VIEW ARTICLE

Ecology and Epidemiology

Spatial and Temporal Spread of Oat Crown Rust. R. D. Berger, Professor, Department of Plant Pathology, University of Florida, Gainesville, FL 32611; H. H. Luke, Research Plant Pathologist, Science and Education Administration, Agricultural Research, U.S. Department of Agriculture, Gainesville, FL 32611. Phytopathology 69:1199-1201. Accepted for publication 15 May 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-1199.

The spread of oat crown rust (caused by Puccinia coronata) in time and space was measured equally well by disease severity assessed on whole plants or on the leaf below the flag leaf (F–1) for cultivars Fulghum (susceptible) and Burt (intermediate). The assessment of leaf F–1 on cultivar Red Rustproof-14 (resistant) underestimated the total proportion of disease (x). The average apparent infection rates (r) for rust on whole plants of Fulghum and Burt were 0.4, and 0.35 units per day, respectively. These rates were significantly faster than that for Red Rustproof-14 (r = 0.2). Rust isopaths spread outward from plot centers at rates that averaged 0.9, 0.4, and 0.35 m/day for cultivars Fulghum, Burt, and Red Rustproof-14, respectively. The rate of isopath movement also was used to measure interplot interference. On Red Rustproof-14, isopath movement increased from 0.2 to 1.2 m/day when secondary foci enlarged. Rust increased equally fast (as measured by r) at centers and peripheries of foci. There was no flattening of disease gradients for Burt or Fulghum when logit x was plotted against log₁₀ d (distance). The log₁₀ x versus log₁₀ d transformation for disease gradients provided an aberration of true gradients.