Since its introduction into the U.S. in the late 1800s, the horn fly has become a persistent challenge for livestock producers in pasture-based systems. For beef and dairy operations, horn flies are more than a nuisance; they contribute to measurable losses in weight gain, milk production and overall animal performance.

Five species of lice parasitize cattle in the U.S. Four of these are blood feeders, and the fifth is a biting or chewing louse. Cattle with hair loss, an unthrifty appearance, and leaving hair on fences and other objects from rubbing may be a sign of lice infestation.

The horn fly is a major pest of pasture and rangeland cattle throughout the U.S. Adult horn flies are blood-feeding flies taking, on average, 30 blood meals per day.