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 2nd week of August (32nd 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 (43rd 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.