I went into winter with two of the strongest hives I've ever had. Tens of thousands of bees in each, one hive stacked two high and one stacked three high - all loaded to the gills with honey. The bees had plenty of numbers and plenty of food.
Fast forward to now. The hives are dead and moldy. They are still full of honey (but some was consumed). In each hive, about two inches of dead bees in the bottom and dead bees scattered about on the frames. Small moldy cluster in each hive.
I have no explanation. My thought is that I may have made a mistake by allowing too much ventilation up top. I used moisture quilts on top of each hive to try to mitigate condensation but in each one, I put several large 1.5 inch ventilation holes, screened over, with a very small exit hole up near the top for the bees. I'm wondering if this created a "chimney effect" that allowed cold air to flow up through the hive. I'm also wondering if I should have reduced the stack size - maybe three full supers was too much ... I don't know.
I didn't see any evidence of disease and the hives didn't appear to have a mite problem, unless one flourished undetected late in the season.
Meanwhile, I have 40 frames full of honey but they are moldy not no useable. Into the fire they went.
I'm taking a pause to try to figure out what went wrong. I'm hoping to catch a swarm this season and work a hive or two but I'm not buying package bees this year. Hopefully I get lucky with a swarm but if not, I'm done killing bees for a while... :(
Comments? Ideas on what might have happened?