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Spring Pear Psylla Update April 2023

Written by Robert Orpet, Washington State University, April 6, 2023

Pear psylla management pre-bloom

Effective pre-bloom pear pest management is highly related to pear psylla and pear tree phenology. Pre-bloom pear pest management programs were outlined in an article in last month’s Tree Fruit Matters.

To help manage pear psylla, updates on pear psylla degree-days are available publicly from Decision Aid System. Corresponding phenology-based integrated pest management guidelines for pear are also publicly available: Pear Psylla Phenology Model.

You can sign up for Pear Entomology Weekly, a new resource with weekly scouting data, pear psylla degree-days, and management guidelines by e-mailing

Current pear psylla behavior and phenology, Wenatchee Valley

We are tracking current pear psylla behavior from the unsprayed Wenatchee Tree Fruit Research and Extension Center pear orchard (Fig. 1a). Pear psylla adults are laying eggs on woody areas below dormant buds (Fig. 1b). As buds break dormancy, pear psylla adults will start to lay their eggs on the emerging green tissues (Fig. 1c). Pear psylla adult movement into pear orchards is ongoing. We saw a disappearance of overwintering pear psylla adults in an adjacent WSU apple plot in March that coincided with increased adults in the neighboring pear orchard (Fig. 2). According to current pear psylla-degree days and the pear psylla phenology model, movement of pear psylla adults is mostly completed but can continue until the end of April across the Wenatchee Valley.

Many natural enemies of pear psylla also overwinter both in and outside pear orchards. Adult Deraeocoris (Fig. 1d), for example, can be found with tray tap monitoring at this time. Though they are scarce in spring, these adults will lay eggs and start the new generation of predators that will be the key to success for integrated pest management programs. Keep an eye out for it!

Project Update: pear psylla phenology-based IPM

Our evaluation of phenology-based integrated pest management guidelines at commercial orchards in the Wenatchee Valley began for this year in March. Data from the project in 2022 are archived online and we discussed the results recently in Good Fruit Grower magazine.

You can follow the project this season by signing up for Pear Entomology Weekly. Please e-mail Robert Orpet to be added to the e-mail list.

Project Update: new earwig augmentation project – free

A new project is starting this year to assist with inoculation of pear orchards with European earwigs. European earwig is an important pear psylla predator that has been lost in many pear orchards. These predators are slow to disperse, so it may take years for them to repopulate orchards that transition to organic or integrated management. If you are interested in obtaining free earwigs for your farm, please e-mail Robert Orpet to receive updates on an earwig distribution event tentatively scheduled for July 2023. A future Tree Fruit Matters article will highlight this project in greater detail.

four pictures - trees, eggs on branch, adult on bud, and an adult and predator bug on a beat tray
Figure 1. Photos from Wenatchee-TFREC pear orchard 4/6/2023. a.- Pear trees. b.- Early pear psylla egg on woody areas below buds. c.- Pear psylla adult eager to lay eggs on emerging green tissues. d.- On beat tray sampling, a pear psylla adult (left) and a beneficial Deraeocoris bug predator (right). [photo credits: Robert Orpet]
graphs of pear psylla found
Figure 2. Pear psylla adult counts on tray traps on the grounds of the Tree Fruit Research and Extension Center, 2023. [Figure credit: Robert Orpet)
European earwig nest
Figure 3. A European earwig mother and her offspring in a nest found below a cinder block on April 27, 2019. The cinder block was respectfully replaced after the earwigs were photographed. [Photo credit: Robert Orpet]


Robert Orpet professional photo

Robert Orpet
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.

Fruit Matters articles may only be republished with prior author permission © Washington State University. Reprint articles with permission must include: Originally published by Washington State Tree Fruit Extension Fruit Matters at and a link to the original article.

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