Insecticide resistance in house flies from caged-layer poultry facilities

The frequency of resistance of eight strains of house flies, Musca domestic a L., collected from caged-layer poultry facilities across New York state, to nine insecticides (dimethoate, tetrachlorvinphos, permethrin, cyfluthrin , pyrethrins, methomyl, fipronil, spinosad and cyromazine) was measured rel ative to a laboratory susceptible strain. Percentage survival was evaluated at five diagnostic concentrations: susceptible strain LC99, 3 x LC99, 10 x LC99, 30 x LC99 and 100 x LC99. The highest levels of resistance were note d for tetrachlorvinphos, permethrin and cyfluthrin. There was substantial v ariation in the levels of resistance to the different insecticides from one facility to another, independent of their geographical location. There was very little cross-resistance detected in these populations to either fipro nil or spinosad. Overall, there was a good correlation between insecticide use histories and the levels of resistance. The apparent isolation of fly p opulations within poultry facilities suggests that there are good opportuni ties for the implementation of successful resistance management strategies at these facilities. Differences between these results and those of a resis tance survey on New York dairy farms in 1987 are discussed. (C) 2000 Societ y of Chemical Industry.