Hi All
Much work was done on powders about 1982 @ the Research institute Dol (czech
republic) I think the person to contact would be Vladimir Vesely.

The work was mainly aimed at reducing mite numbers rather than as a dection
method.

The powders included:- Talc, wheat flour, wood flour, flowers of sulphur,
Icing sugar, powdered coltsfoot, and various mixtures of these were tried.

I think the powders work in two ways with a third way possible...

1, the dry powder soaks up the moisture that helps the varroa grip (the
gripping is possibly partly due to surface tension of this moisture).

2, The powder acts like ball bearings causing loss of grip due to skidding.

3, There is the possibility of delivering active substances by the powder
method (hence Sulphur and Coltsfoot in the list).

A search for    Bee Institute Dol, vesely     may throw up something
interesting


Best Regards, Dave Cushman
G8MZY
Email: [log in to unmask]
Website...Beekeeping and Bee Breeding
http://website.lineone.net/~dave.cushman