Project Number: 3607-22000-010-07
Project Type: Specific Cooperative Agreement

Start Date: Sep 28, 2004
End Date: Sep 30, 2008

Objective:
1. Document interspecific variation in resistance / susceptibility of major North American and Asian species of ash to emerald ash borer in a replicated, experimental ash plantation. 2. Characterize mechanisms of resistance / susceptibility of ash species to EAB, focusing on phloem biochemical responses (secondary metabolites) to larval feeding.

Approach:
Emerald ash borer (EAB) has killed more than 6 million white, green, and black ash trees in Michigan, Ontario, and Ohio since its accidental introduction from Asia. However, EAB does not devastate its native hosts in Asia. The objectives of this proposal are to determine why EAB is such an aggressive killer of North American ash trees, and to identify mechanisms by which Asian ashes resist EAB. Our working hypothesis is that Asian ashes are resistant because they possess targeted defenses to EAB by virtue of their long coevolutionary history. Deciduous trees are thought to resist borers by means of rapid feeding-induced defensive responses of phloem tissue, including biosynthesis of defensive secondary metabolites and formation of wound periderms that encapsulate larvae. We plan to characterize and quantify these defensive responses in an experimental, replicated ash plantation in Michigan planted with major North American and Asian species of ash. Our specific objectives are to (1) document variation in resistance / susceptibility of Asian and native ashes to EAB, and (2) identify the mechanisms of resistance that may be present in Asian species. Identification of resistance mechanisms will facilitate screening, selection, and/or breeding of resistant trees for use in urban forests.