> >The hive was completely devoid of any live bees.


Mike, the lack of dead bees helps to limit the suspects, since that means
that the bees flew out on their own.  Would rule out tracheal mite or
starvation.

If you look at the core of the last place that brood was raised, you
diagnose other causes.  A few scattered capped cells with some bee faces
looking out, and white guanine deposits on the cell ceilings would indicate
high varroa and DWV collapse--very common.

Scattered drone cells would indicate had gone laying worker.

The supersedure cell is strongly associated with colony loss--could have
been a failed queen and the colony was unable to supersede.  Bees will
drift to other hives.

Could be due to pesticide/miticide exposure, but that would likely have
affected all other hives in the yard.

If AFB or EFB, generally shot brood look with scattered sealed brood
remaining.

The symptom of the supersedure cell is more typical of N ceranae and/or
paralytic viruses, although with N ceranae a small cluster is often left.
 Collapses from either of these typically follow a cold snap, and you will
often see a ring of beebread that was stored around the brood.


-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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