Winter survival of nuisance fly parasitoids (Hymenoptera: Pteromalidae) in Canada and Denmark

Independent studies were performed in Canada and in Denmark to assess the survival of parasitic wasps (Hymenoptera: Pteromalidae) wintering in puparia of house fly, Musca domestica Linnaeus (Diptera: Muscidae). Data in Canada were collected for Muscidifurax raptorGirault & Saunders, M. raptorellus Kogan & Legner, M. zaraptor Kogan & Legner, Nasonia vitripennis(Walker), Spalangia cameroni Perkins, Trichomalopsis sarcophagae (Gahan) and Urolepis rufipes (Ashmead) in three microsites at an outdoor cattle facility in southern Alberta. Survival was highest for N. vitripennis, T. sarcophagae and U. rufipes, ranging from near zero to c. 7%. No survival was observed for S. cameroni. Daily mean values for ambient air temperature (DMAT) averaged about -3.5 degrees C during exposure periods. Data for Denmark were collected for M. raptor, S. cameroni and U. rufipes in a dairy barn and in a swine barn. Survival of M. raptor and U. rufipes was higher than that of S. cameroni in the dairy barn (DMAT = 8.6 degrees C), with the three species having similar survival in the swine barn (DMAT = 15.4 degrees C). In both studies, parasitoids in egg stages were least likely to survive. These results identify the potential for T. sarcophagae and U. rufipes to be commercialized for use in northern climates as biocontrol agents for nuisance flies, compare directly the cold-hardiness of commercialized species (i.e. all of the above species excluding T. sarcophagae and U. rufipes), and document the importance of microsite on winter survival.