Abstract

Alternaria leaf blight is one of the most important diseases of potato (Solanum tuberosum L.) worldwide. The disease was prevalent in all the potato growing areas of Kashmir valley surveyed during 2009 and 2010. The overall mean disease incidence and intensity ranged from 24.54 to 28.23% and 13.84 to 15.98%, respectively. The highest disease incidence (39.09%) and intensity (22.54%) was recorded in district Budgam. The lowest level of disease was in district Shopian (14.89 and 8.05%, respectively). The pathogen associated with the disease was identified as Alternaria solani (Ellis and Martin) Jones and Grout. In early stages of disease development, small irregular to circular dark brown spots on lower leaves appear, measuring 0.5 mm in size. Upto fourth week of June concentric  rings  form  as  a  result  of irregular growth patterns by the organism in the leaf tissue giving the lesion a characteristic ‘target spot’ or ‘bulls eye’ appearance. The maximum lesion size 7.4 mm was recorded in the second week of August.

Key words: Potato, Alternaria solani, survey, disease incidence, symtomatology.