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Disease Detection and Losses

Cercospora Leaf Spot of Cowpea: Models for Estimating Yield Loss. R. W. Schneider, Research Assistant, Department of Plant Pathology, University of Illinois, Urbana 61801, Senior author's present address: Department of Plant Pathology, University of California, Davis 95616; R. J. Williams(2), and J. B. Sinclair(3). (2)Plant Pathologist, International Institute of Tropical Agriculture, Ibadan, Nigeria; (3)Professor, Department of Plant Pathology, University of Illinois, Urbana 61801. Phytopathology 66:384-388. Accepted for publication 10 November 1975. DOI: 10.1094/Phyto-66-384.

Yield loss of cowpea was correlated with Cercospora leaf spot disease severity from artificially-simulated, chemically-regulated, and naturally-occurring epidemics at Ibadan, Nigeria. Areas under disease progress curves were correlated with yield loss regardless of the shapes of the curves. The yield-loss-estimation model was not accurate for low disease levels. A critical-point model was constructed and tested that related time of occurrence of specific disease severities to percent yield loss. However, the model could be used only for uninterrupted disease progressions. A third model that integrates these two methods is discussed in relation to chemical control programs.

Additional keywords: epidemiology, disease control, benomyl, foliar diseases.