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A Model for the Effects of Metalaxyl on Potato Late Blight Epidemics. M. G. Milgroom, Department of Plant Pathology, Cornell University, Ithaca, NY 14853; W. E. Fry, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 78:559-565. Accepted for publication 20 October 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-559.

Dose-response relationships of Phytophthora infestans to metalaxyl and a description of metalaxyl residue dynamics were incorporated into an existing simulation model of potato late blight. The existing model was modified to include the effects of metalaxyl on lesion establishment, lesion expansion, and sporulation. The model was used to simulate epidemics when metalaxyl was applied under a variety of conditions and compared with observed epidemics in the field. Model predictions for area under the disease progress curve (AUDPC) and final disease level (Yf) were almost always within the range of observed values from the field epidemics. The model predicted well for a variety of metalaxyl treatments, including: beginning metalaxyl applications when disease reached levels between 0 and 10%, different doses of metalaxyl, and metalaxyl applied to both susceptible and resistant potato cultivars. Development of a model that realistically simulates the effects of metalaxyl on late blight epidemics may allow the identification of optimal use of metalaxyl for late blight control.

Additional keywords: systemic fungicides.