Female horse flies feed on the blood of warm-blooded mammals. Their bite is very painful. When biting, they stay and suck blood for a couple of minutes. They also can transmit diseases such as anthrax, hog cholera and tularemia. They are commonly found in wooded areas with streams or other bodies of water.
Mix one cup of Ivory liquid dish detergent with one gallon of water. Put the solution into a spray bottle. When you see the horse flies during the day, spray them with the solution. The soap mixture suffocates the flies, and it's organic, so it is not harmful to animals and vegetation.
Combine mint flavored mouthwash, lemon dish soap and lemon ammonia in equal parts. Put the mixture into a spray bottle and spray your yard. Spray it on the grass, bushes, trees, lawn furniture and plants. This solution is also not harmful to plants or animals. The smell is appealing to humans but repels horse flies.
Use a fly swatter to swat and kill horse flies. While it is impossible to completely get rid of a large horse fly population this way, if you are aggressive enough you can seriously decrease their number.
Locate the horse flies nest. Get rid of the entire population by spraying the nest with Raid or Sevin, chemical products sold for use on horse flies. It is important to spray the nest at night when the flies are inside. Saturate the nest thoroughly with the insecticide.
Purchase a horse fly trap. Horse flies are not attracted to bait that works by scent, they are visual hunters. Horse fly traps are visual targets that lure the flies into a bottle where they get trapped and then die from the heat of the sun.