Howdy, 1st post on boingboing - go easy on me.

This isn't terribly new stuff. The idea was initially floated in the late 60's that bioaerosol might be an efficient ice nuclei.

A good review can be found in introduction of 'The ice nucleating ability of pollen Part I' (Diehl et al, 2001) for anyone interested in the workings of it. A pdf should be available - try sciencedirect.

Some new aerosol fluorescence technologies should make measurement of this sort of thing much easier and I look forward to getting some kit on an aircraft and dragging it through some cloud!