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A Flexible Model for Studying Plant Disease Progression. S. P. Pennypacker, Associate professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802; H. D. Knoble(2), C. E. Antle(3), and L. V. Madden(4). (2)Research associate, The Computation Center, The Pennsylvania State University, University Park 16802; (3)Professor, Department of Statistics, The Pennsylvania State University, University Park 16802; (4)Graduate assistant, The Pennsylvania State University, University Park 16802. Phytopathology 70:232-235. Accepted for publication 22 August 1979. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-232.

It is desirable for several reasons for epidemiologists to be able to depict with a single mathematical function the full range of shapes found in disease progress curves. Because of its simplicity and flexibility of application, the Weibull probability density function and cumulative distribution can be applied as such a disease progress model. Disease progress curves corresponding to “simple interest” and “compound interest” disease were accurately fit with the Weibull function. The Weibull model also was used to depict the full range of shapes possible for disease progress curves. Its flexibility and accuracy make the Weibull function a useful technique for modeling plant disease epidemics.