A beekeeper on the island of Newfoundland recent said:

I fed my bees sugar syrup until it was too cold for them to take any more of it, which isn’t always the smartest thing to do because even though the bees are able to store the syrup, they may not have time to cure it (evaporate most of the water from it) and cap it like they would with honey during warmer weather. Subsequently, as in my case, the ole beekeeper discovers a top third deep filled mostly with uncapped syrup — or as we like to say in the real world, moisture. Not enough moisture to drip down on the bees and kill them, but enough to dampen the frames and allow some mold to grow.

I wholeheartedly agree with that beekeeper. He seems like a smart guy.

Coincidentally, I replaced some hard insulation with moisture quilts on two of my hives five days ago because I found a thin layer of mold covering the comb in the top deeps. Hard insulation cuts down on condensation building up inside the hive in the winter, but it doesn’t always do so well in exceptionally foggy, swampy or wet climates. I removed the hard insulation even though I don’t think the climate of my new beeyard is particularly wet. Better safe than sorry. Moisture quilts are supernatural devices that keep the insides of Langstroth hives warm and dry all winter long. With all due respect to hard insulation, nothing beats a moisture quilt.

My big theory was that moisture from the uncapped sugar syrup caused the mold to grow, especially with the bees clustered deep down in the hive for winter. If the bees were covering the frames, they would likely clean up all the mold. But they’re not and they can’t. But the main culprit is that uncapped sugar syrup. To test my theory, all I had to do was take a peek under the hood of my hives that have had moisture quilts keeping them cosy and dry since the fall. So today I did just that — and I found mold on the frames inside the hives with moisture quilts too.

I’m not too concerned about a thin layer of mold over the comb. I don’t think it’ll hurt the bees. But for me this is proof enough that feeding the bees syrup until it’s too cold for them to take it down can add moisture to the hive — and subsequently allow mold to grow — because the bees aren’t able to evaporate or cap the syrup before winter sets in.

Anyway, I probably could have left the hard insulation on my hives.

FEBRUARY 02, 2016: Yeah, it’s been two and a half months and I’m pretty sure I didn’t need to remove the hard insulation. The mold on the comb probably came from the uncapped syrup creating moisture, but now that the bees in most of the hives have moved to the top box, the mold and any extra moisture definitely is not an issue. In fact, it’s so dry inside the hives that the sugar I put in isn’t hard or moist — which means it may not be easy for the bees to dissolve it and digest it. It’s almost too dry inside the hives because of the moisture quilts. If I knew the bees had enough honey to eat, I wouldn’t care. Dry is good. But if they’re running low on honey and need to eat the dry sugar to stay alive, they need some moisture to make the sugar soluble enough to digest. That’s why I’ve decided to put hard insulation back on two of three of my hives. My plan for next year: put the moisture quilts on, but as soon as the bees are just below the tops bars and the sugar, switch to hard insulation. It’ll still keep them warm (and maybe warmer) and it’ll give them enough moisture to digest the sugar easily. Though I could probably put on hard insulation from the start and not have to worry about any of it.