I use a bit of citronella in my nest boxes and have found it to be a good mite deterrent. i had an infestation late in summer of 2013. Did a clean out + treated birds x 2. All clear until spring 2014, when I found a couple of juvenile mites in the nest box. I bought a citronella plant and put a chopped leaf in the bottom of each box. No mites detected since then. Now, I do agree regarding birds being sensitive to aromatics. Not just chickens, but all birds. Any how, I have asthma, and give the strength of anything I put in the coop a nose test. Though species vary, if my nose tolerates it w/o complaint, I figure the birds are good to go. Will continue using small dose of aromatics in the nest box, as I figure that is less problematic than using insecticides.You can feed them citrus fruit. Most just don't like it much. I wonder where those rumors get started. Citronella is different from citrus fruit. It's a very strong smelling aromatic.