Those pesky heavy-duty, blood-sucking bombers that line up on a horse’s neck like shingles on a roof…….awfully irritating. We have problems with them here in the Colorado foothills near our creeks and springs for about two weeks this time of year and on trail rides in the timbered areas most of the summer. I’ve seen first hand how they can drive a horse crazy and cause large welts from their painful bites. Read more about horse flies and deer flies at the University of Kentucky site.
I’ve found that a long-sided fly sheet that has a neck extension used in conjunction with a fly mask with ears and nose shield are a great deterrent to any flies. If you armor your horse like this, the only place you’ll have to spray or apply fly cream is under the jaw, and on the belly and legs.
Unfortunately, as you’ve probably discovered, application of fly products don’t seem to deter horse flies and deer flies for very long. And the fly traps that I talk about in Fly Control are effective for trapping house flies and stable flies but don’t attract horse flies and deer flies.
I’m not aware of any fly predators that target horse fly or deer fly larvae.
There is a trap specifically designed to capture horse flies which you can read about here.