ESTABLISHMENT, DISTRIBUTION, AND IMPACT IN SOUTHERN NEW-ENGLAND OF LATHROLESTES-NIGRICOLLIS (THOMPSON) (HYMENOPTERA, ICHNEUMONIDAE), AN INTRODUCED PARASITOID OF THE BIRCH LEAFMINER, FENUSA-PUSILLA (LEPELETIER)(HYMENOPTERA, TENTHREDINIDAE)

Lathrolestes nigricollis (Thompson) (Hymenoptera: Ichneumonidae) was r eleased in New England against Fenusa pusilla (Lepeletier) in 1979-198 0 and again in 1989-1990. By 1991, the parasitoid was widely establish ed in southern New England. From 1979 to 1990 the commonness of leafmi ners at the original release site in the first generation declined fro m 50-54% of leaves mined to under 3%. Over 4 years at five sites, para sitism of larval birch leafminers increased between leafminer generati ons from 10.3% (G(1)) to 27.6% (G(2)) to 39.2% (G(3)). In Massachusett s, parasitism decreased (from 28 to 14%) with increasing distance from the original release site, while corresponding damage increased (from 6% of leaves mined to 33%). In areas local to the original release si re (<4 km) parasitism has reduced damage from birch leafminer to incon sequential levels. Some sires in other parts of southern New England, particularly roadside sites, still have high levels of mined leaves in spite of the parasitoid's presence in the general area.