Agree with what others have said about fly masks/fly sheets. Find a spray that you and your horse like, that will help somewhat. Also, when my mare gets really bad bites, or tick bites, particularly on her face, she tends to rub those bites raw. So, I cover them with Swat before she goes out (even under the fly mask), and I think that helps a little.
For general fly control, definitely look up Fly Predators (you can search on here or do a Google search to find the website directly). It's not too late to get them for some relief this summer, and they get pretty universally good reviews. The Spalding Labs website, where they sell them, has a pretty active discussion board where you can read other opinions too.
For me, the biggest problem is black flies, and I don't know of any retailer that has a good product for those. They are just tortuous right now- I myself am covered in huge welts from them. Unfortunately, it's just a function of where I live.
Last edited by egrogan; 06-28-2013 at 04:07 PM.