National Symposium on Strategic Issues in Plant Pathological Research held at Department of Plant Pathology, CSK HP Krishi Vishvavidayalaya, Palampur on November 24–25, 2011
Late blight (Phytophthora infestans (Mont.) de Bary) is a devastating disease of potato worldwide including India. To develop web-based forecasting model, disease occurrence in the Punjab state was monitored for 20 crop seasons from 1989–90 to 2008–09 and prevalent weather factors including temperature, relative humidity etc were recorded. Epidemic years viz. 1985–86, 1991–92, 1992–93, 1997–98 and 2006–07 were correlated and regression equations were obtained with prevailing weather factors. Based on this information, disease forecasting model was developed where number of hours with higher relative humidity (> 90%) are evaluated by the prevailing temperature range of that period. The disease severity value (DSV) is then determined ranging from 0–4. The decision support system (DSS) assumes that primary source of inoculum is present in the field and DSV depends upon number of hours in the temperature range from 7.1oC to 11.0oC, 11.1oC to 20.0oC and 20.1 – 25.0oC, with RH greater than 90%. Weather data for potato growing areas during crop season of 2009–10 and 2010–11 were recorded from automated weather stations (AWS) installed in six districts viz. Hoshiarpur, Nawan Shaher, Jalandhar, Ropar, Kapurthala and Bathinda to get regular data. DSV was determined as 0–1 in all the districts in November and December. Low level of disease severity started appearing in January in districts of Nawan Shahar, Hoshiarpur, Jalandhar, Ropar and Kapurthala. The daily weather data are used in the model to forecast disease severity values and accordingly advice can be issued to the farmers whether to spray the fungicides or not.
