Off-list exchanges between Stan and I produced the following, which we
both agreed afterwards is appropriate for the entire list, so here goes.
 
Stan wrote:
 
I thought this thread was getting used up, so I am not posting this to
the list.  Besides, you capitulated, (hesitantly, but gracefully) :)
 
>Having said all this, I'll capitulate.  I guess drone trapping could
>select for mites that prefer worker brood.  I do not know for sure that
>ALL mites will target drone brood if the drones are available.  It COULD
>BE that there is a population of mites out there who prefer worker brood
>and it COULD BE that drone trapping will select for that portion of the
>varroa population.  Current research has not detected that population
>(which does not mean it does does not exist)...
 
This is cut from Jan's post:
 
>Research from the University of
>Wageningen (The Netherlands) has shown that the Varroa mites are 12 times more
>likely to enter drone cells versus worker cells.
 
That means that one in twelve mites DOES enter worker cells, so current
research DOES show a that such a population exists.  But Jan does not say
whether this research shows that these mites will still choose those cells
if there is an overabundance of drone cells (not the usual conditions in my
hives).  But as long as some small percentage will still enter worker cells
then a population exists that can be selected for.
 
I agree with all your other comments about IPM.
 
Have a nice day
Stan
 
My response to Stan was:
 
> I thought this thread was getting used up ...
Perhaps so, but it wouldn't be the first bloodied horse on BEE-L!
 
I'm still not convinced that drone trapping will select for worker brood
loving mites.  I'm not withdrawing my capitulation, but the plain fact
is we just don't know.  It is a far leap from:
>That means that one in twelve mites DOES enter worker cells,
>research DOES show a that such a population exists.
to conclude that there is a portion of the varroa population that
PREFERS worker brood.  It may be that for every 11 mites that find their
preferred host there is one mite that searched for a drone cell until it
nearly starved to death and finally settled for a worker larva because
it was so hungry that it just couldn't search anymore.  And if that's
the case there is no basis to expect that the progeny of that particular
mite will have a genetic preference for worker brood; the progeny may
have better luck in their days of searching for drone cells.  Of course,
the progeny may inherit its mothers poor hunting skills and may end up
as the unlucky 1 in 12 mites who have to "settle" for worker brood, we
just don't know.
 
The point is that making a claim that drone trapping may not be as good
as it sounds based on Rimantas' assertion that drone trapping may select
for worker preferring mites is a red herring!  The fear of genetic
selection is based on the developing resistence of mites to Apistan.
I doubt highly that a similar effect will happen with drone trapping -
the dynamics (to me) seem totally different.  Repeated use of Apistan
leaves ONLY those mites that don't die from Apistan poisoning.  We do
not yet know (but perhaps we'll find out) if repeated use of drone
trapping will leave ONLY mites that prefer worker brood or if the
offspring of worker-bred mites will find their way into subsequent
drone traps.  The selection pressure is not the same, it's apples and
oranges.
 
However, this does make for good speculation and possible research if
anyone is willing to do it and able to get the funding.  IPM skirts the
real answer (as if the REAL answer is even out there).  I like the idea
that drone trapping offers a chemical free alternative whose only cost
is my time.  Although I admit that drone trapping COULD lead to a worker
preferring mite population, I HIGHLY DOUBT such speculation will be
borne out in the field, even if drone trapping were the sole mechanism
for mite control.
 
Sorry we moved this off-list, I think it's one of the better topics as
of late.  Thanks for the exchange.
 
Sincerely,
Aaron