Five Fraxinus species against one Agrilus beetle: adult emerald ash borer survival and host response to feeding

In North America, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) attacks healthy and stressed trees within the genus Fraxinus regardless of genetic origin. However, host feeding preference or the ability of trees to resist A. planipennis varies across Asian and N. American Fraxinus species. To date, the mechanism or suite of mechanisms that drive this host preference or tree resistance have not been identified. The purpose of this study is to determine 1) adult A. planipennis host feeding preference across five Fraxinus species (four native to North America, one native to Asia) and 2) how host leaves respond to A. planipennis feeding. Adult bioassays suggest that A. planipennis prefer to feed on leaves from F. pennsylvanica and F. nigra trees over leaves from F. mandshurica and F. quadrangulata trees. Adult mortality follows a similar pattern. Chemical defense induction is often the result of signaling from wounding events inflicted on leaves by insect herbivores. Peroxide (H₂O₂) manufactured in leaves after wounding can act as a signaling compound for chemical defense production. To further investigate the results of our leaf feeding bioassays, we used Amplex^® red, a fluorescent microscopy stain that binds to H₂O₂, and a confocal laser scanning microscope to determine H₂O₂ concentration and production in leaves after wounding. We hypothesize that leaves from F. quadrangulata and F. mandshurica trees will have higher concentrations and more rapid induction of H₂O₂ than leaves from F. pennsylvanica and F. nigra trees.