Early blight is a very common disease of potato in Iran. It causes leaf spots and tuber blight on potato. The disease can occur over a wide range of climatic conditions and can be very destructive if left uncontrolled, often resulting in complete defoliation of plants. In contrast to the name, it rarely develops early, but usually appears on mature foliage. This study was performed to forecast potato early blight in Kermanshah province, west of Iran. Hourly meteorological data were recorded by an iMETOS automatic weather station installed in the field and were compared with regional station. The primary symptom occurrence of early blight lesions was predicted by Phenological day (PD) and degree day (DD) models during 2013 and 2014 growing seasons. By application of both models using two data sets, the time of symptoms appearances was predicted between 1 to 3 days in advance. Results showed that early symptoms of disease can be observed after 300P-day and 625DD in the vision. The results suggested that in case of unavailability of on-site meteorological parameters, the data obtained from a close weather station (with less than 10 kilometers distance) can be used for disease epidemic forecast. Further studies in other climates are suggested for more scrutiny.
