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Analysis of Epidemics of Northern Leaf Blight on Sweet Corn in Israel. Yehouda Levy, Department of Life Sciences, Bar-Ilan University, Ramat Gan 52900, Israel; Phytopathology 79:1243-1245. Accepted for publication 20 June 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-1243.

Epidemics of northern leaf blight of corn incited by the fungus Exserohilum turcicum were monitored in five corn fields (cv. Jubilee) during 19861988 at various locations in Israel. Infection efficiency, sporulation, and lesion expansion of isolates collected in these fields were measured in growth chambers. Apparent infection rate (r) in the field varied from 0.05 to 0.20/day. There was a low correlation between temperatures and dew periods favorable for disease development and r in the field. A significant and high correlation was found between r and components of fitness measured in the growth chambers. A simple northern leaf blight simulator used to examine the influence of fitness of the pathogen on development of disease indicated that the importance of weather conditions decreases when fields are infected with a highly aggressive population of the pathogen.