Flies are annual summer pests of cattle and other livestock. Controlling them could mean happier, healthier and heavier livestock, said Lee Townsend, Extension entomologist with the University of Kentucky College of Agriculture.

Horn flies are small flies that feed off the blood of cattle and in rare cases, horses. Young animals are the most susceptible to horn flies, as large numbers of flies feeding on an animal can cause lower weights.

“Weaning weights of calves with an average of 200 or more horn flies during the summer are about 15 pounds less than those that are protected from horn flies,” Townsend said. “The same type of impact has been seen on yearling cattle.”

Since the flies spend most of their time on their host, they are an easy target for insecticide treatments, with dust bags and ear tags providing the most consistent control. The goal is to get fly populations lower than 100 flies per animal.