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 raptorell us (Kogan and Legner) from eastern Nebraska was evaluated in the field for its potential as a biological control agent for the house fly (Mi csca domestica L.) and stable fly (Stomoxys calcitrans (L.)). Muscidif urax sp. was released at three beef cattle feedlot pens, three times a t S-week intervals at 50,000, 100,000, or 200,000 parasitized hosts pe r treatment. Mean host mortality in sentinel house fly pupae reached 9 4% 2 weeks after the first release, but parasitism decreased to 72% af ter 3 weeks. Similar trends were observed with the second and third re leases. Also, large numbers of parasite progeny were recovered from se ntinel cohorts, suggesting that many of the released parasites found t he sentinel pupae. Parasitism by Muscidifurax sp. was substantially lo wer, 27.4 and 12.2%, respectively, in naturally occurring house fly an d stable fly pupae than that observed in sentinel hosts. Little correl ation was evident between mean host mortality and a given parasite rel ease rate. This Muscidifurax sp. has a high reproductive capacity, is easily reared, and appears to be one of the more effective species com mercially available for fly control on midwestern beef and dairy cattl e confinements. (C) 1995 Academic Press, Inc.