- Programme Title:Development of pest and disease risk models for horticultural production systems
- Programme Title:Pesticide residues in export horticultural crops.
7.2 Facilitating Horticultural Market Access
Research to facilitate market access for exported horticultural produce included developing a pest-disease model that would predict the risks of pest incidence on exported fruit. Research into predictive modelling and analytical methodology for pesticides residues was also undertaken.
7.2.1
Programme Title: Development of pest and disease risk models for horticultural production systemsProgramme Leader:Dr C Hale Institution:HortResearch |
Summary
Prediction of pest risk in export consignments, using models, may permit inspection procedures to be optimised and provide the basis for negotiation of phytosanitary pest risk management procedures. This programme examined the development of a generic model for pest and disease infestation/infection risk using leafrollers, codling moth and fire blight as examples, and filled in gaps in the specific information required.
The level of control of leafrollers in apple crops achieved by growers in the field and the reduction of infestation through picking and grading procedures were investigated. It was found that packhouse graders generally performed poorly in the removal of leafroller damaged fruit and there were substantial differences between packhouses and lines of fruit. It was not possible to present a reliable regression model to predict leafroller risk based on larval infestation in packed export cartons, because no significant relationship between old damage, fresh damage and larval presence was found.
A study of where codling moths prefer to lay their eggs revealed that codling moth strongly prefer to lay on apples rather than on cherries or nectarines. These results, and the absence of codling moth in export cherries and nectarines, indicate that there is no technical justification for the fumigation of these fruits for this pest by New Zealand exporters. Quarantine security for codling moth in cherries and nectarines from New Zealand could be achieved to an extremely high level by an inspection programme combined with commercial insecticide spray programmes.
A model for the prediction of fire blight risk was tested and found to be able to identify infection periods, distinguish low risk from high risk orchards, predict appearance of fire blight symptoms and assist with timing of monitoring and disease management procedures.
The generic pest-disease risk model is now ready for demonstration and installation.
| Objective 1: | Leafroller risk model | |
| Research Leader: | Dr J Walker | |
| Objective 2: | Codling moth risk model | |
| Research Leader: | Dr C Wearing | |
| Objective 3: | Fire blight: area freedom | |
| Research Leader: | Dr C Hale | |
| Objective 4: | Development of the generic pest-disease risk model | |
| Research Leader: | Dr J Walker | |
Description - Objective 1: Leafroller risk model
To develop risk probability estimates for the presence of leafroller larvae in export apple crops by:
- investigating the relationship between larval density, leaf damage, leafroller damage, leafroller damage to fruit at harvest and larvae found on fruit during grading procedures; and
- developing a pilot sampling system to determine the incidence of leafroller larvae in apple crops for quality assurance personnel.
Approach & Outcomes
The aim of this project was to develop a pest risk model for leafrollers as the basis for a generic phytosanitary risk model. Leafrollers are endemic and important phytosanitary pests of several horticultural export crops in New Zealand. Their presence in consignments of export fruit can downgrade large volumes of fruit and threaten access to key North American markets. The specific information sought for this project included the levels to which leafroller is controlled by growers spray programmes in the field and the reduction in leafroller infestation achieved through picking and grading procedures.
The project was carried out in the two major apple growing districts of Hawke's Bay and Nelson. In each district the cultivars 'Braeburn' and 'Fuji' on two orchards were used. Up to twelve bins from each cultivar block (approximately 25,000 fruit each) were sampled and inspected by using detailed inspection procedures to identify the presence of leafroller damage and larval activity within a specified block. This assessment was compared with the outcome of each grower or packhouse's grading and inspection procedures. This was achieved by analysis of the packhouse's reject fruit from grading and packing a known large volume of fruit, picked and harvested from trees within the same block as the researchers’ sample.
Two common species of leafroller were found in harvested fruit. A little known species, Capua semiferana, was also found infesting fruit on two of the properties in Nelson. Leafroller larvae were found on fruit samples taken from seven of the eight researcher blocks, but only one of seven packhouses removed all of the expected larvae from its fruit from the same block when it was graded and packed. In the researchers’ samples most of the larvae (64%) were hidden (usually associated with the fruit calyces) and were likely to escape detection by fruit graders. It is therefore probable that fruit grading did not greatly reduce the incidence of live larvae being packed into cartons.
The expected frequency of live leafroller larvae passing through packhouse grading procedures was calculated. For Hawke’s Bay blocks it was estimated that larval infestation in packed cartons of fruit was between nil and one larva per 48.8 cartons. In Nelson blocks there was less leafroller damaged fruit and it was estimated that the level of larval infestation in packed cartons of fruit was between nil and one larva per 148.4 cartons. For fruit which was submitted for USA export inspection the probability of common orchard pest species of leafroller larvae (Hawke’s Bay data only) escaping detection through grading procedures ranged from P=0.000076 to P=0.00099 which is equivalent one per 132-101 cartons respectively.
The efficiency of packhouses’ removal of leafrollers and their damage to fruit was calculated using the researchers samples. Generally packhouse graders performed poorly in the removal of leafroller damaged fruit and there were substantial differences between packhouses and lines of fruit. The grader removal of damage was in decreasingorder of effectiveness: large or old chews = fresh chews >>> small chews = stem or calyx damage = live leafroller.
The relationship between old damage, fresh damage and larval presence was examined to determine if either factor was a reliable predictor for larval infestation. The strongest relationship, between fresh damage and larval infestation, was not significant. Accordingly, a reliable regression model to predict leafroller risk in packed export cartons could not be presented as anticipated on the basis of this study alone.
Risk prediction in the case of rare occurrences is extremely difficult requiring impractically large sample sizes to get reliable data. The data presented here provides realistic estimates of fruit infested with leafroller larvae following typical production and grading standards.
The results are recorded in HortResearch Client Report No 96/217.
Description - Objective 2: Codling moth risk model
To develop risk probability estimates for the presence of codling moth in export apple and summerfruit crops by:
• investigating codling moth ovipositional preference and larval development on apples, cherries and nectarines.
Approach & Outcomes
The oviposition preference of codling moth for fruiting apple, nectarine and cherry trees was investigated. Diapausing codling moths (in a phase of very low activity) were released in winter 1995 into a cage containing a randomised block of six single tree replicates of each fruit type. The moths emerged during the summer of 1995-96, and mated females oviposited on the host plant of their choice. Egg laying and larval development in the fruits were assessed by sampling fruit clusters on each tree on two occasions; codling moth larval development was further assessed by examining all the fruit on each tree at harvest and all the windfall fruits of the apple and nectarine trees.
No codling moth eggs were found on the nectarine (cv. 'Fantasia') and cherry (cv. 'Stella') trees. In contrast, 82% of the apple fruit clusters (cv. 'Royal Gala') carried codling moth eggs by mid-January. These results were confirmed by the absence of larval entries in the nectarines and cherries whereas 67% of the fruit clusters of the apple trees were damaged in mid-January. This equated to 52% of the apples being damaged. The harvest and windfall records confirmed the results from fruit cluster sampling. About one third (31.3%) of the apples remaining on the tree at harvest, and half (52.5%) of the windfall apples, were damaged by codling moth. No codling moth damage could be found in the nectarine and cherry fruits.
The cage experiment showed that codling moth preferred to oviposit on apple despite the close proximity of the cherry and nectarine trees. Confirmation of this result was sought by examining the incidence of codling moth in harvested cherry and nectarine fruits during pre-export inspections of these fruits from the Otago region. In particular, records were examined from commercial orchards which contained apples which were known to have been attacked by codling moth in the same season as the inspections. This analysis showed that codling moth was never intercepted in Otago stonefruit by Ministry of Agriculture inspections from January 1987 (the oldest records available) to March 1996 (the most recent records available). Codling moth was also absent from the more extensive QC inspections by packhouse operators for 1994-95 and 1995-96 (earlier records were not available). The absence of codling moth in stonefruit inspected by the Ministry of Agriculture was shown to include orchards in which apples were known to have been attacked by codling moth in the same season.
The results of this study of oviposition preference, and the absence of codling moth in export cherries and nectarines, indicate that there is no technical justification for the fumigation of these fruits for this pest by New Zealand exporters. Quarantine security for codling moth in cherries and nectarines from New Zealand could be achieved to an extremely high level by an inspection programme combined with commercial insecticide spray programmes.
The results are recorded in HortResearch Client Report No. 96/146.
Description - Objective 3: Fire blight, area freedom
Development of methods to define areas of freedom from fire blight and determination of the risk of establishment of the disease by:
- evaluating a fire blight predictive model for determining disease risk in pipfruit-growing areas and in high and low risk orchards.
Approach & Outcomes
Prediction of fire blight infection risks was carried out in the 1995/96 season using the MARYBLYT model and a fire blight monitor based on MARYBLYT and the Thomson and Schroth predictor in Waikato, Hawke's Bay and Nelson. Improved monitoring and sampling procedures were used to obtain crop phenology and disease incidence in the monitored orchards. Orchards were monitored intensively from September to December 1995.
Accurate prediction of blossom blight infection events was obtained in the monitored orchards. The majority of the strikes appeared as predicted. No infection events were predicted from early to late flowering this season for all 3 regions. Consequently, relatively fewer blossom blight strikes were observed. Findings this year were in agreement with previous years in that there was an absence of infection events during early to mid-bloom for Hawke's Bay, Nelson and Waikato. Regional differences in climatic conditions did not result in a marked difference in the number of infection events recorded during petal fall to end of November, or in the number of high risk periods recorded. Differences in individual orchards appear to contribute to the differences in observed fire blight incidence.
The fire blight predictive models can be used to identify infection events and establish infection risks of the crop. Information from the orchard including current disease incidence, previous disease history, the crop variety grown and production practices are factors that can be integrated into an expert system to derive a rating system to distinguish the low risk orchards from the ones which are at high risk for fire blight outbreaks.
The results were recorded in several publications.
Description - Objective 4: Development of the generic pest-disease risk model
Development of a functional software prototype of an interactive generic pest-disease risk model using leafroller and fireblight risk probability data by:
- constructing a generic pest-disease risk model as a functional software application; and
- testing the model using the available leafroller and fireblight risk probability data.
Approach & Outcomes
The software of the generic pest-disease risk model is now ready for demonstration to MAF and installation.
Publications
Walker, J.T.S.; Bradley, S.J. and Shaw, P.W. (1996): Leafroller Infestation Risk Model - Larval incidence and efficiency of grading procedures in risk reduction. HortResearch Client Report, September.
Wearing, C.H. and McLaren, G.F. (1996): The risk of codling moth in export fruit 1995-96. HortResearch Client Report, July.
Gouk, S.C.; Boyd, R.J. and Hutchings, S.O. (1996): Assessment of fire blight infection risks. HortResearch Client Report September.
Gouk, S.C.; Bedford, R.J.; Hutchings, S.O.; Cole, L.; Voyle, M.D. and Hoyte, S.M. (1995): Evaluation of the MARYBLYT™ model for predicting fire blight blossom infections in New Zealand. Acta Horticulturae, 411, pp.109-116.
Gouk, S.C.;Bedford, R.J. and Hutchings, S.O. (1995): Applications of a computer model for predicting blossom infections by fire blight. Proceedings of the 10th Biennial Australasian Plant Pathology Society Conference, Lincoln, p.66.
Gouk, S.C.; Bedford, R.J.; Hutchings, S.O. and Voyle, M.D. (1995): Prediction of fire blight in New Zealand pipfruit orchards. Horticulture Beyond 2000. Proceedings of the New Zealand Society for Horticultural Science, Nelson, September, p.37.
Bedford, R.J.; Gouk, S.C. and Hutchings, S.O. (1995): Evaluation of a computer model for prediction of fire blight in Waikato pipfruit orchards. Horticulture Beyond 2000. Proceedings of the New Zealand Society for Horticultural Science, Nelson, September, p.15.
Gouk, S.C. (1996): Fire blight prediction and control. Pipfruit grower field days in Havelock North, Hamilton and Nelson.
Gouk, S.C. (1996): Fire blight prediction and control towards 2000. Mystery Creek Agricultural Field Days.
References
Wearing, C.H. (1979): Integrated control of apple pests in New Zealand. 10. Population dynamics of codling moth in Nelson. New Zealand Journal of Zoology, 6, pp.165-199.
Wearing, C.H. (1991-1994): Leafroller Pheromone Trapping Central Otago 1990-91, 1991-92, 1992-93, 1993-94. HortResearch Internal Reports.
Wearing, C.H. (1995): The risk of codling moth in export fruit 1994-95. HortResearch Client Report, 95/140, p.13 + Appendices.
Wearing, C.H.; Connor, P.J. and Arnbler, K.D. (1973): Olfactory stimulation of oviposition and flight activity of the codling moth Laspeyresia pornonelka, using apples in an automated olfactometer. New Zealand Journal of Science, 16, pp.697-710.
Wearing, C.H. and Ferguson, A.M. (1971): Variation in the fecundity of the codling moth, Carpocapsa pornonella L. New Zealand Journal of Science, 14, pp.233-237.
Wearing, C.H. and Hutchins, R.F.N. (1973): Alpha-farnesene, a naturally occurring oviposition stimulant for the codling moth, Laspeyresia pomonella. Journal of Insect Physiology, 19: 1251 -1256.
7.2.2
Programme Title: Pesticide residues in export horticultural crops.Research Leader:Dr P T Holland Institution:HortResearch |
Summary
Horticultural exports must meet the national pesticide residue limits, and sometimes more stringent requirements, of importing countries. This programme aimed to further develop a model to assist in the development of spraying strategies to meet specified crop residue outcomes and to develop analytical methods to test crops for a wide range of pesticide residues.
Pesticide residue predictive modelling capabilities were enhanced by further development of the HortResearch RESMOD package. Citrus and summerfruit crops were included and the range of output options increased. Literature data on a further 15 pesticides were incorporated into RESMOD. It was found not practical to incorporate rainfall effects on residues into the RESMOD model because of the need for full weather station records. More accurate decay parameters for diazinon were established and data on spray deposition on apples and kiwifruit obtained.
Analytical methodology for pesticide residues was enhanced to meet changing requirements. Methods for further pesticides, including some 'organic' materials, were validated through the researchers’ main multi-residue method which can now determine 140 pesticides in a wide range of crops and foods. An innovative ancillary multi-method was developed to determine residues of four miticides. A method for the herbicide glyphosate was validated for water and plant material.
| Objective 1: | Predictive modelling and data-basing of pesticide residues | |
| Objective 2: | Multi residue analytical methodology | |
Description - Objective 1: Predictive modelling and data-basing of pesticide residues
To enhance the present model developed in the previous year for Quality Assurance/Quality Control of spray programmes on crops by:
- incorporating and validating the crops nectarine and citrus for 4 key pesticides each and preliminary investigation of requirements for blueberries and boysenberries;
- incorporating rainfall effects (residue wash off) through a sub-model for apples and persimmons;
- determining more accurate decay parameters for 2 key pesticides (carbaryl and diazinon) on apples and kiwifruit where current data is inadequate. This residue data will also be very useful for the 1996 Codex review of MRLs for these pesticides;
- developing improved estimates of spray deposition for dense canopies (kiwifruit) or tall crops (large apple trees);
- extending the pesticide rating system based on the Environmental Impact Quotient concept from 15 to 30 pesticides; and
- carrying out field and laboratory studies to develop the key parameters for incorporation into PC/data-base software.
Description - Objective 2: Multi-residue analytical methodology
To extend present multi-methods for testing of export horticultural crops by:
- incorporating 3 'organic' pesticides - mineral oil (not permitted in the UK), natural pyrethrum (MRLs 1-3 mg/kg) and sulphur (MRL 50 mg/kg in some countries);
- incorporating 5 newer pesticides which structurally appear directly compatible with current method (i.e. validation only required);
- developing a separate multi-method for 4 miticides not presently well covered (clofentazine, fenpyroximate, hexythiazox, propargite);
- comparing current NZ/European multi-method with US-FDA multi-method for scope and detection limits; and
- development of an HPLC method for determination of the widely used polar herbicides glyphosate and glufosinate-ammonium.
Approach & Outcomes
Horticultural exports must meet the national pesticide residue limits, and sometimes more stringent requirements, of importing countries. This programme aimed to further develop a model to assist in the development of spraying strategies to meet specified crop residue outcomes and to develop analytical methods to test crops for a wide range of pesticide residues.
Pesticide residue predictive modelling capabilities were enhanced by further development of the HortResearch RESMOD package. Citrus and summerfruit crops were included and the range of output options increased. The RESMOD implementation is a sophisticated tool for analysis of grower spray diaries and planning of spray programmes to meet specific residue outcomes. Literature data on a further 15 pesticides were incorporated into RESMOD.
Investigation of the rainfall effects on residues on apples and persimmons found that the major trends can be explained. However, it was not practical to incorporate this information into the RESMOD model because of the need to access full weather station records which is a complex project in its own right.
More accurate decay parameters for diazinon were established and trials on carbaryl residues on persimmons and nectarines confirmed its variable residuality, due to its susceptibility to wash-off fruit. The data on spray deposition on apples and kiwifruit obtained have important implications for field sampling regimes and interpretation of residue data.
Analytical methodology for pesticide residues was enhanced to meet changing requirements. Methods for further pesticides, including some ‘organic’ materials, mineral oil, pyrethrins and elemental sulphur, were validated through the researchers main multi-residue method which can now determine 140 pesticides in a wide range of crops and foods. An innovative ancillary multi-method based on HPLC was developed to determine residues of four miticides. A facile residue method for the polar herbicide glyphosate was validated for water and plant material.
Contact for Enquiries
Farm Monitoring Programme Manager
Monitoring and Evaluation
MAF Policy
PO Box 2526
Wellington
NEW ZEALAND
Phone: +64 4 894 0623
Fax: +64 4 894 0741
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