Selected Insecticide Delivery Devices for Management of Horn Flies (Haematobia irritans) (Diptera: Muscidae) on Beef Cattle.

The horn fly, Haematobia irritans (L.) (Diptera: Muscidae), is one of the most important pests of the beef cattle industry. Horn fly adults are blood feeders that remain in constant contact with cattle, providing management opportunities via insecticide-impregnated ear tags. Controlling horn flies in the United States is time consuming and costly, but failure to implement management can lead to weight loss and decreased weight gain of calves and yearlings. In the past decade, new chemical combinations have been impregnated into ear tags for pest management. The objectives of this project were to 1) evaluate the efficacy of ear tags against horn fly populations and 2) determine if reduced fly density results in economic return. During 2013, data were compiled by insecticide class; treated cows averaged fly reductions of 198 (s = 38.91; n = 3) for macrocyclic lactone treatments, 175 (s = 62.74; n = 4) for pyrethroid treatments, and 174 (s = 35.28; n = 8) for organophosphate treatments compared with untreated animals (214; s = 50.38; n = 9). During 2014, mean fly reductions were 187 (s = 14.15; n = 4) for macrocyclic lactone, 147 (s = 61.41; n = 13) for pyrethroid, and 143 (s = 77.16; n = 8) for organophosphate treatments relative to the untreated (200; s = 99.83; n = 14). A novel technology, the VetGun application system, tested in 2014, resulted in fly reductions (121 ±, n = 4), but means were not statistically significant from the control (200; s = 99.83; n = 14). Treatment of cattle with ear tags significantly reduced horn fly numbers compared with untreated cattle.