Insecticide resistance of housefly, Musca domestica L. (Diptera : Muscidae) in poultries, with special reference to the yearly changes in resistance levels

Insecticide resistance of houseflies inhabiting a poultry ranch in Hachinohe City, Aomori Prefecture was studied from 1982 to 1998. An outbreak of houseflies in 1989 proved to be highly resistant to permethrin, with the LD_<50> value of 67 times that of the susceptible fly. They were also resistant to organophosphorus (OP) compounds. The LD_<50> value of the field-collected colony in 1989 increased 140 times the resistance ratio for permethrin by succesive treatments of permethrin for 5 generations (Hachinohe R). Houseflies taken from a poultry ranch in Tojo Cho, Hiroshima Prefecture showed drastic development of permethrin-resistance, with the LD_<50> value of 10.1μg per female (673 times that of the susceptible fly). The testing result on the Hachinohe R strain indicates that a recessive kdr gene might participate to develop pyrethroid-resistance. The resistance ratios to Insect Growth Regulators were low or moderate.