Nearly Nontoxic Insect Control

Fewer flies and less chemical warfare can create a healthier barn environment for you and your horse.
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Nearly Nontoxic Insect Control
Fly masks are safe and effective physical barriers between horse and fly, with the added benefit of shielding sensitive horses' faces from the sun. | Photo: Anne M. Eberhardt/The Horse

Fewer flies and less chemical warfare can create a healthier barn environment for you and your horse

Three simple circumstances surrounding horse ownership mean we are destined to deal with flies and insects: moisture, large animals, and their poop. Last summer, many parts of North America experienced a particularly fierce fly season that, because of the extreme heat, began early and continued late into fall, making barn life almost unbearable.

Intense fly seasons like this make some of us want to resort to heavy-hitting chemicals. While there might be a time and a place for chemical warfare around the barn, some big-picture management options are the safest way to begin your fly-control strategy and reduce your need for insecticides and repellents.

In this article we will review some of the least-toxic and most environmentally sensitive methods for reducing and managing your horse facility’s fly and insect populations, including removing insect habitats, using mechanical barriers, putting beneficial insects and local wildlife to work, and setting noninsecticidal traps. We will also describe how to use insecticides, so you can make informed decisions if those chemicals are needed.

Management Options

Farm owners most commonly use insecticides and fly sprays for fly control, but you can greatly reduce your dependence on them if you first manage manure and mud; flies, mosquitoes, and other pests depend on these moist materials for breeding.

“Poop control and sanitation is still top of the list of to-do’s for fly management,” says Todd Murray, extension entomologist at Washington State University, in Stevenson.

Start with removing manure from stalls and confinement areas regularly and developing a composting or manure storage area. Composting manure is effective because the heat produced kills the fly larvae. Covering your compost pile with a tarp helps prevent rain runoff that can contaminate surface water and create more muddy habitats in which insects will breed.

Just half-a-teacup-worth of stagnant water—that which has not been moving or added to for five to seven days—can become a mosquito or fly breeding site. So fix leaky faucets, install gutters and downspouts, and toss old tires, toys, flower pots, birdbaths, dog water bowls, buckets, barrels, trash, or anything that can hold water.

Free Report: Insect Bite Hypersensitivity in Horses
Free Report: Insect Bite Hypersensitivity in Horses

Some insects such as face flies, biting midges (no-see-ums), and deerflies or horseflies do not like to enter darkened barns or stables. Providing your horse with a shelter or stabling horses before and during dusk, when these insects are most active, might help horses escape heavy attacks. Biting midges and mosquitoes tend to be poor flyers, so good ventilation or even a fan secured safely outside a stall to create air movement might provide your horses with some relief.

Whenever possible, graze horses on higher, drier pastures at the beginning of the summer to avoid creating muddy areas. Save the lower, wet pastures (which harbor mosquitoes, deerflies, horseflies, and biting midges) until later in the summer when those areas dry out.

Harrow (or drag) pastures regularly to break up manure piles. Harrowing spreads the nutrients and organic materials therein so plants can use them. It also dries out manure, making it a less attractive habitat for flies. You might, however, want to weigh harrowing’s fertilizing and insect-reducing benefits against the risk of spreading internal parasites around the pasture, if temperatures aren’t prolonged and high enough to desiccate the larvae.

Applying footing materials such as finely crushed gravel (sized 5/8 inch or less) or coarse sand to confinement areas can further reduce insect-attracting mud. Three to six inches of footing material will help build up the area, keeping horses up out of the dirt and allowing rainwater to drain.

Physical Barriers

Most every horse owner knows about this safe and effective fly control method: the fly mask. Fly masks act as physical barriers between horses and insects, with the added benefit of serving as a sunshield for sun-sensitive horses. Some masks protect just the eyes, while others also protect ears and jowls. Similarly, fly sheets are open-weave lightweight mesh blankets that can help keep pesky flies off the horse’s body. Fly boots are also available to protect the horse’s legs.

Good Bugs

People tend to mistakenly label all insects as pests. According to the Xerces Society, a nonprofit organization that works worldwide to conserve beneficial insects’ habitats, only about 2% of all insects are actually considered pests.

One example of a beneficial insect that horse owners can put to work is the fly parasite, a gnat-sized nocturnal wasp that lays its eggs in flies’ developing pupae. This kills the pupae, leading to a reduction or near elimination of the fly population. Fly parasites do not harm humans or animals in any way. Because they are so small and emerge at night, humans rarely even notice them.

You can purchase commercially raised fly parasites from a number of sources easily found with a quick Internet search. For best results, release fly parasites early in the fly season (a month to a few weeks before flies typically appear) and every four weeks thereafter.

“Fly parasite (populations) should be built up so later in the season (when flies are at their worst) there is more control, but it is also important to get there early when flies start reproducing,” Murray says.

Violet-green swallow
Violet-green swallows are common North American insect-eaters. | Photo: iStock

For the Birds

Encouraging insect-eating birds to move into your yard and barn area is another natural way to reduce flying insect populations. Members of the swallow family can be assets to horse facilities as they dive and dart through barns collecting bugs. One adult barn swallow will consume several thousand insects per day—comparable to a bug zapper’s spoils. Common North American insect-eating birds include violet-green swallows, tree swallows, barn swallows, bluebirds, purple martins, and cliff swallows, to name a few. Encourage nesting by installing nest boxes on barns and around your farm specific to the type of bird in your area. To determine which insect-eating birds are common in your part of the country, consult your local Audubon Society, birding organization, extension office, or library.

That’s Batty

Bats play an important part in every healthy environment, eating the nocturnal flying insects that plague our horses and us. Each bat reportedly eats up to 600 mosquitoes an hour, which adds up to more than 5,000 a night. They also eat other agricultural pests such as corn borers, cutworm moths, potato beetles, and grasshoppers.

You might be able to encourage a bat family to move onto your property by hanging a bat box built specifically for the types of bats common in your region. Place bat houses on the south-facing side of a barn, pole, tree, or house. The best habitat is within one-half mile of a stream, lake, or wetland. Install them by early April and be patient, as it can take up to two years for a bat colony to find your house.

Bat Box
Install a bat box to attract these bug-loving flyers - but be patient, it can take up to two years for residents to move in. | Photo: Thinkstock
A word of caution: Because bats (or any warmblooded animal) can carry rabies, consult your veterinarian for recommendations on vaccinating your horses against this potentially fatal disease.

Go Trapping

Several types of simple insect traps can help reduce flying insect populations. The cheapest and easiest are sticky traps, such as fly paper or sticky tape placed in high locations; flying insects happen across them and get stuck.

“I hang a lot of old-fashioned sticky strips, the coiled kind,” says Hank Greenwald, DVM, of Equine Medicine & Surgery, in Preston, Wash. “I might hang 20-25 strips in the barn (suspended from the ceiling). They are at all different elevations and are not particularly pretty, but they are up high and get a lot of flying insects.

Other kinds of sticky traps include brightly colored (which attract flies) hanging sticky tubes. These traps might also have an attractant (an embedded scent) that flies seek. Choose locations carefully so sticky traps won’t snare human hair or swishing horse tails.

Several brands of pesticide-free bait jars and bags are on the market, as well. These products include a food attractant that activates when dissolved in water. Lured by the scent (and perhaps the color), flies enter the trap through the yellow cap top and drown in the water.

Make your own fly bait jar cheaply and easily by punching holes through the lid of a mayonnaise-sized jar. Put a few pieces of raw hamburger or fish on the bottom, and fill it with a couple of inches of water. Set the jar in a safe place where it won’t be stepped on (or investigated by an animal). Biting flies attracted by the meat’s smell soon will make their way into the jar and eventually drown.

Use traps with attractants away from your barn and horses so flies are drawn away from these areas. These traps’ downside is they are smelly—another good reason to locate them away from barns.

Chemical Controls: Insecticides vs. Repellents

An insecticide is a chemical that kills insects, while a repellent is a substance that discourages flies (and insects) from landing. When using insecticides, read and follow directions carefully, avoid using more than necessary, and only use those recommended for use on horses. Generally, insecticides are meant to be used outdoors, in well-ventilated, open places, and not in an enclosed area such as a stall or barn. Indiscriminate insecticide use might even promote resistant strains of flies, kill beneficial insects, or harm birds and bats.

Nearly Nontoxic Insect Control - Fly Spray
Most equine fly sprays are repellents, which are also available as lotions, wipe-ons, gels, dusting powders, ointments, roll-ons, shampoos, and towelettes. Repellents contain a substance that is irritating to flies, such as citronella oil, and most contain some amount of insecticide. | Photo: The Horse Staff
Equine insecticides generally fall into one of four categories—in order from least to most toxic and from shortest to longest lasting): pyrethrins (a botanical insecticide made from chrysanthemums), permethrins (synthetic pyrethrins), carbamates, and organophosphates (the most toxic to horses and not commonly used). Unfortunately, least toxic and most effective don’t always go hand in hand.

“The least toxic ingredients in fly sprays are also not very effective, or not for long. Even the best fly sprays containing pyrethroids (a common household insecticide) don’t last very long,” explains Holly Ferguson, PhD, Washington State University Extension Integrated Pest Management coordinator specialist, based in Prosser.

Most equine fly sprays are repellents, which are also available as lotions, wipe-ons, gels, dusting powders, ointments, roll-ons, shampoos, and towelettes. Repellents contain a substance that is irritating to flies, such as citronella oil, and most contain some amount of insecticide. Repellents also contain a base product that helps hold active ingredients to the horse’s body hair. Bases for these products are most commonly water, oil, or alcohol. Oil-based repellents remain on the horse’s hair shaft longer than water or alcohol, but they attract dirt. Water-based repellents don’t last as long but attract less dirt, and some alcohol-based repellents can dry out the horse’s skin.

Some manufacturers add silicone, which coats the hair shaft and holds the repellent in place longer. Repellents might also contain sunscreen, coat conditioners (lanolin, aloe vera), and other products intended to increase lasting power. How long a repellent remains in place depends on the weather, the horse’s exercise level (how much they sweat), grooming, and rolling.

So which products should you use and when? With both repellents and insecticides moderation is key. “I usually recommend that folks spray or wipe the (repellent) product on the parts of the horse where the flies bother him or her the most—head, neck, back legs, etc.,” Ferguson says.

As for insecticides, “I am not a big fan of spraying the horses every day while they’re in their stalls or pens,” she adds. “That’s a lot of insecticide on the horse and a lot of money. I am a big fan of a residual premise spray as a way to knock the huge population down without drowning the horses in insecticide. The downside of the premise spray is that it will kill any (insect) that comes in contact with the residue, including wasp parasites.”

Goodbye Bugs

The key point to keep in mind when trying to manage insects is first strive to reduce insect habitat—the mud, manure, and stagnant water where they live and breed. After you have these areas under control, battle insects with birds, bats, fly parasites, and insecticidal traps.

If certain insects become problematic, you can choose whether you want to use a repellent on your horse or an insecticide premise spray. With these all of these tips and tools in your arsenal, you’ll be able to pare problematic insects from your property and reduce chemical use in the process.


Written by:

Alayne Blickle, a lifelong equestrian and ranch riding competitor, is the creator/director of Horses for Clean Water, an award-winning, internationally acclaimed environmental education program for horse owners. Well-known for her enthusiastic, down-to-earth approach, Blickle is an educator and photojournalist who has worked with horse and livestock owners since 1990 teaching manure composting, pasture management, mud and dust control, water conservation, chemical use reduction, firewise, and wildlife enhancement. She teaches and travels North America and writes for horse publications. Blickle and her husband raise and train their mustangs and quarter horses at their eco-sensitive guest ranch, Sweet Pepper Ranch, in sunny Nampa, Idaho.

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