The current status of insecticide resistance in Musca domestica in England and Wales and the implications for housefly control in intensive animal units



Following the 1984–85 housefly (Musca domestica L.) resistance survey, a similar survey was carried out between January 1990 and April 1992 in order to monitor changes in UK housefly resistance. Samples of fly populations were collected from 35 farms throughout England and Wales. Dose-response data were obtained by topical application and feeding test methods. For both methods the knockdown (KD) after 48 h was used for all the dose-response comparisons. The ranges of resistance factors for the topical application method were for methomyl, 1·6–20·0 at KD50 and 4·5–34·4 at KD95; for azamethiphos, 2·5–58·5 at KD50 and 5·0–2604 at KD95; for pyrethrins+piperonyl butoxide, 1·2–9·6 at KD50 and 1·6–14·7 at KD95; and for permethrin, 2·2–118·8 at KD50 and 4·3–200·0 at KD95. The ranges of the resistance factors for the feeding tests were for methomyl, 1·2–56·1 at KD50 and 3·1–80·0 at KD95, and for azamethiphos, 3·9–125·0 at KD50 and 4·4–380·0 at KD95. The means of resistance factors for all of the insecticides showed increases over those obtained in a previous survey carried out in 1984–85. The significance of the results for housefly control in intensive animal units in the UK is discussed.