Screening of Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae) crude leaf extracts for larvicidal efficacy against the filarial vector Culex quinquefasciatus say (Diptera: Culicidae)
Annie SW, Raveen R, Paulraj MG, Samuel T, Arivoli S
Vector-borne diseases are one of the greatest contributors to humanrnmortality and morbidity in the tropics and subtropics. Vector control remainsrnthe most effective measure and is often the only way to prevent diseasernoutbreaks as there are no vaccines for many vector-borne diseases. Owing torntheir quick action, synthetic insecticides are the first line of action, butrntheir continuous use led to the development of resistance and permanentrnresidual effect on the bio environment which can be detrimental to animalsrnincluding human. Therefore, biologically active plant materials have attractedrnconsiderable interest in mosquito control programs in the recent time. In thernpresent study, the crude hexane, benzene, ethyl acetate, methanol and aqueousrnleaf extracts of Hydrilla verticillata were tested for the larvicidalrnefficacy against the early fourth instar larvae of Culexquinquefasciatusrnat concentrations of 62.5, 125, 250 and 500 mg/L. Mortality was recorded afterrn48 hours. Amongst the crude leaf extracts of Hydrilla verticillata tested,rnethyl acetate extract was found to be effective and LC50 value ofrn89.57 mg/L. Further investigations are needed to elucidate the larvicidalrnactivity of Hydrilla verticillata crude ethyl acetate leaf extractrnagainst all stages of mosquito species and also the active ingredient(s) of thernextract responsible for larvicidal activity should be identified.