Larvicidal Efficacy of the Combination of Citrus aurantiifolia (Rutaceae) and Lippia chevalieri (Verbenaceae) Methanolic Extracts against Anopheles gambiae Giles (Diptera Culicidae), Malaria Vector

The growing resistance of mosquito vectors towards synthetic insecticides constitutes a major challenge in the malaria control and synergistic action of two or more extracts may decrease the risk of insect resistance. For that, the methanolic extracts of Citrus aurantiifolia peels and Lippia chevalieri leaves were tested individually and in combination of Anopheles gambiae larvae at concentrations of 7.5, 15, 22.5 and 30 mg/mL in the laboratory according to the standard protocol of WHO. Extraction yields were 6.72 and 4.62 for C. aurantiifolia and L. chevalieri respectively. Saponins, terpenoids, flavonoids, tannins and polyphenols were present in the extracts of C. aurantiifolia and L. chevalieri. The 2 plants extracts tested individually and combined, caused a significant (P < .001) larvicidal concentration-dependent activity 24 hours’ post-exposure. C. aurantiifolia peels was revealed as the most potent against the mosquito larvae (LC50 = 9.82 mg/mL), while only the binary combination 50%Ca + 50%Lc (CI: 155.22; SF: 1.55) induced a synergistic action against Anopheles gambiae larvae. Thus, the combination 50%Ca + 50%Lc might be recommended as a natural bio-insecticide in mosquito control program to prevent malaria.