Larvicidal activity of some plant extracts to larvae of the mosquito Culex quinquefasciatus (Say 1823).

OBJECTIVES AND METHODS: Searching for potent plant larvicides, crude aqueous extract of the latex of Uschar (Calotropis procera) and Labakh (Ficus benghalensis) were tested against the fourth instar larvae of the lymphatic filariasis vector Culex quinquefasciatus (Diptera: Culicidae) using the conventional methods recommended by the WHO. Likewise, the toxicity level of Malathion was tested. The dose/response mortality relationship was statistically determined using double transformation regression analysis. The 24-hour LC50 of the test agents was taken as a measure of its acute toxicity. The 24-hour LC50 of Malathion to the larvae was 2.2693 mg/L. The most potent plant extract was the latex of Uschar which killed 50% of the larval population at a concentration of 0.0062% (V/V).

RESULTS: The 24-hour LC50 of Labakh latex was 0.4796% (V/V). A range of concentration extending between 0.0195 and 10% (W/V) of the Labakh fruits (figs) produced more or less the same % of mortality (25%).

CONCLUSION: Since the latex of the plants tested are hazardous to man and his animals, it is recommended that these extract must be used in bodies of water not accessible to man or animals such as pit latrines and septic tanks.