> .... there is a lot of arbitrary thought going  on both side about what
> restiance is,  the ability to live with a certain level,  or remove them
>   or keep swarming and moving.  That "definition" seems to be different
> for everyone.
>
There are reports floating around in the UK that some "varroa tolerance" 
is due to a harmless strain of DWV displacing the usual deadly ones.  In 
that case it's probably nothing to do with the bees but could be due to 
the beekeeper selecting from the survivors and inadvertently selecting 
for the harmless DWV.  It could also be due the the harmless strain 
(type B) being more successful than the 2 harmful ones (A and C) by not 
killing its host.  By constantly treating our bees we might be keeping 
the deadly forms alive.  I believe the harmless DWV was first found in 
Ron Hoskins's hives.  He has been selecting for varroa tolerance for 
many years but, presumably, had no idea that his success was at least 
partly due to the DWV strain he was encouraging.
We are now all hoping for a method of inoculating our colonies with Type B.

Steve Rose
North Wales



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