Larvicidal activity of some botanicals against Culex quinquefasciatus say

The present investigation reports on the larvicidal activity of a) bark of Bischofia javanica, Cinnamomum zeylanicum, and Givotia mollucana, b) leaf o f Morinda umbellata, Trichopus zeylanicus, Erythroxylon monogynum, Oxalis c arnicualata, Solanum verbasicum and Vitex negundo and c) shoot with leaves of Leucas aspera. Solvent residues of these plant components obtained from hexane, diethyl ether, dichloromethane, ethyl acetate and methanol extracts and later dissolved in acetone were separately tested at 1000 ppm on third instar larvae of Culex quinquefasciatus for insecticidal effects. Residues of these solvent extracts procured from shoot with leaves of Leucas aspera and leaves of Vitex negundo were only found to be very effective at such d osage resulting in 100% mortality of the larvae within 24, 48 or 72 h of tr eatment. However, the mortality was significantly reduced at lower dosages (100, 300 or 500 ppm). Solvent residues of the tested plant parts from the remaining eight Botanicals exhibited relatively less toxicity to these larv ae in varying degrees in relation to exposure time and dosage.