FIELD SURVEY OF INSECTICIDE RESISTANCE IN HAEMATOBIA-IRRITANS EXIGUA DE MEIJERE (DIPTERA, MUSCIDAE)

A survey of farms in northern New South Wales and southeastern, centra l, western and northern Queensland was conducted to determine levels o f insecticide resistance in populations of buffalo fly Haematobia irri tans exigua. A field bioassay using discriminating concentrations of 1 0 insecticides commonly used for buffalo fly control was used. Resista nce to all synthetic pyrethroids tested (cypermethrin, deltamethrin, c yhalothrin, flumethrin and cyfluthrin) was common and widespread in co astal zones, but was lower in inland zones. In contrast, there was no resistance to the organophosphate diazinon and only low levels of resi stance to ethion and chlorfenvinfos. Synergism between piperonyl butox ide and cypermethrin was demonstrated.