Turning a pest into a natural enemy: Removing earwigs from stone fruit and releasing them in pome fruit enhances pest control

Authors: HANEL, ALDO - Washington State University; ORPET, ROBERT - Washington State University; HILTON, RICHARD - Oregon State University; NOTTINGHAM, LOUIS - Washington State University; NORTHFIELD, TOBIN - Washington State University; Schmidt, Rebecca

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2023
Publication Date: 11/24/2023
Citation: Hanel, A., Orpet, R., Hilton, R., Nottingham, L., Northfield, T., Schmidt-Jeffris, R.A. 2023. Turning a pest into a natural enemy: Removing earwigs from stone fruit and releasing them in pome fruit enhances pest control. Insects. https://doi.org/10.3390/insects14120906.
DOI: https://doi.org/10.3390/insects14120906

Interpretive Summary: Earwigs are a pest of soft-skinned stone fruits, like cherries, but are important predators of pests in pear and apple orchards. They are currently monitored in orchards using inexpensive traps made of rolled cardboard. Researchers from USDA-ARS in Wapato, WA, Washington State University, and Oregon State University tested whether the cardboard traps could be used as a system for capturing earwigs in orchards where they are pests and moving them into apple and pear orchards to improve pest control. The researchers found that large numbers of earwigs could be captured with the cardboard traps, but removing earwigs from stone fruit orchards did not decrease earwig damage. Earwig releases in apple and pear orchards only increased their numbers if earwigs had previously been absent. Earwig releases reduced populations of pear psylla and aphid pests.

Technical Abstract: The European earwig Forficula auricularia (L.) (Dermaptera: Forficulidae) is an omnivorous insect considered a minor pest of stone fruit, but is a key predator of pome fruit orchard pests. In pome fruit orchards where they are not abundant, it may be desirable to inoculate the orchard with earwigs to improve pest control. This could be especially useful in situations where a grower has previously eliminated earwigs with pesticide applications and is transitioning to organic or “softer” pesticide programs. In a two-year study, we evaluated mass trapping earwigs in stone fruit using rolled cardboard traps to determine if mass trapping could provide an adequate supply of earwigs for augmentation and reduce earwig fruit damage. We also tested whether a single release or multiple, weekly releases of earwigs reduced pests in apples or pears relative to a no-release control. Mass trapping did not decrease earwig abundance or reduce fruit damage in stone fruit orchards. However, trapping was an effective source of earwigs for augmentation. One mass release or multiple releases of earwigs increased their abundance in orchards with few or no earwigs, but not in orchards with a larger established earwig population. However, even in orchards with previously high earwig abundance, augmentation still improved pest control. Earwig augmentation reduced the abundance of woolly apple aphids and pear psylla in apple and pear orchards, respectively. For other pests evaluated, plots with mass releases of earwigs had a slight trend of overall lower pest density when compared to control plots. A trap-and-move strategy for earwigs in tree fruit could be an effective, relatively low-cost method of augmenting orchard predator populations.