Influence of Weather on the Progress of Corynespora Leaf Spot in Cotton

Afield experiment was conducted to study the influence of weather parameters on the progress of Corynespora leaf spot in three BGII cotton hybrids viz., Aadhya, Akira and US 7067 at Regional Agricultural Research Station, Lam, Guntur during Kharif 2023–24. Disease severity was scored weekly starting from the first appearance to boll bursting and picking stage by adopting 0 to 4 scale in twenty plants tagged randomly in each plot. Weather parameters viz., maximum and minimum temperature_, morning and evening relative humidity, rainfall, number of rainy days, number of sunshine hours, wind speed and evaporation were recorded daily at the meteorological observatory. Correlation and multiple regression analyses were carried out between per cent disease index (PDI) and weather parameters using MS-Excel program. Morning relative humidity and sun shine hours expressed significant positive correlation whereas, maximum and minimum temperatures, number of rainy days and wind speed showed significant negative correlation with PDI. Regression analysis revealed minimum temperature, RH II and rainfall as common factors significantly influenced the progress of disease in all the three hybrids.