Local dispersal and deposition of fungal spores from a wheat canopy

Rotorod samplers 1,2, and 3 m above ground level and O, 10, and 30 m downwind of a wheat canopy were used to measure dispersal and deposition of Puccinia recondita and P. graminis urediniospores, and Erysiphe graminis and Cladosporium conidia under various meteorological conditions. Spore concentrations at 1 m decreased by 1.8% m-1 over a 30 m distance downwind at canopy height with wind speeds above 12 km h-1 and 2.7% m-1 in winds of less than 10 km/hr. Spore concentrations at 1 m were significantly higher at the edge of the canopy than at 10 m and 30 m downwind. However, this was not true at 2 and 3 m above the ground, indicating that the decrease was due to spore deposition rather than upward movement of the spores. During sampling periods with winds greater than 10 km-h-1, spore impaction was reduced near the source and increased with increasing distance. However, wind velocities < 8 km h-1 resulted in increased impaction near the source and decreased deposition with distance downwind from the source.