>could the actual reason for Fall collapse be more from
the honey robbed from collapsing colonies and the viral load that comes
with it than the over-all number of mites?

I agree with Mike--generally difficult to infect bees with virus via food.

It's not so much the mite load on the adult bees that's the problem--it's
the percentage of the pupae that are infested.  Once the pupal infestation
rate exceeds ~25%, the colony is "walking dead."  This rate is generally
reached in autumn as the declining bee pop concentrates the mites in the
remaining brood.

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

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