Release of a Gregarious Muscidifurax Species (Hymenoptera: Pteromalidae) for the Control of Filth Flies Associated with Confined Beef Cattle

A recently colonized gregarious species of Muscidifurax near raptorellus (Kogan and Legner) from eastern Nebraska was evaluated in the field for its potential as a biological control agent for the house fly (Micsca domestica L.) and stable fly (Stomoxys calcitrans (L.)). Muscidifurax sp. was released at three beef cattle feedlot pens, three times at 3-week intervals at 50,000, 100,000, or 200,000 parasitized hosts per treatment. Mean host mortality in sentinel house fly pupae reached 94% 2 weeks after the first release, but parasitism decreased to 72% after 3 weeks. Similar trends were observed with the second and third releases. Also, large numbers of parasite progeny were recovered from sentinel cohorts, suggesting that many of the released parasites found the sentinel pupae. Parasitism by Muscidifurax sp. was substantially lower, 27.4 and 12.2%, respectively, in naturally occurring house fly and stable fly pupae than that observed in sentinel hosts. Little correlation was evident between mean host mortality and a given parasite release rate. This Muscidifurax sp. has a high reproductive capacity, is easily reared, and appears to be one of the more effective species commercially available for fly control on midwestern beef and dairy cattle confinements.