I have a politically incorrect method that makes my husband furious. I use OFF. It is the ONLY thing that works imo!! I have tried all products for fly spray but OFF actually keeps them repelled! But my husband is very environmentally correct and worrys about chemicals and he says a horse is an animal that licks itself and you shouldnt put a product on a horse that could have a slow toxicity but i'm sorry you cant tell me fly spray is much better! and also? I have twice been on rides where the group was swarmed by hornets and my horse had hornets zinging all around but none lit and bit him or me and I think it was the OFF! jmo, works for me! Janice -- yipie tie yie yo