I mix 5% in their food and I have never had a worm problem . I also dust the coop and run with it and don't have a mite or flea problem either. I use it on my flower beds and around the house for ants and ear wigs also. I have a little girl so its a safe insecticide for me to use everywhere. Its only 11 dollars for a 40 lb bag here but I undersand its quite expensive if you don't have a local supplier.