We used Starbar Fly Stick Jr. This summer. Our fly problem was horrendous and we tried EVERYTHING (including DE) without much luck. It was as if the flies were nesting in the earth. A few fly sticks out and within a hour, they were covered and our run was fly free. After that, we put one or two out a week for maintenance and our fly problem never got bad. We try to keep everything clean as possible. The star bars have 3d images of flies on them as an attractant and let me tell you - we watched flies leave the poop and fly TO the stick!
Next year we are going with fly predators too! I just visited a farm with 200 hens, horses and puppies and not a single fly. She only uses fly predators!