Invasive ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) threaten the health and productivity of natural and managed forest systems worldwide, however there is a lack of effective tools and tactics to manage these pests. Although these beetles have a nutritional symbiosis with fungi that produce volatiles, little is known about their behavioral responses to these compounds in field settings. Semiochemical-based tools utilizing fungal volatiles may improve early detection of incipient pest populations and support efforts to mitigate economic and environmental damage. In this study, we conducted experiments to test the extent to which a suite of fungal compounds modify the attraction of ambrosia beetles to a known attractant (i.e., ethanol). We focused on the response of three common invasive ambrosia beetle species (Xylosandrus crassiusculus (Motschulsky), Xylosandrus germanus (Blandford), and Xyleborinus saxesenii (Ratzeburg, 1837)) to bottle and multi-funnel traps baited with ethanol and fungal volatile lures in mixed-hardwood forests in Indiana over three years (2018-2020). While fungal volatiles failed to increase attraction of adult beetles to ethanol-baited traps, several compounds reduced the number of beetles captured. Two beetle species were repelled by isobutyl alcohol and benzyl alcohol, while X. crassiusculus was also repelled by isoamyl alcohol. These fungal alcohols may be used as signals of host suitability to colonizing females. The use of repellants may also hold promise to increase the efficacy of ambrosia beetle management, such as in push-pull systems, to protect vulnerable nursery stock and forest trees.
