I can recommend Poultryshield. I got it mail order. It dehydrates the mites so takes a day or so, but then the house is littered with dead ones

You dilute it in water and spray the house, making sure you get right into the joints. I did the repeat spray a week later to get any new hatchlings. Most of the other stuff you can buy deters mites but doesn't kill them, so I just use that as a precaution in the litter and on the birds.
My hen house is homemade but I got rid of my original felt roof and replaced with with corrugated Onduline roofing. Felt provides the perfect mite habitat and you can't get under it to spray.
Like I said - been watching like a hawk and have not seen any mites for weeks now.
Sue
