Host selection and feeding preference of Agrilus planipennis (Coleoptera: Buprestidae) on ash (Fraxinus spp.)

We studied the host selection behavior and feeding preference of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). A. planipennis is an exotic forest insect pest native to Asia that was discovered in North America in 2002 and is causing widespread mortality of ash trees (Fraxinus spp.) in southeast Michigan and surrounding states. We compared host selection and feeding behavior on different species of ash including Manchurian ash (F. mandshurica Rupr.), green ash (F. pennsylvanica Marsh), white ash (F. americana L.), black ash (F. nigra Marsh), blue ash (F. quadrangulata Michx.), and European ash (F. excelsior L). Manchurian ash is native to Asia, whereas the other species (native to North America or Europe) represent novel hosts for A. planipennis. Beetles distributed themselves more frequently and fed to a greater extent on green, black, and white ash compared with blue, European, and Manchurian ash. Although beetles consumed every ash species offered to them, Manchurian ash and blue ash were least preferred in feeding bioassays. When we analyzed the volatile content of intact and girdled ash for quantitative variation in 11 compounds that elicited antennal activity, we found that the overall volatile profiles of the six ash species differed significantly in their relative amounts of antennally active compounds. Green ash has lower relative amounts of volatiles compared with Manchurian ash, which might render it more attractive and less resistant to A. planipennis. Lower tolerance and resistance of green ash might make it more susceptible to mortality compared with Manchurian ash, which coevolved with the beetle in its native range. Repellent odors, potential antifeedants, and genes for resistance in Manchurian ash could be explored for methods to manage A. planipennis populations.