Control flies around your barn with tiny wasps that reduce fly populations, but don't sting horses or humans

Controlling the flies around you and your horses is very important, not just because of the irritating bites, but because flies are also traveling vectors of disease. The housefly alone has been accused of spreading more than 30 bacterial and protozoal diseases. Stable flies resemble houseflies, but they travel greater distances, breed in decaying vegetation, and feed on the blood of warm-blooded animals. Deerflies and horseflies, with their painful bites, can travel for miles and are very hard to control. In this article we’ll look at fly predators as an alternative to chemical fly control. This is not a condemnation of chemical sprays, baits, or traps, but it's presented as a way to expand the arsenal of tools by which owners can protect their horses and themselves.

Fly Predators

Horse owner Cindy Landon of Avoca, Neb., isn’t alone in her quest to find a safe alternative to using a host of chemicals for killing flies. "I've used sticky strips, fly traps, and even chemicals to kill the flies," Landon said. "And the chemicals work, but then I have to worry about the other animals, like the barn cats. And I try to do everything as natural as possible."

Landon is entering the spring season with a renewed sense of purpose. "I didn't realize the last time I tried the fly parasites that you had to keep doing it all season," she said about her failed attempt about five years prior. "This year I’m going to give it another try--the right way."

With six horses on 35 acres, this author was also looking for a way to stay natural and fly-free when information became available about the larvae-eating nocturnal parasites that keep houseflies at bay during the summer months. They don't bite or sting humans, and are gnat-sized, so they are almost invisible. Our farm received the first shipment of Fly Predators in the spring of 2007, and there was a considerable amount of "ewwws" at the smell of the tiny, barely there creatures. We followed the instructions and put the bag in an area about 80 degrees and out of direct sunlight. They were ready to distribute once a dozen or so of them hatched. After hatching, it's as simple as opening the bag and choosing where to distribute the predators.

The gnat-sized parasite wasps feed on the fly pupae at night. They don't affect adult flies, which is why it takes a series of parasite shipments to get and keep the flies under control. For six horses and 35 acres we had five shipments for a total season cost of $142, including shipping. It was a very handy (natural) tool for summer fly management and along with Landon, I plan to do the same for 2008.

You should remember that unfortunately, deerflies and horseflies are impervious to the fly parasites.

  • Around water troughs and barns, grow herbs that are beneficial to the horse and naturally repel insects and flies. Such herbs can include rosemary, basil, tansy (Tanacetum vulgare, a flowering plant), and rue (Ruta, an evergreen subshrub). The horses can feed on the herbs for even more benefits. Using the flowering plant Southernwood (Artemisia abrotanum) where the horses can rub against it can also deter flies and moths.
  • Tea tree oil is a natural fly repellent. You can mix it in water in a clean spray bottle and use it instead of chemical fly sprays. Start with a small amount of tea tree oil and keep mixing in water until the mixture is diluted enough that will not sting or blister your horse's skin.
  • Garlic is wonderful for horses in many ways (it's been touted to boost immunity and a garlic metabolite has shown antibacterial properties), not just as an insect repellent, and you can feed up to five to 10 cloves a day. Soak the cloves in molasses or honey and mix with grain to get your horse to eat them.
  • Arbico-Organics has traps (and not just for flies) that use "bug hormones" in pheromone traps that utilize a scent from female insects to lure male insects, which are then prevented from mating.
  • Arbico-Organics also has Bti (Bacillus thuringiensis israelensis), a bacterial toxin that infects and kills mosquito larvae.
  • Add dung beetles to your property. They actively distribute and destroy the manure in a way that reduces breeding areas for horn flies and internal parasites that prey on your horses. (For more on dung beetles see article #5851.)
  • Clean up all manure on a regular basis. It takes flies a minimum of eight days to grow from pupae. Cut down on their breeding and you cut down on the adults.
  • Secure trash in plastic bags, which cut down on the odor that attracts egg-laying flies.
  • Use garbage containers with tight-fitting lids and place them away from the animals, house, and garage.
  • Get rid of decaying round bales, loose hay, leaves, mulch, and other animal manure.
  • Report dead "ditch animals" to your county officials and ask to have the carcasses removed. Rotting, dead, or dying animals can attract thousands of flies in as little as 24 hours.
  • Mow your weeds. Flies use your weeds to get out of the hot sun and rest. Take away the weeds and you take away their vacation area.
  • We're all pretty familiar with the concept of more rain equaling more flies, generally due to an increase in breeding areas due to standing water: step up your fly control after rainy weather.
  • Research the fly-eating birds and beneficial insects for your area and add those (or attract them with bird houses/plants) to your living/horse area/barn (your local county extension agent is a great place to start your research). (See article #9786 for more information)



About the Author

MaryAnna Clemons

MaryAnna Clemons, is the editor of the Women’s Pro Rodeo Sports News and a freelance journalist. She enjoys specializing in Western and equine writing. You can visit her Web site at

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