Vol. 2, Issue 4, Part A (2015)

Author(s): Annie SW, Raveen R, Paulraj MG, Samuel T, Arivoli S

Abstract: Mosquitoes represent a significant threat because of their ability to vector pathogens that cause deadly diseases that afflict millions of people worldwide. Several species belonging to genera Aedes, Anopheles and Culex are vectors for the pathogens of various diseases like dengue, dengue hemorrhagic fever, chikungunya, malaria, Japanese encephalitis and filariasis. Mosquito control relies heavily on synthetic insecticide application. However, excess and injudicious application of synthetic insecticides has resulted in development of resistance to these insecticides by the mosquitoes and unwarranted toxic or lethal effects on non-target organisms, as well as environmental health problems. Botanicals can be used as alternative to synthetic insecticides or along with other insecticides under integrated vector control programs. In the present study, the crude hexane, ethyl acetate, methanol, benzene and aqueous leaf extracts of Eichhornia crassipes were tested for the larvicidal efficacy against the early fourth instar larvae of Culex quinquefasciatus at concentrations of 62.5, 125, 250 and 500 mg/L. Mortality was recorded after 48 hours. Amongst the crude leaf extracts of Eichhornia crassipes tested, the hexane and methanol extract was found to be the most effective at 62.5 and 500 mg/L and LC₅₀ values were 80.54 and 137.50 mg/L respectively. Further investigations are needed to elucidate the larvicidal activity of Eichhornia crassipes crude hexane and methanolic leaf extract against all stages of mosquito species and also the active ingredient(s) of the extract responsible for larvicidal activity should be identified.