Areawide Cattle Treatments on Populations of Horn Flies (Diptera: Muscidae)1

Abstract

Six hundred mature cattle on 960 km² of New Mexico rangeland were treated with two ear tags, each tag containing 8% fenvalerate (Ectrin^®). This treatment resulted in inhibition of reproduction of Haematobia irritans (L.) in the treatment area. After the removal of ear tags on Cattle in the center of the treatment area, 6–8 km isolation was demonstrated as insufficient to prevent reinfestation since a reproducing infestation was established within 30 days. Within 60 days, counts equalled those on untreated cattle. Treatment of all mature animals in late summer-early fall resulted in the elimination of an overwintering diapausing population and thus a delayed spring population increase of horn flies. The treatments available, in conjunction with the manipulation of treatment later to control diapausing populations, will provide areawide control of horn flies.