Flies and mosquitoes are a nuisance, causing irritation and discomfort as they feed on horses. They can also be a health risk, spreading West Nile virus, encephalomyelitis viruses, equine infectious anemia, vesicular stomatitis, and other diseases. In this article we will share some tips on eliminating these pests and give you some new ideas and insight on what works, and what doesn’t, in the war on flies and mosquitoes.

Eliminating the Source

Lee Townsend, PhD, an extension entomologist at the University of Kentucky, says the ideal situation for controlling insects is to get rid of breeding sites. Often this is impractical or impossible, but it’s worthwhile to identify and remove or alter as many as you can.

Breeding sites for some insects might not be on your farm. “Face flies and horn flies breed in fresh cow manure. If your horses live near cattle herds, you can’t control the breeding sites and are just dealing with the flies that come to your horses,” says Townsend. “Horse flies and deer flies breed in wetlands or along stream banks that may be miles away. Some of the mosquitoes that are problems for horses can fly several miles before they feed, and may also be carried long distances on wind currents.”

Stable flies can also come to your farm from somewhere else. In a Florida study, stable flies were marked and released, and strong winds carried them 135 miles, says Bill Clymer, PhD, BCE, ARPAS from Amarillo, Texas, a parasitologist for Fort Dodge Animal Health. “But most stable flies come from your own place or within a mile or two radius,” he adds. He recalls a farm in Colorado that had a serious problem with stable flies that were coming from a pole barn a mile away. Alfalfa hay had been stored there, but the hay had been taken out, leaving a thick mat of old alfalfa leaves. A blowing rain got the hay leaf litter wet, and millions of stable flies were breed