Deposition of Particles Liberated in Gusts of Wind

Abstract

Theoretically, the aerial transport and deposition of fungal spores near to their source dependon the way in which they become airborne. Spores of some fungi are injected into the air, independentof wind speed, whereas others are blown from the host mainly by gusts. We calculated the collectionefficiency of vertical, sticky cylinders for spores released continuously and steadily, and for spores released intermittently when the wind exceeded a certain speed. We tested these calculations in the fieldby trapping on cylinders of different diameters Lycopodium spores released steadily from an artificialsource, spores of Erysiphe graminis blown from a barley crop and Lycopodium spores blown from a fiatplate or a short crop. The collection efficiency E of vertical sticky cylinders depends on wind speed, and the averageefficiency for an experiment was obtained by averaging E over all speeds during spore release. Thecatch of the spores released continuously can be predicted adequately from E at the mean wind speed. Incontrast, the catch of spores blown from a crop or a plate can be predicted only when speeds below athreshold are excluded. When spores in crops are released by gusts, deposition by impaction will be greater than thatcalculated from the mean wind speed. This effect of the mode of spere release needs to be taken into accountin modeling spore transport in crops.