Emerald ash borer (Agrilus planipennis), a phloem-feeding beetle native to Asia, was first discovered in southeastern Michigan and Essex County, Ontario in June 2002. Initial studies in southeast Michigan indicated that the emerald ash borer (EAB) life cycle was univoltine, but we determined that at least some larvae feed for two summers. Such prolonged development, if common, would strongly influence EAB spread, population dynamics and survey activities of program managers. In 2006 and 2007, we quantified larval survival and development rate on a total of 90 ash trees (Fraxinus sp.) in a plantation with a relatively low density of EAB. Trees were either girdled (30 trees), exposed to the stress eliciting hormone methyl jasmonate (30 trees), or left untreated (30 trees). In 2006, larval densities and proportion of larvae reaching the prepupal stage were higher on girdled trees (89.2% of total larvae with 57.3% developing in one year) than on control trees (4.8% of total larvae with 22.1% developing in one year) and trees treated with methyl jasmonate (6.0% of total larvae with 16% developing in one year). Trees from 2007 will be felled and debarked in the autumn.