Evaluation of the fractions of Eucalyptus camaldulensis (Myrtaceae) as larvicide against Anopheles gambiae Giles and Culex quinquefasciatus Say (Diptera: Culicidae)

Abstract

As an alternative to substitute the hazardous residual chemical insecticides used in mosquito control programs, research on plant-based products is mostly encouraged. This study aimed to evaluate the larvicidal efficacy of the fractions obtained from the methanol extract of the leaves of Eucalyptus camaldulensis against the four instar larvae of Anopheles gambiae and Culex quinquefasciatus in the laboratory. Twenty-five (25) 4th instar larvae of each mosquito species were exposed to various concentrations ranging from 125 to 1000 ppm of the E. camaldulensis fractions following WHO protocol. The commercial insecticide Bi-one® was applied at 1000 ppm as positive control while 1 mL of methanol added to 99 mL of tap water constituted a negative control. Larval mortality was registered after 24 hours of exposure. In results, all the fractions induced a significant larvicidal activity against the two mosquito species larvae. Fraction B was the most potent against the larvae of An. gambiae (CL50= 97.57 ppm) while fraction D was revealed as the most effective against Cx. quinquefasciatus (146.80 ppm) larvae. Fractions B and D of E. camaldulensis could be employed in mosquito control programs or furthermore might be submitted to column chromatography to isolate the active ingredients for the development of botanical larvicides.