I thought there was a flourescent dust often used for this purpose.
You could ask on the pollination line.... Peter Kevan runs it.
Or you could get the book "Techniques for Pollination Biology"
by I can't remember, which is pretty new and supposed to be
good.  Author might be Inouye.  Can anyone fill in the details
on these?
I also believe that the accuracy of results of experiments with
the dust is not all it could be - but I think it depends on
what you want to measure.
I know this is not as helpful as possible, all my files are in
storage (God bless the day I get to live somewhere where all
my stuff will fit inside..)
 
Liz Day
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Indianapolis, Indiana, central USA