> if SC really works, then all that

> would happen is a higher Varroa load from robbing that the SC bees would
> easily overcome.


I'll play Devil's Advocate here again, not that I'm trying to belabor this
increasingly tiresome discussion.

If the effect of SC was that it suppressed the success of mite
reproduction, then we need to look at measured figures for success of mite
reproduction.  They range from about 94% in susceptible stock, to 70% or
less for resistant stock.  At the 70% level (30% suppression), mites are no
longer much of a problem over the course of a season, since their rate of
reproduction barely exceeds mite mortality--mite levels over the course of
a year would rarely exceed 1000 per hive.

Now let's factor in the apiary effect.  Typical mite immigration loads are
often in the several to thousand mites per colony in fall if there are
collapsing colonies around.   Such a level of immigration can simply
numerically overwhelm any resistant stock, if the mechanism for resistance
is suppression of mite reproduction, which would be a delayed effect.

So I can't agree with your assertion that such immigration "would be easily
overcome."

I'm finding that the Excel mite population model spreadsheet that I
described in my recent ABJ article is really helping me to understand mite
population dynamics, and the profound effects of such factors such as
grooming, SMR, and immigration.

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

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