Bio-rational insecticides against tea pests JBiopest. 5(1): 91-95 91 Evaluation of some bio-rational insecticides against the looper complex, ABSTRACT The efficacy of some bio-rational insecticides against tea looper complex, Hyposidra spp. was evaluated at two different locations of Dooars tea plantations, West Bengal. The results indicated that all the insecticides were effective in reducing the looper population to a significant level. However, in comparison to other insecticides, neem based

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... insecticides could not give the desired level of control. Among the different treatments, diflubenzuron 25 WP @ 700g/ha caused maximum reduction of loopers over control in both the sprayings at both the locations [Location I: 66.91% and 65.54% reduction of loopers at 7 days after 1 st and 2 nd spraying respectively) and Location II: 68% and 50.85% reduction of loopers at 7 days after 1 st and 2 nd spraying respectively)] and appeared to be the best treatment against loopers. Bt-k @ 1000 mL/ha was the next best treatment for suppressing looper population at 7 days after 1 st spraying (64.44% and 67.81% reduction of loopers at Location I and II respectively) which was at par with recommended insecticide deltamethrin 2.8 EC @ 200 mL/ha (65.14% and 62.16% reduction of loopers at Location I and II respectively). However, in 2 nd spraying, its efficacy was declined. Both the doses of Neem based insecticides recorded 31-49% reduction of loopers after 1 st spraying but this was reduced only to 9-17% after 2 nd spraying, Thus, in consideration of the performance of the insecticides, diflubenzuron @700 g/ha and Bt-k @ 1000 mL/ha could be included in the IPM package of looper.