> Pete >I don’t see how you can study the relationship of bees and varroa —
> without understanding the environmental connection
>

Varroa population dynamics are all about the environment--that's why in my
Varroa Model it is necessary to input the effect of the environment upon
the amounts and proportions of bees and brood.

Inside the hive, environmental temperature and humidity are typically kept
fairly constant--the outside environment has little effect upon these
parameters.  And although varroa is less heat-tolerant than the honey bee,
in our own operation, run in 100F temps in dark boxes, we don't observe
that the high temps reduce varroa buildup.

Re propolis, keep in mind that the natural host of varroa--*Apis cerana*--uses
very little propolis.  And the high-propolis AHB still has issues with
varroa.  And Renata Borba's extensive research on propolis envelopes has
not supported the hypothesis that propolis will keep varroa in check:
http://jeb.biologists.org/content/218/22/3689

Recent studies have indicated the DWV is a relatively benign virus, which a
colony can typically keep under control.  It's only when the varroa
infestation rate exceeds around 15% that DWV then goes epidemic, thus
overwhelming both individual and colony-level immune response to the virus.

Of course, pesticides can diminish the anti-viral immune response, but
colonies die from DWV quite predictably even in the absence of pesticides
or their residues.

I strongly question whether any "magical" plant metabolite, at field
levels, has much affect upon varroa reproductive success.

All varroa issues are solely about the mite's reproductive success.  The
factors involved in mite reproduction are largely elaborated in my
model--success at cell invasion, mature daughters per foundress, mating
success of those daughters, and daily mortality of the mites.  Any form of
honey bee resistance to varroa must affect one or more of those factors.
The bees can fight back with behaviors or biochemistry.  We still have much
to learn, but in my own operation, we lose close to zero colonies from
varroa/DWV, by simply understanding mite population dynamics, and managing
our hives accordingly.

As far as the 2% of my colonies that are exhibiting near complete
resistance to varroa, I've finally had a chance to inspect their brood
pattern these past few weeks.  I'm not seeing signs of VSH or uncapping to
any extent, so am not clear as to how the individual colonies managed their
mites, nor whether the trait(s) are heritable.  What I *can* say is that at
least some beautiful colonies appear to be able to keep varroa under their
thumbs.  This should give us hope.  The question now is whether we can
shift that apparent resistance to an entire breeding population.  It has
been done elsewhere, so I remain optimistic.

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

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