D3451: Ash stands with and without biological control in the wake of emerald ash borer

Ash stands were examined at 9 Connecticut locations where biological control agents had been released and in 9 nearby control locations. The stands were grouped by release age, 3 sites each of 7, 4 and 1 years at the start of the first survey year. Four meander transects in two consecutive years, in each of the 18 sites documented the abundance, size and condition of ash. Basal area was significantly lower in the three oldest wasp parasitoid release sites compared to intermediate-aged and newer release sites. The differences in live tree size structure in control versus release sites were striking, control sites show a regenerating stand with a high proportion of young, small-diameter trees, while release sites appear to maintain a significantly higher number of larger living ash trees relative to the control sites. The size-class distribution of dead trees in control versus release sites also differed significantly with a higher abundance of large, dead trees at control sites relative to release sites. These data suggest that biological control has positively impacted ash stand structure in Connecticut.