Forecasting system of late blight occurrence in susceptible and resistant potato clones

Forecasting systems and late blight resistant cultivars are important tools to reduce the amount of fungicides and the production cost of a potato farm. The objective of this study was to evaluate the Blitecast forecasting system for late blight occurrence and susceptible and resistant potato clones for managing late blight in Santa Maria, RS, Brazil. Experiments were conducted at the Federal University of Santa Maria during the Spring 2006 and Autumn 2007. Meteorological data were measured continuously above the crop canopy. Ten treatments were used in a completely randomized design, with four replications. Treatments were different values of accumulated severity, calculated by the Blitecast forecasting system and by the potato clones SMIJ461-1 and SMINIA793101-3, characterized as resistant, and the clone Macaca as susceptible to late blight. The Blitecast forecasting system was not effective for predicting the time of fungicide spraying for the control of late blight and, therefore, to be used in susceptible clones it has to be adjusted. For resistant clones, the fungicide spraying based on the Blitecast system has no effect on late blight occurrence and potato productivity.