Written by Robert Orpet, WSU, 5/1/2023
The Prebloom Pear Psylla Problem
A project out of the WSU Pear Insects Lab is in Year 2 of tracking outcomes in conventionally managed Wenatchee Valley pear orchards and orchards following new guidelines that integrate selective biocontrol-safe sprays with phenology-based timings and cultural tactics.
A previous article in Tree Fruit Matters outlined spring pear psylla biology and contrasted management programs. A follow-up article provided observations in the Wenatchee Valley and linked to management resources like links to current pear psylla-degree days and the pear psylla phenology model.
Pre-bloom Pear Psylla Options and Outcomes, 2023
Typical orchards on the project are doing a dormant spray of kaolin and lime sulfur or sulfur followed by 1–2 additional pre-bloom sprays. These sprays include kaolin plus options like pyriproxyfen (Esteem 35WP or Reemit 35WSB) and buprofezin (Centaur WDG). In our current phenology-based integrated guidelines, integrated orchards mostly limit themselves to these options plus one optional broad-spectrum pesticide pre-bloom. Conventional orchards add malathion to their list of insecticides and sometimes also add multiple other broad-spectrum insecticides. Last year, many people used the broad-spectrum insecticide Bexar pre-bloom, but pear psylla pressure is lower this year and integrated orchards typically used options like Cinnerate or azadirachtin if additional control was needed. Looking forward, integrated orchards will be deploying codling moth mating disruption to enable an effective and selective codling moth spray program for the rest of the season. This critical to conserve pear psylla biocontrol agents.
Conventional and integrated orchards saw similar first generation pear psylla abundance last year (Figure 1) and this year (Figure 2) despite variation in insecticide programs. Across 2017, 2018, and 2019, DuPont et al. (2021) also found that conventional, integrated, and organic orchards tended to have similar first-generation pear psylla populations. Notttingham et al. (2022) reports that in each of two years of study (2018, 2019) at our WSU Rock Island pear orchard, two sprays of kaolin clay resulted in similar pear psylla suppression as one kaolin plus four broad-spectrum products (Malathion 5EC, Bexar, Assail 70WP, and Rimon 0.83EC) across two sprays.
How can we explain similar outcomes for first generation pear psylla despite differences in insecticide programs? All the pairs of conventional and integrated sites on the current Pear Insects Lab project are adjacent to each other and have similar characteristics, except two of the pairs’ conventional and integrated sites are about 1 km away from each other. The only outlier site is an integrated orchard surrounded by natural habitat, but it was not skewing the average as it had high adult pressure in spring in 2022 (up to 30–40 per tray in the integrated and conventional orchard pairs) and similar adults relative to its conventional pair in spring 2023 (average of about eight per tray during April). Higher biocontrol in integrated orchards suppressing pear psylla probably does not make up for fewer sprays in spring because predators and parasitoids are not very abundant pre-bloom. Perhaps we underestimate the potential of early season biocontrol in our sampling, or perhaps multiple insecticide sprays are simply redundant with kaolin, which is highly effective at deterring pear psylla adults and egg lay.
Post-bloom outcomes during pear psylla’s second and third generations are a different story. Last year, first-year integrated pear orchards tended to experience pear psylla damage in the middle of the summer, when biocontrol agents were still building their populations. Conventional orchards on the other hand had weak biocontrol and experienced pear psylla outbreaks near harvest, resulting in balance, similar damage averaged across management programs. As biocontrol agents have an opportunity to increase across years in integrated orchards, we might expect less damage in integrated orchards this year. We’ll report what we see in 2023 in future Tree Fruit Matters articles.
Earwig distribution workshop in Wenatchee (free earwigs)
All of the conventional and first-year integrated orchards on our project had no or very few earwigs, while long-term organic orchards could have earwigs. Earwigs are an important pear psylla predator that have been sprayed out of many pear orchards. Earwigs disperse slowly, so they won’t recolonize quickly (Figure 3). If you would like some free earwigs to add to your integrated-management pear orchard, a special workshop is being planned in Wenatchee in mid-July. You can expect an article about the workshop in next month’s Tree Fruit Matters. For now, contact Robert Orpet if you would like to be kept informed on the project mailing list.
Contact
Dr. Robert Orpet
Washington State University
robert.orpet@wsu.edu
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
References
DuPont, S.T., C. Strohm, L. Nottingham, and D. Rendon. 2021. Evaluation of an integrated pest management program for central Washington pear orchards. Biol. Control. 152: 104390.
Nottingham, L. B., R. J. Orpet, and E. H. Beers. 2022. Integrated Pest Management Programs for Pear Psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), Using Kaolin Clay and Reflective Plastic Mulch. J. Econ. Entomol. 115: 1607–1619.
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