The stable fly is a blood sucker that looks like a house fly but has a piercing-type mouthpart that projects forward from the front of its head. Male and female flies feed on warm-blooded animals and humans, usually around the lower leg or ankles. They also will attack dogs, biting them mostly in the ears. Stable flies are not limited to barns and stables; they will rest around houses and attack people, too. Stable flies are strong fliers; they can cause problems at least 2 miles from their breeding sites.
The bite of the stable fly is so painful that cattle and horses will stamp or kick trying to rid themselves of these pests, and the animals may be difficult to handle as a result. Studies have shown that heavy stable fly infestations (50 or more per animal) can reduce feed efficiency by 10 to 13 percent. Stable filies can also carry anaplasmosis from infected to healthy animals.
Many of the insecticides labeled for fly control on cattle and horses are effective against the stable fly but control is difficult. Stable flies feed 2 to 3 times per day, usually biting on the lower parts of the legs, which are difficult to treat or to protect. Also, these flies spend much of their time away from animals while resting on walls, fences, or vegetation. Residual sprays applied to resting sites around stables can help some, but the flies sit on lots of other surfaces.
Sanitation is the key to stable fly management. These flies are common around dairy lots and stables where they breed in a mixture of rotting or fermenting feed, straw, manure, or other types of rotting vegetable matter. They can also be pasture pests in areas where round bales are used extensively or where hay is fed. Stable fly maggots can develop in trampled hay mixed with urine and manure. Each stable fly female produces about 500 eggs, so numbers can increase rapidly.
Space sprays (foggers) or residual sprays can help reduce numbers, but breeding site elimination is the most effective means of control. Stable fly traps are effective at catching flies but are probably better as a gauge of fly activity than in killing large numbers of flies – it is almost impossible to control flies when there are many breeding sites.
By Lee Townsend, Extension Entomologist