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Third-generation pear psylla outlook, August 2023

Written by Robert Orpet & Molly Sayles, WSU, August 2023

What we are doing and what we have found

The Pear Insects Lab at WSU has been testing pear pest management guidelines since 2022 on commercial farms. Our goal is to develop an integrated pest management (IPM) program with less cost and less pest damage than conventional management in the Wenatchee Valley. Central to the IPM program is integration of selective pesticides with conservation of biocontrol (predators and parasitoids).

It is August and the third generation of pear psylla is underway. How are things going?

  • Conventional orchards lack biocontrol and are experiencing an uptick in pear psylla relative to IPM and organic orchards, like last year. Every year, we observe a large increase of pear psylla adults in conventional orchards (Figure. 1A, top chart, red triangles). This very high amount of pear psylla probably contributes to our high areawide pear psylla pressure in the Wenatchee Valley.
  • Integrated and organic orchards’ pear psylla are not increasing and are expected to stay low (Figure 1B). Limited or no spraying for pear psylla is needed in integrated management at this point because biocontrol is in place.
  • Spider mites are high in some conventional orchards, but not in IPM and organic orchards (Table 1). Biocontrol works well for spider mites under the IPM program too.

In summary, things are playing out as expected. Conventional orchards eliminated biocontrol agents and are experiencing pear psylla and spider mite outbreaks. In IPM orchards, pear psylla and spider mites are less abundant. Pear psylla was much less abundant this year than last year, and there was more biocontrol in IPM orchards this year. Part of this is natural year-to-year variation, and part of it is that IPM is expected to work better the longer it is implemented so that biocontrol agents can build up. This year, year two of our trials, makes the IPM program look very promising.

Notes on more resources

  • Pear IPM Field Demo August 16, 2023. Join us in Cashmere to see and discuss an orchard that followed our IPM guidelines! Please RSVP if planning to attend.
  • Pear Entomology Weekly. Every week, we share an updated version of Figure 1 and data for each site like in Table 1 in our newsletter Pear Entomology Weekly. The newsletter also has updates from Tianna DuPont’s Scouting Network Project and scouting data from pears in the Yakima region. You can easily sign up for Pear Entomology Weekly.
  • Earwig Transit Workshop. On July 12, we distributed about 7,200 earwigs to eight pear-growing operations and showed how to mass-collect and release this important pear psylla biocontrol agent using rolls of cardboard. If you are interested in jumpstarting your biocontrol in IPM orchards but missed the workshop, or if you are interested in mass-collection of earwigs where they are unwanted (like peaches) send an e-mail to to get on the mailing list for next year or arrange a special site visit this season. Additional resources are on the Earwig Transit Workshop website.
six graphs showing numbers of natural enemies nymphs and adults Summer-Fall 2022 and Summer-present
Figure 1. Mean pear psylla adults per tray, eggs per leaf, nymphs per leaf, and natural enemies of pear psylla (Campylomma, Deraeocoris, Trechnites, ladybugs, and lacewings) per tray at 7-8 conventional, 7-8 phenology-IPM program, and 3 organic Wenatchee region pear orchards in 2022 and 2023. Importantly, the y-axis scales differ between years. Insect illustrations by T Kent.


Table 1. Site-by-site data for July 24, 2023

Every week in Pear Entomology Weekly (subscribe here), we break up the summarized data from Figure 1 into site-by-site numbers for paired or triplet orchards following different management programs.  At this time of year, we usually see more pear psylla and spider mites at the conventional orchard at each location.

Site Management Pear Psylla
Pear Psylla
Pear Psylla
Rock Island Conventional 2.1 .02 .02 0.1 0
Rock Island IPM 1.2 0.1 0.2 0.1 0.5
Monitor Conventional 0.8 0 0 0 0.1
Monitor IPM 0.5 0 0.04 0.2 0
Cashmere Conventional 4.9 0.2 0.1 0 1.3
Cashmere IPM 1.2 0 0.02 0.4 0
Cashmere Organic 3.6 0 0 3.5 0.02
Dryden Conventional 3.2 0.02 0 0.1 0.4
Dryden IPM 5.7 0.02 0 0.6 0
Dryden Organic 1.0 0.02 0 0.2 0
Peshastin Conventional 10 0.1 0.04 0.04 0.3
Peshastin IPM 7.9 0.1 .01 0.2 0.4
Peshastin Organic 0.6 0 0 0.4 0.1
HWY 97 Conventional 6.2 0.04 0 0 0.02
HWY 97 IPM 0.8 0 0.1 0.5 0
Leavenworth Conventional 22 0.2 0.4 0.08 1.1
Leavenworth IPM 0.3 0 0 0.08 0.02
Average Conventional 7.1 0.1 0.1 0.05 0.5
Average IPM 2.5 0.03 0.07 0.3 0.1
Average Organic 1.8 0.01 0 1.3 0.05



Robert Orpet professional photo

Robert Orpet

Funding and acknowledgements

Thank you Fresh Pear Committee and Processed Pear Committee in addition to WSDA for pear orchard research and Western SARE Project #WRGR23-004 for funds supporting related to earwig workshops.

Additional information

  • Learn about pear psylla management:
  • In previous Fruit Matters, the Pear Insects Lab outlined the IPM program and outcomes in 2023:
  • March Issue – prebloom pesticide programs were defined
  • April Issue – reviewed spring pear psylla biology and where to find pear psylla degree-days
  • May Issue – pre-bloom pear psylla in IPM and conventional Wenatchee Valley pears were similar
  • June Issue (a) – spring pear psylla in IPM and conventional Wenatchee Valley were similar
  • June Issue (b) – explanation of earwig transit into pear orchards to help stop pear psylla
  • July Issue – defined summer philosophy for pear IPM and showed, as expected, quantified more second-generation pear psylla in IPM and organic orchards vs. conventional.


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