Does nobody on this board treat prophylactically?
I was a back yard hobbyist throughout the 1980s in Oklahoma and Virginia and I treated once a year w/terramycin for AFB whether I needed to or not. I never lost a hive (only had 2 at a time) and never had trouble over wintering, etc. I don't remember IPM being a big deal back then, but then we didn't have the internet and access to all the info we do now, especially as hobbyist.
Taking the hobby up again after 20 years, I am overwhelmed by all the stuff there is to deal with now, varroa mites, tracheal mites, shb, etc, that weren't issues back when...I read a report today that said up to 30% or more of U.S. hives now die out each year, and 75% of that die out is probably do to varroa mites. And yes, I have a varroa mite problem. I did 2 24-hr counts the first of the week and they were both over 120. I did a powdered sugar dusting on Thursday but it seemed to really upset the hive. I am sure my technique wasn't the best. So I ordered some Apiguard (temps have been in the 90s this week--should still be in the 80s for a couple of weeks or more). But that is what got me to thinking about using Apiguard and terramycin at the same time.
I can easily be talked out of treating prophylactically, just a carry over of an old habit I guess, and I do have an A.J. Beetle trap on, and the screened bottom board to help with mites, and I will do the powdered sugar dusting a time or two more, hoping my technique improves. But I always thought treating once a year with terramycin was better than risking getting AFB and having to burn up the equipment. A bottle/package of terramycin is a lot cheaper than a new hive set up.