Crop-weather based relation and severity prediction of aerial blight incited by Rhizoctonia solani Kuhn in soybean

Crop-weather based relation and other aspects of aerial blight incited by Rhizoctoniasolani Kuhn were investigated on two mega varieties (JS 335 and JS 97-52, now susceptible) under central Indian conditions during 2017, 2018 and 2019. It was found that aerial severity and sclerotial formation on affected leaves were varied significantly in all three season, and progress of disease was rapid between 63–84 days old crop {full pod (R4) to maturity initiation (R7) stage}.Increasing crop age was also significantly positively correlated with increasing severity (0.732*) and sclerotial formation (0.981**). Mean relative humidity and maximum temperature of current as well as previous week were found to be positively and negatively correlated with increasing severity of aerial blight, respectively. A regression based model with three explanatory variables (Mean RH, Rainfall and Minimum temperature) of current week was found to be most significant in prediction of disease severity (R2=0.946) of aerial blight. Whereas previous week weather variables i.e. rainy days and rainfall were also accounted 71.7 per cent variability (R2 = 0.717) in disease severity. Overall, weekly average maximum temp (27 to 30o C) and mean RH (80 to 90 per cent) in current week coupled with more rainfall and rainy days in previous week were found to be most conducive field condition for rapid progress of aerial blight disease in soybean.