Dispersal of the filth fly parasitoid Muscidifurax raptorellus (Hymenoptera : Pteromalidae) following mass releases in cattle confinements

Pupae of house fly, Musca domestica L. (Diptera: Muscidae), reared in the l aboratory mere used to assess the movement of Muscidifurax raptorellus Koga n & Legner (Hymenoptera: Pteromalidae) following mass releases of this filt h fly parasitoid in cattle confinements. Parasitism of sentinel pupae was 3 4%, averaged for three mass releases (approximate to 220,000 individuals/re lease) at each of two sites. Parasitism declined only slightly with the dis tance (1 to 100 cm) of pupae from the point of parasitoid release (for data combined from all releases, P < 0.001, r(2) = 0.032). Wind direction had n o consistent effect on parasitism for six releases (P > 0.05). Twenty-nine specimens of M. raptorellus mere recovered in 1998, following release of mo re than 1.3 million individuals in previous years. Because the winter of 19 97-1998 was unusually warm, further studies are required to determine wheth er the parasitoid can survive winters more typical of southern Alberta. The se results suggest that (1) mass releases of M. raptorellus can be used to help manage populations of stable fly and house fly in cattle confinements, (2) mass releases at intervals of 200 m should achieve fairly uniform cove rage of the confinement facility with parasitoids, and (3) mass releases wi ll be required each year. Eight additional species of parasitoids (Hymenopt era) were recovered from pupae during the study. Each of these species prev iously has been reported from house fly pupae in Alberta, with the exceptio n of Eupelmus (Macroneura) vesicularis (Retzius) (Eupelmidae). (C) 2000 Aca demic Press.