Control of Face Flies and Permethrin Resistant Horn Flies on Pastured Beef Cattle with Insecticidal Ear Tags, 1990

Twelve insecticide ear tags were efficacy tested against face and horn flies on beef cattle. All populations of horn flies were assayed for resistance to permethrin and diazinon prior to tag application and when possible after the tags were removed. These horn flies were compared to susceptible horn flies obtained from the USDA Livestock Laboratory, Kerrvilie, Tex. Tags were applied to 3 groups of cattle with differing insecticide treatment history. One group had been treated the previous year with diazinon ear tags (group A), another with pyrethroid or Maxcon tags (group B), and the third group with various nontag treatments (group C). Each adult animal in the respective herds received 1 tag/ear. After tagging, counts were made at weekly intervals on 10 randomly selected animals from each herd. Counts were made during the same time period (11:00 A.M.-4:00 P.M.). Horn flies were estimated on one side of each animal and face flies were counted on the head and face of these same animals. Fly populations of treated herds were compared to populations on untreated herds located no closer than 0.8 km. The effectiveness of treatments was determined by calculating the percent reduction of fly populations on treated to untreated herds.