Evaluating the push-pull strategy in eastern apple orchards: verbenone effectively reduces ambrosia beetle populations without the need for a pull factor in a species-specific manner

BACKGROUND: Non-native ambrosia beetles (Coleoptera: Curculionidae: Scolytinae), specifically Xylosandrus germanus (Blandford), Xylosandrus crassiusculus (Motschulsky), and more recently Anisandrus maiche (Kurentzov) are destructive wood-boring pests of apple trees (Malus domestica). Previous studies have demonstrated all three beetle species are strongly attracted to ethanol and verbenone interrupts their attraction to ethanol. We tested a ‘push-pull’ management strategy in eastern United States apple orchards in three states New York, Pennsylvania, and Ohio using verbenone sachets to ‘push’ beetles away from apple trees and high release ethanol lures to ‘pull’ them into clear sticky traps. Three treatment plots were established and replicated twice in each state: (a) ethanol only (pull), (b) verbenone only (push), and (c) ethanol + verbenone (push-pull). RESULTS: The most abundant species captured in the study were X. germanus and A. maiche in both Ohio and New York, and X. crassiusculus in Pennsylvania. Our results showed that fewer beetles were caught in traps paired with the push treatment (verbenone only) compared to traps paired with the pull treatment (ethanol only). However, pairing the push-pull components together did not result in an increased reduction in beetle captures compared to the push only component, unless beetle populations were extremely high. CONCLUSION: Deploying verbenone within orchard rows closest to woodlot edges can significantly reduce beetle migration into the orchard.