>
> >I will say this: last year I split all my colonies in May and June and
> by July the mite levels were over the limit. Again, any procedure that
> focuses only on mite build-up and ignores the summer influx, misses the
> problem.
>

Pete, the last thing that I want to do is to appear to be picking on you,
but I feel that on Bee-L we must be careful about making assumptions and
unsubstantiated statements.

My own research and mathematical modeling strongly support your assertion
that immigration of mites, especially from collapsing colonies in late
summer and fall, can contribute to a rise in the mite population of
recipient colonies. However, the numbers do not support your assertion that
that was the main reason for the high mite levels in your colonies in July.

As far as I can tell (please correct me if I'm wrong), the greatest amount
of mite immigration into a colony was recorded by Greatti, who recorded a
spectacular invasion of nearly 3500 mites into one unfortunate hive over
the course of an entire year.  All other studies (as well as the other 9
hives in Greatti's study) exhibited lesser amounts of immigration.  And
Greatti's June through August counts were in the 200-500 mite range.  So
for the sake of modeling, let's assume that your colonies received 200
mites by immigration between your splitting in May and high counts in July
(which would require you being surrounded by collapsing colonies that early
in the season).

My modeling suggests that a typical colony in your area on the first of
May, exhibiting an alcohol was of only 5 mites per half cup of bees (a
perhaps unalarming infestation rate of under 2%) would contain slightly
over 1600 mites (I'd expect that colony, if untreated, to collapse in
October)..  Splitting that colony in May would leave 800 mites in each
hive.  If each split received a queen (I do not know whether they did) at
that time of season, one would expect that mite level to continue to double
once a month, thus resulting in 3200 mites per hive by the first of July,
exhibiting an alcohol wash of 10 mites--without any immigration
whatsoever.  I'd expect those colonies to collapse by November.

If we add a high figure of 200 mites due to immigration, it would only
increase your July 1 alcohol wash to 11 mites, and accelerate the collapse
by a couple of weeks.

The math indicates that even a extremely high rate of immigration between
May and July was unlikely to be your MAIN problem.  It would certainly be a
problem, but the MAIN problem would have been simple in-hive mite buildup.

That said, later-season mite immigration may be much more substantial if
there are collapsing colonies within flight range, and even within-apiary
drift from high-mite hives to low-mite hives can be a major factor
(Rinderer noted this when following mite buildup in Russian hives when they
were kept in close proximity to high-mite Italian stock).  I see this occur
in my test apiaries where I am tracking mite counts.

Pete, if you'd like to give me more information on your mite counts,
splitting experiments, and treatments (off list), I'd love to use them to
test the accuracy of my modelling.


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

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