Susceptibility of the adult house fly (Diptera: Muscidae) and 3 of its principal parasitoids (Hymenoptera: Pteromalidae) to the GHA strain of Beauveria bassianaand 4 isolates from field-collected muscid flies

House fly (Musca domesticaL.) (Diptera: Muscidae) populations can negatively impact poultry layer facilities, posing a risk to human and animal health and egg food safety. House flies quickly develop resistance to traditional chemical control methods; therefore, improved biological control may provide opportunities for improved integrated pest management (IPM) programs. Biological control methods currently used include augmentative releases of pteromalid pupal parasitoids and application of the fungal entomopathogen Beauveria bassiana(Balsamo) Vuillemin. This study used bioassays to compare the impact of different B. bassianastrains on survival of house flies and of 3 species of filth fly parasitoids. The B. bassianathat were compared were 3 new field-collected isolates, an older field-collected isolate (L90), and a common commercially available strain (GHA). Flies and parasitoids were exposed to filter paper treated with 1.5 × 109spores of each strain and a control. All field-isolated strains induced lower mean survival times in house flies than GHA did. The results for all species of parasitoids demonstrated less difference among the treatment groups and the control than in-house flies. Although there was some effect of B. bassianaexposure on parasitoid mortality, the expected spatial separation of parasitoids from areas of application may offer some protection. Using the most effective tested strains of B. bassianaand filth fly parasitoids jointly could be a biological component of an IPM plan for fly control in poultry facilities.