The future of green ash behind, within, and ahead of the advancing front of emerald ash borer

Emerald ash borer (EAB), (Agrilus planipennis Feirmaire) (Coleoptera: Buprestidae) is a phloem feeding beetle native to Asia. First discovered in Detroit, MI and Windsor, Ontario in 2002, dendrochronological studies indicated EAB first became established in North America at least six to ten years earlier in the metro Detroit area. Since its arrival, EAB has attacked native ash (Fraxinus spp.) trees in forest, rural and urban settings. As ash resources are depleted beetle populations disperse and colonize new areas. The resulting infestation wave appears to expand in all directions. Questions consistently arise as to the status and persistence of the ash resource in areas colonized by EAB. Using a variety of sampling techniques, we sampled green ash (Fraxinus pennsylvanica) in forested settings across an east-west transect in southern Michigan. We expect most ash trees in southeastern Michigan have already succumbed to the beetle, but canopy gaps may enable surviving understory ash to replace dead overstory ash trees. In south central Michigan where EAB populations are at peak densities, we expect overstory ash to be in various stages of decline. Regenerating ash, if present in sufficient numbers, may capitalize on increasing light availability resulting from overstory ash canopy dieback and mortality. Sites in southwestern Michigan show little or no signs of EAB infestation. Understory ash and other species will be quantified to assess potential regeneration in the absence of EAB.