>
> >Two questions:
> 1) Where did you get the assumption that 40% of the phoretic mites drop as
> a result of the sugar dusting?
>

From my own data, by dusting colonies, and then killing all the remaining
bees, and washing the remaining mites from them.   Did not do many
colonies, but range from thorough dusting was 40-60%.  In my spreadsheet,
you have the option of changing the efficacy if you have data to support.

>2) More of a comment - the spreadsheet doesn't account for the theoretical
> increase or decrease in the population of the colony itself, i.e. the "%
> infestation" rather than the total number of mites per colony.
>

Yep.  The "r" of varroa when brood is present is typically close to the r
of the bee population--so the populations tend to build proportionally
during the linear growth phase.  That's why I used total mite pop. rather
than infestation rate, which will change with changes in the amount of
worker or drone brood.

This morning I received a large data set from Amanda Millar (117 mite
counts), from 7 colonies which were dusted on a regular basis.  Her data
strongly support the model with its current values.

Of note is that in spring she increased the frequency of dusting to the
range of every 2-6 days, which appears to have reduced the mite population
despite the presence of brood.  I've gotten conflicting data from other
beekeepers who have tried high frequency dusting, but get the impression
that it does help.  I haven't modeled at such frequency, but would expect
it to have that effect.

The problem in the real world is that few beekeepers would ever maintain
such a schedule of dusting.

BTW, I've shifted the link to
http://scientificbeekeeping.com/simulation-of-sugar-dusting-against-varroa/ so
that I can add comments such as this.


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

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