>
> >My point was that a heavy mite infestation, thousands of mites
> reproducing within an untreated colony can, in and of itself bring about
> collapse. If you add vectored disease it only gets worse. You disagree?
>

Dan, your statement was "In my opinion varroa alone are devastating."  So
yes, I'd need to disagree with that statement.

Obviously, if one allowed varroa to propagate until the mass of parasite
exceeded the mass of host, the host would collapse under the weight of
parasitism.  So the question is about the degree of infestation.

But say that varroa alone are devastating implies something different.
I've seen plenty of colonies that are able to thrive despite exhibiting
mite infestation rates of 15%.  A rate such as this indicates that there
are several thousand mites total in the colony.  Yet these colonies
maintain solid brood patterns and are productive.  So in answer to your
question, the evidence that I've seen indicates that unless viruses go
epidemic, serious parasitism by varroa is not devastating.

Prior to the rapid evolution of the viruses that could take advantage of
the novel vector, we could allow varroa infestation to climb to levels that
would be unimaginable today.  That observation alone suggests that the
problem is mainly viruses, not varroa alone, and that without the presence
of mite-adapted viruses, that even a substantial degree of parasitism by
varroa can be fairly well tolerated by a colony.


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

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