When you're not going to use your camper for a few months, get some SunPac's. They are the little caches that people use in their sailboats and closets to eliminate or prevent mold and mildew. Place several of them in high spots throughout your trailer, with all cabinets and doors open. The Sunpacs emit formaldehyde, and it kills everything including roaches, spiders, ants, and mold and mildew. One word of caution, you do have to thoroughly air-out your trailer before you use it. We use them in Florida in our park model trailer when we close it up for the summer. I've never found a live bug when we returned.