Integrating repellent and attractant semiochemicals into a push-pull strategy for ambrosia beetles (Coleoptera: Curculionidae)

Non-native ambrosia beetles (Coleoptera: Curculionidae), especially Xylosandrus compactus (Eichhoff), Xylosandrus crassiusculus (Motschulsky) and Xylosandrus germanus (Blandford), are destructive wood-boring pests of trees in ornamental nurseries and tree fruit orchards. Previous studies have demonstrated the adults are repelled by verbenone and strongly attracted to ethanol. We tested a "push-pull" semiochemical strategy in Ohio, Virginia and Mississippi using verbenone emitters to "push" beetles away from vulnerable trees and ethanol lures to "pull" them into annihilative traps. Container-grown trees were flood-stressed to induce ambrosia beetle attacks and then deployed in the presence or absence of verbenone emitters and a perimeter of ethanol-baited interception traps to achieve the following treatment combinations: (a) untreated control, (b) verbenone only, (c) ethanol only, and (d) verbenone plus ethanol. Verbenone and ethanol did not interact to reduce attacks on the flooded trees, nor did verbenone alone reduce attacks. The ethanol-baited traps intercepted enough beetles to reduce attacks on trees deployed in Virginia and Mississippi in 2016, but not in 2017, or in Ohio in 2016. Xylosandrus germanus, X. crassiusculus and both Hypothenemus dissimilis Zimmermann and X. crassiusculus were among the predominant species collected in ethanol-baited traps deployed in Ohio, Virginia and Mississippi, respectively. Xylosandrus germanus and X. crassiusculus were also the predominant species dissected from trees deployed in Ohio and Virginia, respectively. While the ethanol-baited traps showed promise for helping to protect trees by intercepting ambrosia beetles, the repellent "push" component (i.e., verbenone) and attractant "pull" component (i.e., ethanol) will need to be further optimized in order to implement a "push-pull" semiochemical strategy.