When it's warm enough to bathe your horse, do an apple cider vinegar rinse once a week. Not only will it repel flies, it will make their coat nice and shiny. My old gelding was allergic to fly bites and an apple cider vinegar rinse was the only thing that kept the flies at bay...plus it's WAY cheaper than gallons of fly spray.
Just mix a cup (or two) of apple cider vinegar in a two gallon bucket with water, then pour it over your horse from neck to tail, refilling the bucket with the same mixture as needed. Use a soft sponge to get it on the head and any other places you miss. Posted via Mobile Device