Platypus quercivorus ambrosia beetles use leaf volatiles in host selection

Although chemical volatiles emitted from host and non-host trees have been suggested as important cues for bark and ambrosia beetles, their responses to leaf volatiles is poorly understood. The oak ambrosia beetle, Platypus quercivorus (Murayama) (Coleoptera: Curculionidae), is a vector for the fungus that causes Japanese oak wilt. Using a Y-tube olfactometer, we tested the behavioral response of P. quercivorus to leaf volatiles emitted from four host trees - Quercus crispula Blume, Quercus serrata Murray, Quercus salicina Blume, and Castanea crenata Sieb. & Zucc. (all Fagaceae) - and two non-host trees, Fagus crenata Blume (Fagaceae) and Cryptomeria japonica D. Don (Cupressaceae). A flight mill was used to evaluate the effect of flight on the behavioral response to leaf volatiles. The bioassays were repeated 10x before and 10x after flight in the flight mill for each of the 54 individual beetles. Leaf volatile components were analyzed using gas chromatography-mass spectrometry. The bioassay results supported our hypothesis: P. quercivorus was attracted by the leaf volatiles of hosts and was deterred by the leaf volatiles of non-hosts. The behavioral response of P. quercivorus to the leaf volatiles was stronger after flight. Males had a stronger behavioral response than females to leaf volatiles. The leaf volatile chemical profile of the non-host C. japonica differed from the profile of the host plants. However, the chemical profile of the non-host F. crenata was similar to the profile of the hosts. Our findings provide insight into the functions of leaf chemical volatiles in the interaction of P. quercivorus with its hosts and non-hosts and may help improve the control of P. quercivorus and Japanese oak wilt.