"...Dusting only removes mites from adult bees and not mites
reproducing in sealed brood cells. We found that, on average
for each sampling month except November, approximately 60%
of the total mites per colony were located in the brood.
For example, since 60 % of mites may be reproducing in brood
at any given time, a control method that reduces even 90%
of the mites on adult bees will only result in a 36%
reduction of mites in the entire colony."

"To account for that in our study, we dusted colonies every two
weeks for an entire year. This should have increased the
efficacy of powdered sugar because we dusted colonies during
times of the year when they were relatively broodless (winter).
We still did not, however, find significant differences in mite
populations between dusted and undusted colonies."

"Our results support the conclusion of Aliano and
Ellis (2005b) that isolating broodless adult bees from their nest
materials and dusting them in a separate box is the only way to
effectively use powdered sugar to significantly reduce varroa
infestations."

The abstract for Aliano and Ellis (2005b) is here:
http://ibra.live.subhub.com/articles/20080612_93

-- 
Peter L Borst

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