biological systems are not that simple as well you know. I would guess pollen availablility and light levels play a part. Even the height of the sun in the brightest part of the day could be in there.
Designing and executing experiments to separate them out/eliminate as factors would not be quick or particularly easy. One thing that has been eliminated is day length. A.m are only very weakly photoperiodic
Beekeeping is not such exact and that difficult. You just live with uncertainty and try to live forward. Nothing is eternal.
I keep spare hives 20% and I do not need to cry for some dead colony.
If you are worry about mites this time of year, you are 5 months too late.
When you kill last mites now, it affect to the next autumn's mite load.
Beekeepers are ordinary people. Mostly they do not understand much about biology.
Beekeeping is not such exact and so difficult. You just live with uncertainty and try to live forward. Nothing is eternal. uncertainty
I keep spare hives 20% and I do not need to cry for some dead colony. There are in my life much more bigger issues that those buggs.
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I loose my hives often to varroa, but I do not tear my game pants
When to treat hive in in the middle of winter????
Forum has been discussed during 10 years.
I have read from forum that some hives have brood in January and some have not. That's it.