Severity, weather influence and prediction of early blight of Tomato for Eastern dry zone of Karnataka

Early blight onset varied from 25 to 28 standard meteorological weeks (SMW) with mean of maximum severity levels of 86.7–100% during five years of kharif 2012–2016. Mean and maximum PDI of early blight was found significantly and positively correlated with morning and evening relative humidity of both lagged by one and two weeks. Relation between minimum temperature and early blight was significantly negative. The multiple linear regression predicting the mean severity accounted 79.0%. Variability due to maximum temperature and morning relative humidity two weeks and a week prior, respectively and wind velocity prior to two weeks. Maximum temperature and wind velocity of two lagged weeks accounted for 78.0% variability of maximum severity of early blight. Validations using 2016 data sets indicated suitability of prediction models beyond 30 SMW, however, the scope for refinement of models existed by removing the cumulative error arising out of mean and maximum severity considered across fields and accounting all individual fields per se. Weather based models developed considering crop age could also be more robust and needs further investigation.