Those Pesky Flies
"Shoo fly don't bother me...Shoo fly don't bother me..." Few things are as annoying as a fly buzzing around one's face and ears. However, flies are a necessary part of our eco system and like bees, actually help in the polination of plants. Quite frankly, without the aid of fly larvae, our planet would become one big garbage dump!
On the flip side of this is the fact that flies can and do spread disease and no responsible horse owner wants to host a "banquet" for them; so proper stable management is a must! Frequent disposal of soiled bedding and droppings, as well as standing water is essential to controlling the fly population. Stabling horses away from cattle is another way to keep flies at bay, since parasitic flies are particularly drawn to cattle. Your best bet to keep your horse happy and fly free, is a combination of on-animal products and premise controls.
Since some insects feed on the secretions of the horse's eyes and nose, simply covering these areas will do much to lend comfort. Most commercial fly masks cover just the top portion of the horse's face, while others also include ear covers to keep biting gnats from irritating the ears. Leg netting is another method of keeping flies from making contact with the skin.
Aerosol sprays administered through automatically timed systems can be located in each stall, and will periodically release a spray of pyrethrins-based insecticide (pyrethrins are a group of chemicals found in chrysanthemums) that will mist down onto the horse and its environment.
Feed-through products are also available and can be added to the horse's grain on a daily basis with the intent of making the manure sterile and unusable as food to fly larvae. Any larvae hatched in the manure produced by a horse on a feed-through product will die before it has a chance to develop. Of course for this to be an effective means of fly control, all the horses in the area would also need to be on this product or flies would simply hatch out in untreated manure.
For the budget conscious, relatively inexpensive commercial Fly Strips can do much to eliminate the immediate problem. Simply suspend these long sticky ribbons of tape from the ceiling and since the flies are attracted to the colors and drawn to the strip, they will stick to it once they alight. Fly Traps usually use bait systems and are also effective, but will cost more.
If you are really environmentally conscious and wish to "go green", you might want to investigate the use of Fly Parasitoids as a safe and gentle means of fly control. The most commonly sold fly parasitoids are tiny wasps in the Chalcididae family, which will feed on the larvae of the fly while it is still in the horse's manure. These wasps do not bite or sting humans or other animals and it is easy to see why they are gaining in popularity.