Weather based relations on different component of epiphytotic for early blight of tomato

Abstract

On the basis of three years data it was concluded that early blight initiates in November from kharif sown tomato and continued upto April-May in rabi sown tomato in Gangetic plains. The disease and its inoculums remain active on different plant parts of tomato starting from seedling and slowly progressed on leaves, stem, flower parts and fruits for nearly nine months in field itself. Kharif and rabi season tomato crop affected by early blight but maximum disease severity was recorded (91.3 per cent) in rabi season crop during March-April. Early blight persists in wide range of temperature and relative humidity. The maximum temperature range was 14.0 to 38.00C and minimum temperature 6.0 to 21.0.0C while maximum relative humidity 54-93 percent and minimum relative humidity 20-68 percent prevailed during the disease development. Multiple regression equation and coefficient of determination value indicate that the temperature and relative humidity reflected during the above mentioned period contribute 84 to 100 per cent in early blight development. AUDPC of early blight vary from 1095.7 to 3650.7 and apparent infection rate from 0.005 to 0.118 in a susceptible variety during epiphytotic period.