Insecticidal activity of certain plants of zingiberaceae and araceae against Spodoptera litura F. and Plutella xylostella saunders in cabbage

Rhizome extracts of different plants viz., Curcuma caesia, C. aromatica, C. longa, Zingiber officinale cv. Nadia, Z. officinale cv. Adi Local, Z. officinale cv. Kekir and Acorus calamus were evaluated for possessing insecticidal properties under the laboratory condition using Spodoptera litura as the test insect. Plants which were found effective under the laboratory condition were selected and further evaluated under field condition against Plutella xylostella. Under the laboratory conditions, hexane and chloroform extracts of A. calamus was found highly effective. Curcuma spp. gave better performance than the Zingiber spp. in similar solvent extracts. Acetone extracts were least effective among the three solvents used. Similarly, under the field conditions, A. calamus hexane extract emerged as the most effective extract with 88.40% reduction of P. xylostella over the untreated control, significantly better than the neem formulation (82.14% reduction). A. calamus chloroform extract (81.70% reduction) was comparable with the neem formulation. C. caesia hexane extract was the best treatment among Curcuma extracts and was at par with A. calamus chloroform extract and neem formulation.