Biological Control ofFenusa pusilla(Hymenoptera: Tenthredinidae) in the Northeastern United States: A Thirty-Four Year Perspective on Efficacy

Abstract

ABSTRACT Parasitoid releases against the birch leafminer Fenusa pusilla (Lepeletier) (Hymenoptera: Tenthredinidae) in eastern North America began in 1974, with releases in eastern Canada, followed by others in the Middle Atlantic States and New England. Of 4 parasitoids released, only 1, the ichneumonid Lathrolestes nigricollis (Thompson), established and spread widely. Studies of its preliminary impacts were made in several locations in the 1980s and 1990s, but full impact of the parasitoid on host density was not yet achieved in that period. Here we report results of surveys in 7 states (MA, CT, RI, NY, PA, NJ, DE) in 2007 documenting the current birch leaf miner levels (as % of leaves mined in spring) and parasitism. Survey results show that the pest has declined dramatically to barely detectable levels in 5 states (MA, CT, RI, NY, PA) but that in southern NJ, the pest remains abundant (ca 50% leaves mined) despite significant parasitism levels. Survey results, in context with previous evaluations made...