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Another option is to mix small amounts of apple cider vinegar with the animal's drinking water; consuming this solution is known to change the blood pH of the horse, thus keeping horseflies away. Cider vinegar, coupled with essential oils, is also used in home sprays as the sharp odor may repeal horseflies.
Disposable fly traps are one of the best methods to trap horse flies. These traps contain an attractant that gets activated by sunlight and water. After getting activated the attractant lures the horse flies to enter the trap, once the flies enter the trap they get trapped.