What keeps horse flies away?

If you've ever spent a summer day at the barn, you know the drill. You're grooming your horse or cleaning stalls when suddenly you hear that distinctive, angry buzzing. Before you can react, your horse is stomping, swishing, and trying to escape the relentless pursuit of horse flies. These aren't your average nuisance insects. Horse flies deliver painful bites that can make your horse miserable and even cause significant blood loss during heavy infestations.

So what keeps horse flies away? The short answer: a multi-layered approach combining physical barriers, environmental management, and strategic use of repellents. Horse flies hunt primarily by sight, not scent, which means the most effective strategies focus on blocking their access rather than trying to repel them with sprays alone.

Let's break down exactly what works, what doesn't, and how to create a comprehensive horse fly management plan for your property.

Understanding horse fly behavior

Before you can effectively keep horse flies away, it helps to understand what you're dealing with. Horse flies are among the largest flies you'll encounter, measuring anywhere from ¾ to 1-¼ inches long. They have stout bodies that range from dark brown to grey to black, with large compound eyes that can appear green or black depending on the species.

Female horse flies are the biters. Like mosquitoes, they need blood meals to produce eggs. But unlike mosquitoes that pierce skin with a needle-like mouthpart, horse flies have scissor-like jaws that slash the skin and lap up the blood. This produces a painful, immediate "ouch" rather than the delayed itch of a mosquito bite.

Here's the critical insight: horse flies hunt primarily by sight. According to entomologists at Michigan State University and the University of Florida, these flies are attracted to movement, dark colors (especially blue), and the carbon dioxide and body heat that warm-blooded animals emit. They're also incredibly fast flyers, among the fastest of all insects, which makes outrunning them nearly impossible.

Horse flies are most active during daylight hours, particularly on hot, sunny days. Their life cycle begins in moist environments. Females lay eggs on vegetation near ponds, streams, and wetlands. The larvae drop into mud or water where they live as predators for months or even years before emerging as adults. This is why properties near water sources often experience the worst horse fly problems.

For horses, the threat goes beyond simple irritation. Horse flies are considered the most dangerous insect pest of cattle in North America according to the University of Missouri Extension. They can transmit diseases like equine infectious anemia, cause significant blood loss during heavy infestations, and create open wounds that invite secondary infections.

Why repellents alone aren't enough

Walk into any tack shop or farm supply store and you'll find shelves lined with fly sprays promising to keep horse flies away. The reality? Most of them won't deliver on that promise for horse flies specifically.

The science is clear: horse flies hunt by sight, not scent. As one experienced horse owner noted on the Horse and Hound forum, "Horse flies don't hunt by scent, they hunt by sight so no repellent will work. You can get DEET-based ones that kill them if they bite, but your only real hope is fly rugs."

That doesn't mean repellents are completely useless. Chemical repellents containing DEET, picaridin, or pyrethrins can provide some protection and may kill flies that do land. But relying on repellents alone is setting yourself up for disappointment. Rain and sweat wash chemical protection away quickly, requiring constant reapplication that isn't practical for horses turned out for hours at a time.

Research from the University of Kentucky College of Agriculture confirms that while DEET "can provide several hours of protection" from deer flies and horse flies, the effectiveness varies significantly based on conditions, concentration, and individual horse factors.

The key takeaway: repellents should be one component of your strategy, not the entire strategy. The most successful horse fly management plans combine multiple approaches working together.

Physical barriers: your first line of defense

Since horse flies hunt by sight, the most effective way to keep them away is to create physical barriers they can't penetrate. This is where your strategy should focus.

For humans working around horses

If you're handling horses during fly season, your clothing choices matter. Horse flies are attracted to dark colors, especially blue. One entomologist at Michigan State University observed 50 to 100 flies buzzing around the black side mirrors of his white truck while driving through swampy areas. Light-colored clothing significantly reduces your attractiveness to these pests.

Cover up as much skin as possible. Long sleeves, long pants, and a wide-brim hat provide protection. Horse flies particularly target the back of the head, so always wear a hat when working in infested areas. For extreme situations, fine mesh head nets provide excellent protection.

For horses: the power of protective gear

This is where you can make the biggest impact for your horses. Physical barriers consistently outperform repellents in real-world conditions.

Fly masks are essential. Horse flies target the head, face, and eyes. A quality fly mask creates a barrier that prevents flies from reaching these sensitive areas. Look for masks with these features:

• Fine mesh that blocks flies while maintaining visibility

• UV protection (horse flies are active during peak UV hours)

• Secure fit that doesn't rub or shift during movement

• Durable construction that withstands pasture wear

At Kensington Protective Products, we've designed our UViator fly masks with 90% UV-blocking Textilene fabric that maintains 78% air permeability. This means your horse stays protected from both flies and sun damage without overheating.

Fly sheets and rugs provide body protection. Research and anecdotal evidence suggest that zebra-striped or plaid patterns may be particularly effective. The theory is that the high-contrast stripes confuse the flies' visual targeting system.

Ride-on fly sheets solve the problem of protection during exercise. Traditional fly rugs aren't practical for riding, but lightweight ride-on sheets allow you to maintain protection while hacking or training. As one forum member joked, "You might look like you're about to go jousting, but they make a huge difference."

Chemical and natural repellents

While physical barriers should be your foundation, repellents have their place in a comprehensive strategy.

Proven chemical options

DEET (20-50% concentration) remains the gold standard for personal protection. Products like Sawyer Premium Insect Repellent with 20% picaridin or DEET-based formulas provide the strongest proven protection. For horses, pyrethrin-based sprays offer a natural pesticide option derived from chrysanthemum plants.

Application tips:

• Apply to exposed skin, not under clothing

• Reapply every 4-8 hours or after sweating

• For horses, spray directly on coat rather than using sponges for better coverage

• Apply before turnout or riding, not after flies are already attacking

Natural alternatives

If you prefer natural options, several have shown anecdotal success:

Citronella oil can help repel horse flies when sprayed on yards or applied as a personal repellent. Many commercial insect repellents use citronella as a base ingredient.

Essential oil blends containing peppermint, eucalyptus, and lavender have been reported to provide some protection, though scientific evidence is limited.

Vinegar applications offer a budget-friendly option. One horse owner on the Horse and Hound forum shared their method: "I used to find covering my bays and roans in vinegar would work very well for up to about 3 hours. Neat malt vinegar, cheapest you can get! Dunk sponge in water first, then drench sponge in vinegar and apply to horse."

Important limitations: Natural options generally provide shorter protection periods and less consistent results than chemical repellents. They work best as supplementary measures rather than primary protection.

Environmental management strategies

Controlling your environment is one of the most effective long-term strategies for keeping horse flies away. Here's how to make your property less attractive to these pests.

Eliminate breeding grounds

Horse flies require moist environments to reproduce. Female flies lay eggs on vegetation near standing water, and larvae develop in mud or shallow water.

• Remove or treat standing water where possible

• Fill in low-lying areas that collect water

• Improve drainage around barns and paddocks

• Keep water troughs clean and fresh

Manure management

Horse flies are attracted to manure and decaying organic matter. Regular cleaning is essential:

• Clean stalls daily

• Remove manure from paddocks and pastures at least twice weekly

• Compost manure away from barns and turnout areas

• Keep the area around your barn clear of spilled feed

Vegetation control

Horse flies love weedy areas and long grass that trap moisture:

• Keep pastures mowed

• Trim weeds and brush around barns and fences

• Maintain a buffer zone between wooded areas and turnout spaces

• Remove overgrown vegetation near water sources

Barn improvements

Simple modifications can make your barn less hospitable to flies:

• Install fans to create air movement (flies struggle in windy conditions)

• Use protective netting over windows and doors

• Ensure garbage bins have tight-fitting lids

• Consider planting fly-repelling herbs like basil, lavender, mint, and lemon balm around barn perimeters

Traps and targeted control methods

When environmental management and barriers aren't enough, traps can help reduce local populations.

DIY trap options

The sticky hat method has gained a devoted following among outdoor enthusiasts. Apply Tree Tanglefoot (a sticky substance used in gardening) to the back of a hat. As one user on Quora described: "I get essentially zero bites from horse flies while wearing it. It catches them so fast, I'm usually not even aware of their presence until I take the hat off and have a look."

Umbrella/Manitoba-type traps exploit horse fly behavior. These traps use a black beach ball as a lure. Flies attracted to the dark, moving object fly upward when they realize it's not a host, becoming trapped under a canopy and eventually captured in a jar. The University of Missouri Extension provides detailed construction plans for these traps.

Apple cider vinegar traps work for various fly species. Fill a jar with apple cider vinegar, add a few drops of dish soap to break surface tension, and create a funnel entrance. Flies enter but cannot escape.

Commercial options

Rescue fly traps use attractants to draw flies into disposable bags. These work best when placed away from barns and living areas (you don't want to attract flies toward your horses).

Automatic sprayer systems can be installed in chutes or gates that cattle and horses must pass through daily. When an animal steps on a treadle, it triggers a fine mist of pyrethrin-based insecticide. The University of Missouri Extension found that daily treatment with synergized pyrethrins reduced biting rates significantly.

When to call professionals

For severe infestations, professional pest control may be necessary. They can:

• Identify and treat breeding sites you might have missed

• Apply targeted insecticide applications

• Provide guidance on integrated pest management strategies

Creating a horse fly management plan

The most effective approach combines multiple strategies into a cohesive plan. Here's how to build yours:

Assess your property

Walk your property and identify:

• Standing water or wet areas

• Manure accumulation spots

• Weedy or overgrown areas

• Proximity to natural water sources

Implement barriers first

Start with physical protection:

• Outfit horses with quality fly masks before turnout

• Consider fly sheets during peak season

• Stock up on light-colored work clothes for yourself

Layer in environmental controls

• Establish a manure removal schedule

• Address standing water issues

• Trim vegetation around high-traffic areas

Add repellents strategically

• Apply chemical repellents before high-risk activities

• Keep natural options on hand for touch-ups

• Remember that repellents supplement, not replace, barriers

Monitor and adjust

Horse fly populations fluctuate throughout the season. What works in June might need adjustment by August. Pay attention to:

• Peak activity times on your property

• Which horses are most affected

• Weather patterns that increase fly pressure

Protect your horses with the right gear

At the end of the day, what keeps horse flies away most effectively is a combination of strategies with physical barriers at the foundation. Since horse flies hunt by sight, blocking their access to your horse's body is more reliable than trying to repel them with sprays that wash away or lose effectiveness.

Quality fly masks, protective sheets, and environmental management create a defense system that works even when you're not there to reapply repellent. For over 70 years, Kensington Protective Products has been developing equine protection gear that stands up to the demands of real barn life.

Our fly masks feature Textilene Solar Screen fabric made in Alabama, USA. This specialized material blocks 90% of harmful UV rays while maintaining 78% air permeability, so your horse stays cool and comfortable while protected from flies and sun damage. The dartless design eliminates vision impediment and reduces wear points, while the CatchMask technology allows the mask to double as a halter for easy leading.

When horse fly season arrives, don't rely on sprays alone. Explore our complete collection of fly protection gear and give your horses the multi-layered defense they need to stay comfortable all summer long.

Frequently Asked Questions

What smell do horse flies hate?

Horse flies are repelled by smoke and certain scents like eucalyptus, citronella, and essential oils. However, it's important to understand that horse flies hunt primarily by sight, not scent. While these smells may offer some relief, they won't provide complete protection. Physical barriers like fly masks and sheets are more effective than scent-based repellents.

How do you keep horse flies away from your yard?

To keep horse flies away from your yard, focus on eliminating breeding grounds by removing standing water, cleaning up manure and decaying organic matter, and keeping grass and weeds trimmed. Secure garbage with tight-fitting lids, and consider planting fly-repelling herbs like basil, lavender, and mint around your property. For severe infestations, traps and targeted insecticide applications may be necessary.

Do dryer sheets repel horse flies?

Some outdoor enthusiasts claim that dryer sheets repel horse flies due to their strong, soapy scent. People rub them on clothing or tuck them into hats. While there's plenty of anecdotal evidence, scientific evidence is limited. A 2010 study found that Bounce dryer sheets repelled fungus gnats, but horse flies are different pests with different behaviors.

What is the best horse fly repellent for horses?

The most effective protection for horses combines physical barriers with chemical repellents. Quality fly masks and fly sheets provide the best foundation since horse flies hunt by sight. For chemical protection, pyrethrin-based sprays or DEET-based products like Deosect or Power Phazer can supplement physical barriers. Apply repellents before turnout and reapply according to label instructions.

What color attracts horse flies?

Horse flies are strongly attracted to dark colors, especially blue. Research from the University of Florida confirms that deer flies and horse flies target dark colors while showing less interest in light colors or white. This is why light-colored clothing is recommended for humans, and why some horse owners report success with zebra-striped fly rugs that use high-contrast patterns to confuse the flies' visual targeting.

What time of day are horse flies most active?

Horse flies are daytime feeders, most active during hot, sunny periods. They typically emerge in early summer (often as early as April) and remain active through the warmer months. Unlike mosquitoes that prefer dawn and dusk, horse flies hunt during peak daylight hours when temperatures are highest. Early morning rides or turnout may help avoid peak activity periods.