My thought about a few weeks doing an OAV treatment in dead of winter. If the bees are in a tight cluster and you spray OAV on them, they will break cluster to clean themselves. Now the issue is after they cleAn themselves, can they reform the cluster that was keeping them warm, and alive. Have you watched a cold bee, they are like watching a drunk. There is no way if they get cold the cluster reforms. So, is a mid winter OAV treatment worth it. But I could be wrong, but if I'm right your bees are dead
OAV is not "spraying" anything on the cluster. OADribble is a different method. If OAV killed the winter cluster a whole bunch of beekeepers would be without bees in the spring. Temp needs to be about 40 degrees F at time of vaporizing.