STABLE FLY (DIPTERA, MUSCIDAE) INSECTICIDE RESISTANCE IN KANSAS CATTLE FEEDLOTS

Insecticide resistance to two organophosphates, dichlorovos and stirofos, and a pyrethroid, permethrin, was detected in stable flies, Stomoxys calcitrans (L.), collected from eight cattle feedlots in southwestern Kansas. The frequency of resistant stable flies ranged from 2 to 100% depending on population and insecticide tested. No resistance was detected to the chlorinated hydrocarbon methoxychlor. Generally, the prevalence of resistance in each fly population in decreasing order was dichlorvos > stirofos > permethrin. Resistant stable flies were found in some feedlots where insecticide use was absent or minimal (i.e., application once per year or less) and was suspected to have resulted from localized dispersal of insecticide-resistant flies from nearby feedlots.