The message <001801c29445$2a21d5f0$2ed3ad8e@HAL>
from Donald Aitken <[log in to unmask]> contains these words:

> From: "James J. Grefig"
> > While not a chemist nor a biologist it seems to me that the mites that
> > survive in a hive that is over wintered with Apistan will be the mites
> > that are resistant (or most resistant) to fluvalinate. As the survivors
> > breed they will pass on their resistant genes. Is this overly simplistic?

> This does seem obvious. However, if you treat as per the label, the
> survivors will also be the ones that are resistant and will pass on their
> resistant genes. I don't see why leaving the strips on over winter would
> make any difference whatsoever in the development of resistance.

We need to get back to basics on this and ask a few fundamental questions.
When fluvalinate was first introduced for the control of varroa, it was only
in the region of 96% effective.  What of the other 4%?  Did they already
have a tolerance (I prefer this to `resistance') to fluvalinate or was
it quite
simply that 4% of the bees in the hive did not come into contact with the
Apistan strips?

If 4% of the mites already had a tolerance to fluvalinate, then they would
survive to breed - no matter how long the Apistan strips were left in
the hive.  However, if the 4% of mites remaining had survived because
they simply had not come into contact with the fluvalinate, then their
descendants would remain susceptible and a 96% kill could be
expected every year - unless we train them to become tolerant by
leaving in the Apistan strips longer than recommended.

Apistan strips release fluvalinate in reducing amounts over time as the
active ingredient is used up and eventually the amount of fluvalinate
released will be insufficient to kill the mites and they will become
tolerant to it.

I am fortunate to live in a part of the UK which is still free of the mite
and we have had 10 years in which to prepare our defences.  When
the mite arrives (as it inevitably must), I doubt very much that Bayvarol
or Apistan will feature in our control measures.  I have been adding
copper gluconate to syrup for the last two years as a prophylactic and
will probably continue to use this together with a package of other
more natural control measures when the mite arrives.

Phil.
(Highlands of Scotland)