I agree with Mary. I have had mites off and on. I've tried many things including DE and still had mites. I do believe if any wild birds get into your coop the mites will be introduced. If you have some type of mites, the best product to get rid of them in my opinion is permethrin which is very cost effective. I had a severe infestation last year and the birds were loosing a lot of feathers which I thought was due to molting but upon closer inspection discovered the mites. I treated the coop weekly for awhile with permethrin because it does not kill the mite eggs. Permethrin works and there is no egg withdrawal. Initially I sprayed the birds too. I also use the dust on the birds and in their nest boxes and spray inside of the coops, every crack and crevice, on and under the roosts, ceiling, walls, floors, anywhere the mites can hide. I buy the concentrate but I have a lot of coops so I mix it in a gallon sprayer and the wand helps me to reach the hard to reach areas. For smaller places the premixed spray is good. It took awhile for the birds feathers to come back in, but they are beautiful again. Wear special clothing including a mask and gloves. Good luck...