Effects of pyriproxyfen on wild populations of the housefly, Musca domestica, and compatibility with its principal parasitoids

BACKGROUND: The housefly, Musca domestica L., is an important pest of animal agriculture. Effective fly management requires integration of manure management, mass trapping, biological control, and selective insecticide use. Insecticidal control of houseflies is difficult due to the rapidity of resistance development, yet the insect growth regulator pyriproxyfen (PPF) is one of few insecticides that may still be effective. Here, we tested the susceptibility of wild housefly populations in the USA and in Israel to PPF, as well as the effect of PPF on housefly parasitoids of the genera Muscidifurax and Spalangia. RESULTS: Most housefly populations from both countries were completely eliminated at PPF concentrations of 100 mg kg^–1 (USA) and 600 mg kg^–1 (Israel). One population from each country exhibited initial levels of PPF tolerance. PPF efficacy significantly decreased in cow manure. Emergence rates of parasitoids developing in PPF-treated hosts at concentrations of ≥600 mg kg^–1 were significantly affected, whereas other fitness parameters were moderately to non-affected. CONCLUSIONS: PPF is still an effective tool for housefly control, but resistance management practices should be employed to avoid resistance. PPF is compatible with principal housefly parasitoids at concentrations <600 mg kg^–1, and is suitable for use in integrated pest management.