Influence of weather variables on the incidence and development of rice leaf blast (Magnaporthe oryzae)​

Rice is the second largest grown cereal crop in the world and the most consumed main staple meal. The devastating nature of rice blast disease has resulted in large annual losses. Therefore, a pot experiment was conducted at Paddy Breeding Station, Tamil Nadu Agricultural University, Coimbatore, during Rabi seasons of 2018-19, 2019-20, 2020-21, and 2021-22, with the objective to investigate the possible role of weather variables on rice leaf blast. Research analysis performed through correlation and decision tree analysis was carried under R studio to study the relation between weather parameters and per cent disease index (PDI) of leaf blast. The results revealed that, morning dew point temperature (X4, r = 0.69** and 0.67**) and minimum temperature (X2, r = 0.68** and 0.65**) had higher negative correlation both in real time and in one week lead time (LT1W) respectively. Further, the decision tree analysis showed the combination of rainfall of 5.9 mm and minimum temperature less than 22.6 ºC helped achieve disease incidence of greater than 80 per cent. Thus, the occurrence and development of leaf blast are significantly influenced by the minimum temperature and dew point temperature with drizzling rainfall, and these weather variables can be employed for weather-based disease forewarning against rice leaf blast.