Abstract

 Weather parameters play a pivotal role in the infection process and spread of pathogen. It also influences the expression of susceptibility/resistance of the host plant during post-infection phases. Therefore, an experiment was conducted for two consecutive cropping seasons (2018 &2019) to study the influence of weather parameters such as temperature, humidity, rainfall and wind direction on the emergence of alternaria leaf blight of makhana in Koshi region of Bihar. Maximum per cent disease severity of alternarialeaf blightwas observed during the peak monsoon months (June to August). Highest disease severity of leaf blight (14.80% & 15.7%) was observed in the mid June during crop season, 2018 and 2019. High temperature (36.9oC & 38.1oC), and relative humidity (94% & 96.4%) of both the year 2018 and 2019 were found correlated with higher severity to alternaria leaf blight. Similarly average HTR values (3.1) were also found correlated with the average high temperature and relative humidity of both years (2018 and 2019) in terms of severity of leaf blight disease. Maximum temperatures, relative humidity and rainfall exhibited strong positive linear relationship and influenced the occurrence of alternaria leaf blight disease significantly. We also developed a geo-phytopathological model for the prediction of alternaria leaf blight disease of makhana on the basis of congenial mean temperature and relative humidity.
Highlights
The minimum temperature 17.4oC and 18oC along with minimum relative humidity54.3% and 58.0% was recorded during the early stage of the crop and the maximum temperature 36.9oC and 37.7oC along with maximum relative humidity 94.7% and 96.4% was recorded by the end of crop season 2018 and 2019, respectively
Data analysis of weather parameters for alternaria leaf blight severityinfers that high temperature, high relative humidity, high rainfall and eastern wind play an important role in the disease development.Leaf blight severitywas observed in the month April and gradual rise in increasing temperature, relative humidity and rainfall was continued up to the harvesting stage
The development of model which shows statistically significant correlation with leaf blight of makhana. The data and their analysis resulted from the present investigation enable the researchers to devise a new system to monitor and develop management strategies for alternaria leaf blight of makhana. Findings of this present investigation reveals that four weather parameters viz., temperature, relative humidity(morning and evening), rainfall and eastern wind direction greatlyinfluences the severity of alternarialeaf blight of makhana
Summary
The present investigation has been undertaken to study the correlation between alternaria leaf blight disease and weather parameters and to develop a geo-phyto-pathological model. Data analysis of weather parameters for alternaria leaf blight severityinfers that high temperature, high relative humidity, high rainfall and eastern wind play an important role in the disease development.Leaf blight severitywas observed in the month April and gradual rise in increasing temperature, relative humidity and rainfall was continued up to the harvesting stage.
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