The relative abundances of Apocrita wasps associated with lowbush blueberry (Vaccinium angustifolium Ait.) were investigated in 33 blueberry fields throughout Washington County, Maine, USA. Wasps were captured during the springs and summers of 1997 and 1998 in Malaise traps erected along a transect in each field. A BACIP (before-after-control-impact-paired) experimental design was used to assess single applications of commonly used insecticides on predator and parasitoid wasp populations associated with lowbush blueberry fields. Insecticides were found to have a negative impact (time x treatment interaction, P < 0.05) on total wasp trap capture when comparing the change in wasp abundance before and after insecticide application periods between paired treated and non-treated fields. Relatively fewer wasps were captured in fields after treatment with insecticides compared to non-treated fields. These effects were found to be taxon-specific with the greatest negative impact observed for wasps belonging to the families Pompilidae and Braconidae.