> Well, it is clear that there is much less chance of viruses being
> spread when there is only one mite per brood cell, which in
> itself is a very interesting approach to the whole idea of
> "treatment thresholds".

I guess this confirms the intuitive understanding of those of use who
are uncomfortable approaching the published threshholds too closely and
feel more comfortable at levels below 1 or 2% as measured by an alcohol
wash.

It seems obvious that, as the ratio of phoretic adult mites to the
number of cells of open brood increases, the probability of multiple
infestation in any given cell increases.  We know that, regardless of
the virus problem, multiple vampires are going to do more serious damage
to a larva/pupa, so we instinctively avoid mite levels where it becomes
statistically probable that multiple mites will enter cells on more than
an occasional basis for reasons having little to do with viruses.

For geometric reasons, I would think the probability of multiple mites
entering a cell is not linearly related to mite/cell ratio, but will
climb more rapidly than mite numbers as infestion rates increase.  I
believe also that I have heard that the mother mites tend to seek out
unoccupied cells in preference to those already containing a foundress
mite.  Whether or not this is true, at low mite loads, the probability
of multiple mites infesting a cell is low.

That seems to mean to me that there is some tipping point at which
things get bad very rapidly, but below which the mites and bees can
co-exist.  Results of many studies seem to indicate (empirically) that
this point is somewhere around 5 mites per 100 bees as measured by
alcohol wash.  The know mite tolerant strains of bees seem to be able to
stay at the 5-6% level and below.  Formic and other 'soft' treatments
seem to work better where initial mite levels are below 5%, but quickly
become ineffective if the initial mite load is much above that point.

allen
http://www.honeybeeworld.com/diary/

::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
-- Visit www.honeybeeworld.com/BEE-L for rules, FAQ and  other info ---
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::