The Effect of Neem (Azadirachta indica) Leaves Extract on the Ecdysis and Mortality of Immature Stages of Common House Mosquito Culex pipiens fatigans

Larvicidal effect of Azadirachta indica on mosquitoes has been studied in the present work. The water extracts of air dried leaves and fresh leaves separately have been used for the study. Different concentrations were made of all these extracts and twenty second instar larvae of Culex pipiens fatigans were placed in each concentration separately. Control was set up for each experiment. Mortality and ecdysis inhibition effect were used as effective parameters. Observations on mortality were carried out after each 24 hours. The 25% stock solution of dry leaves extract showed greatest larvicidal activity i.e. 100% mortality within first 24 hours as compared to the mortality rate of fresh leaves and simple dry leaves extracts. The LC50 of 25% stock solution extract, fresh leaves and dry leaves extracts was found to be 19%, 33%, 40% respectively. Percentage mortality per day, percentage pupation and percentage emergence from pupae are calculated. In lower concentrations 1%, 5%, 10%, pupation was delayed by two or three days. In 40%, 50% and 60% concentration of all these extracts, pupation did not occur. All the larvae died at larval stage but the larval period was extended to 12-14 days. Conclusively it can be said that simple aqueous extract of neem leaves have some biologically active components which show insecticidal activity. So they can be applied easily for the biological control of mosquitoes.