Studies on epidemiology of angular leaf spot disease of common bean in wet temperate conditions of Himachal Pradesh

Epidemiology of angular leaf spot (Phaeoisariopsis griseola) diseases of common bean (Phaseolus vulgaris L.) was studied under natural epiphytotic conditions at MAREC, Sangla, Kinnaur, a hot spot for the disease in wet temperate agro-climatic zone. The relationship of disease with weather parameters revealed that the disease appeared in the last week of July during 2009 in the crop sown in and first week of July in 2010. However, afterward a gradual increase in the disease incidence and severity was noticed during both the years though the values were comparatively higher during 2010. The increase in disease severity coincided with the high rainfall regime during both the years of study. The average disease incidence and severity ranged between 2.5 to 65. and 5.5 to 86.00% whereas the average seveity index ranged between 4.5 to 73.5%, respectively The maximum and minimum temperature ranged between 17.4 to 25.7^oC and 8.0 to 15.5^oC during both the years, however, a slight increase in temperature was observed in 2009. The total rainfall and number of rainy days were found positively correlated with both disease incidence and severity during both the years of study, Correlation and regression analysis between disease incidence, severity and weather parameters further validated their role in epidemic development.