Fly Control

We tried the Spalding Fly Predators this year and we have seen a remarkable drop in the flies around the barn. Fly Predators by Spalding Labs

I came across this info too, worth a try:
REPEL FLIES WITH PLASTIC BAG, PENNIES, & WATER
Many people swear that a zip-lock bag filled half-way with water and attached over entry-ways will repel flies. No one yet knows how or why it works, but there is speculation that it has something to do with the way the moving water refracts light.