I'm posting here because this is the section of the forum where I gathered that this might be possible. I started beekeeping in 2008, and had been using Fum prophylactically in the fall as per how I was instructed. Since then I have seen a few sources that said it made no difference, and some that said it actually caused harm. When I read that Jim Lyon had stopped using it I thought it was worth leaving it off. So far my losses are no worse than they have been before. I am at 36 colonies alive out of 39 entering winter. The three that I lost had starved. Thanks Jim.