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Ecology and Epidemiology

Deposition Gradients of Urediniospores of Puccinia recondita Near a Source. Donald E. Aylor, Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, P.O. Box 1106, New Haven 06504; Phytopathology 77:1442-1448. Accepted for publication 10 April 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1442.

Deposition gradients of urediniospores of Puccinia recondita were measured using potted trap plants exposed at several distances between 0.1 and 3.7 m downwind of a line source of spores in the middle of a 0.4-ha, 1-m-tall crop. Trap plants were exposed for 23 hr on 8 days encompassing a range of average wind speeds of 25 m s-1 measured 1.5 m above the top of the crop. After exposure in the field, the trap plants were incubated and the resulting number, N, of wheat rust pustules was counted. The relative gradient of the number of pustules (dN / dx)/N, or d(ln N)/dx, decreased with distance x from the source. In other words, the length scale of the deposition gradient increased with distance. These results are explained in terms of a derived equation that simultaneously accounts for the combined effects of spore deposition and dilution by atmospheric turbulence and has both an exponential and a power law component.

Additional keywords: spore deposition, turbulent diffusion, wheat leaf rust.