Conophthorin enhances the efficacy of ethanol-baited lures for trapping the granulate ambrosia beetle (Coleoptera: Curculionidae: Scolytinae)

The exotic granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky), is among the most economically important pests of nursery stock and young trees in the United States. Colonizing females chew small galleries in the sapwood of trees where they rear symbiotic fungi that are used as food for adults and larvae. Because these attacking beetles feed on fungi rather than consume host material, it is quite difficult to control them with systemic pesticides. Nevertheless, residual insecticides can protect uninfected trees, but only if applied during the early stages of colonization. Ethanol-baited traps are often used to monitor flight activity and to properly time these insecticide applications. Semiochemical lures can further enhance monitoring efforts and may be used for mass-trapping ambrosia beetles. For example, conophthorin, an angiosperm bark volatile, acts as an attractant for Xylosandrus germanus. Moreover, verbenone is an anti-aggregation pheromone component for several coniferophagous scolytids and acts as a repellent for some ambrosia beetles. In this study, we evaluate the response of X. crassiusculus to conophthorin, and determine whether adding a conophthorin lure to ethanol-baited traps increases their efficacy. Furthermore, we test whether verbenone acts as a repellent of X. crassiusculus. In the field, traps made from plastic soda bottles were baited with individual lures consisting of either ethanol, verbenone, conophthorin, the combination of conophthorin and ethanol, or left blank (control). Traps baited with both conophthorin and ethanol captured significantly more beetles than all other treatments, suggesting that conophthorin synergizes the response of X. crassiusculus to ethanol.