๐๏ธ Poor hive ventilation
Some beehives have poor ventilation. Bees during winter die because of this โ๏ธ Overwintering collapse
Basically its not the -30 degrees that kills the bees, its the humidity that gets accumulated in the hive that makes it hard for them to warm themselves.
Bad ventilation typically happens because
- hive does not have an exit / hole way on top of the hive
- top frames have plastic cover that does not allow for any air to go through
Bad ventilation in turn causes mold/fungi to appear, which is bad for bee health
source - https://www.honeybeesuite.com/physics-for-beekeepers-mold-in-a-beehive/