Abhishek Katiyar, Ram Suman Mishra, Anand Milan, Deepak Singh, Mandeep Singh, Suraj Soni and Shailendra Yadav
Abstract
Downy mildew, caused by Peronospora plantaginis, remains one of the most destructive diseases of blond psyllium (Plantago ovata Forsk.), significantly affecting seed and husk productivity under Indian agro-ecologies. The present investigation was conducted during the rabi seasons of 2023-24 and 2024-25 at the Medicinal and Aromatic Plant Farm, ANDUAT, Ayodhya, to elucidate the epidemiological behaviour of the pathogen under natural epiphytotic conditions and to quantify the influence of key meteorological variables on disease progression. Weekly observations on disease incidence and intensity were recorded along with temperature, relative humidity, rainfall, wind speed, bright sunshine hours, dew incidence, and total evaporation. Correlation and regression analyses revealed that moderate temperatures (20-30 °C) coupled with high relative humidity (70-85%) were the most conducive for disease initiation and subsequent epidemic build-up. Maximum and minimum temperatures exhibited highly significant positive correlations with both disease incidence and intensity, while bright sunshine hours and total evaporation also favoured rapid disease establishment. Wind speed played a crucial role in dispersal of sporangia, thereby enhancing secondary infection cycles. Rainfall showed a negative but non-significant association with disease development, indicating limited involvement of rain-splash in pathogen dissemination. The combined influence of intermittent humidity, moderate warmth, and gentle moisture conditions created an ideal microclimate for P. plantaginis proliferation. The study provides comprehensive insights into weather-disease relationships, contributing valuable information for forecasting models and the development of integrated disease management strategies for blond psyllium.