I have been fighting northern fowl mites since the first of the year and I tried the bird in a bag idea -- forget it -- the bird shreds the bag as someone said. I use Eprinex also but I found a bird yesterday with mites and treated him in the morning before work. After work, he still had mites so I'm not sure if I have mites that have become resistant to it, or if it takes longer than 9 hours to work. I also like the Sevin spray (water based) when the weather is warm. Take out the bedding, spray the coop and put in fresh bedding.