Well, to be completely honest, I don't know at what temperatures mildew, etc., will be neutralized. So I can't answer either way for sure. It would probably be an effective method for killing pests, as would heating up the soil excessively. But again, I don't know enough about mildew/mold to know what temperatures are needed to destroy it. Maybe Stinky can chime in and give you a better idea. Her profession enables her to know a whole lot more about this kind of thing than I ever could.