ap98073 establishment of post-harvest treatment...

AP98073 Establishment of post-harvest treatment standards for apples

F Page, P Nimmo. et al Queensland Horticulture Institute

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AP98073 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 the Queensland Fruit and Vegetable Growers Association.

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) HRDC ISBN 0 7341 0120 1

Published 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: [email protected]

© Copyright 2000

HRDVC

HORTICULTURAL RESEARCH & DEVELOPMENT CORPORATION

Partnership in horticulture

mailto:[email protected]

HORTICULTURAL RESEARCH AND DEVELOPMENT CORPORATION

'ESTABLISHMENT OF POST HAR VEST TREA TMENT STANDARDS FOR APPLES "

AP 98073

Final Report - July 28 2000

F.D. Page, P.R. Nimmo, RJ. Corcoran and P. Peterson.

Compiled by F.D. Page and P.R. Nimmo

Queensland Horticulture Institute Applethorpe Research Station

Horticultural Research and Development Corporation

Final Report for Project AP 98073

Establishment Of Post Harvest Treatment Standards For Apples

by FD Page, PR Nimmo, RJ Corcoran and PM Peterson

Queensland Horticulture Institute Applethorpe Research Station, QDPI

Phone: (07)4681 1255 Email: pageflgtdpi.qld.gov.au

F a x : ( 0 7 ) 4 6 8 1 1 7 6 9 nimmoplaklpi.qld.gov.au

July 2000

Purpose of report: To report on the successful post-harvest immersion dipping treatment for apples using dimethoate and to report failure to achieve adequate control of Queensland fruit fly when using a whole bin flood spray method.

Funding for this research was provided by HRDC, Queensland apple growers, QFVG, Queensland Horticulture Institute.

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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http://nimmoplaklpi.qld.gov.au

ACKNOWLEDGEMENTS 4

MEDIA SUMMARY 5

TECHNICAL SUMMARY 5

INTRODUCTION 7

MATERIALS AND METHODS 8

Apples 8

Infestation - Indooroopilly 8

Treatment - Applethorpe 8

Holding - Indooroopilly 8

Treated larvae, washed and waxed after standing 6 hours 9

EFFICACY STUDIES 13

RESIDUE STUDIES 14

RESULTS 16

Efficacy Trials 1 and 2 1999 16

Residues 16

Efficacy 17

DISCUSSION 24

REFERENCES 25

TECHNOLOGY TRANSFER 25

RECOMMENDATIONS 25

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ACKNOWLEDGEMENTS

The research presented in this report was jointly funded by the Horticultural Research and Development Corporation, Queensland apple growers, QFVG, and the Queensland Horticulture Institute.

The compiling authors wish to acknowledge the assistance of a number of people who allowed the project to proceed successfully.

• Memo and David Mattiazzi, Thulimbah, for the use of their packing shed, flood spray equipment and washing, waxing and packing line. Also for their cooperation in all aspects of the trials carried out at their site.

• Mai and Jeff McMahon, Pozieres, for the use of their packing shed, immersion dipping equipment, washing, waxing and packing line. Also for their cooperation in all aspects of the immersion trials conducted in their shed.

• Chandra Smith, Chris Danaher and Lynette West for their casual assistance with the dipping and flood spray trials at inconvenient times.

• To the post -harvest group at Indooroopilly for their skill in infesting the fruit, breeding out surviving flies, analysing and collating the data (LM Heslin, M. Eelkema, and EV Jen).

• To Alan Noble, Senior Chemist, Bill Osborne and Robert De Hayr, Senior laboratory Technicians, at the Pesticide and Product Quality Resource Sciences Centre for the conduct of the pesticide analyses, fruit residues analyses, and water quality analyses. These data are essential for documenting such trial work.

• To the manager and farm staff at Applethorpe Research Station for the use of vehicles for transporting bins of apples, and the use of the shed.

Media Summary

With the introduction of ICA requirements for interstate movement, several Queensland growers began preparations for accreditation of their treatment and packing facilities. It then became evident that two problems existed with acceptance of current commercial practices.

Firstly, full dimethoate immersion dipping of fruit was the only recognised treatment. Most commercial facilities currently use a "bin flooding" application system similar to that used for the application of DPA prior to placing fruit in controlled atmosphere storage. This application method was not recognised under the provisions of ICA. Secondly, ICA requirements stipulated that the dimethoate application was to be the final treatment applied prior to packing. Commercial packing lines are currently arranged to have dimethoate treatment followed by washing and wax application prior to packing.

During 1999 two dimethoate "Bin flooding" trials conducted in a commercial packing shed failed to meet the required standards of efficacy (99.5%) against egg and larval infestation by Queensland fruit fly, even with the addition of wetting agent. The washing and waxing generally reduced the efficacy of the treatment still further. For the year 2000, Victoria agreed to accept apples from Queensland if treated using the standard ICA treatment of immersion dipping pending further trial work to validate the efficacy for apples. There is no history of fruit fly infestation problems in apples consigned to Victoria.

In March 2000 an immersion dipping trial using apples of the Gala cultivar was conducted in a commercial packing shed at Stanthorpe.

The results of this treatment proved : 1. That commercial full immersion dipping dimethoate application system achieves

the required efficacy of 99.5 % or better against larvae and eggs of Queensland fruit fly.

2. That this same application system followed by washing and waxing of fruit at 3, 6, or 20 hours after immersion dipping still achieves required efficacy. That waxing of fruit after immersion dipping of fruit does not result in excessive dimethoate residues in any part of the fruit.

The results ensure the development and promotion of economical and commercially-applicable treatment procedures which can be incorporated into ICA agreements for Queensland apples destined for the fruit fly sensitive markets of Victoria and South Australia. In the past, approximately $ 750,000 worth of apples have been sent to these markets by Queensland each year.

Technical Summary

With the introduction of ICA requirements for interstate movement, several Queensland growers began preparations for accreditation of their treatment and

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packing facilities. It then became evident that two problems existed with acceptance of current commercial practices.

Firstly, full dimethoate immersion dipping of fruit was the only recognised treatment. Most commercial facilities currently use a "bin flooding" application system similar to that used for the application of DP A prior to placing fruit in controlled atmosphere storage. This application method was not recognised under the provisions of ICA. Secondly, ICA requirements stipulated that the dimethoate application was to be the final treatment applied prior to packing. Commercial packing lines are currently arranged to have dimethoate treatment followed by washing and wax application prior to packing.

During 1999 two dimethoate "Bin flooding" trials conducted in a commercial packing shed failed to meet the required standards of efficacy (99.5%) against egg and larval infestation by Queensland fruit fly, even with the addition of wetting agent. The first trial was conducted in March with a flood spray exposure time of only 20 seconds, without the use of a wetting agent. This exposure time was increased to 69 seconds, with the addition of a wetting agent Agral 600 at the rate of 2.0 L per 2000 L for the second trial in June. It was hoped that the wetter would increase the uptake of dimethoate into the waxy fruit and improve efficacy to the required level. The washing and waxing generally reduced the efficacy of the treatment still further. For the year 2000, Victoria agreed to accept apples from Queensland if treated using the standard ICA treatment of immersion dipping pending further trial work to validate the efficacy for apples. There is no history of fruit fly infestation problems in apples consigned to Victoria.

In March 2000 an immersion dipping trial using apples of the Gala cultivar was conducted in a commercial packing shed at Stanthorpe. All trials were conducted using standard protocols for fruit infestation, treatment in the packing shed, transport, incubation to breed out any surviving flies, data analysis. Trial records for treatments, chemical samples, chemical analyses, results of chemical analyses meet accepted standards. Analyses were performed at a NASA accredited laboratory at DNR, Indooroopilly.

The results of this treatment proved that:

1. That commercial full immersion dipping dimethoate application system achieves the required efficacy of 99.5 % or better against larvae and eggs of Queensland fruit fly. This is the post-harvest treatment that is accepted for a range of other fruits and vegetables. The bin flood spraying method appears to be a much less effective treatment method (Corcoran pers.com.)

2. That this same application_system followed by washing and waxing of fruit at 3. 6, or 20 hours after immersion dipping still achieves required efficacy. That waxing of fruit after immersion dipping of fruit does not result in excessive dimethoate residues in any part of the fruit. The residues analyses for whole fruit and skins only are given in table 5. Note that the immersion dipped fruit which were not washed and waxed had residues less than 2.0 mg/kg. The whole fruit residues for dipped, washed and waxed fruit were mostly below 1.0 mg/kg, and the average residue was less than 1.0 mg/ kg.

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http://pers.com

The results ensure the development and promotion of economical and commercially-applicable treatment procedures which can be incorporated into ICA agreements for Queensland apples destined for the fruit fly sensitive markets of Victoria and South Australia. In the past approximately $750,000 worth of apples has been sent to these markets by Queensland each year.

Introduction

With the introduction of ICA requirements for interstate movement, several Queensland growers began preparations for accreditation of their treatment and packing facilities. It then became evident that two problems existed with acceptance of current commercial practices.

Firstly, full dimethoate immersion dipping of fruit was the only recognised treatment. Most commercial facilities were using Prior to 1999, a cost efficient "bin flooding" application system similar to that used for the application of DP A prior to placing fruit in controlled atmosphere storage. This application method was not recognised under the provisions of ICA.

Secondly, ICA requirements stipulated that the dimethoate application was to be the final treatment applied prior to packing. Commercial packing lines were currently arranged to have dimethoate treatment followed by washing and wax application prior to packing.

During 1998-9 agreement was reached with Victoria to allow dimethoate "Bin flooding" as an acceptable treatment of apples for interstate trade, pending the results of bin flood spray trials to be conducted in a commercial packing shed. Trials had to demonstrate the required standards of efficacy (99.5%) against egg and larval infestation by Queensland fruit fly when followed by washing and waxing after3or 6 hour, and that the levels of dimethoate residues in fruit did not exceed the MRL. There was no history of fruit fly infestation problems in apples consigned to Victoria as normal commercial practices achieve a very high level of control due to cover sprays applied for control of other pests.

It was necessary to modify the project in the year 2000, following the failure of the whole-bin flood spray treatment to achieve the desired results.

New objectives:

1. That commercial full immersion dipping dimethoate application system achieyes the required efficacy against fruit fly.

2. That this same application system followed by washing and waxing of fruit at 3. 6, and 20 hours after immersion dipping still achieves required efficacy. That waxing of fruit after immersion dipping of fruit does not result in excessive dimethoate residues in any part of the fruit.

The project undertook both efficacy and residue studies to develop and promote commercially-applicable treatment procedures which can be incorporated into ICA

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agreements for Queensland apples destined for the fruit fly sensitive markets of Victoria and South Australia.

The project aimed to investigate, document and ratify treatment procedures that enable Queensland apples to be shipped into fruit fly sensitive markets under the provisions of an ICA protocol. As all Qld apple growers who wish to supply these markets must be covered by an appropriate ICA system, and as the treatments derived from this project will be the only treatments accepted under ICA, adoption of the outcomes of this project will be both immediate and widespread.

Materials and Methods

Apples

The Gala apples used for Trials 1 and la were sourced from an orchard where mating disruption was used for control of codling moth. Pesticide residues were low, although bait spraying for Queensland fruit fly had been used. The ordinary delicious apples that were used for Trial 2 were the last pick from an orchard where conventional cover sprays of azinphos-methyl were used for control of codling moth. Picking took place at least one month after the last insecticide application. Fruit was sent to Indooroopilly from Applethorpe. Fruit was held at 26°C overnight prior to infesting.

Infestation - Indooroopilly

Fruit was pin-holed 10 times with a 0.5 mm diameter entomological pin and placed in cages containing approximately 20,000 fertile Queensland fruit flies (1:1 male to female) for 10 minutes. Fruit was placed in the cage in rows of six and one fruit from each row was used as untreated control fruit to estimate the number of insects treated. The fruit was then held at 26°C until transported to Applethorpe. Fruit for the larval treatment was infested 8 days prior to treatment and fruit for the egg treatment was infested 1 day prior to treatment.

Treatment - Applethorpe

Fruit was transported by car to Applethorpe for treatment. A data logger was placed inside the bins of fruit to measure the air temperature. The temperature fell to a low of 14°C for about 1.5 hours during the June trial, which should not have had any mortality, effects on the insects. The control and treated fruit were held in the same conditions.

Some fruit were kept at Indooroopilly and destructively sampled to determine the proportion of each larval instar present at the time of treatment.

Holding - Indooroopilly

Fruit was returned to Indooroopilly laboratory after treatment. The fruit was set up on plastic boxes covered with gauze so that any juice from the decomposing fruit would drain away and not drown the larvae. The boxes were placed in gauzed holding cages over vermiculite as a pupation media.

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Pupae were sieved from the vermiculite 13,16 and 21 days after infestation. The pupae were counted and held for adult emergence. The number of insects treated was estimated from the number of pupae surviving in the control fruit. The arithmetic mortality of each treatment was determined using the number of pupae recovered. The mortality at the 95% confidence level (CL) (Couey and Chew 1986) was also calculated for treatments with 50 or less pupae surviving.

Trial 1. Thulimbah Packing Shed Flood spray efficacy 3 March 1999

The apples which had been infested at Indooroopilly were picked up on the previous day- approximately 500 fruit were infested with eggs and a similar number were infested with larvae. The fruit was transported in orange plastic crates having a capacity of about one carton of apples. Each crate was covered with paper and labelled with the respective treatment.

Treatments

Control eggs (no chemical treatment) Control larvae ( no chemical treatment) Treated eggs, not washed and waxed Treated eggs, washed and waxed after standing 6 hours Treated larvae, not washed and waxed. Treated larvae, washed and waxed after standing 6 hours

Method of packing and separating treatment fruit

The fruit to be flood sprayed were packed in cages constructed of plastic garden trellis mesh. The cages were approximately 500 mm in diameter and just less than the depth of the fruit bin . The egg infested fruit and the larval infested fruit were packed in one bin in separate cages. The remainder of the bin space was filled up with juice grade apples. Apples for residue analysis were placed in another cage in a separate bin that was also filled up with juice apples.

The control (infested, untreated apples) were set aside in the shed away from the treatment area. A Tiny-Tag temperature recorder monitored the temperature in the control fruit at all times.

The flood spray tank was calibrated by measuring in 2000 L of water using 20L polythene buckets. A sample of water was taken in clean glass jar prior to adding the dimethoate. The Nufarm dimethoate was measured in a stainless steel 1L dipper; 2 L of concentrate was added to the water. The dipper was rinsed thoroughly several times. The tank was agitated vigorously for several minutes using a large wooden scraper. A sample of insecticide solution (100 ml) was collected in another glass jar. The chemical and water samples were held in a refrigerator at 3.0 degrees C. prior to transport to the DNR laboratory at Indooroopilly for chemical analysis.

The bins were flood sprayed for 20 seconds at 1400 litres output per minute per square metre. The 20 seconds was from the time the spray hit the fruit in the leading

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edge of the bin until those fruit passed out of the spray. Flood spraying commenced at 1458 h. Half of the flood sprayed egg infested apples was removed after 3 hours standing (this should have been 6 hours), and placed back in the crates. Apples were taken from various levels of the cage. Similarly, half of the flood sprayed larval infested fruit was taken from their cage and placed in plastic crates.

Comparable samples from the uninfested fruit were taken out for residue analysis. After 6 hours, the remainder of the treatment apples were washed and waxed in the order-egg infested, larval infested, and uninfested apples (residue analysis).

As each batch of apples emerged from the drying tunnel they were collected into the labelled crates:

• Samples from uninfested apples were immediately bagged up and labelled (see attached schedule for residue treatments).

• Samples of untreated control fruit (pre- bin treatment) and a sample of 100 apples for chemical recovery work were also taken from Gala fruit from the same source.

The flood sprayed fruit was then stored in the laboratory at Applethotpe overnight and transported to Indooroopilly next morning. The chemicals and water were kept separate from the fruit and delivered to the DNR laboratory in an Esky. The apple samples (whole apples and peel only) were held in the freezer until chemical analyses for residues could be conducted. Samples which had to be peeled were peeled and the peelings frozen as rapidly as possible (completed by 2215 h).

Trial 2. Bin flood spray - efficacy and residues

The crates of egg and larval infested fruit and the controls were picked up from Indooroopilly at about 1130 hrs on 1 June and transported to Applethorpe where they were held in an air conditioned laboratory overnight, prior to treatment next day.

A new variable speed motor with a dial control for varying the speed had been installed, so a calibration was done by changing the settings and then timing the passage of a bin through the spray curtains. The setting for a 60 second exposure to the flood spray was selected.

The flood spray tank was filled to the 2000L mark and special care was taken to mix in the 2.0 L of dimethoate. Two litres of Agral 600 were added to the mixture before agitation. It was then stirred vigorously with a large scraper stirrer.

A water sample was taken for analysis prior to mixing in dimethoate. A flood spray mixture sample was taken at 1733 h after it was mixed. A concentrate sample was also taken. Tlie temperature of the flood spray mixture was 10.4 degrees C. The duration of the flood spray was timed as 69 seconds.

The Procedure for packing the infested fruit (eggs) (larvae), and the uninfested fruit was similar to that in the previous trial-three cages were used and labelled with colour coded flagging tape. The Delicious cultivar was firmer than Gala, so fewer fruit had been rejected following larval infestation. Only one bin was used to hold the three cages of fruit, compared with two bins for trial 1.

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All of the fruit was taken back to Applethorpe Research Station and kept in a heated room (portable heater) overnight. In the morning all fruit was taken to the Thulimbah packing shed for conducting the washing and waxing treatments. Approximately half the apples from each cage were removed, ensuring that samples were taken throughout the profile of each cage. The samples of flood sprayed unwashed and unwaxed apples were placed in labelled plastic crates.

Samples for residue analysis were randomly taken from the uninfested apples and put into labelled plastic bags. Washing and waxing occurred at 0845 h, taking about five minutes for each treatment batch. As each batch came off the conveyor the infested fruit were put into labelled crates

The fruit was transported back to Applethorpe Research Station and placed in the heated air-conditioned laboratory. The samples were processed for residues (skin only-Treatments 7, 9), as well as the 80 apples (skin only) for recovery purposes. All samples for residues were then stored in a freezer. All the crates of treated, infested fruit were taped up and returned to Indooroopilly in the back of a utility. The fruit samples were then incubated to breed out fruit flies.

Trial la. Immersion Dipping -residues. Pozieres, 15 March, 1999.

This trial was conducted using a steel immersion dip tank, which was calibrated, by using a water meter and confirming the calibration by measurement of tank dimensions. The water meter was consistently inaccurate - a reading of 18 L was actually 20 L of water.

A I L stainless steel measuring jug was used to measure out 2L of dimethoate concentrate which was thoroughly stirred around in the tank. Water and chemical mixture samples were taken using standard procedure as in the previous flood spray trial. Before sampling, an empty bin was dumped up and down ten times in the dip to ensure adequate mixing. Only one cage of infested Gala apples (same source as that used for the flood spray trial) was used, and juice apples were used to fill up the bin. Treatment commenced at 1108 hours. A 60 second exposure was used from the time the bin was completely immersed. After 6 hours, samples for residues were taken for treatments 1 to 3 in the same way as samples for residues had been taken for the flood spray treatments.

At 1711 hours the remainder of the apples were washed and waxed. Samples for treatments 4 (skin only), and 5 (whole fruit) were taken and frozen as soon as possible.

Trial 2 a. Immersion dip trial - residues Thulimbah, 8 June, 1999

Similar procedures to those for the previous immersion dipping trial were used. Only one cage of uninfested, ordinary Delicious apples (same source as that used for the flood spray trial) was used. Juice apples were used to fill up the bin. Treatment commenced at 5.48 PM with apples fully immersed for 60 seconds. The temperature of the dip solution was 10.0 degrees Celsius.

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An error occurred in the timing of sampling the dip solution- it was taken just after treating the bin of fruit. The fruit were moist from condensation. .

Trial 1 2000 Immersion dipping trial - efficacy and residues

The project was altered this year to use an immersion dipping treatment of dimethoate with and without washing and waxing the fruit after 3, 6 or 20 hours. The reason for this was the failure to demonstrate the efficacy of the flood spray method as it did not consistently achieve the required level of control of Queensland fruit fly. The immersion dipping trial was conducted at a commercial packing shed at Pozieres using the standard ICA protocol for immersion dipping. Apples used in the trial were sourced from an orchard where mating disruption was used for control of codling moth. No cover sprays were applied, apart from sprays for control of apple dimpling bug and bait sprays of chlorpyrifos and yeast autolysate for control of Queensland fruit fly. Heavily artificially infested Gala apples were transported from Indooroopilly on 29 February, held overnight at approximately 25 degrees Celsius, and dipped in dimethoate the next morning at 12.00 noon for one minute. Both egg infested and larval infested fruits were treated. The target concentration of the dip was 400 mg/ L and the actual concentration as analysed was 383 mg/L( within the acceptable range for ICA. P h was 7.2, although the indicator paper for a rapid field test showed it to be in the range 6.5 to 6.8.

Untreated control apples infested with eggs, and larvae were transported to the shed and not treated. All fruit treated and untreated were returned to Indooroopilly to breed out the fly pupae and adult flies from the treated and control apples at a temperature of 26 degrees Celsius.

The main difference from the experimental procedures used in the previous year was the immersion dipping treatment instead of the whole bin flood spray treatment, and different standing times prior to washing and waxing treated fruit. The procedures for separating the egg and larval infested fruit from the uninfested fruit that were used for residue analysis, and sampling procedures that were used in March 1999 were followed. One difference was that 3 cages of egg infested apples, and 3 cages of larval infested apples were packed into the same bulk bin, and the apples for residues analysis were packed between and on top of the treatment cages until the bin was filled.

Samples of water from the dipping tank, samples of the dimethoate concentrate, and samples of the dip solution were taken as per standard protocol, stored in the refrigerator overnight and transported on the following day, in an esky with freezer bricks, to the DNR chemical laboratory at Indooroopilly for analysis.

Washing and waxing (following treatment and standing) The apples were washed with Campbells Super Apple Wash (IL per 17L of water) for 15 to 30 seconds. The wax used was Campbells Super Hi Shine Apple Wax. Neither of these materials are known to cause breakdown of the dimethoate.

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Weather conditions Temperatures were quite warm on the treatment day (25 Deg. Celsius maximum and 15 Deg. Celsius minimum for the day (Applethorpe weather station). Fruit were sorted under the shade of a tree while being packed into cages and the bulk bin. A Tiny Tag electronic temperature recorders travelled with the fruit to ensure adverse conditions did not occur during transport to and from Brisbane and between Applethorpe and Pozieres.

EFFICACY STUDIES

Fruit used for efficacy studies was "insecticide free" - ie. not have been treated pre-harvest with any insecticide which impacts upon fruit fly. Six different treatments were applied for evaluation of efficacy:

(a) Immersion dipping dimethoate treatment with no subsequent washing or wax application. 3 hours standing (b) Immersion dipping dimethoate treatment with subsequent washing and wax application after 3 hours standing. (c) Immersion dipping dimethoate treatment with no subsequent washing and wax application after 6 hours standing (d) Immersion dipping dimethoate treatment with subsequent washing and wax application after 6 hours standing (e) Immersion dipping dimethoate treatment with no subsequent washing and wax application after 20 hours standing (f) Immersion dipping dimethoate treatment with subsequent washing and wax application after 20 h standing

Each piece of fruit was infested with some 20 fruit fly. In order to generate the required numbers of fruit fly to evaluate efficacy, 500 fruit were required for each treatment. A total of 3500 fruit were used for the efficacy study.

All infested fruit were treated through a commercial packing line using the immersion dipping dimethoate application system at 11.45 AM on 1 March 2000, the morning after the fruit was transported to Applethorpe and held overnight in an air conditioned room at approximately 25 Deg. Celsius. The commercial packing line used for treatment was operated as closely as possible to the desired standard - ie. Using an accurately calibrated tank, correct water quality in an acceptable ph range and a dimethoate concentration of close to 400 ppm immediately prior to dipping, with fruit to be exposed for at least 60 seconds. Washing and wax application followed dimethoate treatment after a delay_of3,6 and 20 h respectively between the completion of dimethoate dipping and the commencement of washing & wax application. However, as the final ICA protocol will be based on the treatment schedule tested, all of these factors were measured and recorded as per standard procedure.

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Additional samples of non-infested treated apples from this same facility were taken for use in residue analyses as outlined in Treatments 3 to 11 of the Schedule for Dimethoate Residue Analysis - Postharvest Treatment of Apples.

Of the 500 fruit treated to evaluate efficacy against eggs for each of the four treatments one half of these fruit (ie. 250) was removed for sampling after the dimethoate application and following the standing time at air temperature 3, 6, or 20 hours. This sample was not washed and waxed. The other half (250) of each treatment was then subjected to commercial washing and waxing treatments after the standing time (3, 6 or 20 hours) before being repacked for transport back to Indooroopilly for incubation.

The remaining 500 fruit for each treatment were treated to evaluate efficacy against larval infestation (specifically third instar larvae). This fruit will was treated through the same commercial packing line in exactly the same way as detailed in point 6 above. Again, half of the fruit was removed for sampling after standing for 3, 6, or 20 hours after the dimethoate application. The remaining 250 fruit after being held in bin storage conditions for 3, 6, or 20 hours at air temperature were then subjected to commercial washing and waxing treatments before being repacked for transport back for incubation at Indooroopilly.

Fruit removed for sampling as outlined in both points 6 and 7 above were returned to QHI Indooroopilly immediately after all treatments were completed. A Tiny Tags temperature recorder monitored the temperature of the fruit while standing and in transit. Fruit were incubated under appropriate conditions (26 Deg.Celsius) to determine the survival of fruit fly after treatment.

RESIDUE STUDIES

All samples were taken during treatment and packing in a commercial grower's operation at Pozieres, using the single-source fruit obtained for both efficacy and residue work. Samples from the immersion dipping treatments were taken at the same time and from the same facility as the infested fruit were treated for efficacy.

Analysis of residues was undertaken from the dipping treatments to enable acceptance of any of these for the purposes of ICA.

In addition to whole fruit and skin only Control (untreated) samples for both treatments, residues were analysed on the following:

1. Full immersion dipped fruit (60 seconds dip), allowed to stand in-bin for 3 h before sampling. No further treatment applied (ie. not washed or waxed). 4 replicates of whole fruit were analysed.

2. Full immersion dipped fruit (60 seconds dip), allowed to stand in-bin for 3 h before being washed and waxed. 4 replicates of whole fruit were analysed. This provided information on what proportion of the dimethoate is removed during the washing and waxing processes.

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3. Full immersion dipped fruit (60 seconds dip), allowed to stand in-bin for 3 h before being washed and waxed. 4 replicates of skin only were analysed. This provided information on what proportion (if any) of the dimethoate residue is bound up in the skin-wax layer and not available for fruit fly control throughout the whole fruit.

4. Full immersion dipped fruit (60 seconds dip), allowed to stand in-bin for 6 h before sampling. No further treatment applied (ie. not washed or waxed). 4 replicates of whole fruit were analysed.

5. Full immersion dipped fruit (60 seconds dip), allowed to stand in-bin for 6 h before being washed and waxed. 4 replicates of whole fruit were analysed. This provided information on what proportion the dimethoate is removed during the washing and waxing processes.


7. Full immersion dipped fruit (60 seconds dip), allowed to stand in-bin for 20h before sampling. No further treatment applied (ie. not washed or waxed). 4 replicates of whole fruit were analysed.

8. Full immersion dipped fruit (60seconds dip), allowed to stand in bin for 20 h before being washed and waxed. 4 replicates of whole fruit were analysed. This provided information on what proportion the dimethoate is removed during the washing and waxing processes.


Storage of trial data for trials conducted in 1999 and 2000

At the completion of the study a copy of all notebooks, worksheets, correspondence and other documents were archived in the files of scientific data held at Queensland Horticulture Institute 's Applethorpe Research Station.

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RESULTS

Efficacy Trials 1 and 2 1999 The results are shown in Tables 1 and 2:

Table 1. Mortality of Queensland fruit fly treated with dimethoate in apples. Trial 1 March 1999.

Lifestage Treated

Treatment Number of Fruit

Total Pupae

Number of pupae per

fruit

Estimate d number

treated

Mortality (arithmetic

)

True Mortality

(95% CL)

Eggs Control 80 1677 20.96 Eggs Bin flood only 201 24 0.12 4213.46 99.43 99.20 Eggs Bin flood plus wax 203 183 0.90 4255.39j 95.70 NA Larvae Control 46 2324 50.52 Larvae Bin flood only 183 53 0.29 9245.48 99.43 NA Larvae Bin flood plus wax 176 178 1.01 8891.83 98.00 NA

Table 2. Mortality of Queensland fruit fly treated with dimethoate in apples. Trial 2 June 1999.

Lifestage Treated

Treatment Number of Fruit

Total Pupae

Number of pupae per

fruit

Estimate d number

treated

Mortality (arithmetic

)

True Mortality

(95% CL)

Eggs Control 139 2944 21.18 Eggs Bin flood only 203 1 0.00 4299.51 99.98 99.89 Eggs Bin flood plus wax 177 0 0.00 3748.83 100.00 99.92 Larvae Control 131 2779 21.21 Larvae Bin flood only* 272 2261 8.31 5770.14 60.82 NA Larvae Bin flood plus wax 203 46 0.23 4306.39 98.93 98.63 * Incorrect treatment applied

Treatments against eggs and larvae in trial 1 were below the efficacy level required by interstate quarantine authorities of 99.5% morality at the 95% confidence level (CL). In trial 2 changes were made to improve the treatment. The efficacy levels for eggs following the flood spray with and without wax were above 99.5% mortality at the 95% CL. Unfortunately, some problems were experienced with the handling of trial fruit that had been flood sprayed, but not washed or waxed, so these data were excluded.

Residues Trial la

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The immersion dip mixture had a concentration of 408 mg/L of dimethoate. The ph was unexpectedly high (8.0). The results of the residue analyses are given in Table 3.

Trial 2a Residues trial-immersion dipping - Thulimbah June 8,1999. The water quality of the tank water was excellent- the ph was 6.6 and the electrical conductivity was 40 uS/cm. The dip analysis result was 372 mg/L, which was below the target concentration of 400 mg/L.

Residue analyses results from the apples which were treated by full immersion dipping are given in Table3.

Table 3. Summary of fruit residues data for immersion dipping

Trial No. Treatment Mean Dimethoate residue (mg/kg) Range (mg/kg)

la Control NDR (nil detectable)

la Dipped, no wash/wax 0.63 0.38-0.77 la Dipped, wash/wax 6h 0.18 ( IRep.) 2a Control (whole fruit) NDR 2a Control (skins only) 0.10 2a Dipped, no wash/wax 1.28 1.07-1.27

(whole fruit) 2a Dipped, wash/wax after 16 h 0.97 0.71-1.06

( whole fruit) 2a Dipped, wash/wax after 15 h 1.89 1.44-2.72

(skins only)

Efficacy Treatments against eggs and larvae in Trial 1 were not effective enough to reach the 99.5 % mortality at the 95 % confidence level (CL) which is the minimum standard required by interstate quarantine authorities. Presumably the waxiness of the fruit caused problems with uptake of the dimethoate. The bin flood spray method is generally less reliable than full immersion dipping, particularly for such a short treatment time. In Trial 2 the efficacy against eggs was above the required standard, even when the fruit was washed and waxed 15 hours after treatment. The use of wetter plus the longer duration of tile flood spray improved the efficacy. However, the flood spray plus the wash and wax treatment against larvae did not meet the interstate quarantine requirement.

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Efficacy Trial 1 2000 - Immersion Dipping Trial

Table 4. Mortality of Queensland fruit fly treated by immersion dipping with dimethoate i

Lifestage Treated

Treatment Holding time (Hrs)

No. of fruit

Total No. pupae

No. pupae per fruit

Estimated No. insects

treated

Mortality (arithmetic)

True (9

Eggs Control 139 6956 50.04

Eggs Washed/waxed 3 125 2 0.02 6255.40 99.97



Eggs Unwashed/unwaxed 3 134 0 0.00 6705.78 100.00



Larvae Control 167 13 103 78.46

Larvae Washed/waxed 3 118 0 0.00 9258.41 100.00



Larvae Unwashed/unwaxed 3 117 2 0.02 9179.95 99.98



Efficacy Trial 1 2000. The results for the immersion dipping trial in March 2000 were excellent as the dipping treatments all achieved at least 99.9 percent control (with 95% confidence limits) of both eggs and larvae of QFF regardless of whether the apples were washed and waxed after 3, 6, and 20 hours standing time; or not washed and waxed (Table 4).

Residues - Trial 1. 2000 Immersion dipping trial. Table 5.

POSTHARVEST DIMETHOATE TREATMENT OF APPLES 1-2 MARCH 2000

Lab. Tr. Treatment Dip Delay Portion Result ( mg/kg) Number No. Description after Wash of Fruit Omethoate Dimethoate Total A

&Wax Dimethoate *

174 /00/R 1 Control (pre-immersion dipping)

N/A Whole NDR NDR NDR


N/A Skin NDR NDR NDR







179 /00/R 3 60 sec dip, no wash & wax N/A Whole NDR 1.44 1.44 180 /00/R 3 60 sec dip, no wash & wax N/A Whole NDR 1.83 1.83 181 /00/R 3 60 sec dip, no wash & wax N/A Whole NDR 0.98 0.98 182 /00/R 3 60 sec dip, no wash & wax N/A Whole NDR 1.36 1.36 183 /00/R 4 60 sec dip, wash & wax 3h Whole NDR 0.60 0.60 184 /00/R 4 60 sec dip, wash & wax 3h Whole NDR 1.09 1.09 185 /00/R 4 60 sec dip, wash & wax 3h Whole NDR 0.45 0.45 186 /00/R 4 60 sec dip, wash & wax 3h Whole NDR 0.49 0.49 187 /00/R 5 60 sec dip, wash & wax 3h Skin NDR 2.18 2.18 188 /00/R 5 60 sec dip, wash & wax 3h Skin NDR 1.54 1.54 189 /00/R 5 60 sec dip, wash & wax 3h Skin NDR 2.45 2.45 1 190 /00/R 5 60 sec dip, wash & wax 3h Skin NDR 2.72 2.72 1 191 /00/R 6 60 sec dip, no wash & wax N/A Whole NDR 1.10 1.10 1

192 /00/R 6 60 sec dip, no wash & wax N/A Whole NDR 0.89 0.89 193 /00/R 6 60 sec dip, no wash & wax N/A Whole NDR 1.33 1.33 194 /00/R 6 60 sec dip, no wash & wax N/A Whole NDR 1.07 1.07 195 /00/R 7 60 sec dip, wash & wax 6h Whole NDR 0.76 0.76 1 196 /00/R 7 60 sec dip, wash & wax 6h Whole NDR 0.70 0.70 1 197 /00/R 7 60 sec dip, wash & wax 6h Whole NDR 0.51 0.51 1 198 /00/R 7 60 sec dip, wash & wax 6h Whole NDR 0.52 0.52 1 199 /00/R 8 60 sec dip, wash & wax 6h Skin NDR 2.42 2.42 2 200 /00/R 8 60 sec dip, wash & wax 6h Skin NDR 2.51 2.51 2 201 /00/R 8 60 sec dip, wash & wax 6h Skin NDR 3.31 3.31 2 202 /00/R 8 60 sec dip, wash & wax 6h Skin NDR 4.04 4.04 2 203 /00/R 9 60 sec dip, no wash & wax N/A Whole NDR 1.51 1.51 2 204 /00/R 9 60 sep dip, no wash & wax N/A Whole NDR 1.46 1.46 2 205 /00/R 9 60 se6 dip, no wash & wax N/A Whole NDR 1.24 1.24 2 206 /00/R 9 60 sec dip, no wash & wax N/A Whole NDR 1.43 1.43 2 207 /00/R 10 60 sec dip, wash & wax 20 h Whole NDR 0.96 0.96 208 /00/R 10 60 sec dip, wash & wax 20 h Whole NDR 0.92 0.92 209 /00/R 10 60 sec dip, wash & wax 20 h Whole NDR 0.84 0.84 210 /00/R 10 60 sec dip, wash & wax 20 h Whole NDR 0.92 0.92 211 /00/R 11 60 sec dip, wash & wax 20 h Skin 0.02 3.39 3.41 212 /00/R 11 60 sec dip, wash & wax 20 h Skin NDR 3.76 3.76 213 /00/R 11 60 sec dip, wash & wax 20 h Skin 0.02 5.04 5.06 214 /00/R 11 60 sec dip, wash & wax 20 h Skin 0.03 5.25 5.28

Method PPQ-02 Dimethoate is the sum of omethoate and dimethoate expressed as dimethoate. NDR = No detectable residue at a detection limit of 0.02mg/kg.

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Residues Trial 1 - 2000 The residues analyses for whole fruit and skins only are given in table 5. Note that the immersion dipped fruit which was not washed and waxed had residues less than 2.0 mg/kg. The whole fruit residues for dipped, washed and waxed fruit were mostly below 1.0 mg/kg, and the average residue was less than 1.0 mg/ kg.

Discussion

Efficacy 1999 whole bin flood spray trials. Treatments against eggs and larvae in Trial 1 were not effective enough to reach the 99.5 % mortality at the 95 % confidence level (CL) which is the minimum standard required by interstate quarantine authorities. Presumably the waxiness of the fruit caused problems with uptake of the dimethoate. The bin flood spray method is generally less reliable than full immersion dipping (Corcoran pers. com.), particularly for such a short treatment time.

In Trial 2, the use of wetter plus the longer duration of the flood spray improved the efficacy, with some treatments achieving the required 99.5 % mortality for eggs. However, the flood spray plus the wash and wax treatment against larvae did not meet the interstate quarantine requirement.

Residues 1999 Immersion dipping trials. Where no wetter was used, the residues were much lower than in the later trial. Residues in the Gala apples (Trial la.) were about one third to half those for the Delicious apples (Trial2a). Some confounding differences in varietal uptake may have also been possible. Washing and waxing 6 hours after immersion dipping of Gala apples, greatly reduced the amount of dimethoate residues-0.18 mg/kg compared with a range of 0.38 to 0.77 mg/kg.

For the Delicious apples, the residues were less than 2.00 mg/kg. This is quite an acceptable result. One exception was one skins only replicate for Treatment 4 which gave a residue of 2.72 mg/kg. Due to the high cost of chemical analyses, residues were not determined for the flood spray treatments as the overall efficacy of these treatments was not up to the required standard.

Efficacy Trial 1 2000 immersion dipping trial

The dipping treatments all achieved 99.5 % mortality of Queensland fruit fly eggs and larvae (with 95 % confidence limits) and this meets the ICA requirements for interstate movement of apples. As the treatment followed by 3 hours standing time is effective it would be the most appropriate treatment to implement under an ICA protocol as there is no advantage in,using a longer standing time after dipping.

Residues Trial 1 2000 immersion dipping trial

As expected, the washing and waxing decreased the dimethoate residues in the fruit (Table 5). There was a trend towards increasing dimethoate residues in whole fruit and skins with increased standing time if washing and waxing were not applied.

Residues were consistently higher in skins only, but skins constitute a small percentage of the mass of the apples. Also, many people peel apples in preference to eating the skin. The normal residue analyses are conducted on whole apples. The efficacy data do not indicate any problems with uptake of the dimethoate into the fruit. Residues are well within acceptable levels when immersion dipping is followed by washing and waxing after 3, 6, or 20 hours standing.

References Couey, H. M. and Chew, V. (1986) Confidence limits and sample size in quarantine

research. Journal of Economic Entomology 79: 887-890.

Technology Transfer

The results of the 1999 trials were presented to and discussed at length at a meeting with the Queensland post-harvest treatment group, and key personnel from the Queensland Animal and Plant Health Services on 19 August 1999. As a result of this meeting, further trial work using full immersion dipping was planned as it was important to prove a reliable method of post-harvest treatment for interstate. Further work with whole-bin flood spraying was abandoned.

Once the results of the successful immersion dipping trial in March 2000 were available, a brief summary report with the attached tables of efficacy data and residues data were provided to Queensland Animal and Plant Health Services, who took this information to an interstate quarantine meeting so that other states could be advised of these results. Local APHS inspectors responsible for supervising the immersion dipping of apples destined for interstate markets were also advised and queries relating to dipping procedures and market requirements were dealt with.

The immersion dipping results will be communicated to most Stanthorpe apple growers at a grower meeting in Stanthorpe in August 2000, although key apple packing establishments would already be aware of the results.

Recommendations

The standard immersion dipping treatment using dimethoate as a post-harvest treatment for apples should be incorporated into ICA agreements for Queensland apples destined for fruit fly sensitive markets of Victoria and South Australia.

If the Queensland growers wish an adequate flood spray system to be developed as an alternative system, this will require a new project to be funded with considerable modification to the treatment procedures that were used in 1999.

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ap98073 establishment of post-harvest treatment...

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