Warmer weather means more activity for owners and their horses, but it also signals the beginning of the dreaded fly season. If you support a horse, chances are you're also supporting entire colonies of flies, and you're convinced that they are telling all their fly friends to head over to your place and your horse.
You can win the war on flies, but only if you work diligently to eradicate them through good stable and pasture management and an integrated system of fly control. You can choose from a wide range of fly control products, and you may need to use several methods. Some, such as fly masks, simply keep flies away from a horse's sensitive areas. Others kill the flies or the larvae with everything from insecticides to bait and natural predators.
Flies not only annoy our horses and us, they carry disease.
"We don't want to eradicate the flies just because they are a nuisance," confirms Dr. Jay Donecker, senior veterinarian with the equine group at Pfizer Animal Health. "In California, for example, horses are having a problem with pigeon fever, and researchers have found that it's spread by the housefly. Studies are looking into whether you can reduce the incidence of pigeon fever by lessening the fly population."
The Center for Equine Health (CEH) at the University of California at Davis reports that flying insects can cause a variety of skin problems in horses. Midges, also called "no-see-ums" or Culicoides, cause dermatitis, leading to lesions on the mane, rump, and belly and sweet itch. A variety of flies can also cause dermatitis, and black flies may produce edema and hives in horses. The CEH says that in extreme cases of fly infestation, pregnant animals may abort, and even death can occur.
Another weapon in the arsenal is the feed-through fly control product. These formulas are designed to work by passing through the horse's system and depositing a fly-control ingredient directly in the horse's manure. When flies lay their eggs in the manure, the product prevents the larvae from maturing, thus killing the insect. Because feed-through products work on fly larvae, they should be started a few weeks before the beginning of fly season. That gives the product time to kill the larvae before flies become a problem.
Ingredients in feed-through products differ depending on the manufacturer. Some include insecticides, while others use natural products like garlic or diatomaceous earth.
Keep Flying Pests Grounded
- An integrated program is best. Attack your fly problem on multiple levels.
- Clean stalls, pens and runs regularly; dispose of manure promptly.
- Situate the manure pile well away from living spaces; cover where practical.
- Eliminate areas of standing water.
- Use fine-mesh screens to keep flies away from stalled horses
- Install horse-safe fans to discourage flies and insects from landing.
Integrated Programs
Even if you choose a feed-through product or rely on other methods, experts advise you to use an integrated system that can get rid of flies in a variety of stages.
"People find they have to use something else too," says Doug Ross, Ph.D, product development manager at Farnam. "No feed-through product will affect adult flies. Plus, flies are very strong fliers and can travel from other barns."
Donecker agrees, noting that owners still have to do the simple things, such as keeping stalls and pastures clean and free from manure. When he had a private veterinary practice and visited farms regularly, Donecker says he was concerned with the effect such things as overhead spray systems would have on people since they put pesticides directly into the air. He suggests that with a feed-through product, a mist system would not have to be activated as often.
An integrated fly control system might include a feed-through product, misters in the barn, fly sprays, fly masks, and fly sheets. Or if you prefer more natural methods, you might choose fly predators (tiny wasps that lay eggs in developing fly pupae, killing them), baits and traps. (For an in-depth look at natural fly control methods, see "Fight Nature With Nature," Perfect Horse, May 2005.)
U.C. Davis' Center for Equine Health also offers the following recommendations: Stable horses at sunrise and sunset, which are insects' peak feeding hours; use ultrafine screens in barn windows; keep horses away from standing water; put overhead or stall fans in the barn to interfere with the flight of flies; and cover manure piles or containers and get rid of the manure as often as possible.
"Manure on site is one of the biggest contributors to fly population," says Farnam's Ross.
