We had a wee infestation last autumn, so after cleaning out and disinfecting the coop, I made up a slurry (runny mud) of Hemexsan D.E. powder and water, and painted it onto the walls and floor, and into all the nooks and crannies I could reach. The 'mud' then dried to leave a dusty residue, which is still there several months later. Anyhow, no problems since, so could be worth a try??