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Optimizing late blight forecasts for improved late blight management
I. M. SMALL (1), L. Joseph (1), Y. Wu (1), W. E. Fry (1). (1) Cornell University, Ithaca, NY, U.S.A.

Late blight is a perennial concern for potato and tomato producers in rain-fed production systems. Calendar-based fungicide application strategies are often employed for the management of late blight regardless of existing disease levels, cultivar resistance, or prevailing weather. Such strategies may result in economically and environmentally inefficient disease management. Forecast-guided fungicide schedules are influenced by prevailing weather and host resistance. The objective of this study was to evaluate and optimize late blight forecasts for fungicide scheduling using computer simulation. Simulation experiments utilized 10 years of observed weather data from 59 locations in potato producing states representing the equivalent of 770 field experiments. For each season at each location, forecast-guided application schedules for susceptible, moderately susceptible, and moderately resistant potato cultivars were compared to calendar-based schedules regarding their expected number of fungicide applications and simulated disease progress. Forecast-guided schedules resulted in fungicide schedules that improved late blight suppression, relative to a calendar-based schedule. Based on simulation results, opportunities for improvement of forecasts were identified and optimization conducted.

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