Screening for antifeedant and larvicidal activity of plant extracts against Helicoverpa armigera (Hübner), Sylepta derogata (F.) and Anopheles stephensi (Liston).

Plant extracts, especially botanical insecticides, are currently studied more and more because of the possibility of their use in plant protection. Biological activity of five solvent plant extracts were studied using fourth instar larvae of gram pod borer Helicoverpa armigera (Lepidoptera: Noctuidae), cotton leaf roller Sylepta derogata (Lepidoptera: Pyralidae) and malaria vector Anopheles stephensi (Diptera: Culicidae). Antifeedant and larvicidal activity of acetone, chloroform, ethyl acetate, hexane and methanol peel, leaf and flower extracts of Citrus sinensis, Ocimum canum, Ocimum sanctum and Rhinacanthus nasutus were used in this study. During preliminary screening, the extracts were tested at 1,000 ppm concentration. The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in peel chloroform extract of C. sinensis, flower methanol extract of O. canum against the larvae of H. armigera (LC50 = 65.10,51.78, LC90 = 277.39 and 218.18 ppm), peel methanol extract of C. sinensis, flower ethyl acetate extract of O. canum and leaf acetone extract of O. sanctum against the larvae of S. derogata (LC50 = 20.27,58.21,36.66, LC90 =113.15,285.70 and 668.02 ppm), peel methanol extract of C. sinensis, leaf and flower ethyl acetate extracts of O. canum against the larvae of A. stephensi (LC50 = 95.74,101.53,28.96, LC90 = 303.20,492.43 and 168.05 ppm), respectively. These results suggest that the chloroform and methanol extract of C. sinensis, ethyl acetate flower extracts of O. canum and acetone extract of O. sanctum have the potential to be used as an ideal eco-friendly approach for the control of the agricultural pests H. armigera, S. derogata and medically important vector A. stephensi.