Janet L Jones, PhD

No flies here yet, but spring mud is emerging and we all know what comes next. A lot of people ask me what sort of fly mask True wears and whether I leave it on at night. The answer? None and no. But you might be curious about the reasons for those decisions.

Clearly, no horse should be left with flies crawling around on his face or any other part of his body. Flies around the eyes cause infections and discharge, flies on the legs cause horses to stomp and harm their shoes or sensitize their soles, flies bite and create painful skin bumps, and flies carry lots of nasty horse diseases that can kill our four-legged friends.

Fly masks are effective at protecting equine eyes, but they impair vision. As you may know from Horse Brain, Human Brain, horses do not have excellent acuity (ability to see detail). Their vision is fuzzier than ours. So under the best circumstances, a horse cannot see a fence, ditch, gate, or other potential hazard as clearly as we can.

Pop a mesh fly mask over those eyes, and you’ve got some serious visual fuzz. Horses who can’t see clearly are much more likely to be injured. In addition, when a horse tangles with some object that was hard to see, the fly mask gets caught. And we all know what happens when a prey animal gets hung up on a piece of equipment. He panics, struggles, tries to get free, destroys the equipment, and injures himself even more. These dangers are reduced when a horse wears a fly mask in a stall or small run. But in a pasture or turnout, it's high.

For those reasons, I use chemical fly protection on my horses and serious fly prevention around the barn. The chemicals in fly spray are nowhere near as dangerous as the diseases flies carry, the risks of injury from poor vision, or the danger of getting caught. None of my own horses or training horses have experienced allergies or skin damage from fly spray. That’s not to say it can’t happen—just that it doesn’t happen often. Certainly not as often as fly mask accidents do.

As far as wearing fly masks at night? No. Just no. Horses do not see as well at night as most humans assume. Add their visual fuzz to a fly mask and darkness, and you have the perfect recipe for injuries. Might as well call the veterinarian in advance!

Around the barn, many products keep flies to a minimum. Options include stall fans, feed-through supplements, predator flies, electric fly killers, sticky fly tape, solar or chemical fly traps, premise sprays, or fly parasites. You can find more ideas in a quick Google search.

Cleanliness helps, too. Most people know that manure attracts flies. Clean stalls, arenas, and barn aisles daily. Remove the manure from muck buckets, wheelbarrows, and other containers by emptying them immediately at a location far from your barn. Some climates allow manure to be chopped and spread in a thin layer that dries to a benign powder quickly. Check your local university extension for more information on manure management in your area.

Equine urine is an even greater draw for flies than manure is. Remove soaked bedding daily, push clean bedding back so the stall floor can dry while horses are in turnout, and check under rubber mats to be sure urine is not collecting there. Powdered zeolite (like Sweet PDZ or Stall Dry) absorbs urine, too. It has the added benefit of reducing ammonia fumes that are so harmful to equine lungs. To help keep stalls dry and air moving, increase barn ventilation as much as possible.

Think about the risks of impaired equine vision, and avoid fly masks. True never wears one, and a small amount of anti-fly ointment rubbed into the hair around his eyes keeps the pests away. Meanwhile, start fly control in the barn in spring, and you’ll have a lot fewer flies come summer.