People recommend permethrin spray. Sevin dust is no longer recommended for poultry and DE is useless in the face of a mites invasion (I know this from first hand experience). I'm in a different country where I can't get permethrin spray. I had a huge infestation of mites last summer and I beat it by painting the nestboxes and roosts with neem oil, spraying it around inside the coop, and using Vetafarm Avian Insect Liquidator on my birds. It's safe to use on newly hatched finch chicks so it's safe for chicken chicks. The only time you can't use it is if you are intending to eat your birds. Completely safe around eggs etc. I really concentrated on the legs of my girls as they have to climb up the legs to have a feast.