Effects of methyl jasmonate trunk injection on phloem phenolics of Fraxinus americana and F. pennsylvanica and associated emergence of the emerald ash borer (Agrilus planipennis)

Widespread ash mortality due to emerald ash borer (EAB) is a serious ecological and economic threat in urban and forest settings throughout the beetle’s North American range.  In a common garden study, EAB emergence from North American ash trees treated with exogenous application of the defense-related phytohormone methyl jasmonate (MeJA) was similar to trees that had been protected with an insecticide. As a follow up, we initiated a three-year study to evaluate different rates of MeJA trunk injections on EAB colonization and phloem chemistry of green and white ash. When treatments were initiated in spring 2011, trees showing no signs or symptoms of infestation. MeJA injections increased and decreased concentrations of individual phloem phenolics, but no relationship between application rate and phloem phenolic chemistry or density of EAB emergence holes was observed in 2011.  Analyses of short and long-term effects of MeJA injections on individual phloem phenolic compounds is ongoing. We are also quantifying MeJA levels in phloem tissues to evaluate uptake by the trees. MeJA may prove to be an alternative to broad-spectrum insecticides for control of EAB.