|Title||Potato late-blight management in the Toluca Valley: Forecasts and resistant cultivars|
|Publication Type||Journal Article|
|Authors||Grünwald, NJ, Rubio-Covarrubias, OA, Fry, WE|
|blitecast, epidemiology, fungicide applications, host-resistance, phytophthora-infestans, yield loss|
We evaluated host resistance and fungicide forecasting as components of integrated management in the Toluca Valley of central Mexico. Potato cvs. Rosita and Nortena showed high levels of resistance (20 and 4% final disease severity, respectively) in the no-spray controls, whereas susceptible cv. Alpha was at 90% defoliation well before the end of the season. Disease on Alpha was well managed with a weekly spray of chlorothalonil. None of three published forecast systems was entirely appropriate far this pathosystem. SIM-CAST accurately allocated fungicide for a susceptible cultivar but needs to be adapted for the high level of resistance of Rosita and Nortena. TOM-CAST and BLITECAST did not recommend the initial fungicide application until after disease was well established in the plots. We believe that the low-temperature response of Phytophthora infestans needs to be reevaluated for the highland tropics.