Submitted to: Environmental Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/3/2006
Publication Date: 2/1/2007
Citation: Geden, C.J. 2007. Development of spalangia cameroni and muscidifurax raptor on live house fly pupae and pupae killed by heat shock, irradiation and cold. Environmental Entomology. 36(1):34-39. Interpretive Summary: Parasitic wasps are among the most important biocontrol agents for filth flies, and there are several commercial insectaries that provide these wasps to farmers. One of the challenges that parasitoid producers face is dealing with fluctuating demands for their products because it takes a week to produce fly pupae for the parasitoids, and these live pupae only have a shelf life of 2-3 days. In this study, conducted by a scientist at ARS’s Center for Medical, Agricultural and Veterinary Entomology, live house fly pupae were compared with pupae that had been killed by heat shock, gamma irradiation and cold for their ability to produce two species of parasitoids, Muscidifurax raptor and S. cameroni. Heat-killed, irradiated, and freeze-killed pupae remained as effective for production of M. raptor as live pupae for 4 months when pupae were stored in freezer bags in a refrigerator. Production of S. cameroni on heat-killed and irradiated pupae was equal to parasitoid production on live pupae for up to 2 months of storage, after which production on killed pupae declined to 63% of that observed with live pupae. Production of S. cameroni on freeze-killed pupae was about 75% of production using live pupae for 8 weeks of storage but declined rapidly thereafter. Killing pupae by heat provides a simple and low-cost method for stockpiling high-quality hosts for mass-rearing both of these filth fly biological control agents.
Technical Abstract: Two-day-old house fly pupae were subjected to heat shock treatments of varying temperatures and durations in an oven at 70%RH; exposure to temperatures of 55oC or higher for 15 min or longer resulted in 100% mortality. Exposure to 50oC resulted in 40 and 91% mortality at 15 and 60 min. All (100%) pupae placed in a -80oC freezer were killed after 10 min exposure; exposure times of less than 5 min resulted in <21% mortality. Progeny production of Spalangia cameroni and Muscidifurax raptor from pupae by killed heat shock or 50kR of gamma radiation was not significantly different from production on live hosts on the day of treatment. Freeze-killed pupae produced 16% fewer S. cameroni than live pupae and an equivalent amount of M. raptor progeny on the day of treatment. When killed pupae were stored in freezer bags at 4oC for 4 months, heat-killed, irradiated, and freeze-killed pupae remained as effective for production of M. raptor as live pupae. Production of S. cameroni on heat-killed and irradiated pupae was equal to parasitoid production on live pupae for up to 2 months of storage, after which production on killed pupae declined to 63% of that observed with live pupae. Production of S. cameroni on freeze-killed pupae was 73-78% of production using live pupae during weeks 2-8 of storage, then declined to 41 and 28% after 3 and 4 months, respectively.