Check out the website Bugspray. com. They have tremendous information on every pest you can imagine. They may can give you some tips. We have the same issue with wasps is our stands. As I am allergic to bees, it scares me to climb into stands early in the season. Usually I wear lots of clothes and a headnet and climb up the stands in August or September with a can of wasp spray to clean them out. Maybe there is a preventive spray. I have not checked Bugspray.com but if anyone has any solution, they should. I have purchased many products from them, from mosquito sprays to beaver traps and lures.