HORN FLY

HORN FLY

The horn fly is a small, bloodsucking fly about one-half as large as the house fly. It lives on cattle, usually resting and feeding on the back and shoulders. During hot, sunny days the flies may concentrate on the under parts to escape the heat. Despite their name, they are seldom seen on horns. Occasionally on cool days hundreds of the flies may concentrate near the base of the horns.

The horn fly breeds only in fresh cattle droppings. Flies will dart from the cattle and quickly deposit several reddish-brown eggs on fresh droppings and then fly back to rest on the animal. In summer the eggs hatch in about 16 hours. The small maggots, or larvae, feed on the manure for 5 days or so and then change to the resting, or pupal, stage. The pupae are usually found in the lower part of the droppings or on or in the soil beneath the droppings. After 4 to 5 days the flies emerge and seek cattle on which to feed. Within a few days they are ready to repeat the life cycle, which, from egg to egg, is completed in about 2 weeks in warm weather. The horn fly lives through the winter in the pupal stage.

The horn fly entered the United States about 1890 and quickly spread. It is found yearlong on cattle in southern Texas and Florida. Early in the spring in the more southern areas and in late spring in the central and northern parts of the country, the adults begin to appear. They quickly increase in numbers as the warm season advances.

If control measures are not taken, horn flies commonly become so abundant that each animal may be attacked by 3,000 to 4,000 flies. Such large numbers cause extreme annoyance and are a constant drain on the blood supply of the animals. Large numbers of the flies can reduce milk production of dairy cattle by 10 to 20 percent and prevent weight gains of beef cattle by as much as one-half pound a day.

Control: Sprays containing toxaphene or at least a 0.5 percent concentration of TDE, methoxychlor, or DDT are recommended for controlling the insect on beef cattle. Apply about 2 quarts of the spray per animal; if the concentration is increased up to 1.5 percent, one needs to apply correspondingly less spray. Spray the backs, sides, and bellies of the animals. When toxaphene is used, do not exceed a concentration of 0.5 percent so as to avoid possible harm to cattle, especially calves. One treatment with any of the insecticides will control the flies for 3 to 4 weeks.

Methoxychlor is recommended as most economical and effective on dairy cattle. Use as suggested for beef cattle. DDT, toxaphene, and TDE are not recommended for use on dairy cows because the chemicals may appear in milk. Pyrethrum sprays that have been fortified with piperonyl butoxide, n-propyl isome, or similar synergists are also recommended for horn flies on dairy cows. Oil-base pyrethrum sprays can be applied in small amounts (not exceeding 1 ounce) to dairy cows at each milking or pyrethrum water-base sprays may be applied at the rate of 1 or 2 quarts per animal for protection up to a week. Oil-base sprays containing lethane and thanite may also be used as a light mist spray at milking time for controlling flies on dairy cattle. Do not soak the animal with oil-base sprays, as the oil alone can be harmful.