Randy Oliver said:
>  it has been shown time and again that CCD collapses are not correlated with mite levels.

And that is why I said that CCD should not be blamed for winter mortality up north, even when the
hives are empty of bees and there is no robbing.  Please read my earlier post again and keep in mind your bees
do not go through a long northern winter.  Your CCD experience is in warm weather and I have no comment on that
situation as it is outside my experience.

Here is the mechanism (in a northern climate):
1) varroa populations build rapidly in the first half of September so that winter bees are fewer in number and weakened sufficiently so their lives are shortened.
2) Beekeeper kills varroa in the second half of September or maybe with OA in November.
3) As the winter progresses, bees that are ready to die look for a chance to fly out and save the undertaker bees some work.  If the hive has some insulation or the front is dark and gets some sun, these end-of-life bees will fly away even at temperatures slightly below freezing.  Many winters in southern NH have plenty of such days.
4) The beekeeper opens the hive in late winter and finds it empty or with a baseball of bees, sometimes dead sometimes alive.  In some cases there will even be brood in that baseball.  Patches of dead brood elsewhere in the hive are common in these situations, and I believe those were left stranded as the population shrank rapidly and the cluster adjusted its position to compensate.
5) If the beekeeper checks the baseball of bees for mites, few if any will be found.

I have been the victim of the above mechanism so many times it is embarrassing to admit it.  My hives are insulated, the fronts are dark, and I have been trying to find the level of mite control that is just barely enough (a fools errand, it seems).  

I will be happy to provide further explanation if anyone wishes.  I believe this is important because the more precisely and narrowly we can define CCD, the sooner it will be figured out.

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