Date of this Version
This NebGuide identifies ways to control horn flies on cattle.
The horn fly is a blood-feeder that feeds 20 to 30 times per day. A population of several thousand horn flies may be present on one animal. When large numbers of these flies are on cattle, the cattle bunch and expend considerable effort fighting the flies. They will often stand in water or seek shade trying to get relief from the flies. When they do this, they fail to graze normally.
Studies in the United States and Canada show that during the grazing season yearling cattle free from horn flies gain from 15 to 50 pounds more than heavily infested animals. Nebraska studies and others show a 10- to 15-pound advantage in calf weaning weights where cows have had good horn fly control. Milk production of dairy cattle pastured during the day may be decreased as much as 20 percent by horn flies. However, horn flies have the most impact on pasture and range cattle.