Earwig Transit Workshop

There was a July 12, 2023 workshop in Wenatchee distributing free earwigs and providing training in how to monitor and collect them.

If you missed the workshop, you can still contact the project director, robert.orpet@wsu.edu, and we may be able to arrange a site visit for earwig distribution and training.

Next year, additional workshops will be held in Wenatchee, Wapato, and Hood River. This project is supported by Western SARE (Project #WRGR23-004).

Permanent resources are housed below on this webpage, and reports on project outcomes will be added when available.

Why earwigs?

Earwigs have a special role in the community of aphid and psyllid natural enemies in apple and pear orchards. Earwigs can be present and able to suppress pests during periods where other predators are not present. Specialist parasitoids lag because they must first grow on a pest population. Predators with multiple generations have gaps in their activity when in the egg stage. In contrast, earwigs have one generation per year and are active in orchard trees June through October. Earwigs are omnivores, so they won’t starve when any particular pest population is low, and they have very low dispersal ability. A combination of “resident” earwigs, which capable of decreasing pest population growth, and other natural enemies, which can knock down larger pest populations, creates a vibrant community capable of keeping pest populations low (Piñol et al. 2009).

We have video evidence that earwigs kill woolly apple aphids (video below). Releasing earwigs into orchards with initially low earwig populations results in fewer woolly apple aphids (Orpet et al. 2019) and fewer pear psylla (Höhn et al. 2007). We’ve also found no evidence that apples or pears are damaged by earwigs in the field. They just feed on fruit that has already been damaged, often by mechanical injury or cracking.

Benefiting from earwig transit

Proven methods exist to monitor earwigs, transport them, and use them to suppress pests (Höhn et al. 2007, Orpet et al. 2019).

These are the considerations:

Will my orchard benefit from an earwig release? If your orchard already has a well-established earwig population, there is not much benefit from adding more. Since earwigs do not thrive in orchards that use broad-spectrum sprays, ideal sites for earwig releases are orchards recently switching to organic or integrated management. Naturally, it can take over three years for earwig populations to establish on their own. To check for earwigs, researchers use rolled strips of corrugated cardboard, which earwigs like to hide in during the day. Crumpled newspapers also can work.
Will my earwigs survive after I release them? Spray programs are probably the most important factor affecting earwig survival in Pacific Northwest orchards. We have a one-page summary table of pesticide safety to earwigs in our handout Orchard Pesticide Safety For Earwigs. The new phenology-based management guidelines for pear psylla are compatible with earwigs.
How many earwigs, where, and how long until I see benefits? If your released earwigs survive, a new generation of earwigs should lead to reduced pests the year after releases. The earwig population will spread about 30 yards per year. At some times of the year in some locations we can find >50 earwigs per cardboard shelter, but finding around 5 per shelter is a good amount associated with biocontrol of pests. Releasing around 100 earwigs per tree in a low density orchard or 100 earwigs every 15′ in a high-density trellised block is the target for this workshop. At that rate, about 1,000 earwigs will cover an acre of orchard.

Resources

Orchard Pesticide Safety For Earwigs

Guide To Earwig Transportation

Citations

Beers, EH, NJ Mills, PW Shearer, DR Horton, ER Milickzy, KG Amarasekare, LM Gontijo. 2016. Nontarget effects of orchard pesticides on natural enemies: Lessons from the field and laboratory. Biological Control 102: 44–52. https://doi.org/10.1016/j.biocontrol.2016.04.010

Crumb, S. E., P. M. Eide, and A. E. Bonn. 1941. The European earwig. USDA Tech. Bull. 766: 76. https://naldc.nal.usda.gov/download/CAT86200761/pdf

Höhn, H, A Lahusen, R Eder, T Ackermann, L Franck, HU Höpli, J Samietz. 2007. Régulation du psylle du poirier Résultats et observations de 2002 à 2006 en Suisse alémanique. Revue suisse Vitic Arboric Hortic 39: 169–176. https://www.researchgate.net/publication/284761529_Regulation_du_psylle_du_poirier

Piñol, J., Espadaler, X., Pérez, N., Beven, K., 2009. Testing a new model of aphid abun- dance with sedentary and non-sedentary predators. Ecol. Model. 220, 2469–2480. https://doi.org/10.1016/j.ecolmodel.2009.06.031.

Orpet, RJ, JR Goldberger, DW Crowder, VP Jones. 2019. Field evidence and grower perceptions on the roles of an omnivore, European earwig, in apple orchards. Biological Control 132: 189–198. https://doi.org/10.1016/j.biocontrol.2019.02.011

Orpet, RJ, DW Crowder, VP Jones. 2019. Biology and Management of European Earwig in Orchards and Vineyards. Journal of Integrated Pest Management 10: https://doi.org/10.1093/jipm/pmz019