Livestock News

Biological Control of Feedlot Flies with a Wasp Parasite

A strain of the pteromalid wasp Muscidifurax raptorellus collected from house fly pupae in eastern Nebraska may be useful against house flies and stable flies in confined beef cattle feedlots. A single release of 200,000 wasp-parasitized house fly pupae resulted in 96% parasitism of sentinal house fly pupae two weeks after release, but parasite activity declined to background levels over the following 3 weeks. When two releases of 100,000 parasitized fly pupae each were made 6 weeks apart, parasitism averaged 70% and 55%, respectively, two weeks after releases. When three releases of 67,000 parasitized fly pupae were made at 4 week intervals, peak parasitism averaged 44%, 58% and 80% respectively, following the three releases.

A single release of higher numbers of parasites may be appropriate, especially during the period of peak fly production in early summer in areas where subsequent drying and higher temperatures generally result in lower fly populations during mid-summer. However, several releases of fewer parasites may result in better overall fly control where continuous fly development occurs. Also, releases at 2-3 week intervals result in a more uniform population of parasites over a given period. This wasp species is gregarious (several parasite wasps develop within a single insect) and can be reared at much lower cost than other solitary (one wasp develops in each host insect) wasp species (Spalangia nigroaenea, S. endius, Muscidifurax raptor, M. zaraptor or Pachycrepoideus vindemiae). Also it is aggressive in searching out potential hosts. These characteristics make this species potentially an important parasite for commercial parasite producers.

Source: J. J. Petersen & D. M. Currey. 1996. Timing of releases of gregarious Muscidifurax raptorellus to control flies associated with confined beef cattle. J. Agric. Entomol. 13: 55-63.

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