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Disease Control and Pest Management

Analysis of Potato Late Blight Epidemiology by Simulation Modeling. J. A. Bruhn, Graduate research assistant, Department of Plant Pathology, Cornell University, Ithaca, NY 14853; W. E. Fry, associate professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 71:612-616. Accepted for publication 17 November 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-612.

A mathematical model that simulates effects of environment, fungicide, and host on asexual development of Phytophthora infestans on potato foliage was constructed and evaluated. In comparisons involving four potato cultivars during three growing seasons the model accurately mimicked actual epidemic development. The model was then used in conjunction with a weather model and a fungicide model to determine the effect of rate-reducing resistance on the performance of various fixed interval fungicide spray schedules. Simulation results indicated that: intervals between sprays can be extended when resistant potato cultivars are grown; plant disease forecasting systems used to time fungicide applications are likely to be most cost effective for cultivars that are most susceptible; and profit maximization, when used alone, is insufficient for evaluating the effectiveness of potato late blight management policy because plant disease control practices tended to reduce both total costs and their associated variability.