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Program summary
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Deciduous fruit pest management
Elizabeth Beers Peryea, Entomologist, WSU
Orchard Pest Management: A Resource Book
for the Pacific Northwest
T
his book by E. H. Beers, J. F. Brunner and M. J. Willett provides a complete reference to the principles and practices of insect and mite management in Pacific Northwest orchards. Pests of the following six deciduous tree fruit crops are covered: apples, pears, cherries, peaches, plums and apricots. The book has three sections. First, there are short chapters on some of the fundamental concepts and tactics: insect growth and development, integrated pest management, sampling, economic thresholds, phenological models, insecticide resistance, mating disruption and insect growth regulators. The central portion of the book is devoted to in-depth coverage of individual pests, including their life history, description of their stages and the damage they produce, how to sample them and how to integrate biological, chemical and cultural control. The final section provides detailed life histories and descriptions of the more important natural enemies of tree fruit pests, supplementing and reinforcing information given under biological control of the pest species. The book is illustrated with about 200 color photographs and an additional 100 line drawings of life history charts, construction methods for sampling devices and detailed drawings helpful for insect identification. Appendices are provided for the calculation and interpretation of degree-day models for lepidopteran and scale pests, and a glossary provides definitions of entomological terms. The book is fully indexed for easy reference.
Orchard Pest Management represents the combined efforts of entomologists, both past and present, from throughout the Pacific Northwest and the nation. Contributors for each section are the authorities in that particular area. It is both a reference book and a practical guide for pest management in orchards. The book is currently out of print, and a revised version will be printed in 1999.
Campylomma verbasci
This hemipteran pest of apple and pear has become of increased concern in the past few years. Although predaceous during much of its life cycle, it feeds on fruit during the bloom period leaving small corky warts or, where multiple stings occur, deformed fruit. Although damage is sporadic, up to 30% of the fruit may be injured. My research on this pest, in conjunction with that of a Ph.D. student, Michael Reding, has addressed the following questions concerning Campylomma management:
- When does damage occur and what is the optimum timing for control measures?
- What materials are effective for control but can be used without harming pollinators?
- What instars are capable or likely to attack fruit?
- Can we predict the occurrence of various instars?
- What components of the orchard biota (weed hosts, prey species) are associated with Campylomma populations or damage?
- Can we predict high risk orchards with catches from pheromone traps placed in the orchard in the fall?
We have made significant progress in the timing and materials for control of Campylomma. Sprays must be timed either before or during bloom in order to prevent the majority of the damage. Pheromone trap catches of adults in late summer and fall have been correlated with spring nymph densities. Although the relationship is not a close one, it is sufficient to group orchards into low, medium and high risk for prioritizing sampling the following spring. No correlation was found between aphid (prey) densities in the fall and spring nymph densities; therefore, suppressing aphids in hopes of reducing C. verbasci damage is not recommended. In addition, no relationship has been found between proximity or density of mullein, the most common summer host of C. verbasci, and spring nymph densities; therefore, removal of mullein as a strategy of pest control is not recommended.
Apple Aphid
We began a study in 1993 concerning the economic impact of aphids (Aphis pomi/Aphis citricola complex) on fruit quality, efficacy of chemical control and side effects of candidate aphicides. Two reduced-effort sampling schemes were investigated, and both were highly correlated with the most labor intensive method. Counting the number of aphid-infested leaves on infested shoots provided a better population estimate in comparison to counting the number of aphids on the most infested shoot. There was no well developed relationship between aphid population and damage as expressed in percentage fruit with sooty mold across a range of orchards, tree ages, and cultivars. Only in a few cases were within-orchard relationships established.
In conjunction with the aphid project, the toxicity of registered and unregistered insecticides to coccinellid larvae has been explored. We now have information on toxicity for most of the commonly used orchard insecticides and on several of the new materials approaching registrations. Most of the broad-spectrum organophosphates are highly toxic to coccinellid larvae. Provado, Vydate and Thiodan are moderately toxic, while Bt, IGRs, Neemix, oil and specific miticides have little or no toxicity. This information has been made available to growers through the Crop Protection Guide for Tree Fruits in Washington (EB 0419 see http://coopext.cahe.wsu.edu/infopub/eb0419/eb0419.htm for the pdf file).
Mite Pests of Apple and Pear
Since 1987, we have studied the properties of abamectin (Agri-Mek) as a miticide. This material is somewhat unique in that it is absorbed into the leaf and held there as a reservoir for potentially long periods of time, during which it is toxic to phytophagous species but not to natural enemies. Large differences in performance on apple and pear in field trials, despite essentially the same mite complex, led us to examine more closely the factors that might cause the observed results. Early studies demonstrated conclusively that pear and apple absorb and/or retain abamectin differently, probably due to waxiness or permeability of the leaves. Adjuvants (e.g., oils or organosilicones) greatly increase the length of residual control, again indicating permeability and penetration as a key factor for this material. Timing studies, where leaves were in various stages of hardening off, further reinforce this concept because the initial mortality and length of residual control were both higher at earlier timings. Differences in stage susceptibility of twospotted spider mite and residual life in different apple and pear cultivars have also been explored.
Resistance Management on Pears
Resistance by mites and pear psylla has been a perennial problem dogging pear growers. The use of Agri-Mek on virtually all of Washington’s pear acreage since 1988 has made the probability of resistance high. Building on work done in the late 1980s, we recently re-examined susceptibility to Agri-Mek and Vendex in populations of mites. Reversion to susceptibility to Vendex in what had previously been highly resistant populations had occurred in all populations tested. Similarly, all populations tested from pear showed an elevated LC50 for Agri-Mek in comparison to the 1989 baselines. In cooperation with Dr. John Dunley, a resistance management program that encompasses both mites and pear psylla is being field tested in commercial orchards (1995-present).
Codling Moth Areawide Program (CAMP)
In 1996, I began participating, along with many tree fruit researchers in the western U.S., in the USDA-ARS sponsored program on areawide control of codling moth. This program uses mating disruption as a primary tactic against codling moth over large contiguous acreage. The program has five pilot project sites in Washington, Oregon and California. I am responsible for sampling secondary pests and natural enemies in the five sites to document improvement in biological control under mating disruption. Comparable blocks under conventional organophosphate-based management outside of the mating disruption areas will be sampled to provide a comparison. In addition, I am responsible for a parallel study (Growers Resource Acquisition Base or GRAB). This program conducts similar types of sampling in orchards under mating disruption. In this project, however, the acreage is owned by a single grower or corporation, as opposed to a group of cooperating growers as in the CAMP study.
Preliminary results from this study are encouraging. In general, secondary pest populations are the same or lower in mating disruption blocks than in conventional blocks. The greatest success has been with pear psylla in pear. In addition, natural enemy populations are the same or higher in the mating disruption blocks, although this cannot be associated directly with a reduction in pest populations. The most consistent example has been an increase in parasitism of white apple leafhopper by the mymarid, Anagrus sp. See http://www.tfrec.wsu.edu/2ndpests/1997ProgressReport.html for the annual report for this sub-project.
Horticultural Mineral Oils
I am part of a multidisciplinary team studying the effects of oil on insect and disease pests, arthropod natural enemies, short- and long-term effects on fruit quality and cropping, and leaf physiology. My studies in this area have included the effect of oils on phytophagous and predatory mites; aphids and their natural enemies; and leafhoppers, both direct mortality and oviposition behavior. This project was taken over in 1998 by a graduate student, Mr. Dario Fernandez.
Other
We are investigating control of western tentiform leafminer [especially Agri-Mek and Success (spinosad)]. We are also working on a long-term, large-block project involving the effect of the aphicides Aphistar and Provado on aphid and natural enemy populations. In addition, we have a long-term project on the effect of aphid feeding on the growth and productivity of apple trees of four cultivars from the time of planting.
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