I am a newbie to raising backyard chickens. I have 2 Black Australorps that are laying and a French Black Copper Marans and Easter Egger that should be laying in a couple of months. I have been shocked by the fly problem I am having. (green flies) My coop has pine shavings and the yard is mostly very hard rocky soil. I cleaned the coop last week, put down DE and then 4 inches of shavings. I also put DE in their yard. Any suggestions? I hate it when I go into their yard I can literally hear the buzzing. Do the flies present any disease danger to the chickens? How can I get rid of them or at least minimize the problem?