2 & 3 august 2011 the royal hotel goondiwindi · 2012-06-27 · 2 & 3 august 2011 the royal...

2 & 3 August 2011The Royal Hotel

GoondiwindiIncluding Seminar Dinner Function 2nd August

One location for technical, product & business information and networking

Special thanks to CCA’s Corporate Partners

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From the President............Welcome to Goondiwindi for Crop Consultants Australia’s second Cropping Solutions Seminar for the year.

Following a successful seminar in Moree earlier in 2011, your feedback has guided the develop-ment of this seminar program. The next two days covers a variety of both agronomic and business topics including a special risk management session. It is always challenging to develop a program that is equally relevant and balanced for younger and experienced members and it is recognized that we can all learn a lot from each other. I encourage you to make the most of question and discussion time, share ideas during the workshop and make use of the other networking opportuni-ties that the seminar provides.

Two new directors, Elle Macpherson and Phil Peterson, were elected to the CCA Board at the AGM in May and they have hit the ground running. The two new directors join Dallas King, Doug McCollum, Nick Gillingham, Iain Macpherson and myself to oversee operations of the association. We encourage you to have a chat with us during the seminar if you have any ideas or feedback about the organization and its activities.

CCA is currently developing projects to secure funding to continue our part in Helicoverpa resis-tance monitoring and the annual collection of data relating to product use, farming practices and decision making in Australia’s cotton growing areas.

There are also a few new initiatives under development which will be highlighted in a presenta-tion scheduled late on Day 1. In recognition of the important role that agronomists and consul-tants play in the cropping industry, we seek your feedback on a proposed new project that we expect will further strengthen your capacity to assist growers to implement best practice and sustainable production systems.

The CCA has been experiencing a surge in membership which is a positive sign for the organiza-tion and reflects the recent good seasons. As a member based organization we are always look-ing at ways to better service our members and I encourage you to chat with Fiona and Fleur, our Executive Officer team, to ensure you are making the most of your membership. Two of our more recent developments are the new look Consultants Catchup E-newsletter and also a modernized, fresh website that allows member interaction. I would like to acknowledge the support we receive from our sponsors and corporate partners which enable us to run these important seminars. CCA has recently introduced an annual corpo-rate partnership program and we are pleased to announce that DuPont, Caltex, AgroBest, Sa-coa, Bayer CropScience, Monsanto and Syngenta are now Corporate Partners of the CCA.

Enjoy the seminar and make the most of this opportunity to liaise with researchers, company rep-resentatives and other agronomists to find out all you need to know for the season ahead.

Regards,Matthew Holding President 2011/2012.

DAY 1 TUESDAY 2nd August

8:00am Registration Desk Opens Tea & Coffee

8:30am WELCOME

Session 1: PLANT NUTRITION & SOILS

8:45am PG 6 Practical Plant Nutrition Solutions & Soil Chemistry Including phosphorus testing

Dr Chris Dowling (Back Paddock Company) 9:45am PG 9 Combating nitrogen losses & maximizing nutrient use efficiency

Product choice, fertilizer placement, timing, rate & splits for cotton. Charlie Walker (Incitec Pivot Fertilisers)

10:30am MORNING TEA Session 2: RISK MANAGEMENT & PROFESSIONALISM

11:00am PG 13 The legalities of operating as a consultant or agronomist

– How to minimize risk Plus tips for making recommendations and agreements – what should you say and write?

Take this opportunity to ask questions and find out what you could be doing to improve your professionalism on a day to day basis and minimize the risk of getting sued.

Don McDougall (ARC Group) 1:00pm LUNCH Session 3: BROADACRE CROPS

2:00pm PG 15 Mungbean roundup Including desication issues

Gordon Cumming (Pulse Australia) 2:45pm PG 16 Summer crop options in Northern NSW – new research & considerations

Sorghum, Soybeans, Sunflowers & Maize Rebecca Byrne (NSW DPI)

3:30pm AFTERNOON TEA Session 4: INDUSTRY DEVELOPMENTS

4:00pm PG 18 Trial work with new herbicide Terbyne Pulse crops, sorghum and fallows

Andrew Somervaille (Jubilee Consulting with Sipcam Pacific) 4:30pm PG 22 The vital role of agronomists in the cropping industry

Provide feedback on a proposed CCA project that aims to coordinate access to the latest research and most up to date information for agronomists resulting in better outcomes for growers.

Fiona Anderson (CCA) 5:00pm DAY 1 CLOSE

6:30pm EVENING FUNCTION at The Royal Hotel Function Room 48 Marshall Street, Goondiwindi Pre-dinner drinks & appetizers commence 6:30pm Official presentations 7:00pm Meal commences 7:30pm Entertainment: Simon Heart Magic

(Note: Agenda is subject to change)

AGENDA - DAY ONE

DAY 2 Wednesday 3rd August

8:00am Registration Desk Opens Tea & Coffee

8:30am WELCOME

Session 1: COTTON & WATER

8:45am PG 25 Dryland Cotton Experiences Rob Holmes (HMAg Pty Ltd)

9:15am PG 26 irriSAT – an irrigation management & crop water use benchmarking system

Improving irrigation based decisions using new techniques and technologies Dr John Hornbuckle (CSIRO)

10:00am PG 28 Row configuration trial update

Including new data and research results. James Quinn (CSD)

10:30am MORNING TEA Session 2: BUILDING A STRONG CONSULTING SECTOR

11:00am PG 30 WORKSHOP: Business & Financial Improvement

Investigate and discuss key issues affecting agricultural consulting businesses. Including pricing, staff and time efficiencies. Take home a new idea or strategy to make a difference in your business. Learn more about what needs to be considered when operating your own business.

Myf Rigby (Insight Business & Financial Services)

12:45pm LUNCH Session 3: PLANNING FOR THIS COMING SEASON

1:30pm PG 34 An integrated approach in managing Silverleaf Whitefly & Aphids

Climatic conditions, lifecyle, impacts & constructing a management program. Mark Congreve (Syngenta)

2:00pm PG 37 Insect Pest Outlook for the 2011/12 season

Interactive session to develop broad regional outlooks for key pests – whitefly, aphids, mites & mirids

Dr Lewis Wilson (CSIRO) & Dr Richard Sequeira (QLD DEEDI)

3:15pm AFTERNOON TEA DAY 2 CLOSE

(Note: Agenda is subject to change)

Disclaimer:CCA recognizes the value of off label research however we remind delegates that special-ized information on the safe use, storage and handling of products is provided on product labels by product manufacturers. Unauthorised off label use or general misuse of products can expose you to risk and possible litigation.

AGENDA - DAY TWO

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Integrity Innovation Mateship

Practical Plant Nutrition Solutions & Soil Chemistry Chris Dowling Back Paddock Company Cleveland, Qld, 4163 INTRODUCTION In recent years research has been struggling to keep pace with changes in soil nutrient status and farm practices to be able to verify their effects on crop nutrition. In the case of nitrogen (N) paddock yields are stretching far beyond the published response database and for other nutrients, for which the rundown phase has in the last few years begun to intersect responsiveness, response criteria have yet to be clearly established. In this environment, developing practical solutions to crop nutrition challenges has been part science, part practical application of base principles of soil chemistry and a touch of creativity (moderated by common sense). For the foreseeable future this is most likely will be the case when considering the list of unresolved issues and the current level of research funding. In this paper I will touch on some of the key issue as I see them based on enquiries and being directly responsible for technical contents in provision of decision support tools for crop nutrition to agriculture on a national basis. My cotton comments are based on a recent review of currently published crop nutrition information and some pers. comms.. For nutrients that are “lean on facts” i.e. those that have been generally adequate, in rundown, and by definition no calibration has historically been possible, some comments are based on learning’s and applicability/ usefulness of principles establish in other agricultural segments. NITROGEN

� General - Its official, shallow samples (<30 cm) for N - a waste of time by themselves both for establishing critical levels and N budgeting!

Figure 1 – Correlation between responsiveness wheat and nitrate-N (kg/ha) soil test improves as sampling depth increases from 10 cm to 90 cm for Queensland vertosols (source BFDC Interrogator).

� Cotton Interpretation o Dryland - no comprehensive published research data relating soil N content to response –

interpret N requirement as for all other dryland crops – why not N budget? Optimum seed protein for N efficiency the missing factor now revealed for irrigated production!

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o Irrigated – managing N for high yield – are you a pusher or puller in managing N? – you cannot push a crop to high yield with extra N, you need to create conditions to pull through the N demand. If you are soil testing to get an idea of likely deficit, sampling depth – 0-30 cm high yield, back to back where subsoil reserves will be depleted and unlikely to be replenished, 0-30 and 30-80 cm for long fallow, rotation or low yield relative to N rate where subsoil mineral reserves unsure of quantity and/or location. N rate is related to yield and efficiency of uptake. Yield potential and N uptake efficiency is a function of soil texture, previous crops, soil physical condition, and water management and speed of crop phenological cycle for yield. Management goal, minimise stress hours from all sources.

PHOSPHORUS

� Dryland Cereals and Cotton In dryland crops it is logical to expect that phosphorus (P) in soil layer below 10 cm influences the crops ability to acquire the amount of P required across the season. In the last couple of years some unexplained crop responses, or lack of, have driven some new investigation of some old concepts i.e. P (BSES) and P below 10 cm as a factors influencing the expression of crop response. Some of the mid-investigation thinking and extrapolation from results and observations includes; BSES P < 20 mg/kg in 10-30 cm suggests that deeper placement of some P may be beneficial (Bell 2010) and that the response type likely to be full season (>500 kg/ha of grain) rather than starter (generally < 500kg/ha of grain). Based on research so far suggest that for where PBSES in 10 – 30 cm is low and someone wants to try something different then try

1. Deep application bands no greater than 50 cm wide 2. At least 1/3 applied with the seed 3. Up to 2/3 applied 15 – 25 cm deep 4. Deep band can be applied 4-5 months prior to planting for soil PBI>140 and closer to planting as PBI

increases above 140. Table 1 is yet untested guidelines for determining the P rate using the combination of P (Colwell) and P(BSES) to apply in particular circumstances. They are based on the work of Whitehouse (1968) and Chisholm and Strong (1982) for Qld soils and climate. They are presented as useful starting point to put down some test strips for interested growers and possibly explain the lack of response in some circumstances. Expect that even that your soils are grey vertosols that being in a cooler area that the rate relationship may be more like the black vertosols.

Table 1 – Example of suggested rates of P addition based on P (Colwell) and P (BSES) in top 10 cm for black vertosols and chromosols (red brown earth) based on Chisholm and Strong 1984. (RYE= Realistic Yield Expectation)

Colwell P (mg/kg)

P (BSES) (mg/kg)

Response probability %

Phosphorus Application Rate Multiple

(kg/ha) black vertosol

Phosphorus Application Rate Multiple

(kg/ha) chromosol

<15 any 100 5 x RYE 8 x RYE

16-24 <50 > 65 3 x RYE 8 x RYE

25-50 <100 > 60 2.5 X RYE 3.5 X RYE

>50 any < 50 nil nil

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� Cotton – Interpretation o Dryland - no comprehensive published research data – interpretation from first principles

using the approaches used successfully in the grain crops grown in rotation. In my estimation cotton most likely to differ from grain crops in response (lower critical level) to 10-30 cm BSES P as a result of greater cation uptake per kg DM (cotton~4% DM, wheat~2.5%DM) affecting rhizosphere acidification.

o Irrigated – scant data on which to base recommendation that account for soil and regional variability.

� Issues include effects of PBI on critical level and early season temperature (Emerald vs Griffith) on critical value application rate and application strategy.

� Role of P and sodium in K deficiency syndrome POTASSIUM The majority of broadacre cropping soils west of the Great Divide have traditionally be moderately to well supplied with potassium (K) for plant uptake and hence characterisation of critical levels has not been possible in the past. This situation has now changed and K responses/ deficiency are being reported from a wider range of locations, crops and situations each year e.g. maize – Inverell, chickpeas – Emerald, sorghum - Kupunn. Soil survey of 6000 + samples (0-10 cm) from the last 2 years in NW NSW and SE Qld suggests up to 10% of soil now potentially responsive.

� Testing and interpretation – learning to date – o Cotton has a higher critical level than most other crops. o It is likely that interferences from high soil sodium (5:1) and magnesium (>40 % CEC) will

modify responsiveness. o In dryland crops availability in 10-30 cm layer may need to be assessed

� Management o General guidelines- dryland cereals < 0.3 meq/100 g or cotton< 0.8 meq/100g response

possible. o Crops low in P may be more vulnerable to K problems. o Rates – if around critical level use maintenance rates. If lower capital+ removal? o Application - widely distributed vertical and horizontal that does not compromise soil tilth o Products – KCl, K2SO4, manure/ bio-solids

SULFUR After the wet summer early indications are that sulfate-S in the surface layers (0-30 cm) of soils is low (<5 mg/kg) most likely as a result of leaching. Should this situation persist there is an increased possibility of early season S availability. Whether this persists will be influenced by the presence, absence and location of bands of higher S that occurs in many broadacre cropping soils. The strength of early season capillary rise of stored soil moisture and organic matter content of surface soil will also have some influence on seasonal S supply.

o Testing - if concerned, test in both surface and subsoil. If surface < 5 mg/kg and DWM for effective root depth < 5mg/kg strongly consider including S in nutrient program.

OTHER Zinc (Zn) – A high proportion (80%> 0.4 mg/kg and 40 % >1 mg/kg) of soils from NW NSW and SE Qld are now moderate to high in Zn after 10 – 15 years of Zn application at low to moderate rates. Consider plant tissue testing to assess ongoing requirement for Zn and adequacy of other nutrients such a P, K and S. REFERENCES Bell M, Lester D, Moody P and Guppy C. 2010. Toward a better P nutrition package: Diagnosing P status and application strategies to improve fertiliser response. Proceedings of GRDC Adviser Cropping Update. Goondiwindi. BFDC Interrogator. 2011. Making Better Fertiliser Decisions for Cropping Systems in Australia. (http://www.gws-bfdcdev.com/homecontent.do;jsessionid=1CBEAD8DE98E1B1B60389917BB88C100) Chisholm, R H, Strong W M. 1984. Improved field methods of soil analysis interpretation. Australasian Field Crops Newsletter 19, 83–86. Whitehouse, M J. 1968. Queensland Wheat Research Institute. Annual Report 1967-68. p 44.

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Combating nitrogen losses and maximising nitrogen use efficiency in summer crops.

Charlie Walker, Incitec Pivot Fertilisers, PO Box 54, North Geelong, Vic, 3215

[email protected]

Two simple frameworks can be applied by agronomists to improve nutrient (nitrogen) use efficiency. CRAFT has been around in Australia for at least 20 years, while more recently, the International Plant Nutrition Institute introduced the 4R’s methodology.

CRAFT

Choice of product

Rate of application

Application technique

Frequency of application

Timing

4R’s

Right source

Right rate

Right place

Right time

Take your pick as the frameworks are basically the same, but consider how they can be used to maximise nitrogen use efficiency. We need to define what is meant by nitrogen use efficiency (NUE). Typically, NUE refers to the proportion of mineral nitrogen available during the crop’s growing period that is actually taken up by the crop. This includes uptake by roots, shoots and harvested parts of the crop. This is difficult to estimate, so often surrogates like nitrogen transfer efficiency (NTE) are used. NTE is calculated by considering mineral nitrogen available through the growing season (nitrate + ammonium N) from residual soil N, fertiliser and estimated mineralisation (N supply). NTE is calculated by dividing nitrogen in the harvested crop parts by N supply. NTE will vary from one crop species to another, for example an average figure for sorghum might be 50%, while cotton might be 33%. A lower NTE does not necessarily indicate that a species is less efficient in using nitrogen – it simply means that the crop transfers less through to harvested parts, possibly leaving more in crop residues for the following crop.

The first step in the journey towards maximising nitrogen use efficiency is establishing your starting point. Unfortunately, this is likely to involve some hard work in the form of taking soil cores to establish what residual soil nitrogen is present and to get a feeling for soil organic carbon levels. These two vital pieces of information are used to create a nitrogen balance:

N balance = N needed In The Soil – (Soil Analysis N + Mineralised N)

N balance represents an estimate of the right N rate. Getting this close to right will not only mean optimising yield, but will also mean that there is less residual nitrogen subjected to loss mechanisms.

The next consideration is how / where nitrogen will be applied. When we talk application technique for summer crops, there are a range of possibilities – top dress, side dress, water run, foliar, banded, incorporated etc. In irrigated row crops, there are also considerations

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around where to place nitrogen in hills or beds. The main reason that placement is important are the loss mechanisms that nitrogen is subject to summarised in figure 1.

In the main summer crop area, nitrate leaching below the root zone is generally limited by the heavy texture of the soils. Where nitrogen is surface applied and not incorporated by cultivation or adequate irrigation within a day or two of application, then volatilisation losses may occur. The extent of these losses will be dependent on a range of factors in particular high temperatures, the presence of surface trash, wind and alkaline soils. While volatilisation is generally associated with surface applied urea, where there is calcium carbonate in the surface soil, products like ammonium sulphate may also suffer significant volatilisation losses. A study by Schwenke and McMullen (2009) showed an 80% increase in volatilisation losses from surface applied ammonium sulphate when compared with urea on a vertosol soil with 7% calcium carbonate content from north west NSW.

Possibly the most significant, least understood loss mechanism in summer crop, particularly in irrigated crops, is denitrification. Freney et al (1993) reported denitrification losses of 43 – 92% of applied nitrogen in irrigated cotton, while Smith et al (1988) showed losses of 35% in sunflowers. While denitrification losses in the form of nitrous oxide have received the most attention in recent times, from an efficiency prespective, losses of nitrogen gas are far more significant on alkaline soils. Placement of nitrogen fertiliser away from areas of frequent

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water logging e.g. furrows, or possibly deeper in the soil where gas movement is restricted are both potential means of reducing denitrification losses.

Another way to look at limiting potential for losses and therefore maximising efficiency is frequency and timing of nitrogen application. A crop will use nitrogen throughout the growing season with peak demand at certain times. It thus follows that the best chance of getting nitrogen into the crop coincides with or just prior to these peak demand periods. In an irrigated system, this is made easy as some nitrogen may be water run. In dryland systems it is a bit trickier. The offset to split applications is the cost and logistics of multiple applications – sometimes the labour simply isn’t available to be messing around with multiple applications. That’s where other elements of CRAFT or the 4R’s need to be relied upon.

The final piece of the jigsaw is product choice. There are numerous products out there that can efficiently supply nitrogen in specific situations. Don’t get carried away however, as nitrogen is still nitrogen, so use the budgeting process and apply the appropriate amount of nitrogen accordingly. Although Australian research into nitrification inhibitors dates back to at least the early 1990’s, it has only been recently that they have become commercially available on nitrogen fertilisers. While some of the earlier work demonstrated production gains in irrigated cotton e.g. Rochester et al (1994), more recent work has focused on the ability of nitrification inhibitors to limit emissions of nitrous oxide from irrigated soils. While inhibitors may have a role to play in limiting greenhouse gas emissions from nitrogen fertilisers, as they become more accessible in the Australian market, they may well play a role in significantly improving nitrogen use efficiency.

To get the best efficiency out of nitrogen, an integrated approach is required. Avoid waste by knowing your starting point, understand the implications of your application technique(s), play around with timing and split if this can fit with the farm operation and makes economic sense and carefully consider what gains there might be from some of the newer nitrogen technologies.

References:

Freney JR, Chen DL, Mosier AR, Rochester IJ, Constable GA, Chalk PM (1993). Use of nitrification inhibitors to increase fertilizer nitrogen recovery and lint yield in irrigated cotton. Fertilizer research 34, 37 – 44.

Rochester IA, Gaynor H, Constable GJ, Saffigna PG (1994). Etridiazole may conserve applied nitrogen and increase yield of irrigated cotton. Australian Journal of Soil Research 32, 1287 – 1300.

Schwenke, G. and McMullen, G (2009). Nitrogen volatilisation from northern cropping soils. Proceedings of the Dubbo GRDC adviser update.

Smith CJ, Freney JR, Chalk PM, Galbally IE, McKenney DJ, Cai GX (1988). Fate of urea nitrogen applied in solution in furrows to sunflowers growing on a red-brown earth: Transformation, losses and plant uptake. Australian Journal of Agricultural Research 39, 793 – 806.

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ALWAYS REFER TO THE PRODUCT LABEL BEFORE USE. Copyright ©2008 E I du Pont de Nemours and Company (DuPont). All rights reserved. Du Pont (Australia) Ltd. 7 Eden Park Drive, Macquarie Park, NSW 2113. ACN 000 716 469. The DuPont Oval Logo, DuPont™, The miracles of science® and Steward® are trademarks or registered trademarks of DuPont or its affiliates. H&T DP1334/AG.

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The legalities of operating as a consultant or agronomist - how to minimise risk

Don McDougall - ARC Group

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Mungbean Roundup

Gordon Cumming - Pulse Australia

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Rebecca Byrne District Agronomist, Moree East NSW Department of Primary Industries Summer Crop Options in Northern NSW; new research and considerations for the 2011-12 season. The north-west grains region extends north from Tamworth to Goondiwindi and west from Inverell to Walgett. This region is the most significant contributor to summer cropping in NSW, growing over 90% of sorghum, 40% of maize, 75% of mungbeans, 99% of sunflower and 30% of soybeans (NSW Grains Report). There are some key considerations for summer crops in the north-west grains region leading up to the 2011-12 season, including insect and disease management, varietal selection and general crop agronomy. Recent research in summer crops has been limited in northern NSW but has focused primarily on general crop agronomy. In particular, there is a stronger focus on adaptability of summer crops across sowing windows and the importance of their rotational benefits. Insect and disease management principles have remained largely unchanged from last season, making it important to reiterate current thresholds and Best Management Practices, both of which are targeted at optimising the economic performance and sustainability of production systems. Management of moisture, both in fallow and in-crop remains a key driver of summer crop production; both in terms of influencing planting opportunities and crop selection as well as impacting on final yield and management of stubble borne diseases such as crown rot. There are also some new varietal releases for the coming season, which will continue to expand choice for the north-west grains region.

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Terbyne Herbicide – Developments in crop and fallow

Andrew Somervaille, Jubilee Consulting

Summary:

Terbyne (active ingredient terbuthylazine) is a pre and post-emergence herbicide having the Photosystem II inhibitor mode of action and belongs to the triazine family of products. Recent developments have underlined the utility of the herbicide in northern farming systems by virtue of physical attributes that allow for the more effective control of a number of broadleaf weeds and greater range of selectivity in rotational crops compared to other triazine products and in particular atrazine.

Terbyne is presently registered as a pre-emergence herbicide for use in TT canola and winter pulse crops for control of a wide range of broadleaf weeds that include flax-leaf fleabane and milk thistle. Field trials have evaluated Terbyne as a pre and post-emergence herbicide in sorghum with registration of this use pattern pending. Field and glasshouse trials are underway to establish safe re-cropping intervals to a wide range of crops that will support both proposed in-crop and fallow uses for Terbyne. At present, indications are for safe re-cropping at proposed and current label rates with no plantback for TT canola, chickpea, faba bean, field pea, lupins, sorghum and maize.

This paper reviews results of field evalutions of Terbyne undertaken in the northern region over the past 4 years.

Introduction

Terbuthylazine was first reported as a herbicide in 1966 and introduced by J.T. Geigy (S.A.) – later to become Ciba-Geigy. The product was developed in many markets around the world but not in Australia until very recently. Terbyne is a 750 gai/ha dry flowable extruded granule formulation developed and marketed by Sipcam Pacific Australia Pty Ltd.

Terbuthylazine differs from atrazine in having a lower water solubility (8.5 mg/L compared to 33 mg/L for atrazine at 20 C). In addition, terbuthylazine has significantly higher soil binding (Koc) compared to atrazine and simazine. This may have a consequential effect on the progressive movement down the soil profile of products and the effective placement of herbicide for activity over time under the influence of rainfall and/or irrigation as well as the duration of control.

A series of experiments were conducted in sorghum, chickpea and fallow over the period 2007 – 2011 in northern NSW and southern QLD to evaluate efficacy and where applicable, crop safety following applications of Terbyne in the range 0.5-2.0 kg/ha.

1. Fallow

Initial evaluation of Terbyne near Jandowae in autumn 2008 demonstrated commercially acceptable knockdown control of 4 to 6 leaf stage fleabane 32 days after treatments with 1.1 L/ha Raze, Raze plus 1 kg/ha Terbyne, 1.4 L/ha Amicide 625 plus 1, 1.5 and 2 kg/ha Terbyne,

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700 mL/ha Tordon 75D plus 1, 1.5 and 2 kg/ha Terbyne and 1.4 L/ha Amicide 625 plus 1.5 kg/ha Nu-trazine 900DF. Atrazine appeared to have better foliar effects on established fleabane but effects were reversed with milk thistle. This was also seen in 2010 where knockdown control of milk thistle up to 8 leaf was generally enhanced with the addition of Terbyne relative to a knockdown control treatment of 2L/ha Roundup DST, while the addition of atrazine was clearly antagonistic. Highest levels of knockdown control of milk thistle were obtained with combinations of 1.2L/ha Roundup DST with 1.4 and 2 kg/ha Terbyne and 1 kg/ha Terbyne plus either 0.5% v/v Hot-Up, Uptake or Hasten spraying oil.

Residual weed control in fallow was evaluated in 3 experiments in the wet year of 2010. In the first study near Jandowae, a March application of Terbyne at 2 and 4 kg/ha provided >99% pre-emergence control of flax-leaf fleabane 32 DAA that continued into the following chickpea crop. A treatment of 1 kg/ha gave 85-95% control based on weed counts compared to an untreated control. In a second trial initiated in May 2010 on a Cecil Vale clay, Terbyne applied at 1, 1.4 and 2 kg/ha gave >99% pre-emergence control of flax-leaf fleabane and 100% control of milk thistle 131 DAA. Standard treatments of 1 and 1.4 kg/ha atrazine gave 32 and 53% control of fleabane respectively while virtually no control of milk thistle was observed based on plant counts 131 DAA.

In a third study initiated on a brigalow grey clay soil near Inveray, Terbyne applied at 1, 1.4 and 2 kg/ha gave >94% pre-emergence control of milk thistle and 100% control of flax-leaf fleabane 71 DAA. A standard treatment of 1 kg/ha atrazine gave 42 and 44% control of milk thistle and fleabane respectively 71 DAA.

2. Sorghum 2.1 Pre-emergence

Three experiments were conducted to evaluate Terbyne for pre-emergence control of weeds in sorghum in 2007, 2009 and 2010 near Brookstead, Dalby and Jandowae East. In the initial study, Terbyne applied at 1.5, 2.0 and 2.5 kg/ha product reduced density from 116 per square metre in untreated controls to between 10 and 29 plants per square metre in plots treated with Terbyne alone. Atrazine (as Nu-trazine 900DF) applied at 2.0 kg/ha product reduced numbers to 33 per square metre. The addition of 2 L/ha Dual Gold (960 g/L s-metolachlor) to 2 kg/ha Terbyne or 2 kg/ha Nu-trazine 900DF reduced infestations to a mean of 0.7 and 0.6 plants per square metre respectively.

In the second experiment, good control of dwarf amaranth, turnip weed, caustic weed, milk thistle and bladder ketmia was obtained 56 DAA with application of 1.4 and 2 kg/ha Terbyne and 1.4kg/ha Terbyne plus 2 and 4 L/ha Strada (metolachlor) that was comparable to 1.5 kg/ha Atragranz. Strada applied at 2 L/ha provided moderate control of dwarf amaranth but poor control of remaining broadleaf weeds

In the third experiment conducted on a red clay loam soil, commercially acceptable control of dwarf amaranth, yellowvine, dwarf amaranth and milk thistle was obtained

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54 DAA with application of 1.4 and 2 kg/ha Terbyne and 1.4 kg/ha Terbyne plus 2 and 4 L/ha Strada (metolachlor) that was comparable to 1.5 kg/ha Atragranz.

Strada applied alone at 4 L/ha provided moderate control of awnless barnyard grass, stink grass, dwarf amaranth and red pigweed but poor control of yellowvine. Control of grasses was noticeably increased with the addition of 1.4 kg/ha Terbyne but not to a statistically significant level.

2.2 Post-emergence

Post-emergence trials with Terbyne were established at 8 locations over the period 2007-2010 at Pittsworth (2), Brookstead (2), Nangwee, Tulloona (NSW), Warra and Jandowae East. A consistent observation was the superior post-emergence activity of Terbyne compared to atrazine for the control of yellowvine.

In the initial study at Pittsworth, Terbyne applied post in early tillered sorghum cv. Buster at 0.75 and 1.0 kg/ha product plus either 0.5 or 1.0% Hasten provided excellent control of yellowvine up to 45 cm diameter as assessed as subjective weed control 9 days after treatment (92-98%) and ground cover 39 days after treatment (1-4%) compared to untreated control of 68%. In contrast, 1.1 kg/ha Nutrazine 900DF plus BS1000 gave only 35% control with the addition of 300 mL/ha Starane Advanced increasing this to 83%. Substitution of Hasten for BS1000 significantly increased activity of atrazine but not to a level equivalent to that provided by Terbyne.

A second experiment established in January 2008 showed that Terbyne applied at 2 kg product/ha plus 0.5 % Hasten in early tillered sorghum cv. MR43 provided excellent control of cowvine and the broadleaf biotype of bladder ketmia (Hibiscus trionum var. vesicarius L.). Terbyne applied at 0.75 and 1.0 kg product/ha plus 300 or 450 mL/ha Starane Advanced provided commercially acceptable control of both bladder ketmia and cowvine in the range (92-100%).

At the Nangwee location, Terbyne applied post in early tillered sorghum cv. MR Buster at 2.0 kg/ha plus 0.5 % Hasten provided excellent control of 4 to 8 leaf broadleaf bladder ketmia (narrow leaf biotype var. trionum) weed control 47 days after treatment (97%). A lower rate of 1.5 kg/ha gave good control (82%) but not quite at a commercially acceptable level. Combinations of 0.75, 1.0 and 1.5 kg/ha Terbyne with 450 mL/ha Starane Advanced provided commercially acceptable control of narrow leaf bladder ketmia with 88, 94 and 96% control respectively. Effectiveness of post-emergence applications of Terbyne plus fluroxypyr against bladder ketmia was also noted in 3 further experiments at Pittsworth and near Brookstead.

Excellent post-emergence control of milk thistle was demonstrated in the trial near Warra in 2010. Excellent control of milk thistle up to 25 cm in diameter was obtained 16 DAA with application of 1.4 and 2 kg/ha Terbyne and 1.4 kg/ha Terbyne plus 500

21

and 750 mL/ha Acclaim (fluroxypyr) that was superior to the standard of 1.4 kg/ha Atragranz (atrazine) plus 750 mL/ha Acclaim. Atragranz alone provide poor control of milk thistle with practically no plant mortality while plots including Terbyne provided 93-98% reduction in starting populations of milk thistle compared to 63% for Atragranz plus Acclaim when assessed 35 DAA. Excellent activity of Terbyne on milk thistle was also observed in one other experiment established near Brookstead. The poor post-emergence activity of atrazine was clearly evident in this experiment.

Other weeds successfully controlled by Terbyne post-emergence in sorghum experiments included turnip weed, dwarf amaranth and black pigweed.

3. Chickpea

Two trials were established in 2010 to evaluate Terbyne alone and in mixtures with Balance Herbicide for pre-emergence control of weeds in chickpea near Brookstead and Jandowae. At Brookstead, Terbyne applied at 0.7 and 1.0 kg/ha alone or in combination with 50 or 100 g/ha Balance provided 100% pre-emergence control of flax-leaf fleabane (Conyza bonariensis) 97 DAA and 98-100% control 131 DAA. Balance alone gave 76 and 95% control at 50 and 100 gc/ha while 0.83 kg/ha simazine provided 93% control. Terbyne alone at 0.7 kg/ha gave 97 and 98% control of fleabane and milk thistle respectively 131 DAA.

Terbyne provided 99-100% control of milk thistle (Sonchus oleraceus) 97 DAA compared to 95% for simazine and 76 and 95% for Balance at 50 and 100 g/ha respectively. Control in plots treated with either simazine or Balance declined markedly at the second assessment with control based on plant counts falling to 56% for simazine and 66 and 89% for 50 and 100 g/ha Balance respectively.

At the Jandowae site conducted on a hard-setting red-brown clay loam, Terbyne applied at 0.7 and 1.0 kg/ha alone or in combination with 60 or 100 g/ha Balance provided 98-100% pre-emergence control of flax-leaf fleabane 132 DAA. Balance alone gave 74 and 92% control at 50 and 100 g/ha while 0.83 kg/ha simazine provided 80% control. The standard treatment of Balance plus simazine gave 96.6% control based on weed counts. In conclusion, Terbyne provided equal to better control of fleabane and milk thistle when compared to a standard treatment of 100 g/ha Balance plus simazine.

22

The vital role of agronomists in the cropping industry

Fiona Anderson CCA Executive Officer

Mob: 0429 925 459 E: [email protected]

Consulting sector snapshot (Cotton Consultants Survey 2011 interim data)

Consultants have influence over substantial cropping areas and direct contact with many growers. For example:

25 consultants cover 39% of Australia’s cotton producing area, providing services to 763 growers.

Half of the growers are cotton clients of which 74% regularly grow cotton with 17% returning to cotton and 9% growing cotton for the first time in 2010/11.

A consulting business has 2 full time staff on average plus an additional 2.7 casual or part time staff.

These consultants provided advice for the following crops over winter 2010 and summer 2010/11 (listed in ascending order, hectares):

Linseed: 40 Vetch: 100 Soybean: 283 Conventional Liberty: 300 Horticulture: 368 Bollgard II cotton: 857 Conventional RR cotton: 1000 Forage Sorghum: 1493 Sunflower: 2260 Conventional cotton: 2649 Faba beans: 2921 Corn: 4020 Mungbean: 6481 Conventional RR Flex: 9238 Oats: 10307 Canola: 14325 Bollgard II RR cotton: 15925 Barley: 25318 Sorghum: 37251 Chickpea: 66191 Winter Fallow: 98535 Summer Fallow: 143402 Wheat: 179659 Bollgard II RR Flex: 189547

Current CCA projects and initiatives: 1. Helicoverpa Resistance Monitoring Egg Collection (CRDC) 2. Helicoverpa Resistance Monitoring Egg Collection (Monsanto) 3. Annual Cotton Consultants Survey 4. Annual Cotton Market Audit Survey 5. Cotton Bunchy Top Survey & Risk Assessment 6. Professional Indemnity Insurance Checklist 7. Review of viability of independent consulting businesses 8. ‘Be a Consultant’ Factsheet 9. 2 x Cropping Solutions Seminars annually 10. E-newsletter & Website 11. Membership Directory publication PROPOSED PROJECT FOR FEEDBACK 12. Industry Liaison Project: Strengthening links between

research, extension & best practice implementation. Recognise that agronomists are closest interface to

growers. Reach a large number of growers and have real impact by linking with and building on the strengths of the existing agribusiness network.

The project focuses on the flow of technical information related to farming systems and building capacity within the consulting sector.

Achieved by CCA employing a dedicated person/s (with an agronomic background) to focus on key industry issues and facilitate access to research.

Project activities would focus on agronomic up-skilling of the agribusiness network through ongoing, targeted training and the distribution of the latest, most up to date information & research via enhancing seminars, e-newsletters and regional meetings/field days.

A two-way feedback loop between R&D, CCA and growers would assist to identify research / development / delivery priorities, identify links with CRC/CRDC/CA programs and provide the capacity to assist with the rollout of industry initiatives to achieve on-ground awareness and change, effective implementation of best practice on-farm and encourage innovation.

CCA’s structure provides a framework to address new issues and hot topics proactively and promptly.

Project provides CCA with the opportunity to bring new people into the organization and build on existing activities.

Project would initially focus on cotton with the view to evolve to include a greater broad acre focus.

23

Cotton Choices

24

FOR LONG-LASTING CONTROL OF MITES

Make sure these mite eggs never grow up

www.sumitomo-chem.com.auParaMite® is a registered trademark of Sumitomo Chemical Co. Limited Japan.

25

Dryland Cotton Experiences

Rob Holmes HMAg Pty Ltd, Moree

Mob: 0429 849 174 E: [email protected]

Points of interest from CCA Cotton Consultants Survey 2011 (interim results)

Of 236,233 hectares of cotton grown by clients, 24.85% was dryland.

Of the dryland cotton grown, the following yields were achieved: Bales per hectare

Dryland hectare yields

(not adjusted for row spacing) 0 - 2 25%

2.1 - 4 60% 4.1 - 6 13% 6.1 – 8 2%

>8 0%

Common row spacings for dryland cotton: Row spacing Dryland hectares

1m rows 1% 1m rows – double skip 49% 1m rows – single skip 30% 2m rows 8% 3m rows 12%

Predicted interest in dryland cotton for 2011/12 season:

Similar interest to 2010/11 88% Less interest 1.6% More interest 0.4%

Agronomists rate availability of information for optimizing dryland cotton production:

Generally poor 12% Adequate on some topics 64% Adequate on all topics 24%

26

IrriSAT - an Irrigation management and crop water use benchmarking system Improving irrigation based decisions using new techniques and technologies Dr John Hornbuckle, CSIRO Land and Water, Griffith, NSW, 2680

28

Row Configuration Trial Update

James Quinn - CSD

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An integrated approach in managing Silverleaf Whitefly & Aphids

Climatic conditions, lifecyle, impacts & constructing a management program.

August 2011

Mark Congreve

Key sucking pests

� Cause early season damage and crop establishment delays

� May be considered a beneficial later in the cropThrips

Aphids

Mirids

� Early season - Bunchy Top transmission, Late season – yield & honeydew

� Populations will build throughout the season if not controlled

� Cause most damage early to mid season via tipping out & square shedding

� Tend to come into cotton blocks when adjacent crops hay off

2

Green Veg Bug

Mites

SL Whitefly

� Cause most damage mid – later season feeding on young bolls

� Tend to come into cotton blocks when adjacent crops hay off

� Yield loss via loss of photosynthetic material

� Populations will build throughout the season if not controlled

� Can become an issue late season due to honeydew production

� Populations build through the season and can explode if not controlled

Aphids – in more detail

� Unchecked, aphid populations build throughout the crop- Heavy populations can cause yield reduction

- Aphids are the vector that transmits Bunchy Top virus

- Produce honeydew which can cause downgrades

� Aphids reproduce asexually (i.e. clones)- No dilution of resistance

� Rapid population increase can occur under favourable conditions

3

- A mature aphid can produce 4 offspring per day which are then able to reproduce themselves within 6 days

� Often aphids start as “hot spots” where winged adults fly in� Aphids generally are more prevalent early season following wet winters, especially

where there is a green bridge or volunteer cotton� Traditionally have been controlled early / mid season by:

- Group 4A seed treatments, endosulfan, Group 4A foliar insecticides e.g. Shield

Cotton Bunchy Top (CBT)

� Viral disease causing reduced height, leaf & boll size and internode length� CBT is a “persistent” virus

- Once infected the virus will persist within the aphid for weeks or months

- Virus is circulated throughout the aphid, not just stylet borne

- Aphids need to feed for a period of time (>30 mins) to pass on the virus to the plant

� 3 to 8 weeks between infection of the plant and appearance of visual symptoms

4

- Even if symptoms are not expressed before harvest they will appear on ratoons

� Host range- Ratoon cotton is the most important host

- Pima cotton is a symptomless host

- Marshmallow weed is confirmed as a host for the virus

Silver Leaf Whitefly – in more detail

� Unchecked, SLW populations build exponentially throughout the season- Heavy, late season populations cause honeydew (worse than aphid

honeydew)- Life cycle is temperature dependent

- 35-40 days @ 15-20oC

- < 20 days @ 30-35oC

5

Silver Leaf Whitefly – in more detail

� Later generations explode� Most people will only see adults� Rain, cold snaps and insecticides reduce

numbers

6

35

Average temperature x location

7

Average temperature x location x SLW lifecycle

2

34

5

1

2

34 5

61

2

34 5

6

7

8

16

1

7

Insecticide Selection

� Efficacy- How well does in work?- How quick will it work?

� Spectrum- What else will it control?

� Resistance

Thrips

Aphids

Mirids

GVB

Mites

SLW

Pirimor

Admiral

Pegasus NR NR

Fulfill NR

9

- Will it work?- Rotation?

� IPM compatibility- Will it flare other pests?

� Cost

Movento

abamectin

Regent

Shield NR NR NR

dimethoate

OP’s NR

Insecticide Resistance

� Resistance monitoring is conducted for aphids & SLW. No monitoring for mirids & GVB

- Pirimicarb / dimethoate / omethoate share the same mechanism- High levels of aphid resistance in the past which has reduced through the 2000’s

- Neonicitinoids (Cruiser, Genero, Amparo, Shield etc) all share the same MOA - High levels of aphid resistance is now present and field failures to foliar applications have been

reported

- Organophosphates (chlorpyrifos, profenofos, phorate) share the same mechanism

10

- Varying levels of resistance are present

- Pegasus (diafenthiuron) is a different mechanism- Recently some low levels of tolerance give rise for concern

- Admiral (pyriproxafen) is a different mechanism- Significant SLW resistance in horticulture but not in cotton to date

- Movento (spirotetramat) is a different mechanism. Launched in 2010

- Fulfill (pymetrozine) is a different mechanism that will be available in 2011

Beneficial Selectivity

Prod

uct

Ove

rall

rank

ing

Predatory beetles Predatory bugs Hymenoptera Pest resurgence

Tota

l

Red

& B

lue

beet

le

Min

ute

2-sp

otee

d la

dybe

etle

Oth

er la

dy b

eetle

s

Tota

l

Dam

sel b

ugs

Big

-eye

d bu

gs

Oth

er p

reda

tory

bug

s

App

le D

impl

ing

bug

Lace

win

g ad

ults

Spi

ders

Tota

l (w

asps

)

Ere

tmoc

erus

Tric

hogr

amm

a

Ants

Thrip

s

Mite

Aph

id

Hel

ioco

verp

a

Toxi

city

to b

ees

Pirimor Very low

VL VL VL VL L L M VL VL VL VL VL M M VL L - - - VL

11

Admiral Very low

M - M M VL - - - - L VL VL L VL VL VL - - - L

Pegasus Low M H VL M L M VL L H VL L L H VL H L - - +ve M

Fulfill Low M M M M L L L VL H M L L L L M VL - - - VL

Movento Mod M L H H VL VL VL VL M VH M M - M M M - - - -

abamectin Mod L M H VL M L M M H VL M M H M H M - - - H

Regent Mod L VL H L M H H L VH L M M - M VH VH +ve - +ve VH

Shield Mod H VL - VH M M L VL H H M M VH H VH VL +ve - +ve -

Dimethoate High VH M VH VH M M L L VH VL M M - M M H +ve +ve - M

OP’s High H M H H H M H H VH L M H VH H VH H +ve - - H

Source: Cotton Pest Management Guide

� ~ 500 000 additional ha’s of volunteer RR cotton this spring which we have never had to deal with before

� Host for mites, whitfly and aphids (& Bunchy Top)

2.4L/ha Spray.Seed on RR cotton

Start with a clean field !!

12

Unsprayed

36

Group 4A Seed Treatments are still highly valuable

� Reduced thrips damage

� Wireworm management

Thrips damage

13

Loss of plant stand due to Wireworm

� Early season aphid & SLW population management

� Early plant vigour

� Unique MOA (Group 9)

� Translaminar and systemic movement within plant

� Suited to early to mid season when targeted against aphids

� Also has activity on Silverleaf Whitefly (adults only)

� IPM friendly�Selective Feeding Blocker�Within 1 hour of ingestion stylet is withdrawn�Death by starvation in 5 to 7 days. �“Dead aphid walking”

14

� Dead aphid walking

Cruiser / Cruiser Extreme

• broad spectrum controldimethoate

• fast acting

Shield• ensue break spray if following neonic seed treatment

At planting Early season Mid-late season Defoliation

Endosulfan

15

Pirimor• specific to aphids• avoid use if dimethoate was used at defoliation in previous season

• convenience of a seed treatment

Regent• disruptive• mirids & GVB only

• broad spectrum• high levels of resistance in the past

Thimet• granular OP at-planting treatment •main alternative to Gr 4A seed treatments• not recommended if OP/SP used at defoliation

• also mirids & GVB

Fulfill• unique MOA• death by starvation• also suppresses whitefly

Pegasus• unique MOA• also SLW, mites (& mirids) chlorpyrifos / profenofos

• fast acting• broad spectrum• different MOA to dimethoate

Movento• unique MOA, • slow, active on immature stages• also SLW

Nil at planting• foliar insecticides required earlier

Admiral• slow, long residual• SLW only

Pegasus• unique MOA• slower than OP’s

• now withdrawn

abamectin• mites• also suppression of H. punctigera

Notes on sucking pest management programs� Ratoon cotton and marshmallow weed are ideal hosts for cotton aphid. Keep fallows clean in winter / spring

� Cross resistance exists between dimethoate and pirimicarb but not dimethoate and chlorpyrifos / profenofos.

- Where possible, avoid the early use of Pirimor if dimethoate was used as the last spray in the preceding crop

- Always apply a different MOA in between Pirimor used early in the crop and dimethoate at defoliation

� All currently available insecticide seed treatments contain a Group 4A neonicitinoid MOA. High levels of aphid resistance have now been detected to this MOA.- Ensure a different MOA effective on aphids is applied to crops treated with a Group 4A seed treatment before application of foliar product

from this group (e.g. Shield), even if the foliar applications are targeted at a different pest i.e. mirids

� Early season aphicides- Pirimor – aphid specific, fast knockdown

F lfill i MOA d th b t ti ( l t t) t i ithi th l t ill l h i t SLW l ti

16

- Fulfill – unique MOA, death by starvation (slow to act), systemic within the plant, will also have impact on SLW populations

� Mid season sucking insecticides- Pegasus – active on aphids, SLW, mites and mirids (not on label), unique MOA, slower than Regent or Shield

- Movento – active on immature stages of aphids & SLW, new MOA, slow to act

- Regent – active on thrips, mirids & GVB, disruptive to IPM programs (low rate + salt is better)

- Admiral – active on immature stages of SLW, different MOA, resistance in horticultural markets in NQ, slow to act

ALSO consider - Affirm – active on Helicoverpa but will also suppress mites & mirids

- Steward - active on Helicoverpa but will also suppress mirids

In Summary

� Keep the fallow clean !!

� Insecticidal seed treatments still have a valuable role to play in establishment

� Endosulfan will be missed by some – but there are other options

� More early season selective aphid sprays are likely

- especially in areas with Bunchy Top

- aphids will be more of an issue in years with a wet spring

� Rotate chemistry for aphid control

- ALWAYS apply a break spray between an insecticidal seed treatment and Group 4A foliar

17

application (even if targeting mirids)

- ALWAYS apply a break spray between an early season Pirimor and dimethoate at harvest

- Where possible

- use Pirimor early season and chlorpyrifos / profenofos at defoliation

- use Fulfill early season and dimethoate at harvest

� Silverleaf whitefly will be a problem in “hot regions” in most years however is only likely to be a problem in “cool regions” in very hot years

- consider an mid to late season spray to knockdown numbers

37

On Farm Series: How To | May 2008 Issue Research & ScienceOn Farm Series: How To | August 2008 What’s NewOn Farm Series: How To | November 2007 Issue 1 How To

On Farm Research & Science

Cotton insects On Farm Series: How To | August 2008 Issue | Produced by Cotton Catchment Communities CRC

Aphid ecology in cottonResearch :Lewis Wilson1 Grant Herron2 , Tanya Smith1, Bernie Franzmann3 and Simone Heimona1 Review Input: Rod Gordon4, Tracey, Farrell2 James Hill2 ,David Larsen11 CSIRO Plant Industry, 2 NSW Department of Primary Industries, 3 Department of Primary Industries, Queensland 4Auscott Ltd , Formerly Cotton CRC

Aphids, once only a secondary pest in cotton are now a major problem for growers in some regions. Problems associated with aphid in Australian cotton include vectoring of cotton bunchy top disease, yield reductions from large early season infestations and late season effects of honeydew on fibre quality. Aphids ability to reproduce asexually has an impact on resistance management as does their ability to overwinter on non cotton hosts.

IntroductionThis is a companion document to ‘Strategies

to manage aphids in cotton’ available from the Cotton CRC web site.

Aphids, once considered only a secondary pest in cotton are now a major problem for growers in some regions. Three species are commonly found on cotton, the cotton aphid (Aphis gossypii), green peach aphid (Myzus persicae) and cowpea aphid (Aphis craccivora). The cotton aphid is the most common. Occasionally there are early or late season infestations of green peach aphid, which die off during hot periods. Cowpea aphid is sometimes found on seedling cotton in late spring after legume crops die off, but rarely establishes effectively in cotton plants.

DamageAphids insert their stylets into leaf or terminal

tissues of plants and probe until they contact a phloem vessel. The phloem is the tissue that distributes the products of photosynthesis

(assimilates) required for plant growth throughout the plant. The sap in the phloem is under pressure and is basically ‘forced’ into the aphids, which regulate the flow. Phloem sap is rich in sugars, but poor in amino acids which aphids need for growth. To accumulate enough amino acids for growth the aphids ‘pass’ a lot of excess sugar, which is excreted onto plants as a shiny sugar-rich deposit known as ‘honeydew’. Honeydew encourages the growth of sooty moulds on leaf surfaces. Aphid feeding causes economic damage to cotton in four ways;

1. Competition with young growth and developing fruit (squares and bolls) for assimilate. If this is beyond the capacity of the plant to compensate, reduction in growth is likely.

2. Reduced photosynthesis due to the presence of aphids on leaves. The cause of

Picture1: Leaf affected by Aphid honeydew (left)

www.cottoncrc.org.au Page 1 of 6

38

On Farm Series: How To | May 2008 Issue Research & Science

this effect is not well understood but could be due to a number of factors including; the damage caused by insertion of stylets, (especially when there are many aphids), the effects of assimilate depletion or the effects of saliva secreted in to the plants by the aphids.

3. Secretion of honeydew (Picture:1) onto leaves also reduces photosynthesis.

4. Late season aphid infestations result in honeydew contaminating lint, making it sticky and discoloured. Severe downgrading of sticky lint may result because of the difficulties of processing it in high speed spinning machinery.

Cotton aphids generally prefer to feed on the terminals, young leaves and fruit, sites where the supply of assimilate is high. Damage symptoms from cotton aphids initially appear as crinkled and curled leaves, with the margins of the leaves curling downwards (Picture 2).

Prolonged high populations of cotton aphid will lead to a dramatic shortening of internodes, severely reduced leaf size, leaf / fruit loss and

obvious yellowing or mottling of young leaves. This yellowing or mottling often occurs on areas of leaves heavily damaged by aphids or can occur evenly around the margins of leaves and should not be confused with the angular mottling found with Cotton Bunchy Top (see Picture 4).

Pre-squaring cotton appears to be able to fully compensate for aphid damage as long as the aphid feeding ceases. However, prolonged high population levels up to cut-out (when fruit production slows or stops) can cause substantial damage and reductions in yield. Populations in excess of 90% of plants infested with aphids for 3 or more weeks are likely to result in economic loss. (see companion

article ‘ Strategies to manage aphids in cotton’ for details).

Biology Ecology and Insecticide Resistance In Australia, the life cycle of aphids is quite

different to that of other cotton insects. Cotton aphids (Aphis gossypii) are all females, there are no males and therefore no sexual reproduction. Females give birth to live female young which are clones of themselves, inheriting all of their

Picture 2. Severe aphid damage results in wrin-kling, stunting and cupping of leaves. Younger leaves may show a yellow margin and reddened patches may appear on leaves. Photo: L. Wilson


1s t instar(Live young)

3rd ins tar

2nd ins tar

3rd ins tar (wing buds visible)

W inged adult(Alate)

Non – winged

Adults (Apterae)

2nd ins tar

1s t instar

4th ins tar (wing buds vis ible)

-

-

Suitable host plant (e.g. Cotton) - Population build-up Migration to new host plants

L. Wilson & A. Spora, Australian Cotton CRC, Oct 2001

Winged aphids leave host plant and migrate to new hosts. Settles and test feeds on potential hosts. Migration can be short-range (i.e. between plants within a field) or longer -range (i.e. between fields/farms/regions).

If host is unsuitable the aphid continues migration.

If suitable host then winged adult begins producing young which grow into non-winged adults

Changing Conditions- crowding- poor food quality -short day-length

Adult produces young which which develop on the host into winged adults

KEY POINTS- All females- All clones (range of clones in a region)- No sexual reproduction- Live young (no eggs)- No diapause – in winter reproduce very slowly on available hosts

Cycle continues, adult to adult in about 5-7 days in summer. Adults birth 4-6 young per day.Short range dispersal by walking (i.e. leaf-leaf, plant to plant).

Summer - many generationsWinter - fewer generations

Good Conditions - quality feed - low population density

Figure 1: Life cycle if cotton aphid

39


characteristics including insecticide resistance. A female aphid can produce live young at the rate of 4 - 6 per day, which in summer can mature through four nymphal stages into adults in 4 - 7 days. They can immediately begin producing live young. Female aphids have within them many live young at various stages of development. These cloned offspring already have clones developing within them before they are born. This is how so many generations can be produced in such short periods. Populations can explode if conditions such as food quality and climate are favourable.

Biology, Ecology and Colonisation of Cotton Colonisation of a new host plant usually occurs

by the winged (alate) adult. Aphids will settle on the plant and test feed. If the plant is unsuitable the winged adult will resume the “flight, settle and test feed’ pattern, until it finds suitable food or dies. If the plant is suitable, production of live young commences quickly. These mature through four nymphal stages into wingless adults (apterae). The wingless cycle will continue until some aspect of their environment triggers the switch to the production of dispersing (winged) forms. This switch can be caused by declining food quality, for instance if the host plant is senescing, by overcrowding or by reduced day-length.

Once triggered to disperse, the adult aphid produces live young which develop wing-buds. These nymphs mature into winged adults, which then fly off to find a new host plant. This could entail only a short flight, to another uncolonised plant in the same cotton field, or depending on wind currents, a longer flight to a new crop or weed host further away.

Resistance in aphid populationsAphid populations in a region will consist

of a number of different clones. These clones will appear identical but as there is no sexual reproduction the clones are essentially separate sub-populations. Different clones may display differences in biological features, for instance a degree of specialisation toward a particular type of host plant. They can also vary in their resistance to insecticides.

It is likely that there is a range of resistant and susceptible clones in a region. Normally when resistance develops in an insect population there is some penalty in growth or reproduction in that population. In the absence of insecticide selection the resistant individuals are not favoured, though this is not always the case, and some resistant aphid clones appear as well adapted as non-resistant clones. Table 1 summarises current resistance in aphids found in Australian cotton.

When aphids are treated with an insecticide (aphicide) the aphids of resistant clones survive and those of susceptible clones die. This leaves a population that is highly resistant which can continue to develop rapidly in the field. Due to the clonal nature of aphid populations one field can have resistant aphids while the adjacent field can have susceptible aphids.

Table 1 Resistance notes for major aphid species found in cotton

Aphid species Resistance

Cotton Aphid Patchy resistance and cross resistance to a broad range of aphicides. In particlular resistance to dimethoate or omethoate and cross resistance to pirimicarb is common. Resistance to profenofos, chlorpyrifos ethyl and methyl, pyrethroids and en-dosulfan is also found in some populations. Patchi-ness of resistance indicates that basic measures like farm hygeine can still limit resistance spread. See Infomation Sheet: Strategies to manage aphids in cotton for latest details.

Green peach aphid

Resistance to OP’s and Pirimicarb. Resistance levels are lower compared to cotton aphid See Infomation Sheet: Strategies to manage aphids in cotton for latest details.

Cowpea Aphid No known resistance.

Overwintering In winter, cooler temperatures slow the growth

rate of aphids dramatically. In Australian cotton regions, neither cotton aphids, nor green peach aphids nor cowpea aphids have an overwintering form. Instead they persist through winter in small scattered populations on whatever suitable host plants are available. In spring as temperatures increase aphid populations begin to build rapidly again.

Picture 3. Cotton aphids on a leaf. Note wide variationin colour and globula shape. Centre left is a predatory larvae of a hoverfly. Photo: C. Mares


40


Predators parasites, parasitoids and pathogens

Beneficial insects play an important role in aphid control at the stage before aphid numbers begin to increases exponentially. Disruption of beneficial populations by some insecticides can lead to earlier, more severe aphid outbreaks.

Aphids are bread and butter for many predators in cotton. Major predators of aphids include the larvae of the hoverfly (Syrphid) and lacewings , and nymphal and adult stages of ladybirds (white collared , transverse, variable ), red and blue beetle and the brown smudge bug.

Parasites of aphids include small wasps (Aphidius colemani and Lysiphlebus testaceipes) that sting developing aphids, inserting an egg which hatches into a larvae that grows and matures in the aphid, resulting in the pale bloated aphid mummies often seen on cotton leaves.

Natural variability in predator and parasite abundance means that some will be more important in different seasons.

During periods of heavy rainfall fungal pathogens can also take a toll on infestations

Cotton aphid

The cotton aphid varies widely in colour. The winged adults are typically black, but the wingless stages can vary from pale yellow through to dark green, brown and dull black (Picture 3). The wingless forms have a typically bulbous round shape.

The development of cotton aphid is favoured by warm temperatures and this species does well on cotton through the peak growing period.

Cotton aphid has a broad host range and has been recorded on members of the following families; Fabaceae (legumes, lucerne, medic), Solanaceous weeds (datura, ground cherry, nightshades), Cucurbitaceae (paddymelon), Malvaceae (bladder ketmia, marshmallow) and Asteracae (sunflower, capeweed, daisies, thistles, bathurst burr). A more complete host range can be found in the IPM Guidelines, or Cotton CRC website (see Useful Documents and Links at the end of this document).

Cotton aphid and Cotton BunchyTop (CBT)The cotton aphid is the only known vector of

cotton bunchy top disease.

Symptoms of CBT include reduced plant height, leaf surface area, petiole length and internode

length. Pale, angular patterns on the leaf margins are often observed with the remainder of the leaf blade usually dark green in colour. These darker leaves have a leathery and sometimes glossy texture when compared to those on healthy plants. Typically, the pale angular patches in field-grown cotton turn red as leaves age. Boll development is also affected, with bolls often less than half the size of healthy bolls.

Host plants for CBT include volunteer cotton and marshmallow and potentially other malvaceous weeds.

Green peach aphid

The green peach aphid is a pale yellow-green and is more tear-drop shaped than the cotton aphid (Picture 4). Colonies tend to be uniform in colour compared with cotton aphid. Seen with a hand lens or microscope, green peach aphid has a small tubercle at the junction of the antenna and head, which is absent in cotton aphid and cowpea aphid. The area between these tubercles is ‘U’ shaped in green peach aphid whereas it is flat in cotton aphid. Also, the green peach aphid has a pair of long, pale, tube-like siphunculi at the tip of its abdomen, whereas those of cotton aphid are quite short and usually dark (see Figure 2).

The green peach aphid causes far more severe effects on plant growth at much lower densities than coton aphid. Symptoms include yellowing of young leaves and the terminal and severe reductions in internode length and leaf / fruit size. Plants generally recover quickly if the green peach aphid numbers decline due to hot weather, beneficial insect activity or insecticides.

Picture 5: Green peach aphid, note pale green/yellow colour and tubercules with indented ‘U’ shape between them (see Figure 1). Photo: L. Wilson

Figure 4: Leaf symptoms of Cotton Bunchytop in the field



Fortunately this pest rarely establishes well on cotton.

The green peach aphid prefers cooler conditions. It is sometimes found on cotton early in the season but populations do not usually persist once hot conditions commence. Green peach aphid also has a wide host range and is often found on members of the following families. Fabaceae (legumes, lucerne and lupins), Asteraceae or all Brassica sp. They are also often found on peach and plum trees.

Cowpea aphidThe cowpea aphid is very similar to the cotton

aphid in appearance. However, the wingless adults of this species are a shiny black, in contrast to cotton aphid, which is always a dull colour.

Cowpea aphid will colonise a range of hosts but prefers legumes and is often found on medics. This species is often found on cotton early in the season but seldom establishes, though it may sometimes produce a small number of offspring. More common hosts include the Cucurbitaceae, Asteraceae, and Fabaceae families.

Other species of aphids on cottonA range of other aphid species are occasionally

found on young cotton. These are mostly the winged forms of species that have migrated from other hosts, especially leguminous weeds. These include pea aphid (Acyrtosiphon pisum), blue green aphid (Acyrtosiphon kondoi) (Picture 7) and the spotted alfalfa aphid (Therioapihs trifolii).

These species can settle on cotton to test feed but will not normally establish. Populations of winged adults on seedling cotton may initially be high but will usually decline quickly over two or three weeks. A wide range of beneficial insects also enters cotton crops at this time.

Winged forms of the corn aphid (Rhopalosiphum maidis) and the oat or wheat aphid (Rhopalosiphum padi) may also migrate from grasses, cereals or sorghum into cotton but do not establish. Aphis spiraecola (apple aphid) is also sometimes found on cotton , and probably originates from certain Asteraceae such as Conyza spp. (fleabane) or Chrysanthenum.

Soil aphidsBean root aphid (Smynthurodes betae) is a

rare aphid pest that feeds on the roots of cotton seedlings (Picture 8).

Death of seedlings can occur and bean root aphid damage may be mistaken for seedling disease. The aphids are small, pale, globular and wingless.

The presence of aphids can be detected by carefully separating the soil away from the roots of seedlings. Aphids can be found on the roots at a depth of about 10 cm and they are tended

Picture 7: Winged adult of blue green aphid, (Photo NSW Agri-culture)

Picture 6: Cowpea aphid showing shiny black wingless adults Photo J. Wessels

Figure 2. Green peach aphid (left) and cotton aphid (right). - extracted from Forrester and Wilson 1988.



by ants which construct small chambers to allow movement of aphids around the roots. The chambers are covered in a white, waxy dust from the aphids. Infestations so far have tended to occur in fields previously heavily infested with burr medic.

If infestations are discovered after seedling emergence there is no effective chemical control for the aphids. If planting cotton into seedbeds which have been infested with burr medic then granular insecticides applied to control other pests may coincidentally control bean root aphid.

AcknowledgmentsResearch: Lewis Wilson, Grant Herron, Simone

Heimoana , Tanya Smith and Bernie Franzmann

We thank Dr Amelia Reddall (CSIRO Plant Industry), Dr Neil Forrester (formerly NSW DPI ) and David Larsen (NSW DPI) for their input into this review, Dr Mary Carver, Dr Paul de Barro and Dr Owain Edwards (CSIRO Entomology) for assistance with aphid identification, ecology and life cycles and the CRDC and the Cotton Catchment Communities CRC for funding.

Useful documents and links Strategies to manage aphids in cotton:

Companion information sheet

“Integrated Pest management Guidelines for Cotton Production systems in Australia” (IPM Guidelines) Hardcopy or COTTONpaks CD versions available from The Cotton TRC or from the Cotton CRC website:

http://www.cottoncrc.org.au.

Cotton aphid hosts in Australia Web link: http://www.cottoncrc.org.au/content/Industry/

Publications/Pests_and_Beneficials/Aphids__Bunchytop/Overwinter_host_plants_of_Cotton_Aphid.aspx

Cotton Pest Management Guide: Published yearly by NSW DPI also web: http://www.dpi.nsw.gov.au/agriculture/field/field-crops/fibres/cotton/cotton-pest-management-guide


43

ISSN 1327-0303

RE

SEA

RC

H R

EV

IEW

CRC Newsletter for the Research Extension Education ProgramVolume 3 Number 4 August 1997

Inse

cts

CSIRO1 – NSW Agriculture2 – Qld Department of Primary Industry – University of New England–University of Sydney – Cotton research and Development Corporation

SummarySpider mites (Order Acarina) are a major problemin most Australian cotton production areas. Earlymite infestations which develop quickly can causesubstantial reductions in lint yield, fibre quality(particularly micronaire) and oil production if notcontrolled. Mites are a true ësecondary pestí in thatmanagement of primary pests, especiallyHelicoverpa, reduces populations of mite preda-tors which in turn allows mite populations todevelop to economic levels. The information pre-sented in this review is designed to help growersand consultants manage mites effectively withminimal reliance on acaricides. The accompanyingpublication, Managing Mites on Cotton, coversissues in mite management that may change fromyear to year.

Key IssuesThe integrated approach to mite management canbe summarised in the following key points:

ï Reduce mite overwinter survival by ensuringgood weed control in and around fieldsthrough winter and spring. Rotation cropssuch as safflower, faba beans and field peasare good hosts for mites which may migrate tocotton seedlings as these crops senesce.Insecticides applied to rotation crops may exac-erbate mites by eliminating their predators.

ï Ensure regular and adequate sampling ofmites, even at early stages of crop develop-ment.

ï Conserve and utilise mite predators by adher-ing to economic thresholds for other pests andavoiding broad spectrum sprays where possi-ble. Predators help to control other important

OOPERATIVE RESEARCH CENTRE FOR

USTAINABLE COTTON PRODUCTIONCS

Reviewers: Lewis Wilson1, David Larsen2 and Victor Sadras1

Researchers: Lewis Wilson, Victor Sadras

pest species such as Helicoverpa and aphids.

ï Balance the damage associated with early sea-son thrips infestations (often no yield or earli-ness penalty) with their role as predators ofmite eggs.

ï Use thresholds or yield-loss tables to deter-mine if mites warrant control.

ï If mites are likely to cause economic loss, con-trol them at, or close to, 30% of leaves infested.Delaying control may increase the need torespray. If mite control is indicated early in theseason, use selective acaricides (i.e. dicofol), ifpossible, to limit disruption of predator pop-ulations.

ï Use okra leaf varieties if the potential for miteinfestation is high.

ï Avoid planting corn and summer legumesnear cotton fields as these crops are good hostsfor mites.

size – 0.5mm Photo:Lewis Wilson

Figure 1: Two spotted spider mite, Tetranychus urticae,showing characteristic green spots on either side. Alsonote the relative size of the mite egg above adult.

MITEEcology on Cotton

442

Mite Species in CottonThe two-spotted spider mite, Tetranychus urticae, is themajor mite pest of Australian cotton (Fig. 1). The beanspider mite, T. ludeni, which is deep red, is also occa-sionally found and causes damage similar to two-spotted spider mite (Fig. 2). T. lambi, the strawberryspider mite is also occasionally found in cotton. It issmaller than the others species (about 2/3 the size)with three small spots along either side (Fig. 3), andonly causes very slight, non-economic damage. Thebrown wheat mite, Petrobia latens, may be found onseedling cotton, but rarely requires control.

Figure 2:

Tetranychus ludeni – simi-lar in size to T.urticae butdeep red. Note translucentmite egg in upper right ofphoto and pale adult malein foreground.Photo: M Hill (NSW Ag)

size –0.5 mm

Figure 3:

Tetranychus lambi – notesmaller size and character-istic spots (6) along sidesPhoto: C Mares (CSIRO)

size – 0.3 mm

Mite BiologyThe two-spotted spider mite develops from an egg,through three immature stages, and finally becomes

an

adult (see Fig. 4). Development from egg through toadult take from 7 to 14 days in typical summer condi-tions. After a further day. female mites will begin tolay eggs at a rate of about 6 - 7 per day for the nexttwo weeks.

In regions with cold winters, adult mites developingin autumn change to a bright orange ëdiapauseí formmore tolerant of cold conditions (Fig. 5). They leavethe host and seek dark, humid, protected sites to over-winter, such as the crotches of trees and under leaf lit-ter, and do not feed or reproduce.

Figure 5:

Diapause form of Two-spottedspider mite, T. urticae – notebright orange colourPhoto: C. Bower (CSIRO)

size –.5 mm

Diapause mites become active as temperatures anddaylengths increase in spring and move back ontohosts, resume their normal green colour and com-mence feeding and reproducing.

In regions with mild winters mites do not diapauseand survive on suitable hosts. Intermediate strawcoloured forms are often seen in cotton regions. Theseare not in diapause and will feed and reproduce if theyfind a host.

Mite EcologyMites are adapted to exploit ephemeral hosts, espe-cially weeds, and to produce large numbers of off-Figure 4: Life cycle of T. urticae

Egg

This is followed by twoeight legged nymphal

stages.

Adult

As host plantsmature andsenescece adultmites move first tohigher positions inthe plant andcluster. Mites thenleave the originalhost carried bywind currents

In autumn, in cold areas,Orange non feedingoverwintering form

Mite eggs are the favoured stage formany predators

All active mitestages feed in thesame manner, usingpiercing mouthpartsto repeatedlypenetrate planttissue.

Larvae

ProtonymphDeutonymph

•Female mites produce around 70spherical semitranslucent eggs in theirlife

•Unfertilised adult female mitesproduce viable male eggs

•Fertilised females produce eggs ofboth sexes in the ratio of 3 females to1 male.

Visible tonaked eye

Hand lens required tosee this and earlierstages

6 legged whitelarval stage .

7 to 14 days in summer from egg to adult

0.5mm

45 3

spring to ensure some will migrate successfully tonew hosts before the current host dies.

Mated adult females, the main dispersing stage, areready to start another colony as soon as they settle ona new host. The two-spotted mite in particular has abroad host range, ensuring that at least some migrat-ing mites will find suitable food.

The adaptations for this mode of existence (fast devel-opment, broad host range) mean that mites are wellequipped to take advantage of highly fertilised andwell watered cotton crops.

Mites move to new hosts by crawling (short dis-tances), or are carried passively on wind currents forconsiderable distances (at least 1.5 km). Movement ofchippers, checkers and machinery can also assist inspreading mites which can adhere to clothing, tyresand chassis and thereby transfer to new plants.

Sources of mites entering cotton cropsIn cotton regions, mites mostly survive the winter asactive colonies on hosts such as winter weeds or rota-tion crops. Key weed species include: turnip weed,medics, sowthistle, deadnettle, wireweed. Importantcrops include safflower, faba beans and field peas. Inspring, as these hosts senesce, mites are forced tomigrate to new hosts, like cotton seedlings. As mitesare blown into cotton fields more are intercepted byplants on the edge of a field than reach the interior:resulting in an edge effect. This initial influx of mites-forms the ëseedí for populations that develop later.

Mite infestations on seedling cotton tend to be higherin seasons following wet winters when there are moreweed hosts, and lower following dry winters.Controlling weeds within fields and along fieldboundaries helps reduce mite survival through winter.

Irrigated winter rotation crops provide hosts for mitesin dry winters when there would otherwise have been

few. Winter cereal crops are poor hosts for mitesalthough broadleaved weeds within these crops maybe good hosts. Winter cereals are, however, goodsources of thrips which are predators of mite eggs.Chickpeas are also poor hosts for mites due to thesticky leaves and stems of these crops.

Mite survival may be increased if rotation crops aresprayed with broad-spectrum insecticides to controlother pests, as these sprays reduce mite predators. Forexample, safflower is a particularly good host formirids which may migrate to and damage nearby cot-ton. Insecticides applied to control mirids in either thecotton or the safflower can substantially increase thelikelihood of mite outbreaks in cotton due to suppres-sion of predators in the sprayed crop (see Fig. 6).

If cotton crops mature very late, mites may enter dia-pause and move into leaf litter and trash. Cultivationof the soil, as employed for pupae busting (seeResearch Review Vol 3 No 2), will also help reduce sur-vival of diapause mites.

Avoid planting maize and summer legume crops nearcotton. These crops are both good hosts for mites. andthere is no effective means of controlling mites on them.

Factors affecting population increaseFields with high mite infestations at the seedlingstage are more likely to suffer mite outbreaks.Sampling cotton crops at this stage is critical fordetecting mites and adjusting management strategiesto reduce potential losses where necessary.

Survival and development of mite populations onyoung cotton can be affected by weather (rain andhail can temporarily reduce mite populations), in-fur-row insecticides (crops treated with aldicarb or phor-ate will have fewer mites), and predation.

Mite populations are normally held in check by preda-tors, including thrips, big-eyed bugs, two-spotted

% In

fest

ed P

lant

s

Nov Dec Jan Feb Mar

20

40

60

80

100Initialcolonisationof cottoncrops atemergence

A decline innumbers

Increase inmid to lateseason.

Often found oncotyledons afterseedling emegencemostly on field edges.

Scattered on plantswith slight bias toupper nodes.

Most mites in upper third ofplants. Sample at 3rd to 5th nodefrom terminal. Look at base ofleaf first then leaf folds.D

istr

ibu

tio

n

without predators

with predators

Figure 6: Common population cycle T. urticae

46

ladybeetles and other ladybeetles, tangle web spi-ders, apple dimpling bugs, brown smudge bugs,pirate bugs and damsel bugs. Early season reduc-tions in predator abundance, due to application ofbroad spectrum insecticides, allows increased mitesurvival and earlier development of economicallysignificant outbreaks (see Fig. 6). If control is neces-sary, adhering to economic thresholds for other pestsand selecting the least disruptive insecticide, willhelp to preserve predators and delay mite outbreaks.The most recent information on the effects of currentinsecticides on beneficials is available in the accom-panying publication Managing Mites on Cotton.

Acaricides and Resistance ManagementMites live on the undersides of leaves which makesthem difficult to target with acaricides. With all aca-ricides good coverage, especially underleaf, will givebest results.

In many other agricultural and horticultural systemsmites have rapidly developed resistance to a widerange of acaricides. A strategy to avoid resistance,based on the lack of cross resistance between any ofthe acaricide groups, is outlined in the accompany-ing publication Managing Mites on Cotton.

Sampling for Mites on CottonThe sampling protocol developed for mites is basedon their preference for mature active leaves ratherthan young unfolding leaves, or old senescent leavesand their highly clumped distribution (patchiness)across fields. This patchy distribution is often seen asëhotspotsí or small areas of reddened, mite-damagedplants distributed across a field. Sampling as widelyas possible increases the chances of detecting miteoutbreaks before they cause economic loss.

1. Walk into the field about 40 m. Early in the seasonit is also advisable to sample near the field edgesto see if significant influxes of mites haveoccurred.

2. Take a leaf from the first plant on the right or left.The leaf should be from the third, fourth or fifthmain-stem node below the terminal. If the planthas less than three leaves, sample the oldest. Notethat early in the season, it is simpler to pull outwhole plants.

3. Walk five steps and take a leaf from the nextplant, on the opposite side to the previous one,and so on until you have 50 leaves.

4. Once all the leaves have been collected score eachleaf by turning it over, looking at the underside,first near the stalk, then scanning the rest of theleaf. If mites of any stage (eggs or motiles) arepresent score the leaf as infested. A hand lens willbe needed to see mite eggs.

5. Repeat this simple procedure at several widelyseparated places in the field to allow for differ-ences in mite abundance within the field.Depending on the size of the field, 4-6 sites areneeded to obtain a good estimate of mite abun-dance. When finished sampling, calculate theoverall percentage of leaves infested with mites.

Damage and ThresholdsSpider mites feed by piercing leaf cells and removingthe contents of palisade and mesophyll cells, whichare the primary sites of photosynthesis. Initially mitefeeding has little effect on photosynthesis, though itcauses visible signs of damage (Phase I, Fig 7). Thisis indicated by white ëstippledí areas on the under-surface of the leaf, usually begining at the base of theleaf blade and seen as corresponding small bronzedor reddened areas on the upper leaf surface. As pop-ulations increase, leaf damage also increases andphotosynthesis is severely reduced (Phase II, Fig. 7).Reductions of photosynthesis at this stage lead toreductions in crop growth, fast leaf senescence, andeconomically important yield reduction and qualityloss (reduced micronaire).

Figure 7: Cumulative mite damage and yield loss

If unchecked by predators or acaricides, mite popu-lations increase exponentially until they eventuallycause plant defoliation. Yield loss is a function of thetiming of mite population increase and the rate ofincrease: early, fast increase has the greatest effect,and later, slower increase the least.

General thresholds for mites are given overleaf.Even though mite damage does not begin to affectphotosynthesis until populations are quite high, con-trol is difficult if mites are allowed to reach these lev-els. Optimal control is achieved at lower densities ofabout 1-2 adult female mites per leaf or about 30% ofplants infested.

Cro

p P

hot

osyn

thes

is

(%

of

cont

rol)

0 4 8 12

Increasing mite damage(arbitrary units)

Phase I Phase II

100

about20 mites/leaf

0

4

47

Mites in dryland cottonMites are usually less prevalent in dryland cotton.This may be partly because there is often less conti-nuity of mite hosts on dryland farms which do nothave a continuous cycle of irrigated crops and asso-ciated weeds, and water-stressed crops tend to beless suitable for mite development possibly due toharder leaves. In terms of yield loss, healthy drylandcrops with good soil moisture are equivalent to irri-gated crops. Crops that are already stressed may suf-fer less damage from mites than irrigated crops butwell established mite populations with fast rates ofincrease will still cause economic loss (Table 1).Precise recommendation are not yet possible sogrowers and consultants will need to use their ownjudgment regarding the need for mite control in dry-land crops.

Table 1 Comparative effects of mites on irrigated anddryland cotton. Dryland crops suffered less yield loss dueto mites than irrigated crops despite similar levels of miteinfestation. Experiments at Narrabri, 1996/97.

Lint yield (b/ha)

- mites + mites

Irrigated 7.7 0.6

Dryland 5.4 2.1

Companion Publication:Managing Mites on Cotton

Tables of yield losses expected from mite outbreaks,based on time and rate of increase (see Managingmites on Cotton) provide a more accurate

Figure 8: Stippled and bronzed areas on a cotton leafindicating moderate and heavy mite infestation.

basis for decision making. NB The tables and calcu-lations are built into the entomoLOGIC decisionsupport system. Be aware also that the effect ofpredators may be altered by recent sprays.

Control of mites is warranted if the value of poten-tial yield loss is double the cost of control (i.e. makemoney, not just recover costs). The impact of preda-tors is built into these tables as effective predationwill lower rates of increase, leading to low yield losspredictions. Similarly mite populations also increaselater and more slowly on okra leaf varieties givinglower yield reductions than for comparable normalleaf varieties.

General thresholds for mites on cottoni. Seedling emergence to squaring. Mites are nor-

mally suppressed by predators, especially bythrips during this period. Mite populationsonly need to be controlled if they begin toincrease, which indicates that natural controlsare not keeping them in check.

ii. Squaring to first open bolls. Control if mitepopulations increase at greater than 1% ofplants infested/day in two consecutive checks,or if more than 30% of plants are infested.

iii. First open bolls to 20% open bolls. Control isonly warranted if mites are well established(greater than 60% plants infested) and areincreasing rapidly (faster than 3% of plantsinfested/day).

iv. Crop exceeds 20% open bolls. Control is nolonger warranted.

Acknowledgementsï Thanks to Neil Forrester, Gary Fitt and Sandra

Deutscher for critial appraisal of this review

ï Editing layout and design - Maris Rea, TRC/CRCfor Sustainable Cotton production

5

Silverleaf whitefly (SLW): Factors Likely to Influence In-crop Population Growth in NNSW & SQ in 2011-12 R. Sequeira Agri-Science Queensland, DEEDI, Emerald. Q 4720 Email: [email protected] Mobile: 0407 059 066 Factors likely to influence in-crop population growth (Fig. 1) Climate & weather patterns • Number of warm weather generations (October-

March) – Table 1 o SLW is already well established in

NNSW and SQ but damaging population levels may not eventuate every year

o Expect 6-7 generations (roughly 25-30 days per generation) under long-term average weather conditions – this equates to low-medium density in-crop populations that may require control in some crops, depending on crop stage, abundance of beneficial insectss, pest management practices, etc.

o If 2011-12 is warmer than long-term average, expect greater risk of pest population development

Table 1

Fig. 1. Major influences on whitefly biology and ecology (After P. De Barro)

• Winter-Spring rainfall pattern – good rains in winter and early spring that sustains large weed host populations (broadleaf species) followed by dry, warm weather and rapid drying of host vegetation will facilitate whitefly dispersal from feral host plants to crops – maintain good farm hygiene, keep fallow fields weed-free.

Cropping system • Founding populations in spring

o Detection of significant adult and nymph densities on feral hosts in late August-early September increases probability of in-crop population development (Fig. 2). Feral plant surveys should be conducted in September to quantify overwintering whitefly load and associated risk. Note the relationship between high winter abundance (Fig. 2) and pest abundance in cotton (Fig. 3 below).

• Crop sequences and layouts –

presence of melon, soybean and sunflower crops in a cropping area with cotton will increase the probability of whitefly population development in cotton.

o Melons, Soybean and sunflower and all excellent host plants on which reproduction and survival of whiteflies is very high.

Pest Management practices • Dynamics of beneficial insect populations

o Absence or low levels of parasitism and predation early in the season increases the probability of whitefly build-up in crops. Note increase in whitefly population in relation to November mortality of SLW in Fig 3.

Fig. 3. Profiles of whitely populations (line graphs) and parasitism (bars) in cotton crops in the Emerald area.

Fig. 2. Winter abundance of SLW in the Emerald irrigation area was highly correlated with significant populations in cotton.

• Insecticide use patterns o Conditions in winter that favour development of whitefly populations in

spring/summer will also favour aphid and mite population development. o Use of broad-spectrum insecticides for managing other pests such as

aphids, mites and mirids early in the season increases probability and rate of whitefly population development by knocking out beneficial insect populations.

Silverleaf Whifely damage risk associated with grain crops Table 2. Expected overall and seasonal crop damage risk resulting from whitefly infestation in major cropping areas of Queensland and northern New South Wales.

Silverleaf Whitefly sampling guidelines for cotton, grain and other crops • No population or damage thresholds available for crops other than cotton BUT

sampling is important to track in-crop population growth. Where to sample within crops: Table 3. Main-stem leaf nodes within plants (from the terminal) best suited for detecting the presence of adult and nymph stages of silverleaf whitefly. Crop

Stage Sampled Cotton Mung bean Soybean Sunflower

Adults 3-5 2-3 2-3 3-5

Large Nymphs 8-9 7-8 7-8 11-12

Sampling units • Adults – count numbers on whole leaves (use binomial sampling where

appropriate); sample 20-30 leaves per 25 ha of crop. • Nymphs – use a circular disc of known area; 20-30 discs per 25 ha of crop.

Insect Pest Outlook for the 2011/12 season

Summary of prevalence of key pests in the previous season (2010/11), averaged. Data sourced from interim results of Cotton Consultants Survey 2011

Pest Central Qld

Darling Downs

Gwydir Macintrye Macquarie St George/ Dirranbandi

Upper Namoi

Lachlan

Whitefly Helicoverpa in Bollgard Stinkbug complex Cluster caterpillars Mirids Aphids Key Less prevalent Similar to previous season More prevalent

Regional outlooks for key insect pests for 2011/12 season Pest Central

Qld Darling Downs

Gwydir Macintrye Macquarie St George/ Dirranbandi

Namoi Lachlan/ Sth NSW

Whitefly

Aphid

Mite

Mirid

Key Unlikely to be high pressure unless………………………refer to cautions below Possible pressure – monitor conditions .........................refer to cautions below Likely high pressure based on current conditions ……..refer to cautions below

Cautionary footnotes:

1……………………………………………………………………………………………………………………………..

2……………………………………………………………………………………………………………………………..

3……………………………………………………………………………………………………………………………..

4……………………………………………………………………………………………………………………………..

5……………………………………………………………………………………………………………………………..

52

www.precisionsprayoils.com.auFor more information contact your local supplier or visit our website.

��IPM control of sucking pests

��Enhanced performance from tank mixed insecticides

��Superior, low rate defoliant aid

��All trial proven, registered label claims

��Economical to use

��Ongoing R&D support program

��From loyal supporters of the CCA

CANOPY PASSES THE BEAT SHEET TEST.��

Thank you for another great Seminar and your support of the

CCA

Travel Safe, Have a great summer & see you in Moree 2012

May 2012 - Moree

For information on our new Corporate Partnerships Program for the 2011/2012 financial year

please speak with Fiona at the seminar or visit www.cropconsultants.com.au/partners

for more information