>
> > whereas less powerful fume or biological methods can result in
> incomplete control
>

I certainly observe this.  Since I intentionally avoid applications that
result in high efficacy mite control, due to my dual desires to select for
mite resistant bees, and to *not* breed for resistant mites, I will often
get good control in the majority of the colonies, but there will generally
be a few outliers in either direction.  The only way to actually tell is to
go back and individually sample every treated hive in a trial (obviously,
can't do for the entire operation).

One could argue that the few colonies in which the treatment was
inadequate, for whatever reason, should be allowed to die to improve the
stock overall (assuming that the failure of the treatment was due to some
property of the colony).  Unfortunately, the parasites (such as varroa) may
then be spread back to the successfully treated colonies.  So best to
confirm that the treatment gave the results that you expected.

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

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