Downy mildew of opium poppy is a major threat to opium cultivation in sub-tropical zone of India. Wet and humid conditions favour to pathogen Peronospora arborescence for rapid perpetuation in opium growing season. Therefore, epidemiological study was undertaken to investigate the factors affecting to disease developments in opium poppy crop. Downy mildew disease has appeared on opium plants in 2nd week of December with the occurrence of conducive environmental condition at eastern part of Uttar Pradesh such as minimum temperature (9.25°C), maximum temperature (22.75°C), relative humidity (91.6%) and sunshine hours (4 hrs). The disease was observed as peak in the 7th meteorological weak (2nd February) with minimum temperature (9.7°C), maximum temperature (25.6°C), relative humidity (91.15%) and sunshine hours (6.8hrs) The results of observation showed that minimum temperature was positively highly significant at establishing phase, positively significant at progressive phase and negatively highly significant at decline phase of downy mildew disease in the year 2020-21 and 2021-22. Maximum temperature was found negative significant at establishing and progressive phase however it was positively highly significant at decline phase in both the years. The minimum relative humidity was showed linear relationship at establishing and progressive phase of disease. Whereas maximum relative humidity was found positively highly significant in 2020-21 and positive significant in 2021-22 at establishing phase in case of phase (B) positive significant in 2020-21 and positively highly significant in 2021-22 in case of decline phase negatively highly significant in both year. However sunshine hour were showed negative relationship in phase (A) and (B) both year and positive relationship in phase (C) which indicating that if sunshine hours are increasing then disease incidence will be reduced.

Downy mildew, Epidemiology, Per cent disease incidence, Temperature, Humidity and Sunshine

It is concluded that percent disease incidence of downy mildew of opium poppy was recorded highest when mean atmospheric temperature was 5.0-27.2°C, relative humidity 45-93.1% with sunshine hours 2.8 hrs.

Shivam Singh, R.S. Mishra, Manish Kumar Maurya and Jaish Raj Yadav (2022). Epidemiological Studies of Downy Mildew Disease incited by Peronospora arborsence (Berk.) de Bary in Opium Poppy under Natural conditions. Biological Forum – An International Journal, 14(4a): 195-198.