Trap captures of invasive ambrosia beetles (Coleoptera: Curculionidae) as influenced by ethanol release rate

Abstract

Infestations of ambrosia beetles in the tribe Xyleborini (Coleoptera: Scolytinae) are associated with economic losses to horticultural trees due to branch die‐back and tree death. Ethanol is a key attractant used for monitoring flight activity. Trapping experiments were conducted in woodlots in Ohio, USA, and Veneto, Italy, to characterize the effect of ethanol release rate on captures of Anisandrus maiche, Xyleborinus saxesenii, Xylosandrus crassiusculus and Xylosandrus germanus. In Ohio (2019, 2020 and 2021) and Italy (2021), traps were baited with centrifuge tubes that were modified to achieve ethanol release rates of 0.1–13.2 g/day. In Ohio (2022), traps were baited with varying quantities of manufactured lures to achieve release rates of 0.02–1.4 g/day. There was no consistent relationship between ethanol release rate and trap captures for the modified centrifuge tubes. In nine of sixteen analyses, traps baited with the centrifuge tubes releasing ethanol at 1.1 g/day or higher collected more A. maiche, X. saxesenii, X. crassiusculus and X. germanus than traps baited with centrifuge tubes releasing 0.1 g/day. In contrast, the manufactured lures releasing 0.1–1.4 g/day attracted more A. maiche, X. saxesenii, X. crassiusculus and X. germanus than lures releasing 0.02–0.05 g/day. This comprehensive study provides important insights into monitoring tactics for ambrosia beetles along with implications for optimizing ethanol‐baited traps as part of a ‘push‐pull’ strategy whereby repellents are used to ‘push’ beetles away from vulnerable trees and attractants are used to ‘pull’ them into annihilative traps.