Evaluation of seven essential oils identifies cubeb oil as most effective attractant for detection of Xyleborus glabratus

Abstract

Redbay ambrosia beetle, Xyleborus glabratus, is an exotic wood-borer that vectors the fungal agent that induces laurel wilt. Since its introduction into Georgia in 2002, X. glabratus has spread throughout the southeastern U.S., and laurel wilt has decimated native Persea trees, particularly redbay (P. borbonia) and swampbay (P. palustris). The lethal disease now threatens avocado (P. americana) in Florida. To control the spread of laurel wilt, effective attractants are needed for early detection of the vector. Phoebe oil lures are the best known attractant, but they are no longer available. Current detection relies on manuka oil lures, but our previous research indicated they have a field life of only 2–3 weeks in Florida. Therefore, we evaluated seven essential oils as attractants for X. glabratus, and ethanol as a potential synergist. Field tests and electroantennography (EAG) were conducted to compare attraction and olfactory response to angelica seed, cubeb, ginger root, manuka, phoebe, tea tree, and orange oils. The highest captures were obtained with cubeb, manuka, and phoebe oils; ginger and angelica oils were intermediate, and tea tree and orange oils were not attractive. Addition of ethanol to oil lures did not increase captures. In subsequent tests with commercial formulations, cubeb lures captured more X. glabratus than manuka lures, were better for early detection at low population levels, and had longevity of at least 8 weeks. The highest EAG responses were elicited with phoebe and cubeb lures. Our results indicate that cubeb lures are the best attractant currently available for detection of X. glabratus.