Here in Northern Illinois, we're *almost* at spring....saw my first dandelion yesterday, woodland violets just starting, not too much in terms of nectar flow yet (maples froze, pussy willows got rained out).
One of my two Ktbh's died in our extreme cold this past winter. And in preparing to utilize the hive for a new walk-away split from my survivor stock (hopefully in the next two weeks - we will get warmer!)....I found black mold in the back of the hive near the floorboard (where sidewall and floor meet). Knowing mold abhors sunlight, I've left the hive open during the brightest part of the day in order to kill it off. (Removed the bars and left the lid open).
Other than killing the mold with light and air - I'm not sure what else I can/should do. I will not treat the hive with any chemicals - and while vinegar does do some good....not sure if it's necessary for me to do anything. Do I leave it for the new girls to treat? It'll be behind the follower board for a long while yet and out of the reach of the house bees.