Seasonal incidence of rice leaf folder Cnaphalocrosis medinalis (guenee) in kharif rice under terai region of West Bengal

In 2-year field studies on seasonal incidence of rice leaf folder on rice variety MTU 7029, results revealed that the leaf folder infestation (0.56%) started in the rice field during the 2^nd week of August (32^nd standard week) and remained low to moderate throughout the tillering stage. The infestation was found to increase in the month of October and it reached the maximum level (6.01%) during the end of October (43^rd standard week). It has also became evident from the study that minimum temperature have significant negative correlation (r = -0.493) with rice leaf folder percent infestation. Both the maximum and minimum relative humidity were negatively correlated but were not significant. Rainfall was also found to have significant negative correlation (r = -0.488) with the percent larval infestation. Correlation study between rice leaf folder percent infestation and plant phonological parameters like average tiller/hill, average leaf/tiller as well as Growing Degree Days (GDD) revealed that the percent infestation was strongly and positively correlated with GDD.