Trunk and canopy volatile organic compound profiles of black and Manchurian ash implicated in stress-mediated ovipositional preferences of emerald ash borer

Emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae), is a destructive invasive forest pest of ash (Fraxinus spp.) in North America. Black (F. nigra) and Manchurian ash (F. mandschurica) are two closely-related, chemically similar species with almost completely opposite resistance phenotypes, making them an ideal comparison in host-resistance investigations. EAB adults locate hosts via volatile attractants and visual cues, and past studies have demonstrated that black ash is a much more preferred host for oviposition than Manchurian ash. Application of methyl jasmonate has been shown to induce resistance of ash to EAB, and field studies and olfactometer assays show that girdled trees are especially attractive to EAB adults. In this study, we analyzed trunk and canopy volatile organic compound (VOC) emissions from, and EAB ovipositional preference, for constitutive and methyl jasmonate-induced Manchurian and black ash, as well as VOC’s emitted from the canopy and trunk of girdled Manchurian trees (both above and below the girdle). Several VOC’s of interest and species differences were identified, including VOC’s with known insect behavioral activities. Our findings have implications for understanding EAB ovipositional preferences, as well as EAB trapping and monitoring methods.