Livestock and Insects

Flies on Livestock

Gaines W. Eddy.

Horn flies are small black flies that somewhat resemble house flies but are only about half as large. They feed chiefly on cattle but may attack sheep, goats, horses, and a few other animals. Most of their adult life is spent on an animal. The horn fly lays its eggs only on fresh droppings. The larvae feed and develop in the manure. About 2 weeks are required for the horn fly to develop from egg to adult.

The cheapest and most effective way to get rid of horn flies is to apply an insecticide on the animals.

Methoxychlor is recommended for use on dairy animals at a concentration of 0.5 to 1.0 percent. To prepare the lower concentration, use 8 pounds of a 50-percent wettable powder to 100 gallons of water, or 16 pounds (2 gallons) of a 25-percent emulsion concentrate to 100 gallons of water. About 2 quarts is enough to spray an animal of average size. It will protect the animals for about 3 weeks. If a higher concentration is used, reduce the amount of spray proportionally.

Pyrethrum sprays also can be used effectively and safely on dairy animals to control horn flies, but more frequent treatments are necessary. DDT is not recommended for use on dairy animals.

Other insecticides as well as methoxychlor can be used safely for horn flies on beef or range cattle or on cows not being milked. DDT or TDE at 8 pounds of 50-percent wettable powder to 100 gallons of water are effective. Several different emulsifiable concentrates of toxaphene are also available. The manufacturer's directions for mixing and applying them should be followed closely. All four insecticides are effective. One spraying normally should protect the animals for about 3 weeks.

No special spray equipment is needed for applying insecticides to cattle to control the horn fly. High-pressure spraying is unnecessary. The number of animals to be treated largely dictates the type of sprayer. Small numbers can be treated satisfactorily with hand air-pressure sprayers of the cylindrical or knapsack type. For large numbers, a power sprayer with adjustable nozzle, operated at 100 to 200 pounds pressure, is suggested. Regardless of the sprayer used, the operator should make sure the insecticide always is well mixed.

STABLE FLIES look like house flies and are of about the same size. Stable flies have long, piercing mouth parts, however, and the wings at rest are held at an angle to the body. Stable flies feed on several species of warm-blooded animals but cause the greatest annoyance and damage to cattle and horses. The flies bite mostly on the legs and lower parts. The females lay their eggs in moist fermenting organic matter. Manure, especially when mixed with straw, is a favorite breeding place. Development from egg to adult takes about 3 weeks.

The stable fly is usually controlled through one or a combination of the following methods: Destruction of breeding places; application of residual insecticides to buildings, sheds, corrals, and other places where the flies rest; and application tides to the animals.

Only methoxychlor, lindane, or pyrethrum sprays should be applied to dairy barns to control the stable fly. If a wettable powder of methoxychlor is used, a concentration of 2.5 percent is suggested. An emulsion may be used at a concentration of 2.5 to 5 percent. Lindane is recommended at a concentration of 0.25 to 0.5 percent. Pyrethrum sprays are not very effective as residual treatments against stable flies.

Those materials, as well as DDT and chlordane, may be used in or outside other types of buildings. DDT is recommended at the same concentrations as those I gave for methoxychlor. Chlordane is recommended at a concentration of 2 percent. The relative merits of the various materials as residual treatments against stable flies have not been determined. Residual sprays may not effectively reduce stable fly populations when used without other control measures, however.

The amount of spray to apply to barn surfaces depends on the type of surface. One gallon of spray will cover about 500 to 1,000 square feet. The surfaces should be wet with the spray just to the point of runoff. All buildings poultry houses, hog pens, corrals, and such should be sprayed at the same time. For treating barns or large buildings, power sprayers are most satisfactory.

Pyrethrum is one of the most effective materials against stable flies. It is used alone or in combination with other materials activators, synergists, or antioxidants that make pyrethrum more toxic or longer lasting. Among the better-known synergists used with pyrethrins are piperonyl butoxide and n-propyl isome. Pyrethrins are generally used against stable flies at concentrations of 0.05 to 0.1 percent. A concentration of 0.1 percent will protect animals from stable fly attack for 1 or 2 days. A combination of 0.1 percent of pyrethrins and 1.0 percent of piperonyl butoxide will usually give complete protection for 2 days and partial protection for 2 or 3 days longer.

The residual toxicity of pyrethrins is affected by weather conditions. Somewhat longer protection is had in the spring and fall than in summer. Pyrethrum sprays are rather expensive to use on range stock and generally are not considered practical for this purpose. They are widely used on dairy animals and around dairy barns, however.

A concentration of 0.5 to 1.0 percent of methoxychlor, the only chlorinated insecticide recommended in 1952 for the control of stable flies on dairy animals, will give some protection and cause a high mortality of the feeding flies during the first few days after treatment. DDT and methoxychlor can be used on beef or range animals. DDT is recommended at the concentration suggested for methoxychlor.

In treating animals for the control of stable flies, the lower half of the animal, especially the legs, should be sprayed thoroughly.

FARMERS AND RANCHERS are familiar with the large bloodsucking flies known as horse flies, but less familiar are the deer flies, which in some parts of the United States cause great annoyance to livestock. Horse flies and deer flies are members of the family Tabanidae.

As a group, the horse flies are more numerous, cause more trouble, and are considerably larger than deer flies. The several hundred kinds of horse flies have different breeding and feeding habits. Most of the species breed in moist places. Development from egg to adult may require only a few months or 1 to 2 years or more, depending on the species. Like stable flies, horse flies and deer flies feed on many different warm-blooded animals but cause the greatest annoyance and damage to cattle and horses.

For horse flies and deer flies, no satisfactory methods of control have been developed. Repellents in use in 1952 were not effective enough or were too costly for use on a large scale. The practical value of insecticides such as DDT or methoxychlor, which kill some of the feeding flies, was not fully determined in 1952.

Pyrethrum has been used often as a repellent against horse flies. Sprays containing 0.1-percent concentration of the pyrethrins will protect animals from fly attack for about 24 hours. The addition of piperonyl butoxide will extend the protection to about 48 hours.

Striped horse fly.

Stable fly.