A phase Doppler anemometry system in combination with a laser light sh
eet was used in a low-speed recirculating wind tunnel to examine the f
low field around an individual leaf. Turbulence similar to that encoun
tered near the surface of the earth in a neutral stability boundary la
yer was generated using a grid at the upwind end of the wind tunnel te
st section. Individual healthy and diseased plant leaves were introduc
ed into the tunnel with the leaf tip pointing downwind. The Mie-scatte
red radiation from the spores departing the diseased leaf was captured
on videotape. Image processing software was used to enhance the visua
l quality of the individual frames from the videotape and to make spor
e velocity calculations. Three main vortex regions around the leaf wer
e identified. The importance of these regions to the separation of the
spores from the leaf surface and their subsequent downwind movement w
as analyzed.