Emerald ash borer (EAB), a phloem-feeding beetle native to Asia, was first discovered in southeastern Michigan and Essex County, Ontario in June 2002. Little information about EAB biology or control options was available from Asia. Initial studies indicated that the EAB life cycle was univoltine but our recent observations showed 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, we measured larval survival, growth and development rate on a total of 90 ash (Fraxinus sp.) trees that were either girdled (30 trees), exposed to the stress eliciting hormone methyl jasmonate (30 trees), or left untreated (30 trees). Pairs of adult beetles were caged on the trunk of 20 trees in each treatment and females were allowed to oviposit. Four cages were placed on 10 trees per stress treatment to simulate high density conditions; one cage was placed on 10 trees per stress treatment to simulate low density conditions and 10 trees per treatment were not infested. Number of larvae, development stage, gallery length, and related variables were determined when caged areas of trees were debarked in August.