I agree with Peter to some degree
on herd immunity, specifically 
areas without a feral population.

In areas which can support feral bees, 
I'm not sure how 'herd immunity' can 
exist where colonies which rely on 
pesticides for mite control dominate 
the herd.  Bees will continually swarm 
off into the wild, becoming mite 
reservoirs until they succumb. This will 
play havoc with herd immunity thresholds.   

Perhaps, herd immunity can exist in 
areas where trait based resistance
in the feral population / domestic
beekeeping dominates the herd, bees
swarming off then become part of the 
herd immunity.
 
Best Wishes,
J Waggle

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html