Efficacy of certain plant essential oils as larvicides and repellents on mosquitoes

Abstract

Mosquitoes are noxious nature Dipteran insect vectors responsible for transmitting the life threatening pathogenic organisms and connected diseases in humans such as malaria, dengue, filariasis, chikungunya, Japanese encephalitis etc. The female mosquito bite, by piercing and sucking type mouth parts, causes localized skin irritation and injects pathogenic organism in to the skin through its saliva. The mosquito borne diseases chances and cases are showing increasing trend regularly in India and across the world due to some adverse environmental changes as global warming and climate change. Due to the lack of proper sanitary conditions, cleanliness and presence of open stagnant water sites and drainage, the mosquitoes population is increasing. The stagnant water is the breeding place for mosquitoes, as its eggs and immature stages survive in water. In India, a big number of people suffer from mosquitoes borne diseases every year, causing disease burden in public. The present study is focused on the control strategies of mosquito population in aquatic environment by aqueous solution technique, using some plant essential oils, EO, in certain concentrations mixed in water, such as Peppermint, Lemongrass, Citronella, Neem ( Azadirachta indica), Eucalyptus sp. Essential oils etc . The taken essential oil formulations were applied to test their repellent efficacy for adult mosquitoes by using liquid vaporizer machine in experimental box and room. In aqueous solution technique, the larval mortality was found hundred percent in the combination of Neem EO 1%, lemongrass-1% and Eucalyptus-1% after 24 hours. The LC 50 assessed as 0.4738%. The combination of peppermint and neem EO in 0.1% each was observed potent controlling mixture for larvae after experimental time period of 24 hours, with LC 50 as 0.0521 percent. The lemongrass and peppermint EO in 0.1% separately were found quite effective to kill hundred percent the immature stages of mosquitoes after 24 hrs. Neem and peppermint EOs were found effective killing in 0.1% combination. The repellent efficacy of taken plant EOs was found effective by using liquid vaporizer, LV. On exposure to plant EO mixture solution, the restlessness, convulsions, tremors, nervous breakdown and knockdown responses were noticed in adult mosquitoes. The experimental formulations repelled and knock downed the adult mosquitoes in iron net-wired experimental box and room, preventing from the mosquito bites.