Horn Fly (Diptera: Muscidae) Control on Beef Cows with Permethrin-Impregnated Ear Tags and Effect on Subsequent Calf Weight Gains

Abstract

Permethrin-impregnated ear tags effectively reduced horn flies during the 1981 and 1982 fly seasons by 96 and 99%, respectively. Calves nursing treated cows compared with calves nursing untreated control cows gained 6.7 kg (P < 0.05) more in 1981 and 4.4 kg (P <0.01) more in 1982. Calves nursing treated cows were on an average 5.6 kg heavier at weaning time than calves nursing untreated cows during the 2 year study. Analysis of male calf weight gains from late September through mid-November showed that the average increase in nursing gain was not compensated for following the horn fly season.