COMPARATIVE EFFICACY OF SOME NEWER INSECTICIDES AGAINST RICE LEAF FOLDER (CNAPHALOCROSIS MEDINALIS GUEN.) AND THEIR EFFECTS ON NATURAL ENEMIES IN RICE ECOSYSTEM

In the present study, some new generation insecticides were evaluated against rice leaf folder (RFL) infestation and their toxic effects were also observed on some natural enemies in the rice ecosystem. Data were collected on percent hill infestation, percent leaf infestation, number of moths/sweep, grain yield (t/ha) and abundances of natural enemies/m2. Results clearly showed that Serput (Bifenthrin) 2.5EC @ 2.0 ml/L water resulted in the greatest reduction of RFL and increased the grain yield compared to the untreated control which was followed by Envoy (Fipronil) 50SC @ 1.0 ml/L, Libsen (Spinosad) 45SC @ 0.40 ml/L, Acemida (Acephate + Imidacloprid) 51.8WDG @ 1.0 g/L, Suspend (Emamectin benzoate) 5SG @ 1.0 g/L, Combi-DT (Deltamethrin + Triazophos) 36EC @ 0.50 ml/L and Altima plus (Thiamethoxam + Emamectin benzoate) 40WG @ 0.20 g/L respectively. To know the toxic effect of selected insecticides, abundances (number/m2) of some natural enemies were counted at 7 days after given each spray. It was found that the highest numbers of natural enemies (m2) were recorded in the untreated control plot. In all field trials, the harmful effects of the seven insecticides were in the following rank order (least harmful to most harmful): Suspend 5SG, Serput 2.5EC, Envoy 50SC, Libsen 45SC, Acemida 51.8WDG, Altima plus 40WG and Combi-DT 36EC. Based on the reduction in rice leaf folder infestation, increase in grain yield and compatibility with natural enemies, Serput 2.5EC @ 2.0 ml/L proved to be the best among all the selected insecticides.