: Project Officer: Project Location:

Objectives:

1989-1997 J Lloyd Darwin frimor Sea

*****

Obtain information on the biology and population parameters of goldband snappers (Pristipomoides spp) and red snappers (Lutjanus spp) in waters between 127°_137°E; Model population dynamics and assess stocks of goldband and red snapper; Refine fishery models and review stock assessments.

Background: This program provides research information for the Timor Reef and demersal fisheries, to ensure the long-term viability of these resources. Over the period 1989 to 1992 there was a four fold increase in the value of the Timor Reef fishery. The commercial catch has a current Territory market value of over $2 million. It is expected that this fishery will continue to develop over the next 5 years.

Method: Field work is carried out on commercial boats in conjunction with normal fishing operations. Ageing studies using otoliths (earbones) from Pristipomoides multidens and P. typus was carried out at Day Street Laboratory. Otoliths were embedded in resin, sectioned, then read using image analysis software. Daily logbooks were introduced for the Timor Reef fishery in July 1995 to obtain better catch and effort information.

Results: Present estimates of sustainable yield of goldband snapper range from 250 t-12,000 t depending on whether the stock is closed or mixes over the entire Timor Sea. This estimate was obtained during a workshop in October 1996 conducted by international stock assessment expert Prof. Carl Walters. Recommendations were made by Prof. Walters on how to improve these estimates of sustainable yield. Specifically, he recommended that further research be carried out to determine movement rates of goldband snapper (target species), and suggested methods for directly estimating the current size of Australian stock.

COASTAL FISHERIES RESEARCH

Project Period: Project Officer: Project Location:

Objectives:

1995- 2000 THay Darwin

*****

Provide baseline information on Northern Territory coastal fisheries. Identify major coastal fish species and collect biological information to assist in determining and implementing management priorities. Develop a plan of management for the fishery.

208

Background: In the Northern Territory coastal fisheries are those in the coastal zone, from estuarine waters to 15 nm offshore, this includes rivers, bays, inlets, intertidal areas, extensive areas of mangroves and seagrass as well as open water. These various areas encompass a range of habitats such as coral or rock reefs, fringing reefs, coral rubble, sand and mudflats, which in turn support a diverse range of fish and other aquatic species. There is also a variety of user groups including commercial fishermen, fishing tour operators, recreational fishermen and Aboriginal communities. Further pressures are placed on the coastal zone by continuing urban, tourist and commercial development and the growing Top End population.

With the complexity of habitats included in the coastal zone, the diversity of species exploited and the varying aspirations. interactions and needs of the user groups, it is important to attempt to ensure that the region is not degraded. An important part of this is the proper management of the fisheries which occur in this region.

In June 1995, the Department and the Northern Territory Fisheries Research and Development Advisory Committee (FRDAC) supported a proposal to implement a preliminary coastal fisheries research project. The project was designed to give the Fisheries Division preliminary baseline information on the coastal line and coastal net fisheries in the Northern Territory and examine the dimensions and directions of research and management priorities for these fisheries.

Further research commitment was identified as a pnonty and recommended by the Coastal Line Fishery Advisory Committee (COLFAC) on the presentation of the results for the preliminary coastal fishery project 1996.

Method: Monitor and review the literature on coastal fisheries in the Northern Territory and relevant fisheries in other regions. Provide annual summaries of the catch and effort data from compulsory fishermen's logbooks with relevance to Northern Territory coastal fisheries. Increase the presence of the Department amongst user groups of the coastal fisheries. Develop liaison between the Department and various user groups to document important issues and facilitate education on fisheries related matters. Collect base level biological information on fish caught in coastal fisheries, especially jewfish, snappers and emperors. Prepare and submit preliminary coastal fisheries research project report. Participate in workshop held by Prof Carl Walters on assessing the status of the stock of Northern Territory coastal line species, state of the fishery and future management and research options.

Results: The preliminary project report has been finalised and presented to and endorsed by the Coastal Line Fishery Advisory Committee (COLFAC). This report details initial results, including four fishnotes detailing the preliminary findings on the life history and biology of golden snapper Lutjanus johnii, black jewfish Protonibea diacaNorthem hus, Spanish flag Lutjanus carponatatus and tricky emperor Lethrinus laticaudis.

A more substantial ongoing research project has begun and the coastal database is updated with the findings. Analyses of these findings will see further species examined, updated and new fishnotes and a scientific paper prepared for publication during 1997. A draft plan of management has been considered at COLFAC and implementation of the plan is expected during 1997.

A recreational possession limit for black jewfish came into force in 1996 and a general possession limit of 30 fish has been endorsed and is awaiting implementation.

Prof Carl Walters determined that the use of trend index statistics such as CPUE was not suitable for undertaking accurate stock assessment in the coastal fishery. He proposed a number of management and research initiatives and strongly recommended that collection of fishery independent data be made a priority. Identification of spatial habitat patterns and densities per unit habitat area are prerequisites to future stock assessment. The continued collection of the baseline biological data was also endorsed. A review of the coastal net fishery commenced during 1996/97. Three formal meetings were held to document the various issues and positions held. *****

209

EQUITABLE UTILISATION OF COMMERCIAL AND TRADITIONAL FISHERY RESOURCES

Project Period: Project Officers: Project Location:

Objectives:

1996 - 1997 R Mounsey, J MacCartie Northern Territory coastal seas

Evaluate the use of a modified Queensland type tunnel net to catch live coastal pelagic species, reduce dugong mortalities and supply bait to crabbers. Encourage, support and enhance near shore commercial fishing activities by Aboriginal people.

Background: The problems of landing dead fish and the capture of dugongs and turtles have been associated with the use of gillnets. Initial trials with an alternative Queensland tunnel net demonstrated that commercial quantities of fish could be landed live and large animals such as turtles and dugongs could be released alive.

Aboriginal community representatives were making increasing requests for assistance in up-grading from traditional fishing practises to viable commercial fisheries.

Resnlts: Trials have continued to be encouraging. Approximately 90% of all fish caught were landed alive or released alive. No dugong have been caught in the tunnel net and the few turtles captured were released in good health. Further work is needed on wing length and funnel design.

A small mullet fishery was set up at Elcho Island. Two CDEP vessels are now regularly landing commercial quantities of sea mullet. The people of Elcho Island highly regard mullet as an eating fish and are purchasing most of the CDEP catch.

The potential to export mullet interstate is high. One Sydney based company has purchased Elcho Island mullet and is prepared to take substantial quantities. Although the resource of mullet around Arnhem Land is under exploited and could possibly meet the export demand, resource allocation problems between barrarnundi fishermen, Darwin based coastal net fishers and potential Aboriginal mullet catchers first need to be resolved.

In November 1996 15 traditional fishers were trained at sea in the techniques offish trapping, drop lining and coastal line fishing around the English Company Island Group. In June 1997 traditional fishers were trained and advised on commercial fishing methods in Mountnorris Bay, Arnhem Land.

*****

DEVELOPMENT OF THE DEMERSAL FISHERY

Project Period: Project Officers: Project Location:

Objectives:

1996 - 1997 R Mounsey, J MacCartie Northern Territory offshore seas

Locate new fishing grounds closer to Darwin. Improve passive fishing techniques and provide an extension service to the industry.

Background: The demersal fishery is struggling to develop. Although commercial quantities of red snapper have been landed using passive fishing methods in the Gove region, the vast distance from Darwin has made it difficult to take advantage of cheaper freight rates to Brisbane and Sydney and effectively market the fish. Tiger sharks were found to be destroying dropline rigs. This problem and the fishers' lack of experience needed to be addressed.

210

Results: A survey in October 1996 identified commercial quantities of red snapper approximately 90 nautical miles west of Darwin. Over 5 tonnes of fish were sold at the Sydney and Brisbane fish markets. The report of the survey was published in April 1997 and has generated renewed interest in the demersal fishery.

During the survey a new chain rigged dropline was used to overcome the gear losses caused by tiger sharks.

Workshops using under water video footage of traps and droplines have assisted demersal and potential demersal fishers in present and future fishing strategies.

GEAR LOAN SCHEME

Project Period: Project Officers: Project Location:

Objectives:

1996 - 1997 R Mounsey, J MacCartie Darwin

*****

To assist fishermen entering into new fishing or marketing operations by providing selected gear on a short term basis.

Background: Many Northern Territory fish stocks are under exploited. Often fishermen interested in developing these resources are unwilling to invest in expensive fishing gear for such a high risk venture. In 1985 the Northern Territory Fishing Industry Council in collaboration with the Fisheries Division set up the Gear Loan Scheme. In recent years the Fisheries Division has taken over the scheme and maintained it through supplying gear used on exploration and development projects.

Resnlts: During the past year the scheme has been well utilised by the fishing industry. The two hydraulic dropline machines have been continually on loan. Other fishing gears on regular loan have included fish traps (30 available), droplines, bait nets, mullet nets and a 300 metre purse seine. Three X-actic interstate fish transport bins have also been highly sort after.

SQUID FISHING

Project Period: Project Officers: Project Location:

Objectives:

1996 - 1997 R Mounsey, J MacCartie Darwin

*****

To investigate the potential of a Northern Territory based and controlled squid fishery and to assist industry development.

Background: The Northern Prawn Fishery (NPF) regularly lands substantial quantities of squid. In recent years some NPF vessels have at times been targeting breeding aggregation of squid. The nets not only catch the squid but also remove the eggs on or near to the sea floor.

A more passive fishing method which does not significantly impact on the reproductive cycle of the squid would help ensure their long term viability.

Results: During the past year only one reasonable size concentration of squid was reported east of Groote Eylandt. The single Northern Territory licensed jigging boat found no significant concentrations of squid in the Darwin region.

211

A number of other fishermen applied to the Fisheries Division to use a variety of passive gears to capture squid. None of these development licenses have yet been approved.

*****

TECHNICAL COOPERATION NETWORK IN FISHING TECHNOLOGY BETWEEN THE NORTHERN TERRITORY AND INDONESIA

Project Period: Project Officers: Project Location:

Objectives:

1996 - 1997 R Mounsey Darwin

To establish and strengthen fisheries links between eastern Indonesia and the Northern Territory. To encourage viable passive fishing techniques in eastern Indonesia.

Background: Eastern Indonesian and Northern Territory fishers share fish resources as stocks of snapper and emperor are jointly fished along the Australia / Indonesia sea border.

Many of these fish stocks depend on the continued existence of natural demersal habitats, both inshore and offshore. The reported destruction of coral reefs and trawl grounds in eastern Indonesia could be adversely effecting fish concentrations in Northern Territory waters.

Resnlts: On going communications have been taking place with Indonesia's highest ranking fisheries officers both in Australia and Indonesia and also overseas at BIMP-EAGA Fisheries conferences.

A project to assist Indonesia to develop its aquaculture milkfish industry is presently underway. A Darwin-based company will soon attempt to deliver broodstock milkfish to Gondol in eastern Indonesia.

The Indonesian Government has supported two Northern Territory initiated fisheries projects for eastern Indonesia. The first focuses on introducing passive drop lining and trapping techniques to the Timor region and the second concentrates on establishing stock sizes and fish movement along the Indonesia / Australia border.

The Indonesian Director of Research is also considering internally funding a Northern Territory proposal for a coral reef rehabilitation project.

*****

UNITED NATIONSIFAO INDIAN OCEAN WORKSHOP ON BYCATCH EXCLUSION DEVICES

Project Period: Project Officers: Project Location:

Objectives:

May 1997 R Mounsey Darwin

Establish, introdnce and encourage less destructive catching methods.

Background: Some fishing gears accidentally catch non target species. These non target species are often important to the sustainable harvest of other fisheries. Non target species can also include protected or endangered species such as turtles.

The success of the Northern Territory Fisheries Division in developing less destructive fishing methods and the chairing of the first Asian United Nations Code Of Conduct meeting on Responsible Fishing in China by a Territory fisheries officer, lead to the Northern Territory hosting the UN funded Indian Ocean workshop.

212

Results: The Workshop has been postponed until July 1997. However as a lead up to the workshop a Northern Territory fisheries officer presented a paper in Bangkok at the second Asian Code of Conduct Meeting and chaired the opening session of the Asia Pacific Fishing Conference in Cairns.

*****

213

PUBLICATIONS, CONFERENCE PAPERS, PRESENTATIONS

Anon (1996). Northern Territory Primary Industry and Fisheries Statistics 1994-95. DPIF Tech. Bull. No. 247. Anon (1996). Northern Territory Primary Industry and Fisheries Statistics January December 1995. DPIF Tech.

Bull. No. 248. Anon (1996). PrimeStats: Rural and Fishing Industries in the NT 1994-95. DPIF incidental publication. Anon (1996). PrimeS tats: Rural and Fishing Industries in the NT 1995. DPIF incidental publication.

Behjatnia, S.A.A., Dry, LB., Krake, L.R., Conde, B.D., Connelly, MJ., Randles, J.W. and Rezaian, M.A. (1996). New Spindle Tuber Viroid and Tomato Leaf Curl Geminivirus Strains from a Wild Solanum sp. Phytopathology 86(8):880-886

Bryce, C.R,Brown,P., Buckworth,RC.(In Press). Fish Otolith Sectioning And Preparation For Microscopic Examination, DPIF TechNote (in print) .

Buckworth, R (1996) A road test of EcoPath. In "Mass Balance Models of Northeastern Pacific Ecosystems". (Eds. D. Pauly and W. Christensen, with N. Haggan). pp 81-82. Fisheries Centre Research Reports 4(1) (University of British Columbia: Vancouver). ISSN 1198-6727.

Buckworth, R. C. (1997). Age structure of the commercial catch of Northern Territory narrow-barred Spanish mackerel. Project T94/o15. Final Report to the Fisheries Research & Development Corporation, DPIF Fishery Report 42.

Buckworth, R C. (in press). World fisheries in crisis? We must respond! In, Pitcher, T. J., Hart, P. J. B., and Pauly, D. (eds.), "Reinventing Fisheries Management". (Chapman & Hall: London.).

Calogeras C.E. and Knuckey,I. (1995). Status Report 1994- Coastal Line. Northern Territory Department of Primary Industry and Fisheries.

Calogeras C.E.and Knuckey,I. (1996). Mud crab "96 Your fishery. Newsletter No.2 Northern Territory Department of Primary Industry and Fisheries.

Calogeras C.E.and Hay, T. (1996). Status Report 1995- Coastal Line. Northern Territory Department of Primary Industry and Fisheries.

Calogeras C.E.and Hay,T. (1996). Status Report 1995- Coastal Net. Northern Territory Department of Primary Industry and Fisheries.

Calogeras C.E.and Hay,T. (1997). Mud crab "97 Your fishery. Newsletter No.3 Northern Territory Department of Primary Industry and Fisheries.

Calogeras C.E.and Hay,T. (1997). Status Report 1996- Coastal Line. Northern Territory Department of Primary Industry and Fisheries.

Calogeras C.E.and Hay,T. (1997). Status Report 1996- Coastal Net. Northern Territory Department of Primary Industry and Fisheries.

Calogeras, C.E. (1995). Coastal Line Fishery, An Explanation of Amended Fisheries Regulations Which Came Into Force on 3rd February 1995, Fishnote 16, Northern Territory Department of Primary Industry and Fisheries.

Calogeras, C.E. and Knuckey,I. (1995). Don't Be Caught Short, The Minimum Size Limit of Female Mud Crabs In The NT Will Increase In January 1996, Fishnote 18, Northern Territory Department of Primary Industry and Fisheries.

Calogeras, C.E.and Knuckey,I. (1995). Status Report 1994 - Mud Crab Fishery, Northern Territory Department of Primary Industry and Fisheries.

Calogeras, C.E.and Knuckey,I. (1996). Status Report 1995 - Mud Crab Fishery, Northern Territory Department of Primary Industry and Fisheries.

Calogeras, C.E.and Hay,T.(1997). Status Report 1996 - Mud Crab Fishery, Northern Territory Department of Primary Industry and Fisheries.

Cameron, A. (1996) Evaluation of tropical Pasture Species as leys in the semi-arid Tropics of North-west Australia, Aus.J Exp.Agric. 36: 929-35.

Cameron, A and Ross, B. (1996) Fertiliser Responses of Established Grass Pastures In the Northern Territory , Tropical Grasslands 30: 426-29.

Cameron, A. Improved pastures: Weeds or what?, in 15th Annual Weeds Branch Meeting proceedings pp 34-36. Cameron, A., Nutrients in pasture legumes in the Top End of the Northern Territory, DPIF Technical Bulletin 262. Cameron, A., Nutrients in pasture grasses in the Top End of the Northern Territory, DPIF Technical Bulletin 191. Cameron, A. (1996) Bullrush Millet, DPIF Agnote E 58. Cameron, A. (1996) Cavalcade and Bundeey Seed Production, DPIF Agnote E 37.

214

Cameron, A. (1996) Buffel Grass, DPIF Agnote E 28. Cameron, A (1996) Milgarra Blue Pea, DPIF Agnote E 59. Cameron, A (1996) Indian Blue Grass, DPIF Agnote E 25. Cameron, A (1996) Fertilisers for Grass Pastures, DPIF Agnote E 60. Cameron, A (1996) Fertilisers for Legume [Grass Mixed Pastures, DPIF Agnote E 61. Cameron, A (1996) Fertilisers for Legume Pastures, DPIF Agnote E 62. Cameron, A (1997) Glenn American Joint Vetch, DPIF Agnote E 22. Cameron, A and Lemke,B. (1996) Para Grass, DPIF Agnote E 30. Cameron, A and Lemke,B.(1997) Basilisk Signal Grass, DPIF Agnote E 19. Cameron, A and Austin,J. (1997) Sabi Grass, DPIF Agnote E 27 Cameron, A (1997) Seasonal changes in soil available phosphorus concentrations, DPIF Technote No. 92. Chin, D. (1996). Integrated Pest Management in Tree Crops. Lecture to Horticulture students, Northern

Territory University, Casuarina, NT. 05 November 1996. Chin, D. (1997). Biocontrol of Palm Leaf Beetle. Illustrated talk and discussion delivered to NTU students. May

1997. Chin, D. and Brown, H.H. (1997). Integrated Pest Management in Fruit Trees, mango pests and live displays of

beneficial arthropods. Fred's Pass Rural Show. 17-18 May 1997. Conde, B.D., Pitkethley, R.N., Smith, E.S.C., Kulkarni, V.J. (1997). Mango Scab and Its Control.DPIF, Agnote

133. Conde, B.D., Pitkethley, R.N., Smith, E.S.C., Kulkarni, V.L, Thiagalingam, K., Ulyatt, L.I., Connelly M.1. and

Hamilton, D.A. (1997). Identification of mango scab caused by Elsinoi! mangiferae in Australia. Australasian Plant Pathology 26(2):131

Conde, B., Connelly, M. and Pitkethley, R. (1996). Potato Spindle Tuber Viroid, Darwin Strain - Further Investigations in Darwin. Pacific Association of Tropical Phytopathology Newsletter 14:7-9

Conde, B., Ulyatt, L. and Pitkethley, R. (1996). Occurrences of Australian Papaya Dieback, Yellow Crinkle and Other Diseases or Disorders of Papaya With Similar Symptoms Recorded From the Northern Territory of Australia. Pacific Association of Tropical Phytopathology Newsletter 14:2-6

Conde, B., Ulyatt, L. and Pitkethley, R. (1996). Occurrences of Papaya Diseases in the Northern Territory. Papaya Post 3:28-29 [extract from above paper]

de Witte, K., (1996), Pompes Disease Update, Katherine Rural Review No.179. de Witte, K., (1996), A Show of Defiance, Katherine Rural Review No.181. de Witte, K., (1996), Short Head Cattle, Katherine Rural Review No.182. de Witte, K., (1997), Don't Go Batty, Katherine Rural Review No.184. de Witte, K., (1997), Black Soil Blindness, Katherine Rural Review No.185. de Witte, K., (1997), Dropped Ovary Spay Technique, Katherine Rural Review No.185. de Witte, K., (1997), Three Day Sickness Update, Katherine Rural Review No.18S. K de Witte, and T F Jubb, Australian Association of Cattle Veterinarians Proceedings 1997, Brisbane,

Queensland 5-9 May 1997, "Delayed Post Mortems - A Practice of Special Value for Veterinarians Servicing Extensive Beef Herds in Remote Areas".

Diczbalis,Y., (1997). Environmental factors influencing the growth and yield of rambutan and cupuacu. Final Report Rural Industries Research and Development Corporation and NT Department of Primary Industry and Fisheries Project DNT-IOA.

Diczbalis,Y., and Menzel,C.M. (1997) Low temperatures decrease CO2 assimilation and growth in the tropical rarnbutan. Jounrnal of Horticultural Science (in press) ..

Diczbalis,Y., Eamus,D. and Menzel,C.M. (1996). Environmental factors influencing the growth and yield of rarnbutan grown in the wet/dry tropics of Northern Australia. Vol II Proceedings of the International Conference on Tropical Fruits, Kuala Lumpur, Malaysia, 23-26 July 1996.

Diczbalis,Y., Hofman,P., Landrigan,M., Kulkarni,V. and Smith,L. (1996). Mango irrigation management for fruit yield, maturity and quality. Proceedings Mango 2000 mertketing seminar and production workshop. 3 August 1995. Townsville, QDPI.

Diczbalis,Y., Rann,R., Carneron,Aand Sawyer,B. Floodplain farming systems trial rice-legume pasture rotation trial, Conservation Farmingfor the Semi-arid Tropics, Proceedings of Workshop NT Rural College, July 1995, pp 78-92.

Diczbalis,Y., Wicks,C. and Landrigan,M. (Draft). Heat Sums to predict fruit maturity in Mango(cv.Kensington Price). Final Report Horticulture Research and Development Corporation Project FR605.

Eggington A. and Cameron A. (1996)The Value of Improved Pasture DPIF Agnote E32.

215

Entomology Branch DPIF (1996) Insecticides for use on Fruit, Vegetables and Ornamentals in the Northern Territory, 4th Edition, 18pp,

Greenwell, S" (1997) Asian Vegetables, DPIF Technical Bulletin No, 259, Griffin R.K., c.P. Keenan and P.I. Pender. 1996. Refinement of barramundi stock definition: particularly in

relation to access and allocation to competing user groups. Final report to Fisheries Research and Development Corporation, Canberra. 31 pp.

Griffin, R.K. 1997. An assessment of the barramundi and saratoga population of Yellow Waters Billabong, Kakadu National Park, October 1995. A report prepared for the Australian Nature Conservation Agency. Northern Territory Department of Primary Industry and Fisheries, Darwin, Australia. 9 pp.

Griffin, R.K. 1997b. BARRACADE 96 - Preliminary report of closed area depletion experiment, Corroboree Billabong, September, 1996. Unpublished report. Northern Territory Department of Primary Industry and Fisheries, Darwin, Australia. 9pp.

Grimister, S., (1997) Tropical Fruit Market Survey. DPIF Technical Bulletin No. 252.

Hay T.A., I. Knuckey & C.E.Calogeras. 1996. NT Coastal Reef Fish. Population biology of the Golden Snapper Lutjanus johnii. Fishnote 21. Northern Territory Department of Primary Industry and Fisheries.

Hay T.A., I. Knuckey & C.E.Calogeras. 1996. NT Coastal Reef Fish. Population biology of the Black Iewfish Protonibea diacanthus. DPIF Fishnote 22.

Hay T.A., I. Knuckey & C.E. Calogeras. 1996. Preliminary Coastal Fisheries Research Project- Final Report, to COLFAC, Iune 1996. Northern Territory Department of Primary Industry and Fisheries.

Hristova, V.I. (1999). The Cost of Weeds to the Pastoral Industry. Top Paddock Newsletter No.12, October. NT Dept. of Primary Industry and Fisheries.

Iang, E.; Smith, E.S.C. and Armstrong, J. (1996).Kenna,G. and Mansfleld,I. Central ian flower potential of Centralian species. Literature Review for RIRDC Project No. DNT-16A.

Iang, E.; Smith, E.S.C. and Armstrong, I. (1996).Assessment of the Papaya Fruit Fly eradication program in North Queensland. Report to QDPI and Plant Health Committee of visit from 04-08 November 1996 by scientific assessment panei. 14pp.

Kirby, G.W.M., Hristova, V.I. and Murti, S. (1996). Conservation tillage and ley farming in the semi-arid tropics of northern Australia - some economic aspects. Aus!. I. Exp. Agric. 36:1049-57.

Knuckey I., and Calogeras,c.E. (1995). Mud crab "95 Your fishery. Newsletter No.1 Northern Territory Department of Primary Industry and Fisheries.

Knuckey I., and Calogeras, C.E. (1995). Status Report 1994 - Coastal Net. Northern Territory Department of Primary Industry and Fisheries.

Knuckey I., Calogeras,c.E. and Hay, T. (1995). Coastal '95 Your Fishery. Newsletter No.1 Northern Territory Department of Primary Industry and Fisheries.

Knuckey I., Hay, T.A. and Calogeras,C.E. (1996). NT Coastal Reef Fish. Population biology of the Tricky Snapper Lethrinus laticaudis. DPIF Fishnote 23.

Knuckey I., Hay, T.A. and Calogeras, C.E. (1996) NT Coastal Reef Fish. Population biology of the Stripey Lutjanus carponatatus. DPIF Fishnote 20.

Knuckey, I. 1995. Laxothylacus ihlei And Its Effect On The Mud Crab Scylla serrata in northern Australia, Journal of Fish Disease, 18, 389-395.

Knuckey, I. 1996. Maturity in Male Mud Crab, Scylla serrata, and the use of mating scars as a functional indicator, Journal of Crustacean Biology, 16, 487-495 ..

Knuckey, I. 1996. Northern Territory Mud Crab Research Program, 1996 Report Prepared for the Mud Crab Fishery Advisory Committee, Northern Territory Department of Primary Industry and Fisheries.

Knuckey, I. and Calogeras, C.E. (1992). Mud Crabs - The Biology and Fishery, DPIF Fishnote 11. Knuckey, Land Calogeras,C.E. (1995) Tie Me Muddie Up Tight Sport, How to Handle, Tie and Store Mud

Crab, DPIF Fishnote. Knuckey, Land Calogeras, C.E. (1995). The mud crab fishery in the Northern Territory, Australia, The Crab

Newsletter Canada Vol 2 October 1995. Knuckey, I. and Calogeras, C.E. (1996). Good Management And/Or Good Luck? Timely Introduction of Input

Controls in the Northern Territory Mud Crab Fishery, 2nd World Fisheries Congress Proceedings Vol I. in press.

216

Knuckey, I., Calogeras, C.E.and Johnson,P. (1992). Muddled Muddies, A Look At The Parasite Loxothylacus ihlei And Its Effect On The Mud Crab Scylla serrata, DPIF Fishnote 13.

Knuckey, I., Johnson, P. and Calogeras, C.E. (1995). Catch Trends in the Northern Territory Mud Crab Fishery: Market Implications for Prospective Mud Crab Farmers, Mud Crab Workshop Proceedings, Broome, Western Australia.

Kulkarni,V. and Hamilton,D. An integrated approach towards improving mango productivity. Oral presentation at 5th International Mango Symposium Tel Aviv Israel. 1-6/9/96.

Kulkarni,V. Anew mango selection from Australia's Northern Territory. Poster presentation at 5th International Mango Symposium Tel Aviv Israel. 1-6/9/96.

Kulkarni,V. Mango varietal research - some new approaches. Oral presentation at 5th International Mango Symposium Tel Aviv Israel. 1-6/9/96.

Kulkarni,V. The Florigen concept and its horticultural implications in tree fruits. Proc of 5th Australasian Conf. on Tree and Nut Crops, Lismore, Sept.1995.

Landrigan,M., Morris,S.C. and Gibb,K.S. (1996). Relative Humidity Influences Postharvest Browning in Rarnbutan. HortScience (Nephelium lappaceum L.) Vol. 31(3):417-418. June 1996

Landrigan,M., Morris,S.C. and McGlasson,B.W. (1996). Postharvest Browning of Rarnbutan is a Consequence of Water Loss. J.Amer.Soc.Hort.Sci. 121(4):730-734.1996

Landrigan,M., Morris,S.c., Eamus,D., and McGlasson,W.B. (1996). Postharvest water relationships and tissue brownig of rambutan fruit. Scientia Horticulturae 66 (1996) 201-208

Lim, T.K. (1997). Boosting durian productivity, RIRDC report, 167pp. Lim, T.K. (contributor). (1995). Producing quality Kensington Pride mangoes for the Australian market.

Department of Primary Industry and Fisheries, Northern Territory. Lim, T.K. and Bowman, L. (1995). Control of sapburn on "Kensington" mangoes with postharvest chemical

treatruent. ASEAN Food Journal 10(3): 83-89. Lim, T.K. and Chung, G.F. (1995). Occurrence of the entomopathogen, Hirsutella versicolor Petch on

Jdioscopus nitidulus Wlk. the mango leafhopper in Malaysia. The Planter, Kuala Lumpur 71:207-211. Lim, T.K., Luders, L., Diczbalis, Y. and Poffley, M. (1997). Rarnbutan nutrient requirements and

management.DPIF. Tech. Bulletin No. 261. Lim, T.K.,Luders, L. and Poffley, M. (1996). Studies on fruit deformity and nubbin in Irwin mango. Proc. Int.

Conf. on Global Commercialisation of Tropical Fruits. Kuala Lumpur, Malaysia. pp. 287-298. Lim,T.K. (1995). Chapters on carambolas, rarnbutans and durians in Horticulture Australia (ed B. Coombs)

Morescope Publishing Pty Ltd. Victoria, pp. 392-396, Lloyd, J.A. (1996) Long-term abundance Index for goldband snapper in the Timor Sea-A pilot study. FRDC

final report for project T94/155. Lloyd, LA. and Clarke, R. 1997). Logbooks-A prime source of Research and Management information. NTFIC

newsletter July 1997. Lloyd,J.A. (1996). Goldband snapper pilot project in the Timor Sea. DPIF Fishery Report 37.

MacGilvray, J. G., Mounsey, R. P., Robins, 1. B., and Buckworth, R. C. (1996). Trawl industry considers new AusTED design. Second World Fisheries Congress, Brisbane, Australia, July 1996. Poster Presentation.

McLoughlin, K., and Rarnm, D. (1995). Northern Shark, pp. 31-35. In 'Fishery Status Reports 1994 - Resource Assessments of Australian Commonwealth Fisheries' (Eds McLoughlin, K., Wallner, B., Staples, D.). Bureau of Resource Sciences, Canberra.

Murti, S. and Kraus, C. (1996). Live Cattle Exports to SE Asia. Top Paddock Newsletter No.12, October. NT Dept. of Primary Industry and Fisheries.

Murti, S. and Kraus, C. (1997). Live Cattle Exports to SE Asia. Top Paddock Newsletter No. 14, April; Katherine Rural review, March; Alice Springs Rural Review, March. NT Dept. of Primary Industry and Fisheries.

Ngo, H. (1996). Economic Assessment of Asparagus Production in the Katherine Region., DPIF Tech. Bulletin. No. 243.

Ngo, H. (1997). Trade with Indonesia and Philippines. DPIF Tech. Bulletin. No. 258. Northern Territory Department of Primary Industry and Fisheries, Fisheries Division, 1991, Mud Crab Fishery

Management Plan, Government Printer of the Northern Territory.

Olesen,T., McConchie,C., Menzel,C., Greer,N. and Diczbalis,Y. (1996). Progress report on the canopy management of lychees, longans and rarnbutans. Living Lychee. May 1996.

217

Olesen,T., McConchie,C., Menzel,C., Greer,N., Diczbalis,Y. and Wicks,C. (1997) Further studies on canopy management in lychee, longan and rambutan. Living Lychee. May 1997.

Olesen,T., McConchie,C., Menzel,C., Greer,N., Winks,C., Diczbalis,Y. and Wicks,C. (1997). Update on canopy management in lychee, longan and rambutan. Living Lychee. January 1997.

Pender, P.J. and RK. Griffin. 1996. Habitat history ofbarramundi (Lates calcarifer) in a north Australian river system based on barium and strontium levels in scales. Transactions of the American Fisheries Society 125:679-689.

Pitcher, T., Buckworth, R, Gillette, V., Lee, T., Mackinson, S., Salas, S., and Sumaila, R. (in press). Report to the Skeena Watershed Committee from a demonstration decision analysis workshop, June 1996. Fisheries Centre, Univ. British Columbia.

Pitkethley, R and Smith, S (1997) Investigations on Dieback of Native Trees at Kata Tju!a in the UlUIU I Kata Tju!a National Park. A report the Australian Nature Conservation Agency, NT Department of Primary Industry and Fisheries, January 1997.

Pitkethley, R N. (1996). Monitoring Rehabilitation Success of the South Waste Dump and Northern Pit Areas at Pine Creek Goldfields Ltd - Vegetation Health Assessment NT Primary Industry and Fisheries, report prepared on a consultancy for ERA Environmental Services, December 1996.

Poole S., Hay TA, Mikolajczyk.A and Julius,C.(1996). Edibility characteristics of fish species from Northern Territory waters. DPIF Fishnote 19.

Price, T.P., O'Gara, F., Smith, E.S.C., Pitkethley, R and Hausler, P. (1996). Proc. Workshop on Conservation Farming for the Semi-Arid Tropics. Sturtz, J.D. and Chapman, AL. (Eds.) Katherine NT. 18-20 July 1995. AIAS, December 1996. pp. 208-220.

Price, T.P., O'Gara, F., Smith, E.S.C., Pitkethley, R. and Hausler, P. (1996).Commercial experience in developing ley farming systems for the Katherine-Darwin region, Northern Territory. Aus!. J. Exp. Agric., 36(8): 1059-1068.

Radunz, B., (1997) Stock Movement Conditions Within the NT Relating to Cattle Tick, DPIF Agnote I 35. Radunz, B., (1997) Introduction of Stock into the Northern Territory, DPIF Agnote K 36. Radunz, B., (1997) Horse Movements Within the NT Relating to Cattle Tick, DPIF Agnote K 38. Radunz, B., (1997) Tick Fevers of Cattle, DPIF Agnote K 7. Radunz, B., (1997) The Cattle Tick, DPIF Agnote K. 39. Radunz, B., Update on interval between slaughter and treatment of cattle tick and buffalo fly, Barkly Beef Vol 3,

No 2 June 1997 Radunz, B., Documents for Stock Movements, Alice Springs Rural Review, April 1997. Radunz, B., Changes to Tick Areas, Alice Springs Rural Review, April 1997. Radunz, B., Tailtags or eartags for interstate cattle movements Alice Springs Rural Review, March 1997 Radunz, B., Tailtagging cattle moving within the NT, Alice Springs Rural Review, March 1997. Ramm, D. C. (Ed.) (1997). Towards the sustainable use of Northern Territory Fishery Resources: Review

workshops led by Carl J. Walters. Project 961158. Final Report to the Fisheries Research and Development Corporation, DPIF Fishery Report 39.

Ramm, D., and McLoughlin, K. (1995). Northern Trawl Fishery, pp. 25-29. In 'Fishery Status Reports 1994 -Resource Assessments of Australian Commonwealth Fisheries' (Eds McLoughlin, K., Wallner, B., Staples, D.). Bureau of Resource Sciences, Canberra.

Ramm, D.C. (1995). Collaborative research and management - the key to the sustainable management of groundfish resources in the Timor and Arafura Seas. Proceedings of the conference on "Neighbours at Sea - The Shared Interests of Australia and Indonesia in the Timor and Arafura Seas", Darwin, November 1995, and Australian Centre for Maritime Studies, Maritime Studies, 85,4-12.

Ramm, D.C. (1995). Dynamics of the deepwater snapper (Pristipomoides) resource in the Timor Sea. South Pacific Commission and Forum Fisheries Agency Workshop on the Management of South Pacific Inshore Fisheries. Manuscript collection of country statements and background papers - Volume n. South Pacific Commission. Integrated Coastal Fisheries Management Project Technical Document, 12, 23-38.

Ramm, D.C. (1996). Collaborative development and management of groundfish resources in the Timor and Arafura Seas - A research perspective. Directorate General of Fisheries, Jakarta.

Ramm, D.C., and Mounsey, R. (1996). Initiative of the Australian Northern Territory in resource assessment and fishing technology. BIMP-EAGA Working Group on Fisheries Cooperation, First Meeting of the Task Force on Resource Assessment, Quezon City. Discussion Paper.

Ramm, D.C., and Xiao, Y. (in press). Catch, effort and yield in Australia's northern trawl fishery. Proceedings of the International Workshop on Tropical Groupers and Snappers, Campeche, 1993.

218

Ramm, D.C., Mounsey, R., and Slack-Smith, R. (1995a). International Collaboration Policy. Fisheries Division, report, DPIP Darwin.

Ramm, D.C., Mounsey, R., and Slack-Smith, R. (l995b). Australia-Indonesia collaborative development and management of snapper and other groundfish resources in the Timor and Arafura Seas. Fisheries Division report, DPIP Darwin.

Robins, J., Buckworth, R., Mounsey, R., and Dredge, M. (1997). Development and application of Aus1ED in the Australian trawl industry. Project 931231.07 Final Report to the Fisheries Research & Development Corporation. Q097014 Project Report Series. ISSN 0727-628152 pp + 4 app.

Smith, E.S.C. (1996) Pesticides - Hazard to Honey Bees (updated version). DPIP Agnote K12. Smith, E.S.C. (1996) Mediterranean Fruit Fly (updated version). DPIP Agnote Al Smith, E.S.C. (1996)Control of longicorn beetles in mango trees. DPIP Agnote 129 Smith, E.S.C. (1996) Mango seed weevil control. Litchfield Times. 01 August 1996. Smith, E.S.C. (1996) Cicada damage to young citrus trees. Citrus Growers' Newsletter. July 1996, I pp. Smith, E.S.C. (1996) Mango Seed Weevil. DPIP Agnote no. Smith, E.S.c. (l997)Sending Entomological Specimens for Identification. DPIP Agnote 136. Smith, E.S.C. (1996). Development of an on-farm hot water technique for dinfestation of mangoes.

Presentation to South Australian Research and Development Institute, Adelaide, South Australia. II October 1996.

Smith, E.S.C. (1996). Insect pests of conservation farming systems in the Northern Territory. Proc. Workshop on Conservation Farming for the Semi-Arid Tropics. Sturtz, J.D. and Chapman, A.L. (Eds.) Katherine NT. 18-20 July 1995. AlAS, December 1996. pp. 208-220.

Smith, E.S.C. (1997). Annual Disinfestation Researchers' Meeting. Agriculture Victoria, IHD Knoxfield, Melbourne, Victoria. 25-26 March 1997.

Smith, E.S.C. (1997). Hot water treatlnent and other entomological work on mangoes. Research update - 1996. Presentation to DPIPINTHA Research Review. Taminmin High School, Humpty 000, NT. 15 April 1997.

Smith, E.S.C. (1997). Recent quarantine detections of insect pests in Torres Strait. Talk to NTHA meeting. Humpty 000, NT. 10 February 1997.

Smith, E.S.C. (1997). Research update - 1996. Entomological work on mangoes, other crops and Quarantine certification. Presentation to DPIP Horticulture Division Research and Development Meeting, Katherine Region, Katherine Research Station, Katherine, NT. 03 May 1997.

Smith, E.S.C. (1997). Disinfestation - Situation Report for the NT. Presentation to HRDC sponsored Annual Disinfestation Researchers' Meeting. Agriculture Victoria, IHD Knoxfield, Melbourne, Victoria. 25-26 March 1997.

Smith, E.S.C. and Chin, D. (1997). Entomology of exotic fruit tree crops. Presentation to DPIPINTHA Research Review. Taminmin High School, Humpty 000, NT. 12 May 1997.

Smith, E.S.C. and Young, G.R. (1997). Pest management strategies and practices for Asian Vegetable crops. Presentations to NTHA sponsored meeting of vegetable growers. NTHA Coolalinga Office, NT. 18 March 1997.

Smith, E.S.C., Conde, B.D. and Neal, MJ.(1997) Lenticel blowout - A new disorder on mangoes in the Northern Territory. Pacific Association of Tropical Phytopathology (PATP) News Newsletter No. 15 June 1997.

Stur,W. and Cameron, A.(1996) Brachiaria brizantha CIAT Forage Seeds Project publication 6780, Inter. Centre for Tropical Agric.

Stur,W. and Cameron, A(1996) Brachiaria humidirila CIAT Forage Seeds Project publication, Inter. Centre for Tropical Agric.

Stur,W. and Cameron, A(1996) Centro, CIAT Forage Seeds Project publication 15160, Inter. Centre for Tropical Agric.

Stur,W. and Cameron, A.(1996) Stylo, CIAT Forage Seeds Project publication 184, Inter. Centre for Tropical Agric.

Stur,W. and Cameron, A.(1996) Gamba Grass, CIAT Forage Seeds Project publication, Inter. Centre for Tropical Agric.

Stur,W. and Cameron, A(l996) Signal Grass, CIAT Forage Seeds Project publication, Inter. Centre for Tropical Agric.

Wallace, H. Training on techniques for the joint HRDC fruit fly tolerance project, QDPI, DPIP and WADA. QDPI, Indooroopilly Laboratories, QLD. 25-29 November 1996.

Wilson, A. (1997) - Fanwort, Cabomba. DPIF Agnote F88 ..

219

Young, G.R. (1996) An association between the crazy ant Anoplolepis longipes (Jerdon) (Hymenoptera: Formicidae) and coconut spathe moth Tirathaba rufivena (Walker) (Lepidoptera: Pyralidae) on coconut palms in the Morobe province of Papua New Guinea. 1. Survey to determine the extent of crop loss. Papua New Guinea Journal of Agriculture, Forestry and Fisheries, 39(1): 1-6.

Young, G.R. (1996) An association between the crazy ant Anoplolepis longipes (Jerdon) (Hymenoptera: Formicidae) and coconut spathe moth Tirathaba rufivena (Walker) (Lepidoptera: Pyralidae) on coconut palms in the Marobe province of Papua New Guinea. 2. The effect on yield and nut shedding of ant and moth exclusion. Papua New Guinea Journal of Agriculture, Forestry and Fisheries, 39(1): 7-11.

Young, G.R. (1996)The Crazy Ant, Anoplolepis longipes (Jerdon) (Hymenoptera:Formicidae) on coconut palms in New Guinea. Papua New Guinea Journal of Agriculture, Forestry and Fisheries, 39(2): 10-13.

Young, G.R. (1997). Biology and Control of Redbanded thrips. NTHAIDPlF, Redbanded thrips Field Day, Taminmin High School, Humpty 000, NT. 22 March 1997.

Young, G.R. (1997). Integrated Pest Management Training Seminar. Presentation to the Plant Protection technicians of the Bureaux of Agriculture and Forestry, Xingtai County, China. 10-11 June 1997.

Young, G.R. (1997). IPM on Vegetable Crops in the Darwin Area. BARC Seminar. 14 February 1997. Young, G.R. AQIS Workshop to develop a protocol far direct release of bio-control agents of weeds. Canberra,

ACT. 3-4 October 1996. Young, G.R. (1997) Mites and Sucking Insects attacking Orchids. Australian Orchid Review, 62(2): 11-14.