Estimation of damage and yield losses by the rice leaf folder Cnaphalocrocis medinalis (guenee) at panicle initiation stage

Abstract

Rice leaf folder larvae at population levels 0, 2, 4, 6, 8 and 10 larvae/were released at panicle initiation stage to assess damage and yield loss in rice. The results revealed that the maximum leaf damage was 24.5% with 10 larvae/hill, and the least (6.9%) at 2 larvae/hill. The avoidable losses at levels of 2, 4, 6, 8 and 10 larvae/hill 0.9%, 6.4%, 14.8%, 23.4% and 28.9%, respectively. Grain yield at 2 larvae/hill was found to be at par with that of pest free level. The linear regression equation between grain yield and levels of larvae revealed that a unit % increase in damage resulted in yield reduction to the extent of 0.5 g/hill. Drastic decrease in yield was observed with increase in level above 4 larvae/hill, which indicated that economic threshold level for rice leaf folder should be two larvae/hill.