DETERMINATION OF ECONOMIC THRESHOLD LEVEL (ETL) FOR THE CHEMICAL CONTROL OF RICE LEAFFOLDER, CNAPHALOCROCIS MEDINALIS GN. (PYRALIDAE: LEPIDOPTERA)

The research was conducted during 2008-09 at the Agronomy Research Farm, University of Agriculture, Faisalabad in order to determine the Economic Threshold Level for the chemical control of rice leaf-folder (Cnaphalocrocis medinalis Gn.). The experiment was laid out in Randomized Complete Block Design (RCBD) having six levels of infestation (0%, 2%, 4%, 6%, 8%, and 10%) with three replicates. To mimic the insect behavior of rice leaffolder, the simulative injury technique was used. Results showed that mean values of grain yield obtained after harvesting, percentage of filled grains, 1000-grain weight varied significantly but parameters like number of productive tillers/m2, number of grains per panicle did not vary significantly with infestation levels. The economic analysis showed that cost of application of cartap 4G (cartap hydrochloride) at 2 % infestation level, the cost of chemical control was approximately equal to the yield reduction and this level can be considered as economic threshold level for rice leaffolder.