I had a horrible problem with horse flies and my horses. I never could figure out a way to get rid of them.
I tried everything, both chemical and natural, at one time spraying/wiping them 3 times a day AND applying drops at all top points for supposedly long-term protection.
Nothing worked. They all had blood running down their inner thighs all summer long, stamping and scratching at themselves. It was awful.
I wish I knew
the answer.
We were surrounded by cattle pastures and had ponds around us, so there was ample breeding grounds for them.