Inundative releases of pteromalid parasitoids (Hymenoptera: Pteromalidae) for the control of stable flies, Stomoxys calcitrans (L.) (Diptera: Muscidae) at confined cattle installations in west central Nebraska.

Fly pupal parasitoids, primarily Muscidifurax raptor Girault and Sanders and Spalangia nigroaenea Curtis, purchased from commercial insectaries, failed to reduce numbers of stable fly, Stomoxys calcitrans (L.), significantly despite weekly releases of high numbers at one feedlot and one dairy during 1990 and a different feedlot and dairy in 1991. Parasitoid emergence from stable fly puparia were not significantly greater in the confinements where releases were made compared with confinements where no releases were made. The level of parasitism increased at all four confinements during and following parasitoid releases. Shipments of parasitoids contained neither the number requested or the species purity that had been anticipated. Both quantity and quality of parasitoids improved the second year of the research. The most numerous naturally occurring parasitoid species were also present at a new, relatively isolated feedlot by mid-July.