I'd like to clarify the 34% drop figure.

Of the total number of phoretic mites at that moment, 34% were dislodged
from the bees within the first hour of dusting.

Over the course of 24 hrs, with a really good dusting, you will cause the
drop of close to 50%.

Unfortunately, if there is much brood, up to 70% of the total mite
population can be in the brood, and will emerge over the course of the next
12 days.

You can see the result of these mathematics in my "Brass Tacks"
article--sugar dusting can be effective, provided that it is done thoroughly
(frames stacked, humidity not too high), and frequently. Dusting broodless
colonies daily for 5 days will eliminate most mites.

If colonies contain brood, then the break even point with dusting (at which
the mites reach zero population growth) occurs at roughly weekly dustings.
 If one wishes to actually drop the total mite population, you'd have to
dust more frequently.

Even though I no longer dust, it is a very effective method for estimating
mite populations, and a mite management tool that can be used by
recreational beekeepers, provided that they realize its limitations.

I know of plenty of recreational beekeepers who keep resistant stock, and
simply dust several times when mite populations climb, and manage to
maintain healthy colonies.  Commercially, though, I don't find it to be the
most cost effective method of mite control.

Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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