Interesting discussion.  I also observe similar when I bring some claimed
resistant stocks to my area for testing.  But others perform well for a
generation or two.

I agree with Jose that the hard data on SMR and VSH fully support that
there are indeed genetically-passed mechanisms for resistance.  And with
Pete that there will likely be environmental effects, and the problem of
diminution of traits due to outcrossing.

But the reality is that hypothesis that has been tested : the genus Apis
exhibits plenty of examples of instances where a stable host-parasite
relationship has developed.
-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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