Toxicity of Some Insecticides against Chrysoperla zastrowi sillemi (Esben-Petersen) (Chrysopidae: Neuroptera)

Relative and persistent toxicity of insecticides is reported against Chrysoperla zastrowi sillemi by leaf dip method at three different doses; half, recommended and double the recommended. Pyridalyl 10 EC (37.5, 75 and 150 g a.i. ha⁻¹), indoxacarb 14.5 SC (37.5, 75 and 150 g a.i. ha⁻¹), chlorfenapyr 10 SC (50, 100 and 200 g a.i. ha⁻¹), triazophos 40 EC (125, 250 and 500 g a.i. ha⁻¹) and chlorpyriphos 20 EC (125, 250 and 500 g a.i. ha⁻¹) were tested for relative toxicity study. Persistent toxicity was evaluated at only the recommended dose of each insecticide. Pyridalyl treatments recorded the lowest larval mortality ranging from 6.67 to 26.67 per cent even after 48 h of exposure and it was significantly different from other treatments. At lower dose (6.67% mortality) pyridalyl was at par with control (3.33% mortality). Chlorfenapyr and indoxacarb caused moderate toxicity with 13.33 to 60.00 and 43.33 to 66.67 per cent larval mortality, respectively, at different doses. Conventional insecticides, triazophos and chlorpyriphos, caused 100 per cent larval mortality after 48 h of exposure. By food treated method at 48 h of exposure, 100 per cent larval mortality was observed in chlorpyriphos followed by triazophos (23.33 to 100%), chlorfenapyr (30.00 to 66.67%), indoxacarb (0.00 to 20%) and pyridalyl (6.67% at double dose). No significant ovicidal action of insecticides was observed during the study. Chlorpyriphos and triazophos were more persistent insecticides on cabbage in field, as compared with chlorfenapyr, indoxacarb and pyridalyl.