Ask the Vet

Fly Control for Horses

To get the best performance, many fly control products need to be started prior to fly season. (DTN/Progressive Farmer photo by Victoria G. Myers)


I read your column that mentioned minerals or feed supplements that help with fly control in cattle. Is there anything like that for horses?


I don't do any equine work anymore, but when I did, fly control was a huge problem. Talking with horse owners and veterinarians, I'm told it still is.

There are many flies that can be a problem around horses, include biting midges, horseflies, deer flies, stable flies, horn flies, face flies and houseflies. Each may require different control measures. Sanitation and moisture control are universal recommendations. Many flies breed in mature and decaying organic material -- including feed and hay. Manure must constantly be removed from stalls, barns, paddocks and other high-use areas and properly disposed of. Leftover feed, grain and hay should be cleaned up daily.

Remedy any moist areas.Two insect growth regulators are approved for use with horses. Both interfere with formation of chitin, the primary component of the insect exoskeleton. They prevent molting of fly maggots, and can help with species that use manure in their life cycles.

Diflubenzuron is sold as SimpliFly and Equitrol II. The products are identical and are top-dressed onto grain or mixed into the ration. The dose is 6.8 mg per 100 pounds of body weight. For a 1,000-pound horse, the dosage would be 1 ounce per day. Cyromazine is sold as Solitude IGR. It is an alfalfa-based pellet dosed at 1/2-ounce per day.

These products must be started before fly season starts to be most effective. If neighboring livestock are not on an IGR, these products are likely to be less effective. Not all flies are controlled by IGRs, in which case additional premise or on-animal fly-control products will probably be needed.