Quantifying the active space of the repellent verbenone to enhance management of non-native ambrosia beetles

Anisandrus maiche Stark (Coleoptera: Curculionidae: Scolytinae) is a non-native ambrosia beetle native to Asia that is currently in nine states in the eastern US, where it is a pest on a variety of hardwood trees. Although its host range is not well characterized, A. maiche attacks black walnut (Juglans nigra) trees growing in plantations and forests in northwestern Indiana. Due to its large host range and few effective management methods, A. maiche has the potential to become a widespread invasive pest in the US and threatens the health and productivity of economically important tree species. Although semiochemical-based management options for many ambrosia beetles are lacking, it has recently been established that A. maiche is attracted to ethanol and repelled by the plant volatile verbenone. These two compounds could be used in a push-pull strategy to suppress populations of A. maiche in high value plantings of black walnut. However, the operational capacity of verbenone as a repellent is hampered by our lack of understanding regarding its active space. In this study, we quantified the spatial extent to which A. maiche is repelled by verbenone by conducting a field experiment to compare the capture on sticky cards at varying distances from traps baited with an ethanol lure alone or ethanol paired with verbenone. This study was conducted at multiple sites, including black walnut plantations and natural forest. Knowledge generated from this study may have applications in managing A. maiche and other ambrosia beetles in tree plantings, nurseries, orchards, and forests.