Pesticidal activities in five medicinal plants collected from mid hills of western Himalayas

A screening for pesticidal activity of plant extracts with some known medicinal attributes could lead to the discovery of new agents for pest control. In the backdrop of recent revival of interest in developing plant-based insecticides, the present study was carried out to evaluate the pesticidal properties in five medicinal plants (Berberis lycium L., Hedera nepalensis L., Acorus calamus L, Zanthoxylum armatum L. and Valeriana jatamansi L.), growing abundantly in the region of mid hills of western Himalayas, against some agriculturally important pests (Aphis cracccivora Koch, Tetranychus urticae Koch and larvae of Spodoptera litura Fab, Plutella xylostella L. and Helicoverpa armigera Hub). Most of the extracts/essential oils were active only against A. craccivora. The activity of the test samples was significantly and negatively correlated with contact time. However, at the end of 48 h contact time, all the test samples were almost equal in their efficacy with LC50 in the range 55-60 ppm, which is comparable with that of the chemical insecticides (dimethoate and parathion methyl) at 24 h contact time that demonstrated LC50 in the range 25-51 ppm against A. craccivora. The results of the present study would be useful in promoting research aiming at the development of new agent for pest control from the plants with medicinal values. (c) 2005 Elsevier B.V. All rights reserved.