Atmospheric Dispersion of Wheat Rust Spores: A New Theoretical Framework to Interpret Field Data and Estimate Downwind Dispersion

Theoretical predictions for dispersion of heavy particles above an area source are used to formulate a new framework to interpret measurements of spore concentration above an infected field. Experimental measurements of mean spore concentration above an infected wheat field are used to validate theoretical predictions. The framework is then used to estimate total spore flux from the infected field and deposition patterns downwind. Results suggest that for the present case, consisting of a very low open canopy and friction velocity between 0.2 and 0.5 m s−1, the properties of the spore plume above the source field are mostly determined by the source strength (i.e., spore release rate) and are approximately independent of turbulence properties. Turbulence conditions have a strong effect on the distance downwind from the source traveled by spores, however, and are therefore critical in the spread of the disease. In addition, effects of spore clumping on dispersal are explored, illustrating the strong effect of clumping on reducing spore dispersal distance.