I would use the permethrin concentrate and mix for the (0.5%) solution 6.4 oz to a gallon of water and just spray weekly for 3 or 4 weeks. I had some birds that were severely infested. I thought they were just molting but weren't getting their feathers back in when I discovered they were loaded with mites. The first thing I tried was DE. The birds weren't improving and still had mites. I first discovered them in only one coop but eventually found them on birds in another coop. I dusted the birds and the coops with the DE and no improvement after treating them for a couple of weeks. Next I did use some Sevin dust that I had but it was almost gone but it did help but is no longer approved for use on poultry. I did some research and came up with permethrin and have been using it ever since when needed. There are certain times in the year when I have an overload of flies around and in the coops. Permethrin also worked to eliminate flies. I was treating for mites and also had a lot of flies in the coops and the permethrin eliminated them too, to my surprise.