Persistent Toxicity of Selected Insecticides on Biotic Potential of an Egg Parasitoid, Trichogramma brasiliensis

Insecticides hamper the effectiveness of Trichogramma brasiliensis not only through direct mortality but also as a result of sublethal effects affecting the parasitisation capability and per cent emergence. Among all the tested insecticides only Bt was found non toxic to T. brasiliensis followed by NSKE which could be applied in conjunction of T. brasiliensis for controlling the insect pest with little care. The study on per cent parasitisation and emergence of T. brasiliensis adults was done by exposing adults to treated leaves and survived female were later exposed to fresh radiated Corcyra eggs. The maximum toxicity on fecundity and fertility was observed on zero days after treatment (DAT) and declined as the DAT progress. On the basis of different exposure period among 2, 4 and 6 hours, 2 hours of exposure period significantly gave high parasitisation and emergence upto 3 DAT. The persistent toxicity of different chemicals on per cent parasitisation and emergence lasted for 9 DAT.