Evaluation of Toxic and Antifeedant Properties of Some Plant Extracts against Major Insect-Pests of Cabbage

The studies were carried out to evaluate toxic and antifeedant properties of 5% aqueous extracts of eight plant species against major insect pests infesting cabbage viz., diamondback moth, Plutella xylostella (L.), cabbage white butterfly, Pieris brassicae (L.) and cabbage aphid, Brevicoryne brassicae (L.). The exposure of third instar larvae of P. brassicae to plant extracts resulted in maximum mortality (55.2%) with Lantana camara (L.) and minimum in M. koenigii (12%). A similar trend in mortality amongst diamondback moth larvae was evident. However, the corrected mortality of fourth instar nymphs of B. brassicae was observed to be significantly high (39%) in Melia azedarach (L.), while Murraya koenigii (L.) extract reflected mean minimum mortality (17.1%). The corrected mortality of aqueous extracts of Artemisia brevifoiia Wall., Chromalaena adenophorum (Spreng.), L. camara, M. azedarach and Rumex nepaiensis Spreng reflected varying degree of antifeedant effect in all the three test insects. Reduction in feeding over untreated control in P. brassicae and P. xylostella was observed to be 45–61 and 34–48%, respectively, in these plant extracts. Similarly the plant extracts also exhibited 14–27% reduction in settlement of B. brassicae on the treated leaf surface of all the plant extracts evaluated.