Written by Robert Orpet, Louis Nottingham, and Molly Sayles, Washington State University, March 2023
Spring Pear Psylla Biology
Right now (March 2023), overwintering pear psylla adults are beginning to disperse into pear orchards. Pear psylla adults overwinter both in and outside pear orchards, but most fly out of orchards in fall and overwinter outside of pear. Then, they fly back into pear the following spring. This means that pear psylla pressure in spring is related to regional patterns of management the previous year. Conventional pear pest management in the Wenatchee Valley results in effective chemical control of pear psylla’s first and second generations, but commonly leads to a flareup during the third generation near and after harvest time because intensive spraying has killed pear psylla’s natural enemies (Fig. 1). This results in extremely high production of overwintering pear psylla for the region. In contrast, “integrated pest management” (IPM) involves selective pesticides and cultural controls to suppress pear psylla and conserve the pest’s natural enemies. The IPM strategy results in some risk of pear psylla damage in the second generation during summer, but natural enemies generally suppress late season psylla. Given these observations, a major focus of pear entomology research at Washington State University is testing ways to improve effectiveness of IPM programs and comparing results with conventional management.
Managing Pear Psylla in Spring
Kaolin clay (Surround WP or Surround CF) is the core of any spring pear psylla management program. Kaolin is highly effective at keeping pear psylla adults off of trees and reducing egg lay. Particle films reduce pear psylla adult colonization and egg lay by 80–100%, which reduces pear psylla pressure for the first generation (Hull et al. 2008; Nottingham et al. 2020; Nottingham and Beers 2022).. Additional insecticides in spring sprays can improve pest suppression, but tank mixes of multiple broad-spectrum insecticides are largely redundant with each other and with kaolin. Pre-bloom, there are three potential timings for kaolin and insecticide applications:
- Dormant. The most effective timing for Kaolin is dormant, before most pear psylla adults have migrated into the orchard. Kaolin at this timing keeps adults off trees and protects wood from egg lay. Lime sulfur can help manage mites and will also kill pear psylla. Since pear psylla adults are still moving into orchards, it’s probably too early for adulticides to be very valuable.
- Budburst (right when green tissues of buds become exposed). A second Kaolin application now will continue to keep adults off trees. Pear psylla like laying eggs on green tissues, and an application of pyriproxyfen (Esteem 35WP IGR) will sterilize these adults right before green tissues become available (Higbee et al. 1995; Dunley et al. 2001; Nottingham and Beers 2022). Since considerable adults have finished dispersing, adulticides now are justified if populations are high.
- Green cluster. If any previous timings were missed, or if pear psylla adult populations are high, another Kaolin application now will cover green tissues and reduce egg lay going into bloom time. Buprofezin (Centaur) now will also harm pear psylla eggs and young nymphs, and this material is effective against mealy bugs. If pear psylla pressure is very high, tolfenpyrad (Bexar) is the most effective broad-spectrum material, but if you use it now, please do not use it against the next pear psylla generation to help slow insecticide resistance evolution.
In 2022, our team evaluated IPM spray programs for spring pear psylla management at eight paired orchards, with one site in each pair following our guidelines and the other using a conventional spray program. Orchards following IPM guidelines (Table 1) had similar outcomes in spring as orchards making extensive use of broad-spectrum sprays.
Prebloom is a relatively safe time to use broad-spectrum chemicals if you are trying to preserve natural enemies. However, most pear psylla predators and its specialist parasitoid overwinter both in and outside pear orchards, so avoiding broad-spectrum sprays in spring may help set up the season better in IPM programs. Summer IPM guidelines are available on our website and will be covered in future newsletter articles.
Table 1. IPM guidelines compared with an example conventional insecticide program for spring pear psylla management.
|Example conventional program
|1–2 sprays including some combination of:
|No mating disruption, as it would be redundant with harsh spray program
|Phenology-based guidelines with selective insecticides like:
|Broad spectrums not recommended for IPM:
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Dr. Robert Orpet
Research Assistant Professor, Entomology
Washington State University
Dr. Louis Nottingham
Assistant Professor, Entomology
Washington State University
Funding and acknowledgements
Thank you to our funding sources for this project, the Fresh and Processed Pear Committee of the Washington Tree Fruit Research Commission and the Washington State Department of Agriculture Specialty Crop Block Grant Program.
Related topics were covered in previous newsletter articles:
- Potential for fall kaolin sprays to suppress spring pear psylla: Orpet and Nottingham 2020
- Implications of high production of overwintering adults in conventional orchards: McCullough et al. 2022
- Season-long IPM vs. conventional spray program outcomes: Molly Sayles et al. 2022
Season-long pear psylla management information is located:
Dunley, J.E., B.M. Greenfield, G.T. Hannig, and L.H. Bennett. 2001. Control of Pear Psylla with Diflubenzuron and Pyriproxyfen, 2000. Arthropod Management Tests 26(1):A33. https://doi.org/10.1093/amt/26.1.A33
Hull, L.A., F.U. Zaman, and K.J. Neelendra. 2008. Control of Seasonal Pear Psylla Populations in Pears. Arthropod Management Tests 34:A23. https://doi.org/10.4182/amt.2009.A23
Nottingham, L.B., R. Orpet, and E. Beers. 2020. Greenhouse Test on Repellents of Winterform Pear Psylla. Arthropod Management Tests 45(1). https://doi.org/10.1093/amt/tsaa079
Nottingham, L., and E.H. Beers. 2022. Improving Pear Pest Management with Integrated Approaches. Washington State Tree Fruit Research Commission, Wenatchee, WA. https://treefruitresearch.org/report/11394/
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