Hi Everyone,

Several folks have posted comments in this thread which don't make
biological sense.   The example below is from Phil but is very similar
to others.

Phil wrote in part:

"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."

This is a very basic misunderstanding of the development of resistance
to a treatment.  First and foremost for selection to occur some of the
population ( the mites in this case ) have to be killed.  If there is
not enough treatment material to kill the mites there is no selection
for resistance  because they all live.  You have to kill some of the
mites to select those that are able to tolerate the treatment in order
to select for resistance.  The greater the percent of the population you
kill, the faster you are selecting for resistance ( stronger selection
pressure ).  It is like breeding bees to produce more honey: to make
progress in breeding you have to select the colonies with the most
productive ( in terms of honey ) hives to breed from and cull those that
don't produce as much honey.
Any use of a mite treatment selects for resistance to that treatment.
You would like to have a period of time when the mites are not exposed
to the treatment ( no selection ) to help slow the development of
resistance to the treatment.  This is the logic of relatively short
treatment periods but with treatments that are absorbed into the beeswax
we can't remove the treatment by simply removing the strips.  I think
this is why we are seeing resistance developing to treatments that
absorb into the beeswax like fluvalinate and coumaphos but don't see
such resistance to things like organic acids that don't absorb into the
wax.

I recall a few years back an impassioned "sermon" from Dr Bill Wilson
now retired from USDA regarding the manufacturers blaming beekeepers for
the emergence of resistance to fluvalinate when beekeepers were not
given any other treatment options and everywhere in the world where
fluvalinate was used as the only or main treatment for about 10 years
the result was fluvalinate resistant varroa mites.


Hope this helps.
FWIW

blane





******************************************
Blane White
MN Dept of Agriculture
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