The War on Flies

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If you have horses, you have flies. And while you battle flies year after year, you can never rid yourself of them completely. You can only hope to contain them.

First, know thine enemies. There are many different types of flies, but the biting stable fly is the most common. Stable flies feed by sucking on the horse’s blood. They most commonly bite the lower legs, flanks, belly, under the jaw and on the front of the horse’s chest. Very sensitive, thinned-skin horses may be intolerant of biting flies. These are the critters that cause all the foot stomping and belly kicking so common in the summertime.

Open any horse supply catalog and you will find pages upon pages of fly control products. In the current era of “going green” and being kind to the environment, many people are turning to more natural methods. Regardless of the number of horses you keep and the approach you take, a good defense is really your best offense.

The first step in fly control is to keep flies from breeding. Failing that, the next step is to keep any larvae from hatching. The third step is to capture and kill any flies that survive into adulthood (or come visiting from another farm). And finally, for those flies that survive all attempts to eliminate them, the final step is to protect your horses from them.


The most important step is proper manure management. Like many aspects of horse ownership, simple hard work and dedication to a clean environment are the best ways to keep the fly population down. That means cleaning and removing manure and soiled bedding on a daily basis. It is equally important to remove all uneaten feed, and to keep new feed covered. You can even go so far as to cover grain buckets or remove them from feed areas.

However, it is not just about cleaning the horse’s living environment. That manure has to be dealt with. On large farms, often there is enough acreage to spread the manure so that it is exposed to the sun and dries out, making it an inhospitable environment for fly breeding. (Stable flies breed in moist manure.) To render it unsuitable for fly reproduction, manure must be spread very thinly, i.e. less than ½ inch thick, and it is best to spread it in areas where horses aren’t actively grazing.

Composting the manure is another option. Be sure to check with local zoning ordinances before establishing a large compost pile. It should be out of sight and downwind of any neighbors and your own house and barn. Locate a compost pile away from the stable, yet close enough for easy access for dumping and getting equipment in to turn the pile.

If your farm produces more manure that can be easily composted, it is best have someone haul away the manure.


For larval control, tiny, stingless wasps commonly known as fly parasites are a safe and non-toxic option. Two main companies offer these tiny wasps—fly predators from Spalding Labs, and fly eliminators from Arbico Organics (see sidebar). These wasps, a mere 1/8-inch long, lay eggs in the fly pupae, killing them before they mature.

The number of fly parasites needed is directly proportional to the number of horses on your property. You release a first bunch before the start of fly season, and then at least monthly thereafter. At the height of fly season, you many need to release them in larger numbers or at more frequent intervals. They should be released in manure areas, wet, boggy areas, and places where horses typically defecate. [Author’s note: I have used fly parasites on my small farm for five years now and have been extremely happy with the results. The number of flies on my property is far less than at other farms in the area.]

One word of caution: if you also use any type of insecticide to control flies, it will also kill your wasps.

So you’re cleaning manure every day and release your fly parasites on a regular basis, but some flies slip through your defenses. How can you get rid of them without using insecticides? Fly traps and tapes. Many traps use a natural pheromone to attract and trap flies. Traps aren’t exactly aesthetically pleasing and can have a foul odor, but they do catch thousands of flies. (The worse they smell, the more flies they seem to attract.) You may need to experiment with locations and heights to find the spots that attract the most flies. Once you find the right locations, they fill quickly.

The traps can be messy to dispose of, but some brands use containers that can be easily sealed.

Sticky tapes can also be used to catch flies, but they can trap other creatures, such as small birds, as well. Also, high dust levels in the barn can render sticky traps less effective. One convenient example: Mr. Sticky offers a rolled form of non-toxic tape. It traps flies on the tape and, once full, you simply roll it onto the disposable wheel, exposing fresh tape.

Other mechanical approaches: Bug zappers have a light that attracts the flies and the electricity kills them. Another form of mechanical control is simply to run fans in your barn. Flies do not like moving air. In the summer, if horses can be brought into the barn where fans are running during the day, that can provide some relief. Horses that live outside should at least have access to some form of shade to escape the worst of the flies.


Regardless of your best efforts at fly control, some pesky survivors will continue to pester your horses. You can protect them with physical barriers such as fly masks, fly sheets and leg wraps. These are typically made of lightweight mesh. It is important to make sure that all equipment fits the horse properly, so that it doesn’t rub or gap. On a farm with large numbers of horses, it may be simply too expensive or labor-intensive to provide fly gear for all horses.


Insecticides, chemicals that kill or repel flies, are available in many forms and applications: sprays, lotions, wipes, and roll-ons among them. Some horses and humans have allergic reactions to insecticides, so it is best to try a product first in a small area until you know how the horse will react. Barnwide systems from companies such as Pyranha Inc., Innovative Equine Systems or United Spray Systems can be built into barns. These use automatic misters that spray insecticide every 15 minutes. This is a more expensive option but can be an effective means of control. There are also natural alternatives for barn sprayers, such as those from Nature’s Balance Care.

Another option comes from Bayer Animal Health, which manufactures QuickBayt, an attractant that kills house flies. It comes in a bait form that you scatter, disposable strips and a spray for targeted application. QuickBayt also contains two attractants and a very bitter substance that discourages accidental ingestion by children and animals.

Also available on the market are feed-through fly preventatives such as Solitude IGR from Pfizer, Equitrol II from Farnam and SimpliFly from Equicare. These typically come in pelleted or powdered form and are added to the horse’s grain. When the horse consumes the feed-through, the active ingredient passes through the horse and is excreted in the manure. Flies lay eggs in the manure, but they are not able to develop and die off. Within four to six weeks, there should be a dramatic decrease in the number of adult flies. In addition, a number of natural feed supplement products containing garlic and other ingredients may also discourage flies.

The methods you decide to use to control flies are often limited by the number of horses in your care, cost, labor, and environmental concerns. It may be helpful to contact the county extension agent in your area to help address your specific needs. Regardless, a multi-pronged approach, with proper manure management as your number one factor, is your best bet in the continuous war on flies.

For More Information

To learn more about specific fly control products, contact the following companies.

• Absorbine: Fly control products,

• Arbico Organics: Fly control fly eliminators,

• Bayer Animal Health: Fly control products,

• Epps Biting Fly Trap: Fly control equipment,

• Farmtek: Fly control products,

• Farnam: Fly control products,

• Horse Health USA: Fly control products,

• Innovative Equine Systems: Fly control equipment and systems,

• Mr. Sticky: Fly tape system,

• Natures Balance Care: Natural insect control products,

• O2Compost: Aerated composting,

• Pfizer: Fly control products,

• Pro-Tech Livestock Corp.: Fly control products,

• Pyranha Inc.: Insect control systems,

• SimpliFly: Feed-through fly control,

• SmartPak: Fly control products,

• Spalding Labs: Fly control fly predators,

• Sweet PDZ: Fly control products,

• United Spray Systems: Fly control system,

• Valley Vet: Fly control products,