Persistence and Residual Toxicity of Different Insecticides Against Larvae of Earias vittella on Okra

Six insecticides were tested for their persistence and residual toxicity against first and third instar larvae of E. vittella on okra shoot and fruits. The descending order of residual efficacy against first instar larvae on okra shoots based on PT values was spinosad 0.005 per cent (1026.2), indoxacarb 0.01 per cent (1003.1), endosulfan 0.06 per cent (1002.7), profenofos 0.08 per cent (979.6), cypermethrin 0.01 per cent (793.1) and imidacloprid 0.004 per cent (435.1). However, on the basis of LT50 values the order of residual efficacy was cypermethrin 0.01 per cent (10.41 days), spinosad 0.005 per cent (9.50 days), endosulfan 0.06 per cent (9.39 days), indoxacarb 0.01 per cent (9.13 days), profenofos 0.08 per cent (6.67 days) and imidacloprid 0.004 per cent (3.52 days). The order of residual efficacy against first instar larvae on fruits was spinosad 0.005 per cent (1.59), indoxacarb 0.01 per cent (1.52), profenofos 0.08 per cent (1.52), imidacloprid 0.004 per cent (1.12), cypermethrin 0.01 per cent (1.08) and endosulfan 0.06 per cent (1.00) on the basis of PT values. However, the highest LT50 values to the extent of 14.74 days was observed due to spinosad 0.005 per cent when applied against first instar larvae on okra fruits, followed by indoxacarb 0.01 per cent (13.79 days), profenofos 0.08 per cent (13.49 days), imidacloprid 0.004 per cent (11.94 days), cypermethrin 0.01 per cent (11.24 days) and endosulfan 0.06 per cent (9.75 days). The highest PT value was obtained due to spinosad 0.005 per cent (764.9) followed by indoxacarb 0.01 per cent (718.2), while the highest LT50 value was recorded by profenofos 0.08 per cent (6.07 days), followed by spinosad 0.005 per cent (5.16 days) against third instar larvae of E. vittella on okra fruits.