It's finally fall, so this issue is not as pressing as it was two months ago, but I am trying to prepare for next spring. I cannot live with the flies our chickens -- and I'm convinced it was them, as there aren't other outdoor pets in the block -- brought to our street. Here's what I used, to small effect, this last summer: Food-grade DE in the (regularly raked-out) run and in the dust-bath areas. Five hens, and they range the fenced backyard in the day. Stinky-bait disposable fly traps: Caught tons of flies. Still tons more in the yard. Fly predators: Three shipments for $50. No noticeable effect, though I know it takes awhile. Permethrin spray: Worked like a charm, for a week until it rained. Neither we nor our neighbors could picnic outside all summer because of the flies and they got into the kitchen - 20, 30 at a time - whenever the door opened. Next year I'm either getting rid of the hens or spraying the yard weekly or, if someone has a fool-proof formula to post, trying that.