VIEW ARTICLE

Ecology and Epidemiology

Evaluation of Potato Late Blight Forecasts Modified to Include Weather Forecasts: A Simulation Analysis. R. Raposo,Department of Plant Pathology, Cornell University, Ithaca, NY 14853; D. S. Wilks(2), and W. E. Fry(3). (2)Department of Soil, Crop and Atmospheric Sciences, Cornell University, Ithaca, NY 14853; (3)Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 83:103-108. Accepted for publication 19 August 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-103.

The potential effect of incorporating weather forecasts into potato late blight disease forecasts for timing protectant fungicide applications was investigated. Fungicide applications, fungicide weathering, and pathogen development were simulated with a system of field-tested computer simulation models, using 50 yr of weather data from Steuben County, New York, Weather forecasts were simulated with a probability model that relates distributions of observed high relative humidity periods and mean temperature to forecasts produced by the National Meteorological Center. Simulated weather forecasts (with accuracy equivalent to those of real forecasts) improved the efficiency in the use of fungicide scheduled with BLITECAST: The area under the disease progress curve (AUDPC) was decreased by about 5%, but the same number of fungicide sprays was used. The maximum contribution of a weather forecast was determined by using perfect knowledge of future weather 1 and 2 days in advance as the weather forecast. Such perfect knowledge of future weather used with BLITECAST or with a simulation-based disease forecast decreased AUDPC by about 8 or 10%, respectively. Finally, two additional sets of simulations were done with weather data modified to be less favorable to late blight. In these simulations, weather forecasts provided an increasing benefit as conditions for late blight development became less favorable.