Horse flies are persistent biters, and getting rid of them naturally starts with understanding what draws them to your property in the first place. Female horse flies hunt using a combination of thermal vision, carbon dioxide detection, and attraction to large dark moving objects. That means your body heat, your breath, and even your parked car can bring them in. While no single natural method eliminates them completely, combining habitat control, physical barriers, and natural repellents can dramatically reduce their numbers.
Why Horse Flies Target You
Only female horse flies bite. They need blood to produce eggs, and they’re remarkably well-equipped to find it. Entomologists believe horse flies possess a form of thermal vision that lets them detect warm bodies the way thermal imaging cameras detect heat signatures. They also zero in on concentrated carbon dioxide from exhaling, which is why they swarm around people, horses, deer, and even running vehicles.
Horse flies are strongly attracted to dark colors and large moving objects. If you’re wearing a black shirt and walking through an open field on a warm afternoon, you’re essentially a beacon. Switching to light-colored clothing is one of the simplest ways to make yourself less visible to them.
Eliminate Breeding Habitat on Your Property
Horse flies lay their eggs on vegetation near water or saturated soil. The larvae drop into the wet ground below, where they feed and develop for months. Most species take a full year to complete their lifecycle, with some larger species requiring two to three years. Adults emerge from late spring into summer, which is why horse fly season hits hardest during the warmest months.
The breeding sites are varied: freshwater and saltwater marshes, pond edges, streams, moist forest soil, and even low-lying areas of pastures or fields that hold standing water. You can’t always eliminate a nearby marsh, but you can reduce the wet habitat on your own property. Target these areas:
- Standing water: Overturn or discard buckets, old tires, and containers that collect rainwater. Drill drain holes in tire swings. Clean water tanks regularly.
- Soggy ground: Fix leaky waterers and place them in well-drained areas. Grade low spots in your yard or pasture to improve drainage.
- Manure and organic debris: Clean up manure at least twice a week. Spread or compost it rather than letting it pile up. Remove old hay around feeders and replace soiled bedding weekly.
- Overgrown vegetation near water: Trim back tall grasses and weeds along pond edges, ditches, and marshy spots where females prefer to lay eggs.
Reducing moisture and organic matter won’t just cut down on horse flies. It limits habitat for stable flies, deer flies, and mosquitoes too.
DIY Traps That Actually Work
Horse flies’ attraction to dark, warm, moving objects makes them surprisingly easy to trap. The most effective natural trap design uses a dark sphere (like a large black ball or a dark-painted beach ball) suspended in the open, with a funnel or sticky surface above it. The flies approach the dark target, fly upward when they realize it’s not a host, and get caught in the trap overhead.
You can build a version of this with a dark ball hung from a string beneath an inverted clear plastic funnel that leads into a jar or container. Commercial versions of this design exist (often called Manning traps or H-traps), and DIY plans are widely available. Position traps in sunny, open areas where horse flies are most active, particularly between your property’s wet zones and where people or animals spend time. A single well-placed trap can catch dozens of horse flies per day during peak season.
Sticky traps also work. Coating a dark ball or bucket with a layer of sticky adhesive (like Tanglefoot) exploits the same visual attraction. These are simple to set up but need regular maintenance as they collect insects and debris.
Natural Repellent Sprays
Natural repellents won’t kill horse flies, but they can make you or your animals less appealing targets. The tradeoff compared to synthetic sprays is that natural formulas break down faster in sunlight and need reapplication throughout the day.
A widely used DIY recipe from veterinarian Doug Thal combines two cups of white vinegar, one cup of water, one cup of bath oil, and one tablespoon of eucalyptus oil in a spray bottle. The vinegar and eucalyptus create a scent barrier that horse flies avoid, while the bath oil helps the mixture adhere to skin or hair.
A few safety notes if you’re using this on horses or other animals. Always test a small patch of skin first and watch for hives, welts, or swelling. Keep sprays away from eyes, nostrils, and open wounds. Never use undiluted essential oils on animals. Horses, dogs, and cats absorb essential oils through their skin and mucous membranes, and concentrated doses carry a real risk of toxicity. Citrus oils like lemon and orange are photosensitizing, meaning they increase sensitivity to UV light and can cause skin burns in direct sun.
Physical Barriers and Protective Gear
When horse fly populations are high, physical barriers are often more reliable than sprays. For horses and livestock, fly sheets, fly masks, and ear nets block biting access to the most vulnerable areas. Lightweight mesh fly sheets cover the body while still allowing airflow, and most horses tolerate them well during turnout.
For yourself, long sleeves and pants in light colors provide the most straightforward protection. Horse flies bite through thin fabric, so tightly woven materials work better than loose knits. Head nets designed for outdoor work are inexpensive and effective if you’re spending extended time in horse fly territory.
Fans are another surprisingly effective tool. Horse flies are strong fliers but struggle in sustained wind. Setting up large fans in barn aisles, stall areas, or outdoor seating spots creates enough airflow to keep them from landing. This also disperses the carbon dioxide plume that attracts them in the first place.
Timing and Behavior Patterns
Horse flies are daytime feeders and most active during the hottest, sunniest hours. They rarely bite at night or in heavy shade. If you have flexibility in your schedule, doing outdoor work in early morning or late evening avoids peak activity. Horses and livestock benefit from access to shaded shelters during midday, which naturally reduces their exposure.
Wind suppresses horse fly activity significantly. Breezy days bring far fewer bites, and positioning outdoor activities in open, wind-exposed areas rather than sheltered spots can make a noticeable difference. Horse flies also tend to be worst near the edges of wooded areas and water sources, so creating distance between those zones and your main outdoor living or working spaces helps reduce encounters.