VIEW ARTICLE

Ecology and Epidemiology

The Influence of Soil Environment on the Incidence of Sorghum Downy Mildew: A Principal Component Analysis. W. Schuh, Former graduate student, Department of Plant Pathology and Microbiology, Texas Agricultural Experiment Station, College Station 77843, Present address: Department of Plant Pathology, Oklahoma State University, Stillwater 74078-0285; M. J. Jeger, and R. A. Frederiksen. Associate professor, and professor, Department of Plant Pathology and Microbiology, Texas Agricultural Experiment Station, College Station 77843. Phytopathology 77:128-131. Accepted for publication 25 July 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-128.

The influence of weather variables on disease incidence of sorghum downy mildew at four locations and over 4 yr was investigated by using principal component analysis. Two principal components, derived from the weather data only and representing wet and dry soil conditions, were used as independent variates in regression analysis and explained 41% of the variation in disease incidence. Regression of the disease incidence on the original soil environment variables did not provide significant equations. Results of this analysis could be used to classify sorghum-growing areas, based solely on weather, for their propensity to downy mildew.