Susceptibility of Adult Anopheles gambiae to Cymbopogon citratus and Ocimum gratissimum Essential Oils Using Contact and Fumigant Methods

Abstract

Background: The rise in resistance of Anopheles gambiae resistance to recommended insecticides necessitates effective bioactive alternatives in their control. Mosquitocidal activities of the essential oils of Cymbopogon citratus (lemon grass) and Ocimum gratissimum (scent leaf), in single and combined forms, were evaluated using fumigant and contact exposure techniques. Time-mortality was recorded, and Lethal Times (LT) computed for 50% using probit analysis. Methods: Adult Anopheles gambiaemosquitoes were exposed to 1 %, 2 %, 3 %, 4 %, and 5 % concentrations of C. citratus and O. gratissimum essential oils, in single and combined trials adopting standard protocols by World Health Organization (WHO). Results: Best concentration (5%) of C. citrates demonstrated complete mortality (100% for contact and 78% for fumigant), whereas O. gratissimum at 5% exhibited 93% mortality for contact and 67% for fumigant compared to other concentrations for contact and fumigant exposures (p< 0.05). Notably, the combined oils produced complete mortality at all exposure periods (100%), and concentrations, indicating enhance deffectness over the single dose of oils. Conclusion: It is imperative to adopt the combined oils in vector management trials for adults, following that the findings of this study align with emerging evidence supporting multi-component botanical mixtures to enhance insecticidal efficacy through complementary chemical interactions. Further studies aimed at formulation development are warranted.