Same conclusion I reached. I do use predators in a smaller barn up by the house, and they work well...but not many horses up there and it's an open barn. I've used a spray system in the main barn for years and it seems to be the only thing that really consistently works. Was hoping to do away with it this year, and gave the predators a shot but the flies just got worse and worse until I gave up and filled the spray barrel again. I may not have used enough of them, just as costly I think as using the spray system but I would prefer not having chemicals spray all the time - IF it worked. For an individual spray, I think Endure is the best. Have tried the "green" sprays...not very effective here.I figure the pesticide is less dangerous than the diseases the flys and mosquitos carry.
Jan