Effect of Planting Dates and Weather-Dependent Methods on Incidence of Rice Yellow Stem Borer (Scirpophaga incertulas Walker) and Leaf Folder (Cnaphalocrocis medinalis Guenee) in Bihar, India

The incidence of rice pests like the rice yellow stem borer (Scirpophaga incertulas Walker) and the rice leaf folder (Cnaphalocrocis medinalis Guenee) can be influenced by a variety of factors, including planting dates, planting methods, and weather parameters. The present investigation was undertaken to study the effect of planting dates and methods associated with weather parameters on the incidence of the rice yellow stem borer and leaf folder. The experiment was conducted at the Rice research farm of RPCAU, Pusa, in Randomized Block Design during the years 2019 and 2020 with rice variety ‘Rajendra Mahsuri 1.’ The planting dates were categorized as early planting (15th June), timely planting (5th July) and late planting (25th July) at 20-day intervals. The influence of weather parameters was correlated with the stem borer and leaf folder damage, and they were analysed using the SPSS Package. The results revealed that the early transplanted rice crops had the lower pest incidence recording, 12.39 per cent, dead hearts/white ear due to yellow stem borer and 7.49 percent leaf damage due to incidence of rice leaf folder as compared to late transplanted rice crop which recorded 21.75 per cent DH/WE (Dead Heart/White Ear) due to incidence of yellow stem borer and 13.91 percent DL (Damaged Leaves) due to rice leaf folder. Mean percentage of tiller damage was significantly higher in puddled direct seeding (14.67%) as compared to direct seeding (11.77%) followed by timely transplanting (4.40%) whereas the incidence of leaf folder in different planting methods mean percentage leave damage was significantly higher in timely transplanting (15.39%) as compared to direct seeding (12.83%) followed by puddled direct seeding (11.72%). Maximum and minimum temperature, wind speed and morning relative humidity had a negative effect on stem borer per cent dead heart and white ear head and leaf folder concerned, maximum temperature, morning relative humidity, evening relative humidity and rainfall had positive correlation at different planting dates whereas, maximum and minimum temperature, evening relative humidity had a positive effect on stem borer per cent dead heart and white ear head and leaf folder concerned, maximum temperature and morning relative humidity and evening relative humidity had positive correlation at different planting methods.. The findings of the study revealed that the planting dates and methods greatly influenced the magnitude of pest incidence in rice crops. The study further revealed that early and normal transplanting can reduce the insect pest incidence in the rice crop, particularly rice stem borer and rice leaf folder and farmers can harvest a good yield. It is obvious that delayed transplanting and other methods of transplanting would have more severe pest incidence and, thereby, the huge grain yield losses. Among the parameters, relative humidity and rainfall played a major role, which explained the maximum variability on yellow stem borer and leaf folder incidence at different methods and planting dates.