I find it of great interest to compare the evolution of two
largely-unmanaged populations of honey bees, after being invaded by
varroa.  The two populations that I'm referring to are *A. m. scutellata* in
South Africa, and the European-African hybrid bees in the Americas.  Yes,
both have large managed populations, but matings often largely are
determined by wild-living "ferals."

In South Africa, the bees quickly evolved to be able to largely manage to
keep their mite populations low ("resistance").  And in addition, DWV is
rarely mentioned.
In the America's, on the other hand, there is the question as to whether
colony survival is more a matter of resistance or tolerance.  As with
European stocks, in which Seeley demonstrated that simple frequent swarming
can allow a population of bees to "tolerate" varroa (and DWV), that
mechanism likely applies to AHB too.  I've heard from any number of
beekeepers running AHB that their colonies still suffer from varroa/DWV,
although this appears to vary from region to region.

So what's interesting to me is that *scutellata* in Africa, though hardly
being mite-free, appears to have evolved a suite of mechanisms for actual
resistance, as compared to AHB in the America's, which if kept in managed
hives, appear to continue to often suffer from considerable  mite/virus
buildup.  Why AHB in the Americas haven't evolved as much resistance as has
*scutellata* is a mystery to me.

Of great interest to me is that I'm currently managing a substantial number
of breeder colonies of my European bees in California, which have clearly
demonstrated the ability to RESIST varroa population increase over the
entire course of a year.  I've not yet investigated how they do so, but
during the past few weeks have been able to observe their brood combs, as I
work to prevent them from swarming.  Their mite populations are so low that
VSH would not jump out at me.  Some display completely solid brood
patterns, but others have some open cells, perhaps indicating brood removal
(or perhaps inbreeding), but VSH-chewed pupae are not jumping out at me,
nor are uncapped "bald brood."

It's one thing to observe beautiful individual *colonies* that appear to
have the ability to keep varroa in check, but then another thing to attempt
to selectively breed a *stock* that consistently displays that trait.

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

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