Fly Sprays For Horses: Chemical, Fatty Acid, Essential Oils

Chemical fly sprays are insecticides

• Chemical fly sprays for horses knock down and possibly kill flies and other pests, like fleas, ticks, and mosquitoes. Most chemical-based sprays will also knock down face flies, chiggers, and horn flies.  

• The effectiveness of chemicals that knock a fly down and are strong enough to kill it varies on the fly. Many larger flies of the horsefly family, like greenheads, are too large to be affected by fly sprays.

Ingredients in chemical fly sprays

• You will commonly find pyrethrin as an ingredient in equine fly sprays. Derived from chrysanthemums, pyrethrins must come into contact with a fly to be effective.

• The pyrethrin enters the bug’s nervous system to disrupt functioning and knock it off your horse. They are often paired with synergists to keep the pyrethrins circulating in the bugs long enough to kill them.

• You will also find permethrin, another neurotoxic agent, in fly sprays. These chemicals are similar to pyrethrins but last a bit longer to kill the flies.

How long do they last?

• Pyrethrins don’t last a long time, perhaps an hour or two, depending on the other ingredients in the spray. The effective time may also vary depending on your horse’s exposure to sunlight. You can increase their longevity by spraying on a clean horse after you groom.

Permethrin and pyrethrins are toxic to some animals

• Both permethrin and pyrethrins break down in sun and oxygen, so there’s little toxic risk to the environment, but other animals are at risk.

• Pyrethrin is toxic to fish, bees, and birds, while permethrin is toxic to bees, cats, and fish.

• Cats are particularly sensitive to permethrin and will likely pass after contact. Treatment is possible, but the entire process is heartbreaking and expensive.

• It’s a grand idea to assume that any fly spray has ingredients toxic to some animals. Each product should have clear labeling on toxicity.

Do not touch your barn cat if you have sprayed or touched your horse after using fly sprays with these chemicals.

Deet vs. Pyrethrins and Other Insecticides

• Deet is a repellent but serves the same purpose of protecting us from insect bites. Many flying horse flies, like deer flies, avoid Deet.

• Use Deet by applying it to the skin to work against mosquitoes, gnats, chiggers, and fleas, as well as larger insects. Deet’s warning label is crystal clear about how to use it. Don’t apply it to your face or open wounds, wash your hands after using it, and clean it off once inside. It may also deteriorate synthetic fabrics and irritate the skin. Don’t ingest it, and call poison control if that happens.

• Pyrethrins are usually sprays and work against most flying and crawling bugs. There’s a relatively low toxicity for people and dogs, and it may create skin irritations. Synergistic ingredients will increase toxicity.

• Permethrins are usually applied to pants, shirts, tents, mosquito nets, and fabrics to fight mosquitos, lice, termites, and fleas. They are presumed safe for humans and dogs but not cats.

Fatty Acids in Fly Sprays for Horses 

• These often funny-smelly sprays are designed to mask your horse’s location from flies that rely on a chemical trail to find your horse. Anyone who has tried EcoVet can confirm this.

• The fatty acids mimic your horse’s natural (and weak) bug-repelling smells to create a cloud of confusion around your horse, a fatty acid no-fly zone, if you will.

• Your horse is unbothered, and the flies MIGHT get to live. This fly spray won’t work against the flies that rely on a heat signature or sight to find a meal.

• The smell is quite strange, and many horses (and their people) find the aroma highly offensive.

• You can spray the perimeter of your horse’s paddock or stall with fatty acid sprays to extend the cloud of confusion.

• They may not work well when combined with traditional chemical fly sprays, so check the label’s precautions.

• These fly sprays for horses can last longer than the pyrethrins but work against different insects.

Essential Oil Fly Sprays for Horses are Repellents

• You can also find fly sprays that are primarily based on essential oils. Countless homemade fly spray recipes include essential oils.

• Lavender, peppermint, and lemongrass are popular essential oils for fly sprays.

• The evidence for fly repelling abilities of these fly sprays is based on antidotes, not science, so it’s hard to say if they work or not, and if so, what flies they work on.

• Many recipes include vinegar, an attractant for some insects, like gnats. Some insects and flies use smell to locate their next landing spot, and essential oils put off a scent.

• Your best bet for fly control is to attack all life stages of the flies at your barn. More on that very subject here!

• You might be researching with your local agriculture extension service to learn about the flies in your area. Then, you can create a plan and experiment with fly-repelling strategies.

Fly gear is another layer of protection.  You may want a fly mask that covers the eyes.  

Lotions or Spray?

• It matters how insecticides and repellents apply to your horse. Many horses hate sprays, in which case you can spritz a cloth or brush to use them.

• Lotions and ointments are fantastic for targeted fly control, especially around sheaths, udders, ears, and wounds. Many equestrians love SWAT, and many don’t. Lotions may also interfere with your tack while riding, so sprays may be better.

The best thing you can do before shopping for fly products is to know what flies and pests bother your horse. You’ll spend less money!

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