I

AP004 Reduction of pesticide use in apples by supervised pest and disease control

Dr Colin Bower, et al NSW Agriculture

AP004

This report is published by the Horticultural Research and Development Corporation to pass on information concerning horticultural research and development undertaken for the apple and pear industry.

The research contained in this report was funded by the Horticultural Research and Development Corporation with the financial support of Batlow Fruit Cooperative Ltd.

All expressions of opinion are not to be regarded as expressing the opinion of the Horticultural Research and Development Corporation or any authority of the Australian Government.

The Corporation and the Australian Government accept no responsibility for any of the opinions or the accuracy of the information contained in this report and readers should rely upon their own enquiries in making decisions concerning their own interests.

Cover price: $22.00 (GST Inclusive) NSW Agriculture ISBN 0 7347 1200 6

Reprinted and distributed by: Horticultural Research & Development Corporation Level 6 7 Merriwa Street Gordon NSW 2072 Telephone: (02) 9418 2200 Fax: (02) 9418 1352 E-Mail: hrdc@hrdc.gov.au

© Copyright 2000

HRDXC

HORTICULTURAL RESEARCH & DEVELOPMENT CORPORATION

Partnership in horticulture

HORTICULTURAL RESEARCH & DEVELOPMENT CORPORATION

REDUCTION OF PESTICIDE USE IN APPLES BY SUPERVISED PEST AND DISEASE CONTROL

PROJECT No. AP 004 (1989-1993)

FINAL REPORT

Principal Investigator: C.C. Bower, Program Leader, NSW Agriculture

161 Kite Street, Orange, NSW 2800, Australia

Disclaimer Any recommendations contained in this publication do not necessarily represent current HRDC policy. No person should act on the basis of the contents of this publication, whether as to matters of fact or opinion or other content, without first obtaining specific, independent professional advice in respect of the matters set out in this publication.

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CONTENTS

I SUMMARIES 6 - INDUSTRY 6 - TECHNICAL 7

II RECOMMENDATIONS 8 - IMPLEMENTATION / EXTENSION 8 - FUTURE RESEARCH 8

III TECHNICAL REPORT 9

1.0 INTRODUCTION 9 1.1 Origins and aims of the project 9

1.2 The need to reduce pesticide use

2.0 PESTICIDE USE ON APPLES AT BATLOW 13 2.1 Insecticides and miticides 13

2.2 Fungicides 17

3.0 OPTIONS FOR REDUCING PESTICIDE USE ON APPLES 22

3.1 Organic 22

3.2 Integrated pest management (IPM) 22

3.3 Disease management 25

3.4 Supervised pest and disease control 27

4.0 THE BATLOW SUPERVISED PEST AND DISEASE CONTROL PROJECT 28

4.1 Aims and criteria 28

4.2 The Batlow district 29

4.3 Selection of co-operators and initial survey 29

5.0 GENERAL METHODS

5.1 Project organisation

5.2 Sampling procedures

5.3 Sampling methods and spraying strategies for insects and mites

5.4 Strategy for disease control and fungicide use reduction

5.5 Pest and disease levels

5.6 Number of pesticide treatments

5.7 Amount of pesticide product applied per hectare

5.8 Statistical Analysis

5.9 Weather records

36 36

36

38

42

43

44

44

44

44

6.0 RESULTS AND DISCUSSION

6.1 Apple dimpling bug

6.2 Codling moth

6.3 Lightbrown apple moth

6.4 Woolly aphid

6.5 San Jose scale

6.6 Mites

6.7 Apple scab

6.8 Powdery mildew

6.9 Number of insecticide treatments applied and pest damage

6.10 Number of fungicide treatments applied and scab infection

6.11 Amount of pesticide product applied per hectare

50 50

52

58

58

60

60

62

77

77

77

77

6.12 Number of pesticides treatments, disease and pest damage and the amount of pesticide used averaged over three seasons 82

6.13 Comparison of weather between seasons 82

7.0 OVERVIEW OF PESTICIDE REDUCTION 83

8.0 CONCLUSION 87

9.0 ACKNOWLEDGMENTS 89

10.0 REFERENCES 90

11.0 APPENDICES 96

11.1 Scientific publications 96

11.2 Extension publications 98

11.3 Lectures and conference contributions 98

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I SUMMARIES

INDUSTRY SUMMARY

In response to consumer demand for "clean green" fruit and concerns about human health and the environment, the Australian pome fruit industry is committed to a program of pesticide reduction. This project was undertaken to assist apple growers in the Batlow district to reduce the amount of pesticide required to control insect pests and diseases while continuing to produce top quality fruit.

In the absence of viable alternatives to synthetic pesticides this project aimed to minimise insecticide usage by spraying only when monitoring indicated that economic loss from insect damage was likely to occur. Fungicide use reduction was sought by a reducing the application rates combined with monitoring in the second half of the season. Central to this strategy was an integrated pest and disease management (IPDM) package that consisted of protocols for pest and disease monitoring and spray thresholds. Monitoring and sampling techniques and action thresholds were devised for codling moth, lightbrown apple moth, apple dimpling bug, plague thrips, woolly aphid, San Jose scale, mite, and the diseases apple scab and powdery mildew.

Overseas studies have found that where growers are advised by trained pest mangers, i.e. in supervised pest control (SPC) programs, pesticide usage can be reduced by an average of 36%. In this trial the IPDM protocols were implemented under a supervised pest and disease control (SPDC) program where a trained pest control manager carried out the monitoring and, in consultation with the research team, advised growers as to the number and timing of sprays.

Twenty growers took part in the trial, volunteering to join either the SPDC group or the non-advised control group. The pest and disease status of all twenty orchards was monitored over the trial period. Members of the SPDC group were advised accordingly with regard to pest and disease control. The control group sprayed according to their own observations and individual practices. The number of pesticides applied and the level of fruit damage incurred by each group was compared each season. The IPDM protocols were amended each season as the trial progressed and by the 1992/93 season were sufficiently robust that all the pests and diseases encountered during the trial were managed.

Volunteers for the SPDC group tended to be heavier users of pesticides than the control group. This study found that the growers under the SPDC program benefited from improved pest and disease management and were able to modify their pesticide usage, bringing about a 25% reduction in pesticide usage, i.e. their usage was reduced to the level used by the control group. Unfortunately the program did not result in the SPDC group using significantly fewer pesticides than the non-advised control group.

The study found that in general most growers use pesticides responsibly although they vary in their attitude to risk, with some applying pesticides as a preventative measure with respect to a perceived risk rather than in direct response to observed pest or disease problems.

Many growers are already using minimal spray programs and further large reductions for these growers are unlikely unless alternatives to broad spectrum insecticides are developed. Likewise further reductions in fungicide use will require alternatives to the synthetic fungicides currently available.

The Australian pome fruit industry as a signatory to the 1991 Pesticide Charter has set itself a difficult goal and the likelihood of achieving the 50% reduction in pesticide usage by 1996, based on current pest control strategies is low.

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TECHNICAL SUMMARY

The aim of this project was to assist growers and in particular those in the Batlow (NSW) district to minimise their pesticide usage while continuing to produce a high grade crop. To achieve this an integrated pest and disease management (IPDM) program was devised specifically for growers in the Batlow district. Monitoring and pest management strategies were devised taking into account the districts climatic conditions at different geographical altitudes and the effects on pests and diseases, principally the effects of temperature on codling moth development and rain fall on apple scab.

The IPDM program was implemented in 10 orchards which were volunteered for supervised pest and disease control (SPDC) program under the supervision of a trained pest manager. This ensured monitoring and control action protocols were implemented consistently in all participating orchards. Insect pest populations, the level of disease infection and the extent of fruit damage was recorded in the 10 SPDC orchards and compared with that in 10 non-supervised orchards over the three growing season trial period.

A pre-trial survey showed that growers in the SPDC group applied more pesticides than those in the non-advised control group. This may reflect greater aversion to risk on the part of the grower or possible pest control problems for which they were seeking assistance, either way this may have influenced the grower's decision to volunteer to join the SPDC group.

The results of this trial show that the SPDC group was able to reduce their insecticide usage by 25%, i.e. to the same level as the control group, however overall the SPDC program did not significantly reduce pesticide usage to levels below those applied by the control group.

A large proportion of the pesticides applied in apple orchards each season are fungicides for apple scab and powdery mildew control. However the potential for reductions in fungicide usage in terms of reducing the number of applications is low given the speed at which crop losses occur if suitable climatic conditions prevail and effective fungicide coverage is not maintained. In this study fungicides usage was reduced by spraying at 20% less than the recommended label rate without a significant increase in fruit loss.

This project established, for the first time in Australia, formal sampling and monitoring techniques and action thresholds for the diseases apple scab (Venturia inaequalis Cke. Wint.) and powdery mildew {Podosphaera leucotricha (Ell. & Ev.)), and the insect pests, codling moth (Cydia pomonella L.), lightbrown apple moth (Epiphyas postvittana (Walker)), apple dimpling bug (Campylomma liebknechti (Girault), plague thrips {Thrips imaginis Bagnall), woolly aphid (Eriosoma lanigerum (Hausmann)) and San Jose scale (Quadraspidiotus perniciosus (Comstock)). Mites were managed in accordance with established integrated mite control practices.

A degree-day phenology model was used for predicting the presence of vulnerable life stages of codling moth, i.e. larvae for the azinphos-methyl users and egg laying for the fenoxycarb users, and this delayed the start of spray programs by approximately one week and resulted in some growers saving one spray per season. Unfortunately this may have been responsible for an increase in damage from lightbrown apple moth.

Apple dimpling bug (ADB) causes damage to fruit at blossom time by feeding on the newly formed fruitlets. To protect fruit from this pest two or three sprays of endosulfan are usually applied each season. In this trial a new strategy of applying chlorpyrifos at late pink was evaluated. Applying chlorpyrifos at the late pink stage controlled ADB effectively without affecting bees which were not present until the blossoms opened.

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II RECOMMENDATIONS

Implementation /Extension

The key recommendation of this project is that growers, through their membership of the Batlow Fruit Co-operative, continue with the supervised monitoring services and control techniques established as part of this study.

The benefits of the monitoring and advisory service provided during this project enables growers to make informed decisions based on the current pest status in their orchard and take control actions only when required but before serious damage occurs. Taking control measures, i.e. applying pesticides, only when required will minimise pesticide use and may have some cost reduction benefits. The benefits of a professional monitoring service should be communicated, through technical workshops, to all the growers within the Batlow Fruit Co-operative and extended to other districts through grower support groups and other extension agencies.

The finding that a single application of chlorpyrifos applied at late pink provides effective control of apple dimpling bug replacing multiple applications of endosulfan should also be extended to growers in all apple growing districts.

A reduced rate of fungicide can provide adequate control of scab and mildew in well managed orchards.

Future Research

Further research is required to take into account different climatic conditions, ie, in districts other than Batlow, to prove the effectiveness of reducing fungicide rates by 20% in low pressure situations. Information on the importance of the amount of carry over of scab inoculum and its reduction may give confidence for rate reductions.

To meet the industry's commitment to further reductions in pesticide use will require alternatives to the broad spectrum organophosphate insecticide azinphos-methyl for codling moth control and the synthetic fungicides currently used for apple scab control. A number of alternative strategies for codling moth control are currently being evaluated in other countries and these should be evaluated for their potential under Australian conditions. The techniques showing most potential are those that utilise synthesised codling moth sex pheromone in strategies such as mating disruption and attract and kill, and the new insect juvenile insect hormones (juveniods), eg. fenoxycarb and tebufenozide. Biological control of codling moth is also being investigated using parasitic wasps of Trichogramma spp., nematodes and the biocides codling moth granulosis virus and Bacillus thuringiensis (Bt).

Alternative non-pesticide strategies such biological control by natural enemies and biocides are required for a number of other pests including apple dimpling bug, woolly aphid, early season budworms {Helicoverpa spp.) and the potential of each should be investigated under Australian conditions.

Ill TECHNICAL REPORT

1.0 INTRODUCTION

1.1 Origins and aims of the project

This project arose out of a need perceived by the Batlow Fruit Cooperative, and the Australian apple industry in general, to reduce the amount of pesticide being used to grow apples. The immediate stimulus for the project was the public outcry in 1989 over the use of Alar® (daminozide) on apples and the resultant loss of confidence in the crop among consumers. This caused considerable hardship to growers when apple sales declined by up to 30 per cent for some months. The Alar incident was a symptom of the general public concern about pesticide residues in food. In response to these concerns the Australian Apple and Pear Growers Association made the reduction of pesticide use its top research priority (Anon. 1991a) and committed apple growers to reducing pesticide use by 50 per cent by 1996 and 75 percent by the year 2000 (Anon. 1991a).

The authors were approached by the Batlow Fruit Cooperative in 1989 to assist apple growers at Batlow to minimise pesticide use. The project described in this report had three main aims.

1. To reduce pesticide use on apples at Batlow to the minimum necessary to produce top quality fruit.

2. To develop and evaluate sampling methods, spraying thresholds and other criteria needed for a pest manager to make recommendations to orchard managers.

3. To produce a commercially viable integrated pest and disease management (IPDM) package as the basis for a cost effective commercial monitoring program for the Batlow district.

The principal means of implementing the project was through the employment of a full time tertiary qualified pest manager stationed at the Batlow Fruit Cooperative for the duration of the project. It was essential to base the pest manager at Batlow to provide adequate supervision of the trial blocks and to maintain close contact with cooperating growers.

The following sections provide a brief background to the key issues in pesticide reduction, summarise current pesticide use patterns on apples in New South Wales, evaluate various options for pesticide reduction, and justify the approach adopted in this project.

1.2 The need to reduce pesticide use

Control of pests, diseases and weeds with synthetic chemicals has aroused public controversy for the last 30 years. Despite considerable tightening of regulations on the safety and use of insecticides, fungicides and herbicides, the controversy continues. In spite of the opposition, pesticide use has increased steadily.

Consumer perceptions

There is general concern among consumers that farmers are heavy users of pesticides, that pesticide residues are present in food and in the environment, and that some of these residues are dangerous to health. For example, a survey conducted in 1988 by the UK Consumer's Association found that 74 percent of respondents thought some chemical residues on fresh fruit and vegetables were dangerous to health (Anon. 1991b).

®- Registered trade name

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In reality there is no evidence that correctly applied pesticides result in harmful levels of residues in food. According to Prof Colin Berry, Chairman of the United Kingdom Advisory Committee on Pesticides (Rogers 1990), pesticide residues do not "represent any risk at all that is measurable. Around 70 percent of pesticides leave no residue, and of the remainder the amounts are such that they do not constitute a health risk. Microbial contamination of food, whether caused by poor handling or by moulds occurring on spoiled food before handling, is infinitely more important than pesticide residues."

He also notes that "food additives of one kind or another, including crop protection products, may be important in preventing some forms of microbial contamination, particularly the growth of moulds".

It is now also clear that many of the carcinogens identified during toxicological testing occur naturally in food. For example, the concern about Alar related to its hydrazine content, but hydrazine occurs in fresh mushrooms at levels which can exceed 500 ppm. This is approximately 500 times the level of hydrazine in apples which, if found at all, could be attributed to Alar.

One of the major difficulties in the pesticide debate is that it is not possible to prove the negative proposition that a chemical is totally harmless. This slight element of uncertainty allows opponents of pesticides to create doubt about pesticide safety no matter how exhaustive a testing regime is applied. Nevertheless, the British Medical Association has concluded that "despite the accumulation of evidence in specific areas, the conclusion which has to be reached is that the epidemiological evidence has so far been insufficient to demonstrate clear causal relationships between most pesticides and cancer". (Anon. 1990a).

Studies of pesticide residue levels in fresh fruit and vegetables are conducted in Australia by several State Departments of Agriculture and by the National Residue Survey. The Australian Market Basket Survey determines intake of pesticides and their breakdown products in the diet by measuring pesticide levels in prepared foods. These surveys have shown consistently that around 98.7 percent of samples contain either no pesticide residues or residues below the Maximum Residue Limit (MRL). In most cases where MRLs are exceeded it is by only a small amount and given the 100 to 1000 safety margin incorporated in the MRL, do not represent a threat to human health.

Therefore, it is clear that consumer concerns about pesticide residues in food and their possible effects on health are unjustified. However, these perceptions are very difficult, if not impossible to change. The saying in advertising that "perception is reality" is appropriate here. Since consumers' perceptions determine what they buy, there is an imperative for growers to respond to consumers' desires for pesticide use to be reduced.

Other reasons to reduce pesticide usage

There are a number of valid reasons to reduce pesticide usage. These include development of resistance in target organisms, the cost of pesticides and their application, some overuse of pesticides by growers, environmental effects of pesticides, and the health and safety of applicators.

Resistance

Resistance to pesticides by insects, diseases and weeds is becoming an increasingly serious problem. Some organisms have a great facility for resistance development, eg. two spotted mite, Tetranychus urticae; European red mite, Panonychus ulmi; green peach aphid, Myzus persicae; apple scab, Venturia inaequalis; brown rot, Monilinia fruticola, and there are few pesticide groups available to control them. The key strategy in resistance management and sustainable chemical pest control is to reduce exposure of pest organisms to pesticides, which delays or even avoids resistance development.

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Cost of pesticides

Cost savings are frequently cited as an advantage of reduction in pesticide use. However, this does not seem to be a major incentive for growers to adopt IPDM systems. The reason is that the costs of pesticides represent only a small proportion of the costs of fruit production. In apple production at Batlow, the cost of chemicals (including fertilisers) are only 7.5 percent of the cost of production, compared with handling (grading, packing, cool storage) of 45 percent, marketing (freight, porterage, levies) of 25 percent, harvesting 11.7 percent and other costs (thinning, pruning, etc.) of 7-8 percent (Gordon and Walker 1991).

Pesticides have a high benefit/cost ratio for orchardists (Metcalf 1980). They comprise only 5 to 10 percent of the total costs of apple production in NSW (Mullen and Valentine 1982; Gordon and Walker 1991), yet prevent potential crop losses of the order of 30 to 90 percent (Bower et al. 1993). Given the relatively low cost of each pesticide application, growers generally prefer to spray than to risk damage by not spraying. This can be understood by examining recent economic data (Gordon and Walker 1991). Downgrading of apples from Grade 1 to Grade 2 by pest or disease damage by 1 bushel per 20 bushel bin reduces the gross margin by $2000 per ha. In contrast an extra mancozeb spray costs only $15.48 per ha, less than the value of one bushel of Grade 1 fruit.

Behind these economic considerations are the demands of the market place. Consumers demand attractive blemish-free fruit (Anon. 1991b) and this achieves the highest prices in the market. Growers must therefore minimise damage to remain competitive, and the use of pesticides is the simplest and most effective way to maximise yield and quality. Thus a heavy dependence on pesticides has been unavoidable (Stoneref al, 1986).

Overuse of pesticides

Some pests and diseases of apples have a very high potential for damage, eg. codling moth and apple scab, and failure to control these can be economically ruinous (Bower et al. 1993). Therefore, pesticide spraying represents cheap insurance against damage by growers who are naturally risk averse. This has led to the use of prophylactic routine spray programs which are applied without regard to the actual pest and disease levels present. The calendar approach to spraying resulted in higher pesticide usage than necessary to maximise quality. Clearly, this approach to pest and disease control is wasteful. However, the true extent of pesticide overuse is poorly known.

Another reason for excessive use of pesticides is the difficulty experienced by many growers in correctly identifying some pests. Particular problems occur with the separation of pest and beneficial predatory mites. It is not uncommon for growers to apply unnecessary miticide sprays to large predator populations, which have been misidentified as pests (Bower and Thwaite 1986). Similarly, many growers are unable to reliably identify apple dimpling bug and many mistakenly spray a variety of small innocuous flies and other insects attracted to apple blossom.

Environmental concerns

Environmental problems due to pesticide usage seem to be less frequently documented in Australia than overseas. No adverse effects on wildlife, or fish, of environmental contamination by spray drift or run-off from orchards employing correct application techniques appear to have been reported. However, there are increasing problems at the interface of agricultural and urban land where spray from orchards may occasionally drift over houses and backyards. In this situation reduction of pesticide use will have considerable benefits.

Environmental problems have also lessened due to changes in the pesticides being used in apple orchards. Accession of organochlorines to the environment has ceased with the withdrawal of DDT from use in

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1987. In addition generally less toxic and environmentally safer pesticides are being introduced to replace the organophosphates, eg. fenoxycarb for codling moth and lightbrown apple moth control.

Occupational health and safety

A key incentive for pesticide reduction is the health of orchard workers who handle and apply pesticides. Accidents with pesticides still occasionally occur, though the risks are generally not greater than for workers exposed to a wide range of other substances in the workplace (Anon. 1990a). Organophosphate and carbamate pesticides pose a significant risk of acute toxicity, and may also have sub-lethal effects on cholinesterase levels which can be debilitating. The main problems experienced are allergies, particularly skin diseases, associated with some chemicals.

The issue of long term chronic effects of pesticides on worker health is difficult to address. However, no conclusive evidence of chronic effects has come forward. The group most at risk are workers in pesticide factories. All studies so far have found no epidemiological evidence to link most pesticides to cancer (Anon. 1990).

Nevertheless, growers do not like using pesticides. Spraying is a messy, time-consuming operation, and many orchard workers have experienced dizziness or other debilitating effects from the use of organophosphates at some time. Clearly, it is desirable to reduce exposure of workers to orchard chemicals.

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2.0 PESTICIDE USE ON APPLES AT BATLOW

2.1 Insecticides and miticides

Major pests of apples and their control

Trje most significant pests of apples at Batlow are listed in Table 2.1, with estimates of potential yield losses, and the number of sprays normally needed to control them. Pests are classified as primary when they are always present in the crops, while secondary pests are induced by the sprays applied for primary pests and are rare on unsprayed trees. The most important pests are codling moth, apple dimpling bug and mites.

Codling moth is difficult to control if large populations are present and up to eight sprays per season may be used. The damage potential of lightbrown apple moth in NSW is poorly known as it is usually suppressed by pesticides for codling moth. Apple dimpling bug is a widespread native pest requiring up to three sprays in some years. On rare occasions plague thrips can destroy most of a crop, but is normally controlled by pesticides used for apple dimpling bug. Native budworm and looper caterpillars attack developing fruitlets after petal fall and may be a problem if sprays for apple dimpling bug are omitted.

Two spotted mite and European red mite are major secondary pests of apple and are often difficult to control. The widespread adoption of integrated mite control at Batlow using pesticide-resistant predatory mites has reduced the need for sprays from two to four per season to one at a reduced concentration (Bower and Thwaite 1986), except in drought seasons when more may be required. Woolly aphid and San Jose scale are easily controlled by mineral oil sprays and woolly aphid by systemic insecticide. Lightbrown apple moth has an extensive complex of natural enemies (MacLellan 1973) which may contribute to control on unsprayed trees (Geier et al. 1969).

However, broad spectrum chemicals also suppress a number of other potential pests which are likely to reappear if sprays are reduced or withdrawn. These include the weevils (Perperus spp., Leptopius squalidiis (Boheman), Asynonychus cervinus (Boheman)) and the apple leafhopper, Edwardsiana australis (Froggatt) (Bower 1980).

Chemical control options up to 1990/91, Batlow

The recommended pesticides for control of the major pests of apples at Batlow in 1990/91 are listed in Table 2.2. This range of pesticides was broadly similar over the three years of the project.

Codling moth/lightbrown apple moth

These two pests are controlled effectively by the same chemicals. Azinphos-methyl has been the standard treatment for both pests at Batlow for many years, and is effective mainly on late stage eggs and first instar larvae (Thwaite 1984). Depending on pest pressure a routine program of 3 to 8 cover sprays was used commencing in November and applied every 2 to 3 weeks until the New Year, then monthly until harvest. Provided adequate spray cover of the tree is achieved, azinphos-methyl controls codling moth and lightbrown apple moth on over 99 percent of fruit.

Fenoxycarb (Insegar®) was newly released in 1990/91. Fenoxycarb is an insect growth regulator effective mainly on eggs, and in the case of codling moth is most effective on 1 to 2 day old eggs (W.G. Thwaite pers. comm.). Complete coverage of foliage and fruit is necessary to achieve satisfactory control since eggs are killed after being laid on a sprayed surface.

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Table 2.1 Pests and diseases significant on apple crops at Batlow under conventional chemical control p

Pest or disease Importance Scientific name' Common name Org atta

Primary Pest Major Cydia pomonella (Linnaeus) Codling moth frui Epiphyas postvittana (Walker) Light brown apple moth frui Thrips imaginis (Bagnall) Plague thrips flow Campylomma liebknechti (Girault) Apple dimpling bug frui

Minor Helicoverpa punctigera (Wal lengren) Native budworm frui Chrysodeixis spp. Looper caterpillar frui Phaulacridium vittatum (Sjostedt) Wingless grasshopper foli

Secondary Pest Major Tetranychus urticae Koch Two spotted mite foli Pananychus ulmi (Koch) European red mite foli Comstockaspis perniciosus (Comstock) San Jose scale woo Eriosoma lanigerum (Hausmann) Woolly aphid woo

Diseases Major Venturia inaequalis (Cke) Wint. Apple scab foli Podosphaera leucotricha (Ell & Ev.) Salm

Powdery mildew foli

Insect scientific names as per Naumann I. (1993). No sprays are usually applied specifically for light brown apple as it is normally controlled by the sprays applie Plague thrips and apple dimpling bug may be controlled by the same treatments. Caterpillar pests may be controlled by endosulfan used for apple dimpling bug. The two mite species are usually controlled by the same chemical application.

Table 2.2 Recommended pesticides for control of major pests of apples in NSW

Scientific name' Common name Chemical Trade nam

Cydia pomonella (L) Codling moth Azinphos-methyl Fenoxycarb

Benthion Insegar

Epiphyas postvittana (Walker) -> Lightbrown apple moth as above .

Campylomma liebknechti (Girault) Apple dimpling bug Endosulfan Chlorpyrifos (as from 91/92)

Endosan Lorsban 2

Thrips imaginis (Bagnall) Plague thrips as above _

Helicoverpa punctigera (Wallengren) Native budworm Endosulfan Endosan

Chrysodeixis spp. Looper caterpillar as above _

Eriosoma lanigerum (Hausmann) Woolly aphid Vamidothion Kilval

Comstockaspis pernicisus (Comstock)^ San Jose scale Chlorpyrifos or Diazinon

Lorsban 50 Gesapon

Phaulacridium vittatum (Sjostedt) Wingless grasshopper Chlorpyrifos Lorsban 5

Tetranychus urticae KocrP Two-spotted mite Propargite Omite

Pananychus ulmi (Koch) European red mite Propargite or Dicofol

Omite Kelthane

Insect scientific names as per Naumann I. (1993). Example of product name (there are other products and formulations available) Lightbrown apple moth is controlled by sprays targeted at codling moth San Jose scale is usually controlled by winter oil spray

Mites are usually controlled by predatory mites

Prior to this project very little formal monitoring of codling moth was carried out at Batlow despite the availability of sex pheromone traps and guidelines for their use (Thwaite 1989). Some monitoring was performed by Mr Rob McLeod, a pest management scout employed by the Batlow Fruit Cooperative. However, the results were used as a guide to moth populations only and formal spraying thresholds were not used.

Apple dimpling bug/plague thrips

At the commencement of the project endosulfan was the only registered chemical available for control of apple dimpling bug (ADB) and plague thrips (PT) that was also safe to the predatory mites used in integrated mite control. Fluvalinate (Klartan®), although more effective than endosulfan against both pests, particularly plague thrips, was not recommended for use because of its extreme toxicity to predatory mites. In the second year of the project chlorpyrifos (Lorsban®) was registered for control of ADB. Although safe to predatory mite, chlorpyrifos is highly toxic to bees, which limits its use to the period up to late pink, about 2 days before the flowers open.

Prior to this project, no monitoring techniques were available for ADB or PT. Spray decisions were made by growers either routinely, or on the basis of other inaccurate identification of ADB during checks of blossom, or in some cases by inspecting insects stuck to the wet cowling of spray machines after fungicides were applied.

Woolly aphid

On unsprayed trees woolly aphid is controlled effectively by the introduced parasite Aphelinus mali. Azinphos-methyl used to control codling moth eliminates A. mali from the trees and woolly aphid must then be controlled chemically. Vamidothion is extremely effective against woolly aphid, providing control for 1 or 2 seasons from a single spray, and has been the standard treatment for many years. However, vamidothion has a 6 week withholding period and cannot be used close to harvest. Within 6 weeks of harvest, shorter term control can be provided by chlorpyrifos, diazinon or pirimicarb.

Prior to 1990/91 no formal monitoring systems or spray thresholds were being employed for woolly aphid. Growers applied sprays when they saw infestations developing on their trees, usually on inner laterals and spurs.

San Jose scale

San Jose scale is not commonly encountered in orchards at Batlow. It appears to be well controlled by dormant or semi-dormant oil sprays used to control European red mite. On the rare occasions when infestations occur during the season they can usually be controlled with single sprays of chlorpyrifos or diazinon.

European red mite/two spotted mite

Mites are a potentially serious pest problem at Batlow, particularly European red mite. In the majority of orchards at Batlow substantial control of mites is given by introduced predatory mites, Typhlodromus pyri Sheuten and Typhlodromus occidentalis Nesbitt, especially the former which is effective against European red mite (Bower and Thwaite 1986, 1995). In 1990/91 and subsequent years there was only a limited range of mediocre miticides available to control mites. The most important chemical was propargite, which required high rates and excellent coverage of foliage to achieve good control. Fenbutatin oxide is generally not highly effective. It works best at high temperatures which are not often encountered at Batlow.

Dicofol is an older miticide to which there is widespread resistance and which, although not toxic to strains of T. pyri at Batlow is toxic to T. occidentalis. Mite populations resistant to dicofol usually revert

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to susceptibility after 2 or 3 seasons, allowing 1 or 2 sprays to be used effectively before resistance is reselected. Owing to the small range of chemicals available and their limited efficacy, mite control was often very difficult in orchards without good predator populations.

Since 1987 a commercial mite monitoring service has been run through the Batlow Fruit Cooperative with about 75 percent of the district's growers participating. Regular leaf samples are taken, pest mite and predator populations estimated, and growers advised on the need to spray. The service has assisted growers to maximise the effectiveness of predatory mites and minimise miticide usage.

2.2 Fungicides

Major diseases of apples and their control

Apples are affected by diseases caused by fungi, bacteria, nematodes and viruses. The principal diseases of concern to orchardists on a regular basis and which disfigure fruit are those caused by fungi, mainly apple scab and powdery mildew (Table 2.1) To a much lesser degree late summer diseases, such as sooty blotch (Gloeodes pomigena (Schwein)), flyspeck {Schizothyrium pomi (Mont. & Fr.) Arx) and bitter rot (Glomerella cingulata (Stonem.) Spauld. and Schrenk) can be troublesome in some areas.

Apple scab and powdery mildew

Apple scab, the main disease of apples in most areas of the world causes leaf, flower and fruit infections, which if uncontrolled can result in total loss of crop and premature defoliation. The majority of commercially grown apple varieties (Delicious, Red Delicious strains, Granny Smith, Fuji) are moderately to highly susceptible to the disease.

Generally apple scab control programs are concentrated on the primary infection period (Thwaite et ah, 1993). At this time ascosporic inoculum released during wet weather can cause high levels of infection of both leaves and fruit. Once high levels of infection are established, frequent applications of fungicide may be required to prevent further losses caused by secondary inoculum. The release of ascospores which initiate primary infections is usually completed by early December when the supply of overwintering ascosporic inoculum is exhausted (Brook, 1976). Secondary infections by conidia released from established primary lesions can result in progression of the epiphytotic through the season. If at the end of the primary infection period scab is at a low level the risk of significant further increases infection during the rest of the season may not be very great, depending on inoculum concentration and the weather.

At Batlow apple scab is generally well controlled in most seasons where a strict control program is adhered to. Losses of less than 1 percent are accepted, although with even a slight disruption to the control strategy, losses can quickly rise to 5 percent, and with a major breakdown of control, around 30 percent of fruit is infected.

Powdery mildew is generally less of a problem than apple scab. Delicious is only slightly susceptible, whilst Granny Smith is intermediate, and Jonathan and Bonza highly susceptible. The effects of mildew are to russet fruit and reduce vegetative growth.

Losses from powdery mildew in Delicious are to a minor degree in downgrading of fruit because increase russet, although with highly susceptible varieties such as Jonathan and Bonza this can be serious. Of more concern is the effect on tree growth and therefore yield. It is however generally acknowledge that infection of up to 20 percent of shoots will not materially effect yield in that season, but can have an effect on bud development for the next season, and if unchecked, debilitates tree growth and longevity.

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Typical recommendations (Thwaite et ah, 1993) suggest around eight fungicide applications for scab during the primary infection period (September till December) and around 3 or 4 more during the rest of the season depending on the weather conditions and the amount of infection established. Specific fungicides for powdery mildew are not usually applied to Delicious varieties. Use is made of fungicides which provide a dual control of both scab and mildew. On susceptible varieties like Granny Smith, specific mildew fungicides are required in spring (around 4 applications) and possibly later in the season as well.

Disease control can be attempted using one of two different means of attack, or a combination of the two.

The usual approach to apple scab control is to apply a prophylactic treatment of fungicides with protectant properties. These are applied on a regular basis, at initially 7-10 day intervals in September-October, with the time interval lengthening to 2 weekly in November, and 3 weekly in December. The time interval between treatments and the need to reapply treatments after rain will depend on the weather experienced.

An alternative approach which is sometimes suggested as a means to reduce the number of treatments required, is to apply a curative fungicide after the weather has been conducive for infection (an 'infection period'). These vary in their effective period after infection from 36 hours to 5 days. Most curative fungicides have only a short protectant period.

The favoured approach is to use both methods as required. Protectant treatments are applied on a regular basis, but these are supplemented by curative treatments when protection may not have been adequate because either the spray interval was long, or because heavy rain has reduced the protective cover provided by the fungicide.

Table 2.3 lists fungicides currently recommended for apple scab.

Powdery mildew is usually controlled by protectant fungicides applied mainly around the blossom period (to prevent fruit russet), but these fungicides generally also have some curative (eradicant) action and most are also effective scab fungicides.

Table 2.3 lists currently recommended apple mildew fungicides.

A strategy which is to be highly recommended is the practice of reducing the amount of disease which over-winters. For scab this can be achieved by application of a post-harvest, pre leaf fall urea spray. Scab inoculum can be reduced by 95 percent, and therefore this treatment should be used routinely whether there are high levels of infection present or not.

Powdery mildew carryover can be reduced by pruning out the infected shoots which provide primary infection in the next season.

The fungicides applied to apples fall into four main groups and one miscellaneous group. It is important to recognise the group to which fungicides belong to allow planning of a disease control program which will minimise the chance of resistance arising.

The principal groups at risk from resistance are the benzimidazoles, the dicarboximides, and the ergosterol inhibitors (EBI). The majority of fungicides with curative properties belong to the EBI group.

Table 2.4 lists the fungicide chemical groups.

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Table 2.3 Fungicides for apple disease control*

Apple scab protectant Apple scab curative Powdery mildew

Bitertanol Bitertanol Bupirimate

Dithianon Dodine Penconazole

Dodine Fenarimol Triadimefon

Fenarimol Flusilazole Triforine

Flusilazole Myclobutanil Biteranol

Hexaconazole Penconazole Fenarimol

Mancozeb Pyrifenox Flusilazole

Metiram Triforine Hexaconazole

Myclobutanil Myclobutanil

Penconazole Pyrifenox

Pyrifenox

Thiram

* from Thwaite et al. 1993

Table 2.4 Fungicide chemical groups*

Chemical family Common name Trade name

Benzimidazoles benomyl Benlate® carbendazim Bavistin® FL, Spin® thiabendazole Tecto® thiophanate-methyl Topsin® M

Dicarboximides iprodione Rovral®

Dithiocarbamates mancozeb Dithane DF®, Dithane® M45, Manzate® DF Polyram® DF

metiram Curit® zineb ziram

Fulasin®

Ergosterol inhibitors bitertanol Baycor® fenarimol Rubigan® flusilazole Nustar® hexaconazole Anvil® imazalil Fungaflor®, Magnate® myclobutanil Systhane® penconazole Topas®

Tilt® propiconazole Topas® Tilt®

pyrifenox triadimefon

Boxer® /3\

triforine Bayleton® Saprol®

Miscellaneous bupirimate Nimrod® chlorothalonil Bravo® copper fungicides Blue Shield®, Bordeaux mixture, Copidul®

Kocide®, Oxydul® dithianon Delan® dodine sulfur

Melprex® various

thiram Thiragranz®

from Thwaite et al. 1993

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Older and alternative fungicides

Control of apple diseases from the turn of the century was based on copper materials (Bordeaux mixture, copper oxychloride and the like) for scab control, and sulphur (as lime sulphur or later, wettable sulphur) for scab and mildew control.

The main thrust of research until the advent of modern fungicides (thiram and captan being the first used on apples commercially) was a balancing of efficacy against phytotoxicity. Generally an increase in chemical rates gave improved disease control at the expense of fruit quality (increased russet) and vice versa. The advent of thiram was revolutionary in that a superior level of scab control was obtained, with vastly improved fruit finish. Mildew in susceptible varieties was still based on wettable sulphur, until oxythioquinox, binapacryl and dinocap appeared.

It should be kept in mind that the very high levels of disease control commonly expected these days (generally less than 1% fruit infection) were unobtainable with the older fungicides. A return to these materials is not possible without an increase in fruit loss.

Alternative materials are currently under test. These include biocontrol agents (principally for post harvest diseases) and calcium hydroxide ('Limil') for scab. Time will tell whether these materials have a place in modern disease control.

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3.0 OPTIONS FOR REDUCING PESTICIDE USE ON APPLES

Two approaches to reducing pesticide use on apples at Batlow were considered; 'organic' or 'integrated pest management'.

3.1 Organic

In organic systems all pest, disease and weed control employs cultural methods, spray materials derived from nature and various forms of biological control to maintain pests and diseases at acceptable levels.

As no synthetic pesticides are acceptable on organic produce, there are few pesticidal spray materials available. They include mineral and vegetable oils, copper salts, sulphur, natural pyrethrum, ryania, derris dust and Bacillus thuringiensis (Anon. 1990b). An organic approach was not considered to be viable for this project for several reasons:

- The available chemical control options are not sufficiently efficacious and result in unacceptably high levels of damage. There are considerable economic constraints on the tolerable level of fruit damage (Fenemore and Norton 1985) and growers will not accept alternatives that fail to give fruit quality consistently close to conventional methods.

- By definition, biological controls exist for the secondary pests of apple; predatory mites and a variety of small predatory insects for phytophagous mites, and parasites for woolly aphid and San Jose scale. However, there are no viable alternatives to chemical control for any of the major primary pests, including codling moth, lightbrown apple moth, plague thrips and apple dimpling bug. Similarly, there are no effective alternatives to synthetic chemicals for control of the major diseases, apple scab and powdery mildew. Many attempts have been made, and continue to be made, to discover alternatives for control of codling moth, but none has so far been commercially viable. Extensive work with ryania, a naturally occurring insecticide, met with only limited success (Geier et al. 1969). Other approaches currently under investigation include combinations of alternative approaches, eg. ryania plus B. thuringiensis (Wearing 1991), codling moth granulosis virus (Wearing 1990) and mating disruption using sex pheromones (Tancred and Sexton 1991, Vickers and Rothchild 1991).

- Most alternative control measures are only likely to be effective against pests that are resident in the orchard and have low rates of immigration. Pests which normally originate outside the orchard, often a long distance away, are less amenable to biological control or behavioural manipulation by pheromones. Some use of conventional pesticides against mass immigrations of such pests may be unavoidable.

3.2 Integrated Pest Management (IPM)

Integrated Pest Management (IPM) systems combine the minimum use of compatible synthetic chemicals with all other suitable techniques to maintain pest populations below levels causing economic injury (modified from Smith and Reynolds 1966).

Integrated pest management (IPM) is an umbrella term which encompasses a vast array of approaches to pest control having as their central aim the minimisation, but not necessarily elimination, of synthetic pesticide use. IPM has become a well established and widely accepted pest control philosophy within all sectors of the agricultural industries and government since its inception in the early 1960's (Wearing, 1993). Over the last 30 years there has been a proliferation of alternative approaches to pest management, a considerable development of methodology and an evolution of the concept to embrace the entire production system, as in integrated fruit production (IFP) (Dickler and Schafemeyer, 1993).

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The complexity of the field makes it impractical to comprehensively review here, but it has been the subject of numerous books, for example Flint and van den Bosch 1981, Croft and Hoyt 1983. Instead, the key elements of IPM will be outlined and discussed in relation to the approach we decided to take at Batlow.

Four key elements of IPM may be identified as follows:

1. Alternative pest and disease control technologies 2. Monitoring 3. Spray thresholds 4. Record keeping

The first three of these are disciplines in their own right.

Alternative technologies

Since the primary aim of IPM is the reduction in use of synthetic pesticides, IPM approaches endeavour to incorporate any technologies which replace synthetic pesticides. A wider range of alternative technologies are available for control of pests than for diseases. Many alternative technologies are specific to individual pest or disease species and must be developed and validated for each one. This includes such strategies as biological control using predators, parasites or diseases and the use of insect pheromones for mating disruption or monitoring.

Other technologies may be applied to more than one species, particularly some of the alternative pesticides such as petroleum spray oils, the insect growth regulators (IGRs) (McGhie and Tomkins 1988) or biologically derived materials such as neem. The IGRs are interesting synthetic chemicals that mimic naturally occurring insect hormones. They are more acceptable than broad spectrum nerve toxins such as the organophosphates, due to their more specific toxicity to insects and fewer deleterious effects on non target organisms and users. As a broad generalisation, it is also usually the case that the more selective alternative pesticides are less efficacious than the broad spectrum chemicals they are replacing and are more prone to fail if, for some reason, label directions are not followed precisely, or weather conditions are unfavourable.

In general most research on conventional or alternative pest control is performed on the major pests for which there are large markets for successful products. A major problem for IPM is that relatively little effort goes into alternative control measures for minor pests. Therefore, it is often difficult to create an IPM program with alternative technologies for the entire pest and disease complex of the crop. At the commencement of this project, fully validated alternative control measures were available only for two-spotted mite and European red mite using introduced pesticide-resistant predatory mites Typhlodromus occidentalis and T. pyri respectively (Seymour 1982; Davidson 1988; Bower and Thwaite 1995). Some trials were also showing that new petroleum oil spray formulations had significant potential to replace specific miticides in integrated mite control strategies (Bower 1993).

Several strategies were also under active investigation as potential alternatives to a complete reliance on broad-spectrum pesticides for control of codling moth, Cydia pomonella (Linnaeus) and to a lesser extent for lightbrown apple moth, Epiphyas postvittana (Walker). Mating disruption using massive doses of sex pheromones was being evaluated for both species (Suckling and Clearwater 1990) and trials were showing that the IGR fenoxycarb might be an alternative to azinphos-methyl (Readshaw and Cambourne 1991).

Alternative control measures were not available for any of the other pests of apples.

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Monitoring

A key component of any IPM program is monitoring. Monitoring provides the data on which rational pest or disease control decisions can be made. Monitoring involves the measurement of pest and disease populations, or incidence, the populations of any beneficial organisms, and key environmental variables which can aid in predicting population trends and the potential for damage to the crop. Monitoring systems should be simple, efficient, fast, reliable and cost-effective. It is often difficult to strike a balance between the need for reliability and those of efficiency and cost-effectiveness.

Prior to this project there were existing validated monitoring systems for mites and codling moth, but not for the other pests. Integrated mite control (IMC) has been established in NSW since the early 1980's (Bower and Thwaite 1986, 1995; Seymour 1982) with commercial mite monitoring services operating at Orange (Page et al. 1991) and Batlow, where about 25 and 40 percent of the area respectively was being monitored for pest mites and their predators. Similar programs were operating in Victoria through Crop Watch (D.G. Williams pers. comm.) and the Adelaide Hills in South Australia (J.L. Readshaw pers. comm.).

Monitoring for codling moth, based on the codling moth phenology model developed in the USA (Riedl, Croft and Howitt 1976; Riedl and Croft 1974) has been practiced successfully in the USA (Beers, Brunner, Smith and Willett 1990), and since the late 1980's in some Victorian orchards (D.G. Williams pers. comm.). This system provides accurate estimates of when key life cycle events can be expected and allows much more precise timing of sprays (Beers, Brunner, Smith and Willett 1990), which can reduce spray use. The phenology model uses sex pheromone traps to determine when the first of the overwintering male moths emerge in spring, and maximum and minimum temperature records to calculate development rates and predict when various life cycle events, such as egg laying, will occur.

Spray thresholds

Once monitoring data has been obtained, it must be interpreted so that decisions about the need to spray can be made. Sprays should only be applied if pest or disease population levels indicate that unacceptable amounts of damage to the crop will occur (Cammell and Way 1987). In order to make rational spray decisions it is necessary to know the relationships between pest and disease levels and damage, as well as the economic relationship between the cost of spraying and its benefits in terms of damage prevented. From these relationships relatively simple criteria, referred to as 'spray thresholds' or 'economic thresholds' (Onstad 1987) can be established to guide decisions on spraying. The economic threshold (ET) may be defined as the density in an increasing population at which control measures are needed to prevent future damage that would exceed the cost of control.

A major constraint on the reduction of pesticide use in apples, and indeed in all horticultural crops, is the relatively high value of the crop on a production per hectare basis. This means that even quite small potential crop losses, of the order of one percent or less, can economically justify spraying (Fenemore and Norton 1985; Bower et al. 1991). In general terms a downgrading of fruit by less than one percent has been regarded by apple growers in NSW as acceptable for any one pest or disease, and this has been used as a benchmark for trial work for many years.

For some pests it is very difficult to relate damage to crop losses, particularly those which do not directly attack the fruit. Foliage feeders such as mites can cause considerable visually obvious damage to leaves without reducing yield or quality, (Hoyt et al. 1979; Tanigoshi and Browne 1981; Hull and Beers 1990). However, most growers are not prepared to accept such levels of damage due to their intuitive concerns for the health of their trees. In such cases, spray thresholds are set as much to satisfy grower needs as to meet economic thresholds.

Prior to commencement of this project no spray thresholds or criteria had been published for codling moth, apple scab and phytophagous mites in Australia. Spraying thresholds developed by Madsen and

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Vakenti (1973) for codling moth had been validated in NSW (Thwaite 1989), but had not been widely adopted commercially. Some practical problems in managing the sex pheromone traps, on which the system was based, and the occasional anomalous result prevented wide promotion of this concept (W.G. Thwaite, pers. comm.). Quite detailed spray thresholds have been formulated for integrated mite control based on counts of pest and predatory mites on leaf samples, or simply the percentage of leaves occupied by pests and predators (Seymour 1982; Bower and Thwaite 1986, 1995).

Formal spray thresholds were not available for other pests.

Record keeping

The systematic keeping of records is essential for IPM. This is not often highlighted in the literature. However, the building up of historical databases of weather data, pest and beneficial populations, crop damage estimates and spray records provides an essential foundation for pest management and forecasting.

3.3 Disease management

Diseases are not usually incorporated into integrated pest management programs despite the fact that the majority of synthetic chemical applications made to many crops are fungicides. For example, 70 percent of the spray applications made on apples are fungicides (Fenemore and Norton 1985). The most serious diseases, such as apple scab and powdery mildew, Podosphaera tend to be controlled by rigid programs of prophylactic sprays for which there is currently no viable alternative.

The reasons for the lack of a formal integrated disease management approach are several:

- Diseases have the potential to increase explosively and risks of extreme damage are very high under favourable weather conditions.

- There are no biological agents which have been able to be harnessed to control diseases.

- Alternatives to synthetic chemicals, such as sulphur compounds, copper etc. are not sufficiently efficacious.

We considered two approaches to reducing fungicide use in apples: firstly, by reducing the number of sprays applied, by applying fungicides post infection and by ceasing applications at the end of the primary scab period in orchards where the disease has been well controlled; and secondly, by a reduction in the rate of chemical applied to the trees.

The epidemiological approach to improved disease control has been in favour for many years. An understanding of the disease life cycle, weather conditions favouring infection and the sources of infection can all give potential leads for improved disease control, and perhaps some reduction in fungicide usage.

Taking firstly the effects of weather, Mills at Cornell in the 1940s elucidated the infection requirements for apple scab (Mills 1944). Since apple scab has an incubation period from infection to symptoms of about 10-15 days depending on temperature, it is possible to use post infection treatments with systemic fungicides to eradicate developing lesions.

The newer ergosterol fungicides have increased the available time for effective control up to 6 days after infection took place. The potential of these fungicides means that apple scab can be controlled by spraying only when infection conditions have been met. To provide information on infection conditions a number of dedicated weather stations are available for in-orchard use (Penrose et al. 1985). Unfortunately

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this approach is not applicable to the major apple growing areas of Australia. When spring rain is of frequent occurrence almost as many sprays may be required when applied as post infection treatments as when applied prophylactically (Penrose et al. 1985). Where such devices are of value is in informing the grower of potential infections in situations when his spray program has been undesirably drawn out. In drier areas such post infection treatments can be valuable, although there is some risk that prolonged wet weather following infection may prevent the application of the curative sprays within their period of efficacy.

Nevertheless, a number of useful approaches to disease management have been developed, particularly for disease monitoring. Warning services for apple scab have operated at Orange and Batlow for many years to alert growers when weather conditions have been favourable for infection (Penrose et al. 1985). These services currently use the Apple Scab Predictor manufactured by Reuter-Stokes Inc., Cleveland, Ohio, USA to measure wet and dry bulb temperatures, and the duration of leaf wetness and periods of high humidity. The Apple Scab Predictor incorporates a microprocessor which calculates whether conditions necessary for spore germination and infection have occurred and displays predictions of the severity of infection periods.

The Apple Scab Predictor has been found to provide reliable field indications of apple scab infection conditions in NSW (Penrose 1992).

An approach taken by some growers at Batlow has been to cease fungicide application at the end of the primary infection period. Provided scab has been well controlled, and confidence in this is based on careful regular monitoring, it is possible to cease spraying during the secondary infection period. Jones (McHugh 1991) pointed out that it may well be better to apply more sprays early in the season to obtain good control, so that later sprays can be dispensed with. This approach will be examined further in this report.

Shenk and Wertheim (1992) in the Netherlands highlighted the fact that a reduction of the number of sprays to control apple scab following careful monitoring will only be successful whilst good fungicides remain available. They also point out that good scab waring services are important.

A supplement to disease control using less fungicide is to remove or reduce inoculum sources. Hutton (1954), working in NSW forty years ago showed that urea treatments applied post harvest pre leaf fall reduced the amount of overwintering scab inoculum aiding in disease control in the next season. The function of urea as both a fungicide and as a stimulant of microbiological activity to breakdown the site of the overwintering fungus is a technique which is still relevant today.

The second approach to reduce fungicide use on apples - reducing the concentration of fungicide in each spray - was considered. The basis for attempting this method was that:

i) a reduction in rate may lead to an increase in disease, but probably not total failure, as might occur if particular sprays are missed

ii) modern fungicides are highly efficient and recommended rates have a substantial safety factor

iii) disease levels in well managed orchards are currently low and therefore disease pressures are low

iv) the availability of scab fungicides with good kickback action means that to some degree treatment can be applied after infection

v) scab warning services operated at Batlow and Orange by NSW Department of Agriculture give a good indication of the occurrence of infection conditions

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vi) Australian and overseas data and grower experience suggests that with good coverage, reduction of fungicide rates are possible with little or no reduction in disease control.

The details of these approaches to fungicide use reduction in the Batlow project are given in the next section.

Given the predominance of spray applications for diseases on apples, it is important that diseases be included in pesticide use reduction programs. It is also important to include diseases because pests and diseases are treated equally by the grower and insecticides/acaricides are often mixed with fungicides in the same tank for application to control a number of problems simultaneously. Further, the economies achieved by using tank mixes will often mean that the timing of applications will need to be a compromise among the optimums for the 2 or 3 treatments included. The choice of fungicide is also determined to some extent by its compatibility with beneficial insects or predatory mites used in IMC.

These interrelationships were recognised in the establishment of the Batlow project and a major aim was to develop not just an integrated pest management program, but an integrated pest and disease management (IPDM) system for the district. To our knowledge this is one of the first, if not the first, attempts to do this and certainly the first in Australia.

3.4 Supervised pest and disease control (SPDC)

In view of the lack of alternatives to synthetic pesticides for all apple pests and diseases except phytophagous mites, the only option for reducing pesticide use is supervised pest control (SPC). The aim of this approach is to monitor all significant pests and apply sprays only when economic thresholds are exceeded (Gruys et al. 1980). SPC is a subset of IPM and an essential component of it, the main difference being that SPC encompasses both conventional and IPM systems.

For diseases, monitoring is used to assist in decisions on spraying which supplement a regular scheduled spray program.

Research in the northern hemisphere has shown that SPC can minimise spray use. Average reductions in insecticide and acaricide use of 36 percent were demonstrated by Carden (1987) on apples in southern England. Considerable reductions in pesticide use were also achieved in the Netherlands, from the normal 6 to 8 applications of insecticides/acaricides per annum down to 3.6 to 5, but the published data do not allow a percentage reduction to be calculated (Gruys et al. 1980). A 50 percent reduction in the number of sprays was achieved in Switzerland (Baggiolini et al. 1973) and Canada (Trottier 1980) using SPC. Reductions of this order would achieve the Australian Apple and Pear Growers Association objective of reducing pesticide use by 50 percent by 1996.

It was decided that a supervised pest and disease control (SPDC) project was the most appropriate approach to implement at Batlow. This approach would allow the expansion of the existing mite monitoring service into a pest and disease management infrastructure which could easily incorporate future developments in apple pest management. The system and the district could then move progressively and rapidly to higher levels of IPDM sophistication with future advances in technology.

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4.0 THE BATLOW SUPERVISED PEST AND DISEASE CONTROL PROJECT

4.1 Aims and criteria

In the initial project submission two aims were put forward. As the project developed a third aim was added. The aims were:

1. To reduce pesticide use in apple orchards to the minimum necessary for optimum pest and disease control.

2. To set up and evaluate a comprehensive crop monitoring program for all major pests and diseases of apples.

3. To develop a SPDC package which will provide the basis of a cost-effective commercial monitoring service for the Batlow district.

At the beginning of the project a number of criteria were established to guide it. These were:

1. There should be no significant decline in fruit quality or yield for growers practising SPDC. Yield and quality are the two most important variables in determining profitability (Southwood 1979; Corbet 1981; Fenemore and Norton 1985; Gordon and Walker 1991). Any decline in quality was only acceptable if it was fully compensated by savings in chemical usage. Since maintenance of fruit quality was a paramount concern, all spray recommendations were conservative.

2. Monitoring systems had to be simple, quick, efficient, reliable and cost-effective. It was essential to be able to monitor relatively large areas reliably at low cost.

3. Sampling methods and spray thresholds were not fixed, but were subject to annual review if the data indicated the need for adjustments.

4. SPDC monitoring blocks and control blocks were to be located in different orchards. This was essential as previous experience (Bower, unpublished) and evidence from the literature indicated that the spray programs in control blocks may be influenced by those advised for experimental blocks located in the same orchard (Gruys, 1980).

5. The pest manager employed for the project was to be based at Batlow for ease of management and access by growers (the project supervisors, C.C. Bower and L.J. Penrose, were based in Orange). Location of the pest manager at Batlow would allow him to become part of the community and help to earn grower trust.

6. It was also considered vital that good communication be maintained with cooperating growers, both from the pest manager and the project supervisors.

Measurement of pesticide reduction

As part of the program it became necessary to consider the method for measuring pesticide usage.

In this project we have largely measured pesticide use in terms of the number of sprays applied. It soon became clear that this is an inadequate approach.

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A change from a toxic compound such as azinphos-methyl to the less toxic fenoxycarb will not reduce the numbers of sprays applied, and in fact may increase them. As a supplement to this project, the area of measuring pesticide use was investigated under the project AP430. "A rating index as a basis for decision making on pesticides use reduction and IPM accreditation". Our conclusions are that a system is required which takes into account the properties of the pesticides as well as the number of sprays applied, to enable pesticide use reduction to be measured. A system has been prepared called PESTDECIDE, which will be made available for industry use. The report on this project has been submitted to HRDC.

4.2 The Batlow district

The Batlow district is located on the western side of the Southern Tablelands of NSW and is centred on the town of Batlow (Lat. 35°32°S, Long. 148°09°E). Batlow lies at an altitude of 790m with most of the orchards within a range of 700 to 940m. The soils are mainly clay loams derived from basalt or granite. The subsoils are fertile and well drained, able to store substantial moisture reserves without waterlogging. Rainfall is predominantly in the winter and spring with drier summers and variable autumn falls (Table 4.1). Total annual rainfall averages over 1300 mm. Light snow is not uncommon in winter. The climate is cool-temperate with long cold winters and mild summers. Overall the climate and soils are ideal for pome fruit growing.

In 1991 there were 1500 ha planted to apples at Batlow (NSW Agriculture census), comprising Delicious and Red Delicious strains (845 ha), Jonathan/Red Jonathan (90 ha), Bonza (121 ha), Granny Smith (234 ha), Gala and other early varieties (59 ha), Fuji and other late varieties (116 ha), Crofton and Golden Delicious (31 ha). The area planted to apples has been increasing steadily, by 180 ha since 1986, compared with declines in all other districts in NSW. There are also small plantings of stonefruit; peaches, nectarines, plums and cherries, as well as small areas of pears. Batlow is the second largest apple growing district in NSW after Orange.

4.3 Selection of co-operators and initial survey

Co-operating growers for the project were selected from volunteers who came forward after the aims and methodology of the project were presented to a grower seminar at Batlow in July 1990. Growers volunteered as potential SPDC or control co-operators, or both. A significant number of volunteers indicated that they only wished to be controls.

Potential trial blocks were inspected in August 1990 and growers interviewed to determine block histories, sizes, apple varieties etc. The results of the survey are presented in Table 4.2. The survey was conducted to allow the pairing of SPDC growers with similar control blocks in order to arrive at two comparable groups.

In the event it was not possible to set up pairs of orchards which were similar for all variables. Nevertheless, care was taken to ensure that both groups contained orchards from all parts of the district, similar altitudinal ranges and with similar overall representation of tree ages, blocks with hail net etc. The data in Table 4.2 provides a profile of the characteristics of the trial blocks.

Hail net

Five study blocks (A2 to C2, Table 4.2) were covered in hail netting and block Al was expected to be covered prior to the commencement of sampling, but this did not eventuate. Netted blocks were distributed evenly between the SPDC and control groups to avoid any bias netting may cause.

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Table 4.1 Mean monthly rainfall, evaporation and temperatures at Batlow

Month Rainfall (mm) Evaporation Maximum Minimum (mm) temperature (°C) temperature (°C)

January 72.9 130 27.3 11.0

February 56.6 110 28.8 12.0

March 88.1 95 24.5 8.8

April 90.9 55 19.1 4.5

May 119.6 30 14.8 3.5

June 172.2 0 10.7 1.1

July 157.2 0 8.9 -0.3

August 148.1 10 11.3 0.2

September 117.3 30 13.4 2.4

October 127.0 60 18.7 4.7

November 84.1 85 21.9 6.7

December 76.5 145 25.6 8.0

Total 1310.5 750 - -

'Rainfall records are from 1886-1964; pan evaporation figures are of unknown origin; official temperature records are not available for Batlow. The temperature data are NSW Agriculture data for 1977-1980.

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Table 4.2. Summary of results of initial survey of co-operating growers

Growers designated Al, Bl etc. were the SPDC group; A2, B2 etc. were controls. Spray data and pest dam Volume of sprays: D = dilute or normal concentration in the vat; 2x, 4x etc. refers to the concentration fac

Grower code

Block area (ha)

Altitude (m ASL)

Tree age (yrs)

Apple varieties Hail net (yes/no)

Spray volume

No. of insecticides

No. of fungicides

Al 4 840 8 Red Delicious, Bonza N D/3x 11 14

A2 4 850 9-10 Hi Early, Granny Smith Y D/2x 7 14

Bl 4.8 10-18 Red Del., Granny Smith Y D/5x ? ?

B2 4 860 7-18 Delicious strains, Bonza Y 3x 10 23

CI 5.6 840 6 Royden Red, Bonza Y D/5x 7 14

C2 2.8 730 17-18 Del. strains, GS Y 3x 8 17

Dl 4 810 12 Royden Red, Bonza N D/6x 10 18

D2 4 840 12 Delicious strains, Bonza N D 11 15

El 4.4 940 7 Del. strains, GS, Bonza N 3x 11 18

E2 4 790 8 Royden Red, Bonza N D/3x 11 14

Fl 3 930 7 Del. strains, GS, Crofton N D/3x 10 18

F2 3.2 710 4 Starkrimson, Bonza N 3x 6 10

Gl 4.8 750 13 Del. strains, GS, Jon. N D 13 11

G2 4 760 15 Delicious strains, Bonza N D/3x 8 13

HI 3 730 4-5 Del. strains, GS, mixed N D 8 22

H2 4 730 19 Starkrimson, GS N D ? ?

11 5 820 2-25 Del. strains, GS, Bonza N D/3x 10 14

12 7.6 870 10-30 Del. strains, GS, Crofton N D 8 7

Jl 6 740 ca.15 Starkrimson, GS, Jon. N D/4x 12 27

J2 3.6 770 20 Delicious, GS, Jon. N D/3x 8 14

Block area

A block size of four ha. was considered suitable for study sites as these would provide a test of sampling methods under realistic commercial conditions without being too large. In the event, block sizes ranged from 2.8 to 7.6 ha. with most being in the 4 to 6 ha. range (Table 4.2). Rather than subdividing blocks to have them all about the same size it was considered more important to retain the growers normal units for ease of management and to reduce the possibility of errors.

Altitude and distribution

Trial blocks occurred over a 230 m altitudinal range from 710 to 940 m. This range is sufficient to significantly influence the phenology of tree development and of arthropod pests, there being a two or more week difference between the flowering times of the highest and lowest orchards. Both the control and SPDC groups were distributed over the whole altitudinal range (Table 4.2). Most orchards were located close to the town of Batlow (Map 1), but one SPDC block and one control block (Dl and D2) were about 23 km by road south of Batlow at Willigobung.

Tree age

The age of trees varied considerably between blocks and in some cases within them (Table 4.2). However, most trees in all blocks were in full bearing.

Varieties

The main commercial varieties at Batlow are various strains of red Delicious including Hi Early, Royden Red, Starkrimson and Harold Red. For this reason, sampling concentrated on Delicious strains and all selected blocks had high proportions of this variety (Table 4.2). Other varieties in these blocks, mainly Granny Smith, Jonathan and Bonza, served as pollinators and were less commercially attractive.

Spray volumes

All growers had similar tractor towed air blast spray equipment powered by the tractor via power take-off linkages. These machines generally had nozzles mounted on heads which allowed a choice of two nozzle types depending on the requirements for spray coverage. Generally growers had a set of dilute or high volume nozzles which allowed volumes of 1800 to 2200 L/ha to be delivered. These nozzles were used for applications where it was desirable to achieve as close to complete coverage as practical, for example; thinning sprays, mite control, insect growth regulators. The other set of nozzles was for concentrate spraying, in which a higher concentration of pesticide was mixed in the vat so that the same amount of pesticide per ha could be delivered in a smaller volume of water. This allowed the sprayer to treat larger areas between refills. Concentrate application was used for most spraying including cover sprays of protectant fungicides and insecticides for codling moth. Five growers applied all their sprays dilute and four used only concentrate applications, all 3x concentrate. The range of concentrations varied from 2 to 6 times, but 3x was most usual.

Number of sprays

The number of applications of each spray chemical in the 1989/90 season is summed for each block in Table 4.3. The chemicals are classified according to whether they are mainly insecticidal or fungicidal in activity. Plant growth regulators, including carbaryl, and nutrient sprays are not included. There was considerable variation in the numbers of both insecticides and fungicides applied. An average of 9.4 insecticides (range 6 to 13), 15.7 fungicides (range 7 to 27) and a mean total of 25.1 spray chemicals (range 15 to 39) were applied. These data indicate there was a twofold difference in insecticides and almost a fourfold difference in the numbers of fungicide applications among growers.

32

Map 1 Location (road map) and altitude (m above sea level) of trial orchards in the Batlow (NSW) district

N

t • SPDC blocks

Table 4.3 Comparison of the SPDC and control groups for spray use and pest and disease damage in 1989/90

Parameter SPDC Control

Insecticides (No.)

mean 10.2 8.6

n 9 9

t 1.965

P 0.067

Fungicides (No.)

mean 17.3 14.1

n 9 9

t 1.468

P 0.161

Total sprays (No.)

mean 27.6 22.7

n 9 9

t 1.951

P 0.069

Growers with codling moth (No.) 1 4

Growers with dimpling bug (No.) 4 7

Growers with apple scab (No.) 5 4

Mean damage tolerance (%) 1.95 1.85

mean = mean number of sprays per grower n = number of growers t = value of t in two-tailed t test comparison P = probability of a larger value oft

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Pest and disease damage

Growers were asked to estimate their losses due to pests and diseases in the 1989/90 season. Most losses were attributed to apple dimpling bug and apple scab (Table 4.2). Damage was generally below one percent, but four growers in each case reported significant losses of up to 20 percent for apple dimpling bug and 25 percent for apple scab. Only five growers reported damage due to codling moth; four were below one percent and the other was two percent.

Damage tolerance

Growers also varied in the levels of damage they would accept (Table 4.2). About half had damage tolerances of one percent or less, but the remainder were prepared to accept damage of two to five percent. Three growers indicated very low tolerances (0 to 0.2 percent).

Comparison of the SPDC and control groups

From the point of view of this project the most important parameters to compare between the SPDC and control groups are spray use and pest and disease damage (Table 4.3). Although the usage of both insecticides and fungicides was somewhat higher by the SPDC group, the differences were not significant (two-tailed t test) (Table 4.3). As a group, the control growers indicated greater problems with codling moth and apple dimpling bug than the SPDC group. Apple scab problems were more evenly distributed between the two groups. The tolerance for pest and disease damage was similar for both groups (Table 4.3).

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5.0 GENERAL METHODS

5.1 Project organisation

The project was run from an office/laboratory in the offices of the Batlow Fruit Co-operative Ltd. in Forest Road at Batlow. Mr. Kevin Dodds was employed under the HRDC grant as pest manager. Mr. Dodds roles were to:

conduct the pest and disease monitoring in the 20 orchard blocks run a series of automatic weather stations report the pest and disease status of their blocks to SPDC growers and advise them of the need for sprays advise co-operators of apple scab infection periods and output from the codling moth phenology model and liaise with growers and project supervisors.

The project supervisors, Dr. Colin Bower and Mr. Les Penrose, were based in Orange, 330 km north of Batlow. Their roles were to:

design the project establish sampling protocols and set the spray thresholds provide technical backup and advice to the pest manager inspect all trial blocks at least twice per season, in late December and immediately before harvest to provide an independent quantitative assessment of damage provide an annual report to each co-operating grower convene an annual meeting of SPDC co-operators to report on progress, explain and discuss the results and any problems, determine any changes needed report on the progress of the project to a general meeting of Batlow growers.

5.2 Sampling procedures

Table 5.1 summarises the sampling methods and their frequency, timing and intensity as well as the simpler spraying thresholds. Variable thresholds were used for apple dimpling bug and mites, while spraying for apple scab and powdery mildew was based on a decision tree approach. These methods are explained below. The methods shown in Table 5.1 were those adopted in the first season of the project. Some were altered in subsequent years in response to problems. These changes are explained below under the appropriate pests.

The same sampling procedures were used in the SPDC and control blocks.

Sampling schedule

Most sampling was done on a fortnightly schedule from November to April (Table 5.1). However, more intensive sampling was required (2 to 3 times weekly) during the blossom period (October) for apple dimpling bug and plague thrips. Pheromone traps required weekly counts and maintenance, so that the SPDC blocks were visited weekly; short visits for pheromone trap counts alternated with longer visits for both trap counts and samples of all other pests and diseases.

Sampling strategy

The majority of sampling was done on 25 randomly selected trees per block, which differed at each visit. The pest manager took a zig-zag route through the block allowing him to select his sample over most of

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Table 5.1 Sampling methods for insect pests and diseases of apple under Supervised Pest and Dise

Pest/Disease Monitoring method

Sampling frequency

Sampling period Samples p

Apple dimpling bug Blossom shaking 2-3 times/week early pink to late petal fall

10 inflorescen

Plague thrips Flower inspection

2-3 times /week early pink to late petal fall

10 flowers

Codling moth Pheromone traps weekly petal fall to harvest 1 per ha

Fruit inspection fortnightly November-April 40 fruit

Lightbrown apple moth Fruit inspection fortnightly November-April 40 fruit

Mites Leaf samples, tree inspection

fortnightly November-April 2 leaves

Woolly aphid Presence /absence

fortnightly November-April -

San Jose scale Fruit inspection fortnightly November-April 40 fruit

Apple scab Leaf inspection Fruit inspection

fortnightly fortnightly

November-January November-March

40 leaves 40 fruit

Powdery mildew Shoot inspection fortnightly Novem ber-January 10 shoots

it and to visually inspect it for 'hot spots' of pest or disease activity. It was not possible for the pest manager to see every tree and growers were asked to inform him if they found any hot spots he may have missed. In the event there were few problems with hot spots.

Sampling was largely confined to Delicious strains, because these were the dominant variety. They were also the most susceptible variety to mites and it was important to use them as an indicator of potential mite problems. A variable number of Granny Smith, Jonathan, and Bonza trees were sampled, when present, for lightbrown apple moth and powdery mildew, which favour these varieties.

Sampling intensity

The sampling intensity used during this project was derived in consultation with a biometrician, Ms. Helen Nicol, and after evaluation of the time involved in sampling. The resultant sampling regime is a compromise between the needs for statistical precision in population and damage estimates, and cost-efficiency in sampling time. The sampling level of 40 fruit from each of 25 trees per block allowed for the detection of a real damage level of 1 in 250 with 95% probability, which was considered adequate.

5.3 Sampling methods and spraying strategies for insects and mites

Standard validated sampling procedures and spraying thresholds were not available for all pests. Therefore, trial protocols based on available literature and reasonable assumptions were formulated for plague thrips, woolly aphid, lightbrown apple moth and San Jose scale. The basis of these protocols is explained below.

Sprays for insects and mites were all recommended at standard label concentrations. However, fungicide sprays were recommended at 80 percent of label concentrations for most applications, except where monitoring indicated this was not advisable. The fungicide strategy is explained below.

Apple dimpling bug

Apple dimpling bug (ADB) was sampled by briskly tapping 10 inflorescences per tree over an open container and counting the number of bugs collected. Sprays were applied according to a threshold (Bower et al. 1991) which increased from 1.2 to 35 bugs per 250 inflorescences over the 30 day bloom period. Because ADB is thought to move into orchards during the blossom period from outside, half the sampled trees were around the edges of study blocks with the remainder through the centre.

In the first season (1990/91), the only chemical available to control ADB, that was also safe to bees and predatory mites, was endosulfan. This chemical has limited residual activity against ADB (up to 5 days) and multiple applications are sometimes necessary in plague years.

In the second season (1991/92), a new control strategy was introduced in all SPDC blocks. Trial work had shown that chlorpyrifos applied at the late pink stage (200 g of 25 percent w/w wettable powder per 100 L water) provided residual control up to 10 to 12 days. However, although chlorpyrifos is safe to predatory mites, it is highly toxic to bees. This restricted the use of chlorpyrifos to the period up to late pink, about 3 days before bees become active in orchards. This posed a problem in that chlorpyrifos had to be applied before the extent of the ADB infestation could be determined. However, long term data (Bower et al. 1991) indicated that sprays for ADB are economically justified in nearly all years. Therefore, the adopted strategy was to apply a single chlorpyrifos spray at late pink to all SPDC blocks and then monitor ADB populations to determine the need for follow-up sprays of endosulfan. This strategy was also used in the final season (1992/93).

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Plague thrips

Plague thrips is a sporadic pest whose populations are difficult to assess quantitatively (Lloyd 1975). It was not considered cost-effective to attempt formal assessments of plague thrips numbers. Thrips are dislodged from blossoms during tapping for ADB. The gross numbers of thrips in the container were noted. Specific sprays for plague thrips were to be applied if numbers exceeded 10 per flower. This level was derived from the data of Lloyd (1975).

Codling moth

The monitoring strategy for codling moth changed between the first and second seasons of the project. In the first season, monitoring was based solely on weekly catches in sex pheromone traps and fortnightly examinations of fruit for damage. In the second and third seasons the codling moth phenology model (Williams 1989) was used to time codling moth sprays according to predicted insect development.

Season 1990/91

Pheromone traps of the 'wing' design were suspended from full bloom to harvest at shoulder height from the limbs of apple trees at a density of one per ha according to the methods of Vakenti and Madsen (1976), which were validated for NSW by Thwaite and Madsen (1983). 'Block off or 'outside' traps were placed in adjoining apple blocks to prevent an influx of outside moths into the monitored area (Thwaite and Madsen 1983). Rubber caps impregnated with one mg of the synthetic codling moth sex pheromone attractant were placed in the centre of the sticky base of each trap. The pheromone caps were changed for new ones every four weeks to ensure the traps remained attractive. The base was cleaned of codling moths, other insects and debris at each weekly visit and the sticky adhesive stirred if necessary to maintain catchability. Bases were changed every two months, or sooner if excessively soiled.

Based on trial results in the Orange and Bathurst districts (Thwaite, pers. comm.), a spray threshold of an average of two moths per trap per week was adopted, except that the first weeks catch was ignored as it is likely to represent an accumulation of males that emerged over previous weeks. Sprays of azinphos-methyl were recommended when the threshold was exceeded, provided a spray had not already been applied in the previous 14 days (up to December 31) or 21 days (after January 1). An additional condition was that, regardless of trap catches, no block was to be allowed to go without sprays for more than six weeks.

Five blocks were treated with azinphos-methyl and five with the insect growth regulator fenoxycarb (Insegar® 250W) for control of codling moth. The fenoxycarb sprays were applied according to the manufacturers (Wellcome Australia) directions. The first spray was applied when the pheromone trap catches indicated the first sustained rise in emergence of the overwintering generation of moths was beginning. The second spray was applied two weeks later. Thereafter, sprays were applied at a minimum interval of 4 weeks if trap catches exceeded 2 moths per trap per week or a maximum of 6 weeks if trap catches remained low.

Season 1991/92

A new strategy based on the codling moth phenology model was introduced in 1991/92. Temperature data to input to the model was obtained from 5 weather stations strategically located to sample the full altitudinal and geographical ranges of Batlow district orchards (see section 4.3). This enabled area-specific recommendations to be made on the basis of distinct microclimatic zones. In order to accurately determine when the period of sustained first generation emergence begins (the biofix), pheromone trap monitoring commenced earlier, by the pink stage of bud development in early October. Traps were monitored 3 times weekly in orchards with the weather stations to pinpoint the biofix in each microclimatic zone. Once the biofix was determined, trap sampling reverted to weekly.

39

The simple computerised phenology model employed for this project accumulated day degrees above a developmental threshold of 10°C. Input data were daily maximum and minimum temperatures. These data were fitted to a sine curve to approximate the daily temperature cycle (Baskerville and Emin, 1969).

The strategy adopted for the five azinphos-methyl orchards was as follows:

• The first spray was to be applied just before the phenology model predicted the commencement of first generation egg hatch (140 Celsius degree days after biofix).

• For orchards with high potential populations, based on trap catches and damage in the previous season, 2 further sprays were to be applied at fortnightly intervals.

• Orchards with low potential populations were to receive one further spray 3 weeks after the first. • The first spray for the second generation was to be applied 690 degree days after biofix. • There was to be only one spray applied to the second generation on orchards with low population

potential, while a second was to be applied 3 weeks after the first on high population blocks.

These strategies would result in 3 sprays being applied to low population blocks and 5 to high population blocks.

Following the takeover of the Wellcome company by Ciba-Geigy Australia Limited, and further research results from J.L. Readshaw, a new strategy for fenoxycarb was developed as follows:

• The first spray was to be applied just before the phenology model predicted commencement of first generation egg laying.

• The first 4 sprays were to be applied at half strength (20 g/100 L) at weekly intervals. This was to ensure complete coverage of foliage which is growing rapidly at this time of the year. It was critical that eggs were laid on fenoxycarb residues for successful control to be achieved.

• Two further sprays at intervals of one month were to be applied at full strength (40 g/100 L).

Season 1992/93

A further tightening of the codling moth strategy was made in the 1992/93 season. The phenology model was again used to time the first sprays of azinphos-methyl and fenoxycarb.

Azinphos-methyl blocks were classified early in the season as having high or low populations of codling moth on the basis of trap catches prior to the first spray. High populations were defined by trap catches greater than an average of 5 moths per trap per week in any week after the initial trap clearance. Conversely, low populations were those in which trap catches did not exceed 5 moths per trap per week on any occasion before the first spray. The spray strategies for high and low populations were as follows:

• High population. Four or five applications of azinphos-methyl at two-weekly intervals on the first generation.

• Low population. Three azinphos-methyl sprays at three-weekly intervals on the first generation. • After the first generation emergence declines, the pheromone trap catches were to be used to

establish a biofix for the second generation and a resetting of the phenology model to time second generation sprays. In effect it was realised that the phenology model could be used to determine when egg laying or egg hatch could be expected after ANY peak in codling moth emergence or activity had occurred.

• A maximum of five weeks without spraying was to be allowed between the first and second generations.

• One or two sprays were to be applied to the second generation depending on population pressure as determined by the traps for the first generation.

40

Fenoxycarb was used in 1992/93 as it was in 1991/92 except that the fourth half strength spray was changed to a full strength application, as it had to provide cover for a full month.

The main aim of the revised codling moth strategies was to provide complete suppression of the first generation so that the second generation could be easily controlled by a minimal number of sprays. This would have the added advantage of minimising the likelihood of spray residues persisting on the fruit at harvest.

The fortnightly fruit examinations provided an ongoing check on the effectiveness of the spray strategies and, if excessive damage was occurring, allowed for a change of strategy, particularly against the second generation. Damage from the first generation was evident by the end of December.

Lightbrown apple moth

Lightbrown apple moth is generally controlled by the sprays applied for codling moth. However, it was possible in the first season (1990/91) that if substantial reductions in sprays for codling moth occurred, an increase in lightbrown apple moth may follow. If two or more active lightbrown apple moth larvae were found per 1000 fruit an application of chlorpyrifos was to be recommended. Chlorpyrifos would also provide cover for codling moth for 10 days, as well as providing significant control of woolly aphid and San Jose scale. Because lightbrown apple moth is often mainly a problem in Jonathan and Bonza with their tight fruit clusters, ten trees of these varieties were also to be checked (20 fruit per tree), if present in the block.

In the second and third seasons lightbrown apple moth populations were monitored with sex pheromone traps in the five blocks with the automatic weather stations in addition to the fruit checks. The traps were placed at a density of one per ha in trees adjacent to those with codling moth traps and at similar heights. These traps were used on a trial basis only as there were no protocols for using them in apples. It was hoped the traps may warn of increases in moth activity. If it seemed clear there was a risk of infestation, additional applications of azinphos-methyl, fenoxycarb or chlorpyrifos may have been advised, depending on the situation with other pests. Given the tight spray strategy for codling moth in the first half of the season, no problems were expected with lightbrown apple moth until the second half.

Woolly aphid

At each fortnightly inspection the presence or absence of infestations of woolly aphid was noted on each study tree. In 1990/91 the treatment threshold was 20 percent of trees infested, which triggered advice to apply a spray of vamidothion or chlorpyrifos depending on withholding period requirements, with vamidothion preferred. In 1991/93 and 1992/93 the spray threshold was lowered to 10 percent of trees infested.

San Jose scale

San Jose scale was monitored fortnightly throughout all three seasons on the same fruit as for codling moth, lightbrown apple moth and apple scab. A standard spray of petroleum oil in the dormant period (3%) or at green tip (2%) was recommended. A spray of chlorpyrifos was to be advised during the growing season if 2 or more fruit in a sample of 1000 were found to be infested.

Mites

The integrated mite control methodology which had already been successfully adopted in the Batlow district (Seymour 1982; Davidson 1988; Bower and Thwaite 1995) was used in this project.

European red mite, two-spotted mite and their predators were monitored by fortnightly samples of 50 randomly selected leaves comprising two leaves from each of the 25 monitored trees in each trial block.

41

Each leaf was examined under a binocular microscope for the presence or absence of each mite and predator species. Acaricide sprays were applied when 50 to 80 percent of leaves were occupied by the active stages of pest mites (Bower and Thwaite 1995). Above 80 percent of leaves occupied, excessive damage is likely. Control was imposed at the lower end of the threshold if infestations were patchy with localised severely infested trees and few predators, or if slow acting acaricides such as propargite were to be used. The upper end of the threshold range applied if the infestation was uniform and predators were abundant. No sprays were applied when predators were dominant.

During each fortnightly visit all blocks were given a rating from 0 to 4 for the degree of mite damage (Bower and Thwaite 1995). Knowledge of the overall condition of the trees is important in making decisions about whether to spray earlier or later. The relationship between pest mite numbers and foliar damage is influenced by factors such as water stress and nitrogen levels, so it is important to monitor damage as well as mite populations.

SPDC growers were advised to avoid as far as possible the use of chemicals toxic to the predatory mites, Typhlodromus occidentalis and T. pyri. All insecticides and acaricides advised by the pest manager for other pests and diseases were known to be relatively harmless to the predators (Bower and Thwaite 1986, 1995). The main problem was the inhibitory effect of the dithiocarbamate fungicides, particularly mancozeb and metiram, on the increase of T. pyri (Gruys 1980). Mancozeb and metiram are very important protectants used as cover sprays for control of apple scab. Alternatives are much more expensive or less efficacious. Growers were asked to minimise their use of the dithiocarbamates and to confine them to the early part of the season when there was less mite activity and apple scab control was most critical. In the second season (1991/92) SPDC growers were requested to avoid the use of mancozeb and metiram, and to substitute dithianon, dodine and/or ziram. In the third season they were also asked to avoid ziram as some evidence indicated it may also inhibit T. pyri (Bower and Thwaite 1995).

In 1992/93 an attempt was made to substitute summer oil sprays for synthetic miticides following promising trial work with Sunspray Ultrafine spraying oil (Sun Oil Co., USA). The strategy was to use two sprays at 1% concentration 10 days apart when the spraying threshold was reached. This strategy was tried on six SPDC blocks.

In all three years of the project, the control blocks were monitored for mites by the existing mite monitoring service run by Rob McLeod, Batlow Coop, who provided advice on spray requirements. In view of this it was not expected there would be significant differences in mite management between the SPDC and control groups.

5.4 Strategy for disease control and fungicide use reduction

Initially the strategy consisted of a reduction in the rate of protectant fungicides applied.

Reduction in fungicide rates has been attempted for apples over the past ten years. In South Australia apple scab was controlled with as low as 25 percent of recommended rates in some seasons, when applied in low volumes (100 L/ha) (Wicks and Nitschke, 1986). Similar results have been reported from the UK (Cross and Berne, 1990) although they suggest that commercial success with greatly reduced dose (and volume) rates (25% of recommended rate), requires careful orchard monitoring for pests and diseases, coupled with a flexible management strategy to adjust choice of pesticide, frequency of application and dose and volume rate to suit prevailing conditions.

Our approach at Batlow was to align fungicide rate reductions with disease level assessment, using a threshold system developed to minimise the chance of a major increase in disease.

In the first season, it was suggested that cooperating orchardists continue to apply their current protectant program, using fungicides of their choice but applied at a rate of 80 percent of the recommended rate.

42

This was seen as a less risky approach to reduction in fungicide usage than missing particular sprays or relying only on post infection sprays. The occurrence of an infection period, the detection of apple scab or mildew levels above set amounts, or the occurrence of 25 mm of rain led to certain actions (Table 5.2).

Spray program and actions were recommended to the grower by the Pest Manager. On the basis of access to general district observations, the Spray Warning Service and results of his disease monitoring in the treatment blocks. This enabled a careful check on disease progress and resulted in actions based on well formed decisions.

Fungicide applications were applied through the whole season, where this was the growers' usual practice. The basis of continuing with reduced fungicide rates was the monitoring of scab levels over the season. In the second and third seasons, it was suggested that the reduced rates be followed by cessation of spraying at the end of the primary infection period where thorough surveying had revealed that the disease was well controlled. A set of rules was prepared for this phase of the season (Table 5.3).

A similar approach of a reduction in rates, dependant on monitored disease levels, was adopted for powdery mildew, as shown below. In the first season a conservative level of detection was set, which was increased in the second and third season (Table 5.4).

The sampling strategies during the season for both scab and mildew are shown in Table 5.1. The decision making process is shown graphically in Figure 5.1.

The aim of the program was to remain with the lower fungicide rates throughout the season. Disease monitoring indicated when disease levels became undesirably high, when a return to full rates was made. For scab a post harvest, pre leaf fall spray of urea recommended each season regardless of the level of scab which occurred. This helped to maintain disease pressure at a low level in the next season. For powdery mildew, attention to removal of infected shoots during summer and also during winter was recommended to aid in mildew control.

5.5 Pest and disease levels

Records were made of the levels of pests and diseases detected in each orchard at regular 14-day intervals (Bower et al. 1993). Reports were made to the advised fanners only, giving details of counts of pests, predators and disease in the orchard, with recommendations of whether treatment was warranted. The percentage loss due to pest and disease was also assessed just before harvest by examination of 100 fruits on each of 25 trees selected randomly across the orchard.

Mid-season andpre-harvest damage assessments

Twice per season, in late December and late February/early March, assessments of damage to fruit were made by the project chief investigators. These independent checks provided data for assessment of the effectiveness of the monitoring protocols. The December check was timed for the end of the first codling moth adult flight, by which time larval entries would be visible, and the end of the primary infection period for apple scab, when the degree of primary infection would be obvious. Eighty fruit on each of 25 trees were inspected in each SPDC and control block, making 2000 fruit per block and 40,000 overall.

The second assessment occurred immediately before the commencement of harvest and provided the final estimate of damage for the season. In this case 100 fruit were examined on 25 trees in each SPDC and control block, making 2500 fruit per block and 50,000 overall.

43

5.6 Number of pesticide treatments

Data on the number of pesticide treatments applied were obtained from farmer records. The number of pesticide treatments was totalled, regardless of whether they were applied singly or in mixtures.

5.7 Amount of pesticide product applied per hectare

Using the farmer records the amount of product (kilograms per hectare) applied was calculated from the stated rate per 100 L and assuming an application volume of 2000 L ha"l. Where the farmer failed to indicate a rate, the label rate was used in calculations. For simplicity it was assumed that 1 L of a product equalled 1 kg and the total applied product was estimated by adding litres and kilograms. No account was taken of the concentration of active ingredient (a.i.), which ranged from 50 to 900 g kg"* according to the product, or of the general toxicity or other features of the product.

5.8 Statistical analysis

The means, standard deviation and coefficients of variation were calculated for number of fungicide treatments, percentage scab damage, number of insecticide treatments, percentage insect damage and kilograms of product used, individually for all 3 years and for both groups.

For each year, group means were compared using analysis of variance. The relationship between percentage damage and the number of sprays for both disease and insect damage was established using multiple regression and testing differences in the relationship between groups and years.

All analyses were performed using Genstat 5 (Anon. 1987).

5.9 Weather records

Five automatic weather stations were established over the full altitudinal range and in most of the major parts of the district in 1991/92 (Table 5.5). Two additional stations were set up for the 1992/93 season to provide a more complete geographical coverage of the district.

The stations were set up according to standard Bureau of Meteorology guidelines in a Stevenson screen. A Tain Electronics data logger was used to accumulate half-hourly readings of wet and dry bulb temperatures and rainfall. The data were downloaded periodically into a portable computer using software supplied by the data logger manufacturer. For calculations of day degrees, the maximum and minimum temperatures were read manually from a print-out of the data made in the office. These readings were then entered into the day degree software.

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Table 5.2 Apple season disease control program using reduced rates of fungicides, 1990/91

General Strategic Spraying

SCAB - A. Scab - No disease observed in block, September to early December

STRATEGIC Ai) SCAB CONTROL

Aii)

Apply protectant spray program at intervals and timings used in rest of orchard

selection of fungicides to be by grower selection of timing to be by grower rate 80% of recommended label rate

a) If infection period occursytithin the protectant period provided by the fungicide no action required

Aiii)

b) If infection period occurs after the protectant period has expired apply full rate eradicant as soon as possible recommence cover spraying at 80% rate, as soon as cover provided by the eradicant has expired

When total rainfall exceeds 25 mm within the cover period of the protectant fungicide

repeat cover spray and continue strategic program

B. Scab - Disease found on foliage or fruit at pest-monitoring intervals

Bi)

Bii)

If scab level of less than 0.2% infected fruit (i.e 2 fruit in 1000) or less than 2% infected leaves (i.e. 2 leaves in 100) found

apply two eradicants at 5 day intervals recommence strategic program as above (A iib), using 80% protectant rate.

If scab level of more than 0.2% infected fruit or more than 2% infected leaves found

apply two eradicants at 5 day intervals recommence strategic program as above at full rates for rest of season.

45

Table 5.3 Scab control with reduced fungicides is the second half of the season

C. Scab - Second half of season

Provided scab has been well controlled during the primary infection period, there should be either no need to use any further scab fungicides, or their application could be restricted to wet periods. This period of the season is the time when savings of the number of sprays applied can be made. After the early December inspection of the orchard, the following is suggested

Ci) No scab found cease all further scab sprays for rest of season till harvest apply post harvest urea as usual

Cii) Scab found but level below the thresholds for return to normal rates

apply eradicant spray if wet periods in excess of 8 hours noted from observations

Ciii) Scab found above the threshold level for return to normal rates spray at 4 weekly intervals with protectant at full rates apply curative spray if cover period has been extended and wet condition as in excess of 8 hours occurs ensure a cover spray is applied in the last 4 weeks before harvest to control late infections which sometimes occur in extended wet weather

Table 5.4 Recommended control of apple mildew with reduced fungicide rates

C. Powdery mildew, 1990/91

Ci) Include mildew fungicide at 80% of recommended rate on susceptible varieties with the scab protectant from pink stage until shoot growth ceases about the end of December, or use dual purpose fungicide at 80% rate.

Cii) If mildew level exceeds 2 percent of shoots infected, revert to full rates of mildewicide in all further sprays.

D. Powdery mildew, 1991/92 and 1992/93

Di) Include mildew fungicide at 80% of recommended rate on susceptible varieties with the scab protectant at pink stage, full bloom petal fall and first cover or use dual purpose fungicide at 80% rate.

Dii) If mildew level exceeds 10 percent of shoots infected, revert to full rates of mildewicide in all further sprays.

Figure 5.1 Schematic of decision making process for fungicide* application for apple scab control

a

.2 8

d ^

J-i OH

o

d ^3 o o 00

Key:

Green tip Cu

P80

4

4 Assess scab every 2 weeks from end of October

>2.2% Fruit or

>2% Leaves

>2.2% Fruit or

>2% Leaves

/ l

/ ^ < C100

Nil

Thru Till Dec

P80

4 DECEMBER

Scab - Assess late December only

>2.2% Fruit or

>2% Leaves

4

i< P100 at 4 week intervals

4

>2.2% Fruit or

- >2% Leaves

And > 8 hrs Wetness

/ V \ C100

• ) 4

Repeat as necessary

Nil

No Sprays

HARVEST

i< P80 §< P100 ? C100

80% rate protectant

100% rate protectant

100% rate curative 48

Table 5.5 Locations of weather stations

Orchard Grower name Location Altitude (m)

Year commenced

Springfield J. Reynolds Lower Tumut Rd. 730 1991

Woodburn D. Cathels Lower West Batlow 740 1992

Meryla K. Bagnall South Central Batlow 750 1992

Parkview N. Cook Willigobung 810 1991

- P. Forsyth Central Batlow 820 1991

Mountview J. Robson West Batlow 840 1991

Tingira M. Smart White Gate 930 1991

6.0 RESULTS AND DISCUSSION

6.1 Apple dimpling bug

The numbers of spray applications against apple dimpling bug and the damage found in the preharvest assessment are shown in Table 6.1 for the three years of the project.

Season 1990/91

Apple dimpling bug numbers were fairly low in most blocks early in the flowering period. When sprays were required bug levels only just exceeded the threshold. These early bug populations probably originated from local bush areas. During petal fall there was a sudden large influx of bugs into most blocks. These were probably long distance migrants flying from inland areas on warm northerly winds. They declined almost as suddenly as they appeared once petal fall was complete. It is likely that they would not have done much damage at that late stage in the bloom period.

Similar mean levels of damage to fruit occurred in the SPDC and control groups, 3.8 and 3.6 percent, respectively. However, damage in both groups varied about 10 fold among blocks, with ranges of 0.8 to 10.0 for the advised growers and 0.8 to 8.10 percent for the controls. There was also little difference in the mean number of sprays between the two groups, 2.4 for the SPDC group and 2.1 for the controls. Less variation in numbers of sprays was evident in the SPDC group (range 2 to 3) than the controls (range 1 to 5).

The SPDC growers used mainly endosulfan, but two used a pre-bloom chlorpyrifos. Three control growers used only a single application of fluvalinate, a synthetic pyrethroid, to control apple dimpling bug. Although fluvalinate is very effective against apple dimpling bug, and safe to bees, it is highly toxic to the predatory mites used in integrated mite control and hence was not used in the SPDC blocks.

No correlation is evident between the number of sprays used in the control blocks and damage at harvest. The grower using the highest number of sprays (5) also had the highest level of damage (8.1 percent), but growers using only 1 or 2 sprays had damage levels ranging from 0.8 to 5.9 percent. This variability in damage is typical of apple dimpling bug, whose populations can vary greatly between localities, orchards, blocks within orchards and even within blocks.

Season 1991/92

Apple dimpling bug populations were low throughout flowering in 1991/92. Chlorpyrifos was used at late pink on all SPDC blocks and in all but one case was the only spray needed (Table 6.1). The orchard requiring a second spray (endosulfan) lies at the northern end of the district and appears to be prone to invasion by apple dimpling bug. However, it is unclear whether the lower bug populations were due to seasonal conditions or the widespread use of chlorpyrifos. Six of the control group also used chlorpyrifos, two used fluvalinate and only two relied on endosulfan.

The numbers of sprays used was lower in the SPDC group (11) than in the controls (16) and was lower than the previous season for both groups. Spray use in the SPDC group declined by 54 percent and the controls by only 24 percent.

Damage due to apple dimpling bug was also considerably lower in 1991/92 than in 1990/91 for both groups (Table 6.1). Mean damage was acceptable at less than one percent; 0.7 percent for the advised growers and 0.6 percent for the controls. Two growers in each group had damage at one percent or more, but none exceeded two percent. The results suggested chlorpyrifos had considerable promise for improved control and, as a consequence, for reducing spray usage.

50

Table 6.1 Comparison of SPDC and control blocks for numbers of spray applications and damage due to apple dimpling bug over three seasons (1990/91 to 1992/93)

Grower Number of sprays Fruit damage (%)

1990/91 1991/92 1992/93 1990/91 1991/92 1992/93

SPDC Group

Al 2 1 1 8.00 0.64 1.32

Bl 2 1 1 1.10 0.48 0.80

CI 2 1 1 6.50 0.12 0.48

Dl 3 1 1 10.00 0.16 0.16

El 3 1 1 0.80 0.96 1.32

Fl 2 1 1 1.20 0.48 1.16

Gl 2 1 1 2.30 0.16 1.12

HI 3 2 3 2.30 1.36 5.76

11 2 1 1 3.00 0.92 1.20

Jl 2 1 1 2.50 1.28 2.12

TOTAL 24 11 11 37.70 6.56 15.44

MEAN 2.4 1.1 1.1 3.8 0.7 1.5

Control Group

A2 2 3 1 2.90 0.36 1.16

B2 3 1 1 0.80 0.44 0.32

C2 1 2 1 0.80 0.80 1.52

D2 5 2 1 8.10 0.52 0.84

E2 3 2 2 3.90 0.52 1.16

F2 1 2 1 5.90 1.00 1.56

G2 1 1 0 4.40 0.32 0.80

H2 2 1 1 0.80 1.52 2.92

12 1 1 1 2.40 0.24 0.52

J2 2 1 1 5.90 0.32 0.68

TOTAL 21 16 10 35.90 6.04 11.48

MEAN 2.1 1.6 1.0 3.6 0.6 1.2

51

Some damage due to early caterpillars (budworms and/or loopers) may have resulted from the dropping of endosulfan by most growers. Early caterpillar damage was noted in twelve blocks, but did not exceed 0.3 percent. Season 1992/93

Quite high levels of apple dimpling bug were present in some blocks at early pink, which is earlier than usual. Some damage may have occurred in the period between spurburst and late pink when the first spray is normally applied. Chlorpyrifos was applied at late pink in most blocks and controlled apple dimpling bug very effectively. An additional endosulfan spray was needed in only one SPDC block, so that spray usage was the same as in the previous season (Table 6.1). With widespread adoption of chlorpyrifos, spray use in the controls declined to the same levels as the SPDC group.

Damage at harvest due to apple dimpling bug was higher in 1992/93 than in 1991/92, a mean of 1.5 percent for the SPDC group and 1.2 percent in the controls. Damage exceeded one percent in 12 blocks and two percent in three (Table 6.1). Damage was quite high in SPDC block HI at 5.8 percent. This block, SPDC block Jl and control block H2 all tended to have higher levels of apple dimpling bug damage in both 1991/92 and 1992/93. All three blocks occur in the northern end of the district at lower altitudes than most other orchards and seem more prone to infestation and damage.

There was virtually no damage due to early caterpillars in 1992/93, despite the lack of endosulfan usage.

Overall trends

From 1989/90 to 1992/93 there was a considerable decline in the number of sprays used for apple dimpling bug in both the SPDC and control groups (Figure 6.1). This was associated mainly with the replacement of endosulfan by chlorpyrifos as the main chemical control measure. The reduction occurred faster in the SPDC group than in the controls due to the advice given. However, uptake by the control group was very fast, once the efficacy of chlorpyrifos had been demonstrated. The overall reduction in spray use in the SPDC group was 60 percent from 1989/90.

These results make the key point that minimal spray use depends on having effective chemicals available to use when a chemical solution is needed. If only chemicals of low efficacy are available, such as endosulfan for apple dimpling bug, then more applications are likely to be required to achieve control.

Apple dimpling bug populations and damage vary widely between blocks, in different parts of the district and between seasons. The nomadic movement patterns of apple dimpling bug from one source of flowers to another, and probable occasional long distance movements (Bower, unpublished), also add to the difficulty in deciding when to spray for this pest. Monitoring is a valuable tool for following population trends, particularly since the insect is small and may be difficult to distinguish from many other species which visit apple trees during flowering. The similar spray use by the control group to the SPDC group in the final year may be due in part to a leakage of information about apple dimpling bug pressure from the advised growers to the rest of the grower community, which is very tight-knit at Batlow.

6.2 Codling moth

Data on the damage caused to fruit by codling moth and the number of sprays used against it are given in Table 6.2. Different control strategies were employed in each season and the results need to be interpreted in this light. In field control trials it is more usual to compare the same control strategy over a number of seasons to determine how it performs under different seasonal conditions and whether the strategy maintains control over time. Altering the strategy between years may confound the results making interpretation difficult. Strategies were changed for the following reasons: The strategies adopted

52

Figure 6.1 Apple Dimpling Bug - Number of sprays applied over four

28 -i

26 rd

s

24 CS xi

22 o S

20 c »mm VI >* 18 a u VX 16

^^ a +* © 14 H

12

10

—•— Advised ^ —*-- Control

1989/1990

^ v. s

\ • * .

\

\

1990/1991 1991/19 Seasons -

Table 6.2 Comparison of SPDC and control blocks for numbers of spray applications and damage due to codling moth over three seasons (1990/91 to 1992/93)

Grower Number of sprays Fruit damage (%)

1990/91 1991/92 1992/93 1990/91 1991/92 1992/93

SPDC Group

Fenoxycarb

Al 5 6 5 0.50 0.12 0.08

CI 3 6 4 0.04 0.04 0.04

El 4 6 6 0.20 0 0.04

Fl 4 6 6 0.10 0 0

11 7 7 5

Azinphos-methyl

0.30 0.28 1.68

Bl 6 3 6 0.50 0.20 0

Dl 7 5 6 0.04 0.16 0.20

Gl 6 5 4 0.08 0.04 0.08

HI 6 7 6 0.80 1.20 0.88

Jl 2 5 2 0.40 0.04 0.16

TOTAL 50 56 50 2.96 2.08 3.16

MEAN 5.0 5.6 5.5 0.30 0.21 0.32

Control Group

A2 4 4 2 0.04 0 0.04

B2 6 8 5 0 0 0

C2 3 6 5 0.10 0.04 0.08

D2 8 6 7 0.04 0 0

E2 7 6 6 0 0 0.08

F2 5 5 5 0.10 0.20 0.36

G2 3 4 5 0.10 0 0

H2 4 6 5 0.04 0.24 0.12

12 4 5 5 0.10 0 0

J2 5 5 6 0.60 0.12 0.04

TOTAL 50 55 51 1.12 0.60 0.72

MEAN 5.0 5.5 5.1 0.11 0.06 0.07

54

in 1990/91 and 1991/92 were inadequate and there was no point in continuing with them; the project was developmental in nature and it was always intended that thresholds and strategies would be modified if they proved to be inadequate. It was important to develop reliable thresholds and strategies on which a future monitoring service could be based.

Season 1990/91

Codling moth was the second most significant pest after apple dimpling bug in terms of damage to fruit in 1990/91. The mean level of damage at harvest was below one percent in both the SPDC (0.3%) and control (0.1%) groups (Table 6.2). However, it is likely damage would have been higher if remedial action had not been taken in three supervised blocks when control began to fail. In two of these the strategy recommended by the distributor of fenoxycarb failed and azinphos-methyl was applied to protect the fruit from a large second generation emergence. In block II three azinphos-methyl sprays were applied when patches of excessive infestation began to appear in old trees in which codling moth can be difficult to control. In block Al, a young orchard, a single azinphos-methyl was applied when a localised hot spot of damage appeared.

A problem was also encountered with the strategy for azinphos-methyl in block B1. In this case, codling moth catches in the pheromone traps were very low and did not exceed the spray threshold at any time during the emergence of the overwintering generation. This may have been due to an unusually low population in the block or to a failure of the traps. The former is considered most likely, since most of the damage occurred at the edges of the block suggesting that mated females migrated into it from a nearby block known to have a codling moth problem. Under the 1990/91 strategy both groups used fifty sprays to manage their codling moth populations, although the number of sprays applied by individual growers ranged between 2 and 8.

Season 1991/92

In the 1991/92 season a phenology model, described earlier, was used to establish a date of the codling moth's spring emergence (Biofix) and predict the first generation egg laying for growers using fenoxycarb and first generation egg hatch for azinphos-methyl users. The model was also used to predict second generation events and sprays were applied throughout the season accordingly. This was done for each grower in the SPDC group based on data collected from weather station closest to their geographical location. This allowed some growers to delay their first application by up to three weeks and thus reducing the number of spray applications over the season. An error in the labelling of fenoxycarb (Insegar) and hence the use of fenoxycarb meant that growers applied the fourth application at half rate (20 g/100 L) to provide cover for four weeks. This may have resulted in some growers incurring more damage than expected. The label should have instructed growers to apply the fourth application of fenoxycarb at the rate of 40 g/100 L to provide protection for the four-week period.

The overall level of damage to fruit was lower in the 1991/92 season than in the previous season. The mean level of damage was below one percent in both the SPDC (0.21%) and control groups (0.06%) (Table 6.2). The SPDC group applied 56 sprays (range 3-7, mean 5.6) compared with 55 (range 4-8, mean 5.5) by the control group. Grower Hi's block had high codling moth pressure, as per the previous season, with trap catches exceeding the threshold for most of the season. This high pest pressure and a gap of three weeks instead of two between the first and second sprays resulted in this grower incurring fruit damage of 1.2 percent. This was one percent higher than any other SPDC grower using an azinphos-methyl program.

The degree-day phenology model was expected to enable sprays, taking into account the mode of action of the chemical used, to be timed accurately to the appropriate life stage of each generation. The results from individual growers would suggest that the degree day phenology model, as used in Washington state and now Batlow, was not ideally suited to conditions found in the Batlow district. The model was found

55

not to accurately predict second generation events due to a drift away from reality the further it got from the biofix.

Season 1992/93

The phenology model was used again to predict the first generation egg laying and hatch. However, to overcome the models inability to predict from biofix the second generation events a second biofix was established based on the peak of the second flight, recorded by trap catches, and sprays were applied accordingly. The blocks were classified as having high or low populations and an appropriate spray regime applied (see section 5.3).

Overall the level of fruit damage in the 1992/93 was higher than in the 1991/92 season. The mean level of damage was below one percent in both the SPDC (0.32%) and control groups (0.07%) (Table 6.2). The SPDC group applied 50 sprays (range 2-6, mean 5) compared with 51 (range 2-7, mean 5.1) by the control group. Although there was no real difference between the groups in the number spray applications the SPDC group incurred a level of fruit damage 4.5 times greater than the control group (Table 6.2). However, over 80% of this damage was incurred by two growers II (1.68%) under a fenoxycarb program and HI (0.88%) under an azinphos-methyl program both of whom had high levels damage in previous seasons.

Overall trends

In the 1989/90 season, prior to the start of this study, the ten growers that choose to become part of the supervised group used 54 sprays to control codling moth, which is 30 percent more than the control group who used 41 sprays (Figure 6.2). This suggests that prior to the trial some, if not all, of the SPDC growers had been experiencing more difficulty in controlling codling moth than those who chose to join the control group. The reasons why these growers were using more sprays than the control group is unknown, but common factors known to cause problems include: high pest pressure, the onset of pesticide resistance, poor spray practices and poor orchard hygiene. For whatever reason these growers experienced difficulty, it was likely to have motivated them to join the SPDC group. In the 1990/91 season both groups used the same number of sprays for codling moth control. While the control group's usage increased from the previous season, possibly in response to an increase in pest pressure due to favourable climatic conditions, the SPDC group reduced their spray usage. There was no difference in the number of sprays used by the two groups in the 1991/92 and 1992/93 seasons, the SPDC group used 56 and 50 sprays compared with the control group's 55 and 51 sprays respectively (Figure 6.2).

These results demonstrate that pest population monitoring is a valuable tool. In the 1989/90 season both groups had 'calendar sprayed' according to an expected spring emergence of codling moth and maintained a protective cover spray throughout the season. For the SPDC group this had resulted in them using more sprays than the control group. However, with monitoring to establish the presence and relative density of codling moth in the orchard, and action thresholds in place to guide growers as to the need to spray, the SPDC group were able reduce their pesticide usage by eight percent. While eight percent appears a relatively modest reduction it was made in a season when the control growers used 22 percent more than they had in the previous season.

Introducing the degree-day phenology model in the 1991/92 season enabled the SPDC group to target sprays at the codling moth's vulnerable life stages, i.e. azinphos-methyl at egg hatch and fenoxycarb at egg laying. In the 1992/93 season the degree-day phenology model was used differently to take into account the model's drift from reality, as described previously, and this allowed the SPDC group to accurately target their spray program at the codling moth's second generation events. Introducing the degree day phenology model did not provide further significant reductions in insecticide use over the trial period.

56

Figure 6.2 Codling Moth - Number of sprays applied over four seas

58

56 Of!

54 03

. = U 52 © 13 4> 50 S

• « Of!

>* 48 93 i-ON Of! 46

mm 03

- * - » o 44 H

42 -

40 /

/

/

/

/

/

/

/

/

/ /

^ ^

/ / /

-•— Advised ±- Contro

1989/1990 1990/1991 1991/1992 Seasons

6.3 Lightbrown apple moth

It was thought that if a significant reduction in insecticides for codling moth control was achieved this may lead to an increase in lightbrown apple moth populations and consequently increased levels of fruit damage. As mentioned previously, the number of sprays applied for codling moth control by the SPDC group in the 1990/91 season was eight percent lower than in the 1989/90 season. The control group recorded no fruit damage by lightbrown apple moth during the 1990/91 season whereas four orchards in the SPDC group did incur a mean of 0.7 percent (range 0.1-0.3) damage (Table 6.3). This would suggest that the reduction in pesticides may have been responsible for the higher level of damage incurred by the SPDC group. However, there is no record of the level of damage that occurred in these orchards during the 1989/90 season and it is possible that, as occurred with codling moth, some of the SPDC group's orchards had a history of fruit damage by lightbrown apple moth prior to this study.

In the 1990/91 season lightbrown apple moth was monitored by checking fruit for actively feeding larvae, however this method failed to predict the level of damage that occurred. In the 1991/92 and 1992/93 seasons pheromone traps were used to monitor the lightbrown apple moth's adult population at five locations in the Batlow district in the orchards. The traps were located in orchards where weather stations were situated and monitored lightbrown apple moth populations over the trial's entire altitudinal range. The level of fruit damaged by lightbrown apple moth varied during the trial both between and within the groups. Between the 1990/91 and 1991/92 seasons the level of fruit damage decreased in the SPDC group while increasing in the control group whereas between the 1991/92 and 1992/93 seasons the SPDC group increased and the control group decreased (Table 6.3). In the 1991/92 season three growers from each group recorded fruit damage, whereas in the 1992/93 season nine growers from the SPDC group compared with three in the control group recorded fruit damage. The reason why so many of the SPDC group had fruit damage is unclear, however in this season this group did apply slightly less pesticides for codling moth control than the control group.

At the four highest pheromone trap locations (between 810 m and 930 m above sea level) the trap catches never exceeded 1 moth per trap per week during the spray application period. However, at the lowest site, where temperatures are generally warmer earlier in the season, the population was significantly higher (up to 12 moths per trap) from mid-November onwards. When the spray period was completed trap catches rose at the lowest site, reaching a peak of 21 moths per trap in mid-March. However this higher population of adult moths at lower altitude did not translate into higher fruit damage, in fact the opposite occurred, most of the damaged recorded during the three year trial occurred in orchards at altitudes greater than 830 m above sea level.

6.4 Woolly aphid

In the 1989/90 season both groups, SPDC and control, applied three sprays to control woolly aphid. Each group consisted of ten growers which suggests that for many growers woolly aphid was not a problem and that they did not apply an insecticide in direct response to observed infestation. However, these same growers used endosulfan or fluvalinate (now known as tau-fluvalinate) early in the season for apple dimpling bug control. They also used azinphos-methyl or phosmet and maybe diazinon or a winter oil (2%) at green tip for San Jose scale. These sprays may have suppressed woolly aphid populations to the extent that further treatments were not required. A few other growers were using fenoxycarb which is less harmful to natural enemies than azinphos-methyl and this may have assisted in suppressing woolly aphid to below the action threshold.

Over the trial period the SPDC group consistently used fewer insecticides in direct response to observed infestation than the control group. In the 1990/91 season two of the SPDC group used chlorpyrifos rather than endosulfan to control apple dimpling bug which is known to control woolly aphid. In the 1991/92 season all growers in the SPDC group used chlorpyrifos for apple dimpling bug control, compared with

58

Table 6.3 Comparison of SPDC and control blocks for fruit damage due to lightbrown apple moth over three seasons (1990/91 to 1992/93)

Grower Fruit damage (%)

1990/91 1991/92 1992/93

SPDC Group

Fenoxycarb

Al 0.10 0 0.24

CI 0.10 0.28 0.72

El 0 0.04 0.80

Fl 0.20 0.04 0.16

11 0 0

Azinphos-methyl

0.36

Bl 0.30 0 0.04

Dl 0 0 0.24

Gl 0 0 0

HI 0 0 0.04

Jl 0 0 0.20

TOTAL 0.70 0.36 2.80

MEAN 0.07 0.04 0.30

Control Group

A2 0 0.04 0

B2 0 0 0.08

C2 0 0.48 0

D2 0 0 0.04

E2 0 0 0

F2 0 0.16 0.60

G2 0 0 0

H2 0 0 0

12 0 0 0

J2 0 0 0.24

TOTAL 0.00 0.68 0.96

MEAN 0.00 0.07 0.10

six of the control group. In the 1992/93 season almost all growers had adopted the use of chlorpyrifos for apple dimpling bug control and the difference in the number of sprays applied specifically for woolly aphid control was reduced (Figure 6.3).

6.5 San Jose scale

The recommended petroleum spray oil applied at the rate of 3% during the trees' dormant period or 2% at greentip successfully controlled San Jose scale. None of the growers required further control measures in any season.

6.6 Mites

Mites were a major problem for growers in both the SPDC and control groups over each of the three seasons of this trial.

Season 1990/91

The 1990/91 season was hot and conditions favoured the development pest mite populations. Within the SPDC group there were a number differences between growers, some had more mite problems than others. For some growers European red mite was the major problem for others it was two-spotted mite. Consequently the number of sprays used by growers in the SPDC group ranged from 0 up to 4. Most growers used propargite (Omite_) for their early sprays followed by dicofol (Kelthane-) were necessary. Predatory mite numbers were low in all blocks and contributed little to mite control during the 1990/91 season. In several blocks predatory mite numbers increased towards the end of the season and were expected to provide better control in the coming 1991/92 season. While the number of predatory mites was relatively low in all blocks their populations were particularly low in blocks were fenoxycarb (Insegar-) was used for codling moth control. This suggests that fenoxycarb may suppress predatory mite populations.

Season 1991/92

Within the SPDC group there were again a number differences between growers. Generally predatory mite numbers were slightly higher than in the previous season, with two growers having relatively large populations, nevertheless they failed to provide adequate control of the pests. All growers in the SPDC group, with one exception, were required to spray and the number of sprays used by individual growers ranged from 0-3.

Season 1992/93

This season, six of the SPDC growers took part in a trial using petroleum oil spray oil for mite control. The recommendation was two oil sprays applied approximately ten days apart, as advised by the project pest manager (Mr K. Dodds). The oil sprays appear to have had little or no suppression of pest mites and where suppression may have occurred it also appears to have suppressed the predatory mites. All growers using oil sprays were required to follow up with a miticide and in two cases this was required within two weeks of the last oil spray. Two of the six growers using oil sprays required a second miticide approximately two weeks after the first.

The four growers in the SPDC group who did not use oil sprays incurred different levels of mite infestation. One grower had low numbers of pest mites and relatively large numbers of predatory mites, i.e. a good predator to prey ratio, and did not require any miticide applications. Two growers required a single application of propargite. The fourth grower encountered serious mite problems and required four sprays, i.e. two propargite and two dicofol sprays were applied in rotation. This grower had a high level of European red mite and very low numbers of the predator T. pyri. The six growers in the oil spray trial

60

Figure 6.3 Woolly Aphid - Number of sprays applied over four season

6 - i

5 -50

u xs 4 u o « 3

Of)

at z

a

13 1 o H

0 -

-•— Advised -±- Control

*V \

\

\

1989/1990

/

/

/

/

1990/1991 199171992 Seasons

used eight miticides (mean 1.3) compared with the four non-oil spray users who used six miticides (mean 1.5). Although the sample size is small, this lack of a real difference between the groups would indicate that using oil sprays did not control mite populations. In all but one case the use of propargite, or dicofol, significantly suppressed the number of European red mite with little or no effect on the predator T. pyri populations.

Overall trends

In the 1989/90 season there was no significant difference between the SPDC and control groups in the number of miticides applied, although on average the SPDC group applied slightly more, 16 and 17 respectively (Figure 6.4). As mentioned previously, the 1990/91 season was hot and mite control was particularly difficult for most growers hence the overall number of miticides used increased, nevertheless the SPDC growers managed their infestations using fewer miticides than the control groups, 22 compared with 24 respectively. Similarly, in the 1991/92 season the SPDC group used fewer miticides than the control group, 15 compared with 18 respectively. In the 1992/93 season the trend was reversed, the SPDC group used more miticides than the control group (13 compared with 10), however to what extent this reflects problems that may have been associated with the use of oil sprays is not known.

Overall there was little difference between the SPDC group advised by the project's pest manager and the control group who were receiving advice from the existing mite monitoring service provided by Mr. R. McLeod. There were significant differences in the number of miticides applied by individual growers within each of the groups, the reason for these differences are unclear, but they may be the result of differences in: altitude, i.e. climatic conditions; the grower's choice of pesticides to address other pest problems; poor spray techniques by individuals; the establishment or populations of predatory mites.

6.7 Apple scab

Season 1990/91

Disease was established by the primary infections which occurred in the spring of 1990. Infection periods consisted of 5 low, 2 medium and 1 high level. The high period of 53 hours wetness occurred during late blossoming on October 19 and was preceded by a medium infection period of 20 hours wetness on October 11 and followed by another medium infection period of 23 hours wetness on November 8. Table 6.4 shows the peak levels of leaf infection in December/January and fruit infection in December, January, February, and March of the 1990/91 season. In no case was there as significant increase in the level of infected fruit despite the infection potential indicated by the level of leaf infection in December, and the fungicide program applied which varied form nil to seven spray applications after December.

The level of leaf scab in December varied from zero to 6.2 percent and the level of fruit infection from zero to 7.1 percent. Of the nine orchards which reported no fruit infection in the March assessment, three had no detectable infection throughout the season, whilst the remaining six had reported low levels of infection at some time. The decrease in percentage of infected fruit in January/February in some orchards was due to the removal of infected fruit during hand thinning which is commonly practiced to increase the size of the remaining fruit. In three orchards (B D and M) scab increased slightly from the December to the March assessments, but none were statistically significant. In the remaining seventeen orchards no increase in fruit scab was detected.

No fungicides were applied during January to March in seven orchards. Infected fruit did not exceed 0.5 percent even though infection was recorded in December, either on fruit or leaves or both on six of the seven orchards. The last fungicide was applied by the end of January in a further 7 orchards. The level of infection was not related to the date of the last fungicide treatment.

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Table 6.4 Changes in percentage apple scab infection in fruit during secondary infection period, 1990

Orchard Leaf scab Fruit scab F Orchard Leaf scab

Dec Jan Feb Mar

A 6.2±1.3 1.7±0.6 2.6±0.7 0.8±0.3 0.3±0.2

B 0 0 0 0 0

C 0 0 0 0 O.liO.l

D 0 O.liO.l 0.3±0.2 0.2±0.1 0.4±0.2

E 0.3±0.2 0.8±0.3 0.7±0.4 0.1 ±0.1 0

F 2.9±0.7 4.2±1.0 1.0±0.5 0.7±0.3 1.0±0.4

G 2.2±0.5 0.5±0.4 1.7±0.6 0.6±0..3 0.5±0.3

H 0 O.liO.l O.liO.l 0 0

I 1.4±0.4 0.9±0.4 0.8±0.2 0.5±0.3 0.3±0.3

J 0 0 0 0 0

K 0.2±0.1 0 0 0 0

L 0 0.2±0.1 0.4±0.2 0 O.liO.l

M 0 0 0 0 O.liO.l

N 2.6±0.7 7.1±1.2 6.9±1.0 4.3±0.7 4.2i0.8

0 O.liO.l 0.8±0.2. 2.0±0.5 O.liO.l 0.4i0.2

P 0 0 0 0 0

Q 0 0.2i0.2 0 O.liO.l 0

R 0.5±0.2 0.2±0.3 0.4±0.2 O.liO.l O.liO.l

S 0 0.3±0.2 0 0.2±0.1 0

T 0 O.liO.l 0.2±0.1 0.2±0.2 0 1 Peak leaf infection percentage during December/January 2 Peak fruit infection percentage each month 3 Fungicides applied during January-March Me, metiram; Zi, ziram; F, flusilazole; P, penconazole; Do, dodine; Fe, fenarimo

Table 6.5 Weather data for days on which rain fell, apple fruit maturity and potential susceptibility t to March 1991

Date1 Rainfall mm Mean temp °C^ Fruit maturity-'

1990

Dec 3 5.5 19 8

11 13.5 16 9

20 3.0 17 10

1991

Jan 6 70.5 22 13

12 6.0 26 13

22 12.0 20 15

23 5.0 22 15

24 9.5 20 15

25 12.5 22 15

Feb 6 1.0 28 17

7 8.5 24 17

16 3.5 20 18

24 34.0 22 20

March 10 1.0 18 22

15 2.0 17 22

30 27.5 18 24

31 0.5 12 24 1 Days on which rainfall was recorded at Green Hills, near Batlow 2 Mean of maximum and minimum temperatures 3 Number of weeks from full bloom (mid October) cv. Red Delicious 4 Hours of wetness x °C at this maturity required for infection (Schwbae etal., 1984) 5 Hours of wetness required at the average temperature recorded and at this stage of fruit maturity (adapted from Schwabe et al., 1984) for 2

Infection criteria may have been met

Table 6.5 shows that rainfall occurred on a total of 17 occasions during December to March 1990/91. Rainfall exceeded 25 mm on only 3 occasions. The mean temperature during days when rain occurred rose from December to early February, but declined in March. Schwabe et al. (1984) showed that fruit susceptibility as indicated by an index figure (hours of wetness x °C) decreased through the season. Using this index the number of hours of wetness which would have been required for infection at the temperature recorded was determined.

Although it was not possible to determine the number of hours of wetness which occurred during the following periods of rain, it seems likely that the wetness requirement may have been met on at least three occasions during the December-March period.

During December over the three days it rained, a wetness period of between 17 and 22 hours would have been required for infection. The highest rainfall for December was 13.5 mm. It is unlikely that infection criteria were met.

In January rain fell on six occasions, with one fall of 70.5 mm. At the temperature prevailing that day 19 hours of wetness would have been required for infection. Infection criteria may have been met on this day. All other falls were less than 13 mm and the wetness period requirement for infection on those days ranged from 16 to 23 hours. A wet period of 4 days occurred from January 22-25 and yielded a total of 39 mm of rain. It is likely that the infection criterion of 23 hour's wetness was met over this period.

Rain fell on four occasions in February, with one fall of 34 mm, the rest being below 9 mm. The wetness period required for infection ranged from 17 to 25 hours, but was 24 hours on the day when the highest rainfall was recorded, when infection criteria may have been met.

In March the period of wetness required for infection ranged from 31 to 48 hours, but rainfall only exceeded 2.0 mm on one occasion, on March 30, at which time much of the fruit would have already been harvested.

Season 1991/92

The nil to very low levels of primary infection recorded were associated with a spring in which only five infection periods (four low and one high) occurred from mid September to the end of November. The high infection period which occurred on September 17 near the green tip stage of tree development, was of 72 hours of surface wetness duration, but was too early in the season to cause severe infection, because spore numbers would be low at this time (Gadoury and MacHardy 1986; MacHardy et al. 1993) and little susceptible tissue is exposed.

Table 6.6 indicates that in the 1991/92 season leaf scab was not detected by the end of December. Fruit scab was found in four orchards during the season but in only three orchards at harvest. Fruit scab did not exceed 0.2 percent and did not increase significantly in any orchard. No fungicides were applied during January to March in twelve orchards and two growers applied their final fungicide treatment as early as November.

Surface wetness and temperature data collected at West Batlow (Table 6.7) was used to examine the suitability of weather conditions for fruit infection from December to March 1991/92.

On 15 occasions in the period December to March, rain resulted in wet periods exceeding 10 hours in duration. In December two rain periods yielded in excess of 25 mm of rain. The 32 mm of rain which fell on December 15 caused the trees to remain sufficiently wet (51.5 hours) for Schwabe's index for infection to be exceeded. The wetness period required for infection on the other occasions when rain fell ranged from 23-38 hours but the index was not met by the rainfall which did not exceed 11 mm.

66

Table 6.6 Changes in percentage apple scab infection in fruit during secondary infection period, 1991

Orchard Leaf scab Fruit scab2 F Orchard Leaf scab

Dec Jan Feb Mar

A 0 0 0 0 0

B 0 0 0 0 0

C 0 0 0 0 0

D 0 0 0 0.1±0.I 0

E 0 0 0 0 0

F 0 0 0 0 0

G 0 0 0 0 0.1±0.1

H 0 0 0 0 0

I 0 0 0 0 0.2±0.1

J 0 0 0 0 0

K 0 0 0 0 0

L 0 0 0 0 0

M 0 0 0 0 0

N 0 0 0 0 0

0 0 O.liO.l 0 0 0

P 0 0 0 0 0

Q 0 - - 0 0

R 0 0.2±0.1 0 0 0.2±0.1

S 0 0 0 0 0

T 0 0 0 0 0

1 Peak leaf infection percentage during December/January 2 Peak fruit infection percentage each month 3 Fungicides applied during Janua Me, metiram; Zi, ziram; F, flusilazole; P, penconazole; Do, dodine; Fe, fenarimol

Table 6.7 Weather data for occasions when wet periods exceeding 10 hours and infection December 1991 to March 1992

Date1 Rainfall (mm) Mean temperature °C Fruit matuntyJ

1991

Dec 10 6 10 9

12 11 14 9

13 2 13 9

14 2 15 9

15 32 9 9

21 3 12 10

30 26 14 12

1992

Jan 3 3 11 12

23 15 18 15

Feb 4 4 16 17

6 1 18 17

9 7 13 17

10 25 16 18

12 1 15 18

23 8 13 19

1 No data available from January 5 - January 21 and from March 2 onwards 2 Mean temperature during wet period 3 Number of weeks from full bloom (mid October) cv. Red Delicious 4 Hours of wetness x °C at this maturity required for infection (Schwabe et ai, 1984) 5 Hours of wetness required at the average temperature recorded and at this stage of fruit maturity (adapted from Schwabe et ai, 1984) for 2 * Conditions for fruit infection met

In January rain fell on two occasions which yielded 3 and 15 mm of rain. The 25 to 36 hours of wetness required for infection on these occasions was not met. An equipment malfunction between January 5-21 meant that ASP data was not obtained. Official weather data indicated there was no rainfall.

In February rain was recorded on six occasions, of which one fall was 25 mm and the remainder did not exceed 8 mm. The wetness period required for infection on those days ranged from 30-39 hours and was not met on any occasion.

No weather data was available for March from the ASP, but official weather records showed that 46 mm rain fell on March 3 and a further 8 mm on March 4. Infection requirements are likely to have been met at this time.

Season 1992/93

Scab was well controlled in most orchards by heavy fungicide programs in spite of a wet spring in which thirteen primary infection periods were recorded from mid September until the end of November. Of the four low, four medium and five high level infections recorded, three of the high and one of the medium were recorded during October when trees are at their most susceptible.

In December, scab was recorded (Table 6.8) on either fruit or leaves or both on 9 orchards. The level of scab ranged from zero to 12.3 percent. Management problems resulted in the high levels of scab recorded in orchards I and R and fungicide resistance was detected in orchard O. These three orchards are disregarded in the following comments unless indicated.

There was no statistically significant increase in fruit scab levels in any of seventeen orchards. In four orchards no fungicides were applied in the January to March period. Of these, 3 had no scab recorded for the whole season whilst one (C) had a low level of fruit scab.

The numbers of fungicide applications applied varied from zero to seven. There was no relationship between the number of fungicides applied between January and March and the percentage of fruit infected.

In the two orchards (I and R) where management problems resulted in poor control of primary infection, 1.8 and 12.3 percent of fruit were infected in December. In orchard I no further sprays were applied after 22 December, and infection levels increased to 12.5 percent by March, indicating that infection criteria had been met in the district over this period. In orchard R 12.3 percent fruit infection increased to 23.1 percent in spite of the application of seven fungicide treatments, up to 2 March. These observations indicate the importance of the level of inoculum for disease increase.

Wet periods exceeded 10 hours duration on 15 occasions between December and March (Table 6.9).

In December infection criteria was met on December 3 and December 24 when rainfall of 50 mm and 43 mm resulted in wet periods of almost 37 hours and 44 hours respectively.

One infection period was recorded in January associated with the 21 mm of rain which fell on January 27 resulting in almost 29 hours wetness duration.

Infection criteria were not met in either February or March in spite of up to 33 mm of rain being recorded on one occasion (March 6).

69

Table 6.8 Changes in percentage apple scab infection in fruit during secondary infection period, 1992/

Orchard Leaf scab' Fruit scab F Orchard Leaf scab'

Dec Jan Feb Mar

A O.liO.l O.liO.l 0 0 0.2±0.1

B 0 0 0 - 0

C 0 0.2±0.2 0 O.liO.l

D 0 0.4±0.4 0.2±0.2 O.liO.l 0.2i0.2

E 0 0 0 0 0

F 0 O.liO.l 0.5±0.2 0.3±0.2 0.2i0.1

G 0 0.2±0.2 0 0.2i0.1 O.liO.l

H 0 0.4i0.3 0.4±0.2 0.3±0.1 0.8±0.3

1 1.1 ±0.5 1.8±0.8 2.2±1.0 12.6±4.8 12.5i4.9

J 0 0 0.9±0.4 0.4±0.2 0.6±0.3

K 0 0 0 0 0

L 0 0 0 0 0

M 0 O.liO.l 0 0.4±0.2 0.2i0.1

N 0 - 0 0.2±0.1 0.3i0.2

O 0.6±0.4 1.8±0.7 - 3.6±1.4 1.0i0.3

P 0 0 0.1 0.2 0

Q 0 0 0 0 0

R 12.7±1.8 12.3±2.8 27.2±3.2 14.9±2.3 23.1±2.3

S 0 0 0 0 0

T 0 0 0.6±0.3 UiO.l O.liO.l

1 Peak leaf infection percentage during Decmber/January. 2 Peak fruit infection percentage each month3Fungicides applied during Me, metiram; Zi, ziram; F, flusilazole; P, penconazole; Do, dodine; Fe, fenarimol; Mz mancozeb; Bu, bupirimate; Bi, bitertanol; Pf, pyrifen

Table 6.9 Wet periods exceeding 10 hours and infection periods for apple fruit recorded at Batlow fro

Date1 Rainfall (mm)

Mean temperature Fruit , maturity-^

Total we (h

Dec 3 50 15 8 36:

13 4 15 9 13:

20 12 15 10 2 3 :

22 1 14 10 12:

24 43 17 11 44:

Jan 22 12 16 15 14:

24 7 19 15 19:

27 21 17 16 28 :

Feb 9 11 18 17 12:

20 8 13 19 19:

21 8 8 19 19:

28 2 7 20 14:

Mar 6 33 14 21 35 :

8 6 13 21 32:

24 - 14 23 38:

1 No wetness data available from Dec 29 to Jan 15, but weather dry 2 Mean temperature during wet period 3 Number of weeks from full bloom (mid October) cv. Red Delicious 4 Hours of wetness x °C at this maturity required for infection (Schwabe et al, 1984) 5 Hours of wetness required at the average temperature recorded and at this stage of fruit maturity (adapted from Schwabe et al., 1984) for 2 p

no data * Conditions for fruit infection met

Table 6.10 Comparison of seasonal rainfall at BatlowW over spring and summer periods with long te

Month Long term average ('' >

1989/90 1990/91

September 121 57 94

October 127 125 135

November 85 112 15

Total 333 294 244

December 76 69 16

January 73 44 124

February 56 96 14

March 86 18 24

Total 291 227 178

Grand Total 624 521 422

1 Bureau of Meterology, Batlow Post Office 2 Mean for period 1886-1983

Comparison of seasons

Long-term rainfall averages for Batlow are compared with rainfall over the period of the experiment (Table 6.10). The springs of seasons 1989/90, 1990/91 and 1991/92 were generally below average in total rainfall, although rainfall in October when the greatest susceptibility to scab occurs was around average of slightly above in 1989 and 1990. October of 1991/92 was very dry. The rainfall figures for each month in 1992/93 season were well above average.

Rainfall for the December-March period was below average in 1989/90 and 1990/91, but was above average in 1991/92 and 1992/93.

The use of reduced rates of fungicide in SPDC orchards did not result in an increase in the levels of scab, however most savings of fungicide were brought about in orchards where growers ceased spraying at the end of the primary infection period.

Tomerlin and Jones (1983) point out that conditions for leaf infection and fruit infection differ. They showed that 27 days after petal fall conditions sufficient to establish foliage infection did not establish fruit infection. Fruit were most susceptible to infection until two weeks after petal fall while still pubescent. Schwabe et al. (1984) showed that as fruit increased in age the duration of the wetting period required for infection also increase. They found that infection indices (hour of wetness x °C) increased from 120 one week after full bloom to 590 twenty weeks after full bloom, for a 2 percent level of infection. Interrupted wet periods resulted in less fruit infection than did continuous wet periods, especially on older fruit.

The studies of Schwabe et al. (1984) were conducted with high concentrations of inoculum and estimates made of the infection criteria for a 2 percent fruit infection. Schwabe (1982) showed that as the concentration of spores decreased from 3.7 x 10^ to 1.24 x 10^ viable conidia per mL of spore suspension, the severity of scab on mature fruit decreased from 97.8 to 1.1 percent. They point out that natural infections should be less severe because inoculum levels are low where primary scab has been well controlled. The infection criteria required for a 2 percent fruit infection probably cause significantly less infection in orchards where inoculum potential is low.

Over the three seasons studied fruit scab did not increase significantly in orchards with low levels of infection at the end of the primary infection period in spite of infection criteria being met in each season. The 1990/91 season saw a wet four day period in January which would probably have met infection requirements and this was followed by a marginal potential infection period in February. In the 1991/92 season infection criteria were met in December, but not again for the rest of the season. In the 1992/93 season infection conditions occurred twice in December and once in January. In the latter two of the three seasons studied, where a surface wetness sensor was available, infection criteria were not met after January.

Therefore in orchards with low inoculum levels at the end of the primary infection period, a combination of increasing plant resistance, falling temperatures and the general absence of long rain periods suggest that the risk of infection decreases as the season progresses. Inoculum levels are extremely low in many of the orchards and in all years some orchards recorded nil scab in spite of cessation of spraying early in the season. This indicates that at least at these locations infection from sources outside the orchard in question is extremely low as suggested by MacHardy and Jeger (1983), and that most infection arises from inoculum within the orchard itself.

In the majority of cases scab did not exceed 1% fruit infection regardless of the fungicide program.

In the two orchards experiencing high levels of infection in December 1992, infection levels did increase greatly, in spite of (in one case) the application of seven fungicide sprays.

73

Table 6.11 The effects of weather patterns in spring (September-December) and summer (Janu epiphytotic

Weather pattern Spring weather (Sept-Dec)

Summer weather (Jan-Mar)

Prim inf

A Wet Dry

B Wet Wet

C Dry Dry

D Dry Wet

Table 6.11 indicates the four possible combinations of weather patterns and their relationship to potential scab levels. The weather in the primary infection period establishes the inoculum potential, whilst the weather in the second half of the season provides the conditions for increase in disease levels. In three of the four scenarios, disease increase in the latter half of the season is not favoured.

Of the weather patterns listed in Table 6.11, 1989/90 and 1990/91 correspond to type C, 1991/92 to type D and 1992/93 to type B. Of these season types, only type D favoured a serious epiphytotic.

Since there is currently a strong desire to reduce pesticide residues in food crops (Anon. 1991b), any technique which reduces the number of sprays applied towards the latter half of the season should be pursued. Jones (quoted by McHugh 1991) points out that it may well be better to apply more sprays in the early part of the season to gain disease control so that less sprays are required as the fruit nears maturity. Early season control using a 'strategic' approach (Penrose, 1989) of protectant sprays backed up with curative sprays when required can provide good primary season control. This approach would assist in keeping pesticide residues at a low level.

There is however a need for caution in reducing spray applications in the second half of the season where scab levels are moderate to high, in that prolonged wet weather may see an increase in scab levels and especially storage scab (Schwabe 1980a) if remedial measures such as curative sprays are not applied when required. Schwabe (1980a) found that late applications of curative fungicides (benomyl, dodine and triforine) were only effective if applied earlier than 72 hours after the beginning of an infection period at 15°C. However mancozeb and dodine, when sprayed in the orchard, protected mature fruit for 48 days and 7 to 13 days respectively. He concluded that curative fungicides will control storage scab under conditions of low inoculum potential but that at moderate to high inoculum potential it is necessary to apply a protective fungicide every 3 to 4 weeks during the second half of the growing season. Tormerlin and Jones (1983) showed there was a direct relationship between disease level at harvest and subsequent occurrence of new lesions during storage.

The number of new lesions that appeared during storage was greatest on fruits with most infections pre-harvest. It appeared that the pathogen did not spread from scabbed to uninfected fruit.

Table 6.12, based on the work of Schwabe et al. (1984) shows that the length of wet period required for infection in summer/autumn is relatively long. Therefore it is unlikely that summer storms would provide sufficient surface wetness in most case for infection to occur especially late in the season. It should be possible for orchardists to estimate the likelihood of conditions for infection being met since this will only occur during prolonged rain periods. It is only when infection levels in December are very low that growers are able to take this risk.

Schwabe (1980b) suggested that regular orchard inspections were of utmost importance during the entire growing season so that the scab position of each orchard is always known. Control measures should be adapted to the prevailing weather conditions and the scab potential of the specific orchard. The detailed observations made in an IPDM program mean that the orchardist can be quite sure of the level of scab in his orchard and is therefore in a position to make informed decisions on disease control measures. Knowing the level of inoculum present (i.e. disease potential) and the weather, he can assess the likely risks from either ceasing to spray after the primary infection period or relying on curative treatments.

Good control of scab in the primary infection period will result in little or no inoculum present for the second half of the season. If the second half of the season is wet and no infection is found it is possible to avoid spraying. If low amounts of inoculum are present curative control may be employed to minimise the number of sprays applied.

75

Table 6.12 Wetting requirements for infection of apple fruit (cv. Granny Smith) by apple sca temperatures

Date Fruit Index maturity' required

late December 10 370

late January 15 455

late February 20 525

late March 25 590

1 Weeks after full bloom 2 Adapted from Schwabe et al. (1984) 3 Wetness period required for infection at this maturity and temperatures

6.8 Powdery Mildew

Powdery mildew levels were not of concern in the Delicious variety, on which most assessments relating to SPDC were made. In one orchard Granny Smith continued to suffer undesirably high levels of disease, but this was patchy and related to the density of the canopy.

It is suggested that provided control of scab with reduced levels of fungicide can be obtained, little concern will be required for providing mildew control in the Delicious variety.

6.9 Number of insecticide treatments applied and pest damage

The mean number of insecticide treatments applied (Table 6.13) varied both between and within grower groups and between seasons. The number of insecticides applied by each grower in both groups varied in 1990/91 from 7 to 16; in 1991/92 from 7 to 14 and in 1992/93 from 7 to 15.

The mean number of insecticide treatments applied was more consistent between seasons when compared with the number of fungicide treatments (Figure 6.5).

Losses due to insect damage in 1990/91 ranged from 1.12 to 9.09% in the advised group compared with from 0.76 to 8.2% in the non-advised group. In 1991/92, advised group losses ranged from 0.2 to 1.32% compared with from 0.24 to 2.0% in the non-advised group. In 1992/93, losses in the advised group ranged from 0.36 to 8.8% and 0.4 to 3.2% in the non-advised group.

6.10 Number of fungicide treatments applied and scab infection

The number of fungicide treatments applied varied between growers in each year of the survey and in each group (Table 6.14). In the 1990/91 season, the advised growers applied an average of 15 fungicide sprays but the number ranged from 11 to 22. The mean for the non-advised group was ten, which was significantly less than that used by the advised group with a range 8-20. The level of apple scab varied from 0-1.80% in the advised group, and from 0-5.84% within the non-advised group. There was no relationship in either group between the number of sprays applied and the level of scab (Figure 6.5).

In the second season there was no significant difference between the two groups in the mean number of fungicides applied, but the range between growers was 8-16 for the advised growers in 1991/92, and 5-14 for the non-advised group. There was no relationship between the number of sprays applied and the level of scab, which ranged from nil to 0.12%.

In the third season, there was again no significant difference in the mean number of sprays applied by the two groups, but the range between growers in the advised group was 10-25 sprays and from 9-21 in the non-advised group. Scab level in the advised group ranged from nil to 1.12%, and from nil to 22.04% in the non-advised group.

The mean number of fungicide applications varied by nearly 50% between seasons in both groups (Table 6.14).

6.11 Amount of pesticide product applied per hectare

The amount of pesticide product applied per hectare (Table 6.15) varied from season to season in both groups, the 1992/93 season seeing greatest usage. The total weight of product applied varied between growers in both groups, although this was very much influenced by whether petroleum oil was used, which is applied at higher rates than most products.

77

Table 6.13 Numbers of insecticide sprays applied and the percentage of insect damage fruit reco

Grower and group 1990/91 sprays

Damage 1991/92 sprays

D

Advised A 9 9.09 10

B 11 3.48 9

C 8 6.64 11

D 16 10.04 9

E 11 1.12 8

F 9 1.40 9

G 11 2.50 9

H 12 3.96 11

I 14 3.24 12

J 14 2.04 7

Mean 11.5 4.35 10.2

s d a 2.55 3.16 2.82

Coefficient of variation (%) 22.1 72.6 27.6

Non-advised An 11 3.96 12

Bn 16 0.76 12

Cn 7 0.96 12

Dn 17 8.20 12

En 16 3.92 12

Fn 9 6.00 14

Gn 11 4.56 7

Hn 8 0.92 9

In 8 2.64 12

Jn 11 7.00 12

Mean 11.4 3.89 11.4

s d a 3.69 2.62 1.96

Coefficient of variation (%) 32.3 67.3 17.2

aSample standard deviation

Table 6.14 Numbers of fungicide sprays applied and the percentage of apple scab infected fruit

Grower and group 1990/91 Sprays

Scab 1991/92 Sprays

Advised A 12 1.12 11

B 21 0 11

C 14 0 12

D 22 0.44 13

E 17 0.64 16

F 19 1.80 8

G 11 0.56 10

H 13 0 12

1 11 0.48 9

J 14 0.04 9

Mean 15.4 0.51 11.1

s d a 4.09 0.58 2.33

Coefficient of variation (%) 26.8 113.7 20.9

Non-advised An 8 0 11

Bn 20 0.12 14

Cn 8 0 8

Dn 9 5.84 10

En 12 0.76 11

Fn 8 0 8

Gn 10 0.04 8

Hn 8 0.04 5

In 12 0 10

Jn 9 0.2 9

Mean 10.4 0.7 9.4

s d a 3.71 1.73 2.41

Coefficient of variation (%) 35.6 247.0 25.6

'Sample standard deviation

Figure 6.5 Changes in synthetic pesticide use over four seasons at Batlow, NSW

105

100

95

90

85

80

75

Total insecticides / miticides

Advised

k^ Control > A

198Sl/1990 1993/1991 199171992 1992/1993

CO

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T 3 • >-<

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&

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200

180

160

140

120

100

V .

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1989/1990

Total fungicides

Advised

' A

1990/1991 1991/1992

>

Control

1992/1993

280

260

240

220

200

180

1989/1990

Total pesticides

1990/1991 1991/1992

Advised

Control

1 1992/1993

80

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6.12 Number of pesticide treatments, disease and pest damage and the amount of pesticide used averaged over three seasons

Table 6.16 shows the mean number of pesticide sprays used, the amount of pesticide, and the level of disease and pest damage over three seasons. The coefficient of variation for the number of fungicide sprays applied was 36.5% and for insecticides was 23.1%. This was reflected in a similar variation in the amount of pesticide applied. The coefficients of variation for apple scab and insect damage were 400% and 108% respectively, over the three seasons and between the 20 orchards.

6.13 Comparison of weather between seasons

Long-term rainfall averages were compared with rainfall over the period of the experiment (Table 6.17). The springs of 1990/91 and 1991/92 were generally below average in total rainfall, although rainfall in October when the greatest susceptibility to scab occurs was around average or slightly above in 1990/91. October 1991/92 was very dry. The monthly figures for each month in the spring of 1992/93 were far above average. Rainfall for the December-March period was below average in 1990/91, but was above average in 1991/92 and 1992/93.

Regression analysis over all data showed that there was no relationship either between the number of fungicide sprays applied and the level of apple scab infection, or between the number of insecticide sprays used and the losses due to insect damage. The relationship was not altered by allowing separate regressions for each year and group. The number of fungicides applied varied with the season, being highest in 1992/93 which experienced a wet spring, whilst the number of insecticides used was more constant from season to season.

82

7.0 OVERVIEW OF PESTICIDE REDUCTION

Fungicides comprise the greater proportion of pesticides applied to apples, yet until recently almost all research on SPDC in apples has addressed insect problems and insecticides. This has in part been due to less concerns over fungicides, which are generally less acutely toxic than insecticides, but also because of the problems of setting economic thresholds. The short generation time and the large number of propagules produced by organisms like the apple scab fungus means that an epiphytotic can develop with alarming speed. Because of this farmers are reluctant to reduce the number of sprays applied, and tend to increase applications when seasons are wet, as in the 1992/93 season.

A feature which emerged from the study was the high level of variation between orchards in the number of pesticides treatments applied (both fungicides and insecticides). This variation amounted to 200% or more in the 1990/91 and 1992/93 seasons. Similarly, Wilton (1993), found that the cost of chemicals (and presumably the amount) used on apples in the same season varied by 275% in different orchards in New Zealand. The variability in the number of fungicides applied occurred in both the advised and non-advised groups and was not related to the level of scab infection, when growers were free to choose both the number and timing of fungicide applications.

Penrose (1995) pointed out that reducing fungicide use offers very little cost saving but increases the risk of economic loss. Beresford and Manktelow (1994) found that when the savings from reduced fungicide use (by timing sprays and utilising weather information) were weighed against increased harvesting and grading costs, and the revenues losses from increased disease, there was little economic incentive for apple growers to reduce fungicide use. Consequently growers are inclined to apply extra fungicide sprays as 'insurance' against possible infection.

The number of insecticide sprays applied also varied between growers in each group and there was no correlation between the number of treatments and insect damage. In the advised group all insecticide sprays were advised on the basis of population estimates and therefore the variability was due to differences in pest risks between the orchards. The number of insecticides applied by the non-advised group was similar to the advised group and therefore these orchards were managed equally effectively.

The selection of volunteer cooperators may have biased the work in that the volunteers for the advised program may have felt they had a problem with obtaining a desired level of disease control, or that their use of pesticides was excessive. In contrast non-advised volunteers may have considered they were already using minimum amounts of pesticides. The introduction of SPDC failed to result in a reduction in pesticide use in this district. How then is a move towards reduced pesticide use to be accomplished? This study found, as did Tait (1977) that some growers consistently used more, and others less pesticide than the average. The use of a pest management scout did not reduce this variability in our study and may support the tentative finding of Norgaard (1976) that farmers who adopt pest management consultants perceive greater risks of pest management and are more risk averse than those who do not use consultants.

Mumford (1977) points out that it is the farmer's perception of pest hazard and not the actual level of attack which could occur that causes him to apply an insecticide. The same statement could be made for fungicides. It appears from our work that growers perceive the risks of pests and disease differently. The coefficients of variation of the number of fungicides was much greater than of the insecticides used, suggesting there was more variation between growers in the perceived risks of apple scab than of insect damage. Tait (1978) found that farmers tend to be more risk averse if they had a larger investment in the crop and in most cases attempted to reduce variability as much as possible (Norton 1976).

The problem with targeting pesticide use reduction on a kilogram basis was evident from our study. The amount of product applied varied by over 300% in the 1992/93 season. This variation was emphasised by the use or non use of summer spraying oil for mite control, a chemical which is generally regarded as

83

Table 6.16 Number of fungicides, percentage scab, number of insecticides, percentage insect damage, an three seasons

Number of fungicides Scab (%)

Mean 13.3 0.76

Standard deviation 4.85 3.06

Coefficient of variation (%) 36.5 400.0

Number of insecticides

10.9

2.53

23.1

Table 6.17 Seasonal rainfall over spring and summer periods compared with long-term averages

Month Long-term averagea (mm) 1990/91

September 121 94 October 127 135 November 85 15 Total 333 244

December 76 16 January 73 124 February 56 14 March 86 24 Total 291 178

Grand Total 624 422

a Australian Bureau of Meteorology, mean for period 1886-1983

of low toxicity and environmental impact, but which is applied at high rates per hectare. The determination of the total amount of pesticide product applied per hectare, whilst being a crude measure, indicates the problems of measuring pesticide use reduction in this way.

This study highlights the problem of industry or government targets for pesticide use reduction on the basis of either tonnage or number of sprays applied across an industry, where variability between growers and seasons can be greater than the reductions sought. The authors consider that reductions should be made by attempting to bring heavy users of pesticides to a level found generally adequate for pest and disease control, which could be regarded as best practice for that industry. More account also needs to be taken of the properties of particular chemicals in terms of their environmental effects and compatibility with integrated pest management among others. Because of the effect of weather on pest and disease occurrence, an allowance for this factor needs to be made when setting goals. Penrose et al. (1994) have suggested an index whereby the properties of the pesticides are compared when targeting a reduction of the impact of pesticides on residues in foodstuffs and the environment. An accreditation scheme based on this concept has been developed for apples (Penrose et al. unpublished) which may provide a financial incentive for individual farmers to adopt pesticide reduction strategies and cause heavy users of pesticides to reduce their spray programs.

Unless either the risks of loss associated with less insecticide, and more especially fungicide use, can be reduced, or compensation received for risk-taking, some growers will continue to use more pesticide than is found necessary by their neighbours.

86

8.0 CONCLUSION

The appointment of a full time pest manager and the establishment of a pest and disease monitoring and advisory service was implemented successfully. An integrated pest and disease management (IPDM) package with protocols for monitoring and action thresholds was established and implemented. With amendments over the trial period these successfully managed the pest species as they occurred. Monitoring and action thresholds were established for the insect pests, codling moth, lightbrown apple moth, apple dimpling bug, plague thrips, woolly aphid, San Jose scale, mites and the diseases, apple scab and powdery mildew.

Twenty growers, members of the Batlow Fruit Cooperative, volunteered to take part in the project, ten of whom formed the Supervised Pest and Disease Control (SPDC) group and benefited from the advisory service. The long term financial viability of the monitoring and advisory service will ultimately depend on demonstrating the benefits, increasing grower participation and ensuring the service remains relevant to grower needs, i.e. meets industry standards and embraces new technologies.

This study found that most growers under the SPDC program following advice based on extensive pest and disease monitoring benefited from improved pest management and were able to make some reductions to their use of pesticides, if only to the level used by the control group.

Sex pheromone traps enabled the pest manager to detect the spring emergence of codling moth, establish a biofix, and monitor the moth's population through the season. Starting at biofix the degree-day phenology model was able to predict the presence of codling moth's vulnerable life stages and time the application of an appropriate insecticide, i.e. the egg stage for fenoxycarb users and the larval stage for azinphos-methyl users. In most seasons, depending on temperature, the codling moth has two or more generations. Effective control of the codling moth's first generation is very important and will reduce the numbers in later generations.

Restarting the degree-day phenology model with each subsequent generation's main flight improved the models ability to predict the timing of later generations and their vulnerable life stages, enabling sprays to be applied accordingly. These techniques enabled some growers, who had previously commenced their spray program early and followed a calendar schedule through the season, to delay their first application until the presence of codling moth was detected. For some growers this reduced the overall number of sprays applied for codling moth control by one per season. However, this reduction in sprays may have been responsible for the higher level of fruit damage by lightbrown apple moth incurred by the SPDC group in the 1992/93 season.

The new strategy of applying chlorpyrifos at late pink to control apple dimpling bug was trialed by the SPDC group and found to be very effective. It enabled these growers to replace their previous program of multiple applications of endosulfan with a single strategically timed application of chlorpyrifos with no loss of control. The new strategy was quickly taken up by growers in the control group.

Woolly aphid was not a severe problem during the trial for either group and it is likely that the adoption of chlorpyrifos for apple dimpling control may have some beneficial effects in controlling woolly aphid. San Jose scale was controlled effectively with petroleum spray oils throughout the trial period.

Monitoring allowed the SPDC group to identify an "actual" rather than perceived need for miticide sprays. Eliminating the perceived risk factor so that growers sprayed only when needed resulted in fewer miticides being applied.

SPDC did not result in fewer fungicide applications. However, the study found that the amount of fungicide used could be reduced by 20% without loss of control by reducing the dose rate to 80% of the recommended label rate at each application. Establishing control of apple scab early in the season

87

enabled growers to withhold fungicides after Christmas if monitoring showed that no primary infection was present.

Seasonal variation in weather conditions caused seasonal variation in pest populations and disease threat and hence the variation in the number of pesticides applied each season.

In general most growers use pesticides responsibly, but vary greatly in their attitude to risk, with some applying pesticides as a preventative measure with respect to a perceived risk rather than in direct response to an observed pest problem. Other growers are already using minimal spray programs and further large reductions for these growers are unlikely unless alternatives to broad spectrum insecticides are developed. Likewise further reductions in fungicide use will require alternatives to the synthetic fungicides currently available.

The Australian pome fruit industry as a signatory to the 1991 Pesticide Charter has set itself a difficult goal and the likelihood of achieving the 50% reduction in pesticide usage by 1996, based on current pest control strategies is low.

88

9.0 ACKNOWLEDGMENTS

The authors would like to express their gratitude to the Batlow Co-operative and in particular to those members who volunteered to take part and without whom this project would not have been possible.

Mr. P. Amadio, Mr. K. Bagnall, Mr. B. Bowden, Mr. N. Bowden, Mr. A. Casey, Mr. N. Cook, Mr. D. Duffy, Mr. P. Forsyth, Mrs. M. Gedye, Mr. I. Gilbert, Mr. R. Heatly (Snr.), Mr. R. Heatly (Jnr.), Mr. M. Herring, Mr. S. Kendal, Mr. R. McLeod, Mr. G. Pryce, Mr. J. Reynolds, Mr. J. Robson, Mr. R. Sedgewick, Mr. J. Sharp, Mr. M. Smart, Mr. G. Walsh and Mr. A. Vanzella.

We would like to express our highest regard and thanks to Mr. Kevin Dodds, the project's pest manager, who worked tirelessly to ensure this project was brought to a successful conclusion.

We would also like to thank Ms. Helen Nicol, Special Biometrician, NSW Agriculture, Orange, for her assistance with statistical analysis and Mrs. Marion Eslick, Technical Assistant, NSW Agriculture, Orange for her assistance in the field.

We are grateful to the Horticultural Research and Development Corporation and the Batlow Fruit Co­operative Ltd who provided the funding for this project.

Thank you all.

89

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95

11.0 APPENDICES

11.1 Scientific Publications

Penrose, L.J. 1991. Reducing pesticide usage in apples. Abstract of poster. 8th Australasian Plant Pathology Society Conference, Sydney, 8-11th October 1991.

Penrose, L.J. 1992. The significance of selection of infection model and climatic parameters on the operation and benefits of a primary apple scab warning service. Plant Protection Quarterly 7. 12-16.

Bower, C.C., Penrose, L.J. and Dodds, K. 1993. A practical approach to pesticide reduction on apple crops using supervised pest and disease control - preliminary results and problems. Plant Protection Quarterly 8. 57-62.

Penrose, L.J. 1993. Fungicides in horticulture - avenues and potentials for a reduction. 9th Australian Plant Pathology Society Conference, Hobart. 4-8 July 1993. Abstract No 104.

Penrose, L.J., Thwaite, W.G. and Bower, C.C. 1994. A rating index as a basis for decision making on pesticide use reduction and for accreditation of fruit produced under integrated pest management. Crop Protection 13. 146-152.

Dodds, K.A., Penrose, L.J., Bower, C.C and Nicol, H. 1994. The importatnce of pest and disease damage as a cause of commercial downgrading of apple fruit. Australian Journal of Experimental Agriculture 34. 431-434.

Penrose, L.J., Thwaite, W.G. and Bower, C.C. 1994. Pesticide use reduction - logical decision making. Proc. 47th New Zealand Plant Protection Society Conference, Waitangi, August 1994.

Penrose, L.J. and Dodds, K.A. 1994. Incidence of Venturia inaequalis on apple fruit during the second half of the season under different fungicide and weather regimes. New Zealand Journal of Crop and Horticultural Science 22. 251 -261.

Penrose, L.J. 1995. Fungicide use reduction in apple production - potentials or pipe dreams? Agriculture, Ecosystems and Environment 53. 231-242

Penrose, L.J. and Nicol, H.I 1995. Microclimate variation within apple tree canopies and between sites in relation to Venturia inaequalis infection. 10th Biennial Australasian Plant Pathology Society Conference,Christchurch, NZ. Abstract No 257.

Penrose, L.J. 1996. Reduced dependence on pesticides in apple orchards in Australia. Pesticide Outlook 7. 13-19.

Penrose, L.J., Bower, C.C. and Nicol, H.I. 1996. Variability in pesticide use as a factor in measuring and bringing about reduction in pesticide usage in apple orchards. Agriculture, Ecosystems and Environment 59. 97-105.

Penrose, L.J. and Nicol, H.I. 1996. Aspects of microclimate variation within apple tree canopies and between sites in relation to potential Venturia inaequalis infection. New Zealand Journal of Crop and Horticultural Science 24. 259-266.

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11.2 Extension Publications

Bower, C.C. and Penrose, L.J. 1990. 'Batlow Supervised' Pest Control Project Newsletter No. 1. October 1990.

Bower, C.C. and Penrose, L.J. 1990. 'Batlow Supervised' Pest Control Project Newsletter No. 2. 15 November 1990.

Bower, C.C. and Penrose, L.J. 1990. 'Batlow Supervised' Pest Control Project Newsletter No. 3. 15 February 1991.

Bower, C.C. and Penrose, L.J. 1990. 'Batlow Supervised' Pest Control Project Newsletter No. 4. 24 April 1991.

Penrose, L.J. 1991. Pesticide reduction research. Pomefruit Newsletter, Department of Primary Industry, Tasmania, No. 12, November 1991. AAPGA Conference Supplement, pp.1-5.

Bower, C.C, Penrose, L.J. and Dodds, K. 1991. Batlow Supervised Pest Control Project Newsletter No. 5, 20 December 1991.

Bower, C.C, Penrose, L.J. and Dodds, K. 1991. Batlow Supervised Pest Control Project Newsletter No. 6, April 1992.

Bower, C.C, Penrose, L.J. and Dodds, K. 1993. Batlow Supervised Pest Control Project Newsletter No. 7, 28 January 1993.

Penrose, L.J. 1993. Reducing fungicide usage in apples - the importance of disease carryover. Fruitwise No. 13, NSW Agriculture. 1-2.

Penrose, L. 1993. Importance of disease carryover. Pomefruit Newsletter, No. 18, May 1993. Department of Primary Industry, Tasmania. 49.

Penrose, L.J. 1994. Apple fruits become less susceptible to scab over the season. Fruitwise No. 17, NSW Agriculture. 1-2

Penrose, l.J. 1994. Apple fruits become less susceptible to scab over the season. Pomefruits Newsletter No. 22. Department of Primary Industries and Fisheries, Tasmania. 41.

11.3 Lectures and Conference Contributors

Penrose, L.J. 1990. 'Apple Scab'. Invited speaker to seminar by Batlow Fruit Cooperative Ltd (17th January 1990), Batlow.

Penrose, L.J. 1990. 'Apple scab warning services in NSW. Invited speaker to Cropwatch Conference (24th July 1990), Melbourne.

Bower, C.C. and Penrose, L.J. 1991. 'Reduction in pesticide use in apples by supervised pest control'. Batlow Fruit Cooperative Ltd, Pomefruit Seminar (31st July 1990), Batlow.

Penrose, L.J. 1991. Seminar for cooperators in 'Supervised Pest & Disease Control in Apples' Project. (12th July 1991), Batlow.

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Penrose, L.J. 1991. Reducing fungicide usage in apples. Australian Apple and Pear Growers Association, 46th Annual Conference, Hobart 5-7th August 1991. Invited guest speaker. (7th August 1991), Hobart.

Penrose, L.J. 1991. Apple Pest and Disease Control Seminar, Batlow. Batlow 'Supervised Pest Control Project - Report of First Season's Results'. (20th August 1991), Batlow.

Penrose, L.J. 1991. IPM and Strategic Pest and Disease Management. NSW Agriculture-Incitec Ltd Workshop. Future Horticultural Pest & Disease Management. (26th August 1991), Orange.

i) IPM and Strategic Pest Management Research ii) Pesticide Resistance Management

Penrose, L.J. 1991. Reducing fungicide usage in apples. 8th Australasian Plant Pathology Society Conference, Sydney 9-11th October 1991.

Penrose, L.J. 1992. 'Reducing fungicide usage in apples'. MAF, Hastings, New Zealand (17th August).

Penrose, L.J. 1992. 'Batlow Supervised Pest Control Project Update - Apple diseases 1991/92'. Batlow September 1992 - Plant and Disease Management Seminar (NSW Agriculture and Batlow Fruit Cooperative).

Penrose, L.J. 1992. 'The potential for scab increase in the second half of the season'. Apple Pest and Disease Management Seminar, Batlow 3 September 1992. (NSWAgriculture and Batlow Fruit Cooperative).

Penrose, L.J. 1993. 'Reducing fungicide usage in apples - Progress in NSW. National Field Day on Plant Protection Strategies for Control of Diseases and Pests in Pomefruit Orchards. Grove, Tasmania 23 February 1993.

Penrose, L.J. 1993. Fungicides in horticulture - avenues and potentials for use reduction. 9th Australasian Plant Pathology Conference, Hobart, 6 July 1993. Invited speaker. Plenary session.

Bower, C.C., Penrose, L.J. and Dodds, K. 1993. 'Integrated pest and disease management at Batlow'. The Nature of the Nineties. Proceedings of the Batlow Fruit Cooperative Seminar, 27 July 1993.

Penrose, L.J. 1993. 'Scab and mildew Results' Batlow Fruit Cooperative - NSW Agriculture, Apple Research Workshop, Batlow, 25 August 1993.

Penrose, L.J. 1993. 'Pesticide Reduction Index'. Batlow Fruit Cooperative - NSW Agriculture, Apple Research Workshop, Batlow, 25 August 1993.

Penrose, L.J., Thwaite, W.G. and Bower, C.C. 1994 Pesticides use reduction - logical decision making. 47th New Zealand Plant Protection Society conference, Waitangi, August 1994.

Penrose, L.J. 1994. Pesticide use reduction - logical decision making. Australian Apple and Pear Growers Association Annual Conference, August 22-27, 1994.

Penrose, L.J. 1995. Epidemiology of apple scab, Integrated Pest Management Forum Hobart 27-28 July 1995.

Penrose, L.J. 1995. IPDM fruit - measuring pesticide use by PESTDICIDE. Batlow Fruit Cooperative Ltd Technical Workshop '95, 6 September 1995.

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