Impact of climatic factors on incidence of rice leaf folder (Cnaphalocrosis medinalis, Lepidoptera: Crambidae) in rainfed rice crop of North-East India

To investigate and quantify the impact of abiotic factors viz., temperature, relative humidity, rainy days, rainfall and bright sunshine hours on the seasonal incidence of rice leaf folder ( Cnaphalocrosis medinalis Guenee, Lepidoptera: Crambidae) in rice ecosystem of North-East India.The infestation of rice leaf folder was monitored in the rice field by visual counting of folded leaves as well as the incidence of the pest with larvae and were correlated with the weather parameters during the study periods. Results revealed that leaf folder damage percentage culminated at 34th to 36th Standard Meteorological Week (SMW) during the sali seasons ( kharif crop ) of the stipulated five-year period i.e 2016–2020. Maximum temperature, minimum temperature, morning relative humidity and rainy days significantly effect on leaf folder infestation. Maximum temperature, minimum temperature, morning relative humidity, rainy days and rainfall together contributed about 58–87 per cent of total variation in leaf folder infestation. The principal component analysis was conducted and Minimum temperature exhibit prominence significant effect on the incidence of rice leaf folder among the climatic factors. The climatic factors and its changes during the crop cycle plays crucial on survival and infestation of rice leaf folder.