Fly masks, sheets and boots: what actually helps in fly season?

Penn State Extension calls fly sheets, boots and masks barriers that protect horses from multiple species of biting flies. The University of Kentucky's entomologist puts the other half bluntly: eliminating breeding sites is the key to a successful fly control program, and insecticides cannot be the basis of effective fly management.

That is why this page has both. Gear covers the horse you are looking at today. Barn habits shrink the fly population around him. The table pulls the pieces together using what the extension sources and the makers say.

Fly season is also a good time to know what your own horse reacts to. If he rubs, gets sores or squints, those are vet questions, and the last section covers them.

The guide, reviewed by Kaela Schraer, DVM, says masks reduce bites that cause itching, rubbing, hair loss and sores, and can keep out flies that carry bacteria linked to infections such as conjunctivitis. It adds that a loose mask can shift or sag into the eyes, and a tight one can rub.

Masks come in more than one coverage. PetMD describes eye-only mesh masks that cover the eyes down to the bridge of the nose; ear covers that help keep gnats out and matter most for clipped horses; and nose extensions for horses that are sensitive to bites or prone to sunburn. The same guide says horses turned out can wear a mask day or night if it is properly fitted and checked regularly, and that stalled horses don't need one.

On UV, the guide says UV light can worsen uveitis (moon blindness), and that a vet may recommend a mask to improve comfort during flare-ups, though a mask cannot cure the condition. Makers print UV figures on their masks. Our Woof Wear UV Fly Mask listing, for example, describes 60% UV protective mesh, a padded nose and a three-seam ear design. Treat those percentages as the maker's statement, not an independent test.

Masks have to be looked after. PetMD says to check for damage and dirt at least daily, and to keep a spare to rotate in when one gets wet or dirty. Our fly apparel and summer sheets category lists masks with and without ears and nose pieces; use the size chart on the product page for the one you pick.

Penn State Extension says the sheet is a barrier against multiple biting flies, and that zebra patterns in particular decrease fly attacks because of how horse and deer flies perceive color. Whether you want a neck cover, a belly wrap or a tail flap is a matter of how much of the horse the flies are reaching.

Fabric strength is where horses that wreck gear come in. Makers print a denier number, which is the weight of the thread, so a higher number generally means a heavier fabric. WeatherBeeta describes its ComFiTec Ripshield Fly Sheet as a 1200 denier cross hatch weave built to resist and limit tears for horses that are hard on their gear, and lists 45% UV protection. The Shires Sweet-Itch Combo listing on our site describes a 600 denier ripstop fabric with a belly flap and says it blocks at least 90% UV radiation. Those are the makers' numbers and the two sheets are built for different jobs, so compare what each says it is for rather than the numbers alone. Our blanket labels guide explains denier in more detail.

Fit comes last but matters most. UMN Extension says to routinely check all horse wear to make sure it has not shifted, rubbed or caused other issues, and that goes double for a sheet he wears every day. Measure with our horse blanket sizing guide and then use the size chart on the product page. We don't print sizes here because they differ by maker.

If a sheet is mostly a cover for after a bath or between classes, that is a scrim; see our scrim sheet page for how it differs from a fly sheet. If flies are not just annoying but your horse rubs raw, read what sweet itch is, because full-coverage sheets are one of the things owners use for that.

The makers on our site describe them in similar terms. Horseware says its Newmarket Fly Boots are lightweight mesh that protects the legs from biting flies, with fleece edges that prevent rubbing and keep flies from getting under the boot, and lists 65% UV protection. TuffRider describes its StableShield fly boots as breathable mesh sold in a set of four that reduce stomping by preventing flies.

Whether you need them depends on where the flies bother your horse. The extension sources we read do not say which horses need boots, so this is your call with what you see. If he stamps and kicks at his legs, boots are one barrier to try. UMN's note about checking horse wear applies here too: a boot that shifts or rubs is a new problem, not a fix.

Fly boots are not the same as the protective boots in our horse boots guide, which are for knocks and strikes. Do not use one for the other's job.

The University of Kentucky says barns and corrals should be cleaned once a week to break fly life cycles. UMN Extension is more specific: clean up manure at least twice a week and spread or compost it, replace bedding weekly, and scout weekly for possible maggot breeding sites. It lists muck near leaky waterers, old hay around feeders, piled manure and soiled bedding as common sources.

Kentucky explains why wet matters. House flies lay eggs in moist, fermenting organic matter such as manure, rotting hay, silage or garbage, and stable flies develop in fermenting mixtures of straw, spilled feed or hay with urine or water. Horse manure alone is usually too dry for stable flies unless it is moistened. Good drainage that removes wet manure, spilled feed and wet bedding helps, and the publication advises checking wet areas around waterers. UMN adds that wood shavings and sawdust produce fewer flies than straw, that feed should be kept dry and off the ground, and that waterers belong in well-drained areas away from feeding. The University of Florida's extension blog, which we also read, says composted manure reaches temperatures high enough to kill fly eggs and larvae.

Kentucky also says fans that direct air downward and outward can keep flies out of barns, that screening keeps flies out of feed rooms, tack rooms and box stalls, and that sticky traps are mainly useful for monitoring: a sharp weekly rise in catches is a warning to improve sanitation. UMN says traps work poorly where debris management is poor. One caution: the Kentucky publication is from 2007, and its product tables are for Kentucky registrations, so we used it for barn management, not for products.

Horse flies and deer flies are a different story. Nebraska Extension says control of their aquatic breeding areas is impractical, so barn cleaning will not solve those; barriers and timing matter more for them (next section).

UMN Extension says repellents give temporary relief from stable flies, that you should apply them to the legs and reapply after the horse walks through wet vegetation, and that commercial repellents are not effective against black flies, horse flies or deer flies. Penn State Extension, writing specifically about horse and deer flies, says full-body application of pyrethroid-based repellents seems to be effective, that application needs to be full coverage because the flies bite any area of the body, and that reapplication is likely necessary at least daily. Both say to read the product label; UMN notes EPA-registered products carry an EPA number on the label.

Both can be right at once: they are describing different flies and different evidence. Neither is a reason to skip the barn work. Kentucky says insecticides are a supplement that reduce adult flies but do not touch the breeding sources.

Timing helps with the big biters. Penn State says horse and deer flies are daytime biters that are active in sunny areas and avoid shade, and that turning horses out at night instead of the day can reduce biting. Whether that suits your horse and your barn is a call for you and your vet; we only report what the source says.

PetMD's vet-reviewed guide says to call the vet anytime you notice a change in your horse's eyes, and lists squinting, excessive tearing, swelling, cloudiness, discharge and a closed eye as signs that need prompt care. It also says a mask should never replace veterinary treatment.

Itching, rubbing and hair loss can come from more than one cause. PetMD says bites cause itching, rubbing, hair loss and sores; a vet is the person to sort out whether it is bites, an allergy or something else. If your horse is rubbing his mane, tail and belly raw every summer, see our page on sweet itch and talk to your vet about a plan. For pink skin on the nose or face, see can horses get sunburned.

Fly gear does not treat anything. It reduces exposure. If your horse is already sore, the vet comes first.