Isolation potato with blackleg disease were collected from different fields of Nenava province fifty two isolates of Erwinia carotovora var. atroseptica, 16 isolates of Erwinia carotovora var. carotovora, 21 isolates of Erwinia chrysanthemi Were identified. The results showed that the main cause of blackleg disease of potato in this province was Erwinia carotovora var. atroseptica. The bacteria that cause this disease were isolates from potato tubers, shoots, soil and water. The mother tubers were found to be the major source of inoculum for blackleg disease. The best growth medium for this bacteria at constant temperature (27ْ C) and incubation period for 48 hours, was potato dextrose agar media, while the best medium at varying temperature was nutrient agar medium.