Parasitism rates of Muscidifurax raptorellus and Nasonia vitripennis (Hymenoptera: Pteromalidae) after individual and paired releases in New York poultry facilities.

Commercially reared parasitoids were released into three high-rise, caged-layer poultry houses; one house received only N. vitripennis Walker, the second house received only M. raptorellus Kogan & Legner, and the third house received an equal ratio of both species. Overall, house fly parasitism by M. raptorellus was never higher than 7% in any house. Most parasitism in the M. raptorellus release house was attributed to N. vitripennis. Parasitism of house fly pupae by M. raptorellus did not significantly increase during or after the 6-wk release period in the house that received both parasitoids. However, a depression in total parasitism was not detected when releases of the two species were made in this house.