Efficacy of citrus essential oils for the control of anopheles Gambiae larvae

Abstract

Malaria mosquito vector control is an important strategy in malaria control and elimination globally. Mosquito larvae control using chemicals was effective intervention for malaria reduction but due to adverse environmental effect preference has been shifted to more safe alternatives. The purpose of this study was to assess the larvicidal activity of peel extract from Citrus sinensis, Citrus limon and Citrus aurantifolia against Anopheles gambiae larvae. The peels of each of the three Citrus plant fruit were subjected to hydro-distillation and the resultant extract was filtered to separate oil and water with aid of dichloromethane. Anhydrous sodium sulfate was then added to the oil to remove any water molecules that remained and the citrus peel oil extract (100%) was stored in well labeled bottles for larval bioassay. The Citrus oil extract was diluted in acetone to make 1%, 0.7%, 0.4/0.5%, 0.1%, and 0.001%) concentrations. 0.1ml to 1ml of the diluted citrus oil extract was added to disposable paper cups with 20 third stage larvae of An. gambiae. For each of the three citrus species, five different concentrations were tested in four replicates and the experiment repeated in three different occasions. Larvae mortality was recorded 24 hours after addition of citrus oil extract. Mortality data was subjected to probit analysis to establish the efficacy of each of the three Citrus peel extracts. Lethal concentration values that caused 50% and 95% mortalities of test larvae (LC 50 and LC95 ) showed that An. gambiae were highly susceptible to citrus oil extract from orange, lemon and lime in laboratory conditions. Of the three products tested, C. limon oil extract was significantly more effective in controlling An. gambiae larvae than other products ((LC95=64.258 parts per million (ppm)).

In conclusion: C. sinensis, C. limon, and C. aurantifolia have potential to as biocontrol agents against An. gambiae based on their larvicidal effects and for application as an environmentally friendly mosquito control agents.