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Disease Forecasting System for Warm Weather Pythium Blight of Turfgrass. F. W. Nutter, Former Research Assistant, Pennsylvania State University, University Park 16802. H. Cole, Jr., Professor of Plant Pathology, and R. D. Schein, Professor of Plant Pathology, Pennsylvania State University, University Park 16802. Plant Dis. 67:1126-1128. Accepted for publication 18 April 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1126.

A forecasting program based on weather monitoring was developed to help turfgrass managers predict warm weather Pythium blight. Two weather variables were associated by chi-square analysis with Pythium outbreaks during the 1978, 1979, and 1980 growing seasons: 1) a maximum daily temperature higher than 30 C, 2) followed by at least 14 hr of relative humidity greater than 90%, provided the minimum temperature was higher than 20 C. A forecasting day ran from noon to noon. When fungicides were applied soon after these criteria were met, significant Pythium blight damage was prevented. In contrast, in areas where fungicide treatments were not applied, Pythium blight infection and damage usually occurred.