Bio-Effects of Eucalyptus globulus Essential Oil Extract in Aedes aegypti Control

Abstract

Aedes aegypti is known widely for its role in transmitting globally significant diseases such as Chikungunya, dengue, Zika virus and yellow fever, hence the need to control them remain a necessity. In recent times, the use of botanical insecticides in the control of mosquitoes have been adopted, due to the development of resistance mechanism in mosquitoes against synthetic insecticides, and also because botanical insecticides pose no threats to human health and the environment. Following this great need, the bio-effects of Eucalyptus globulus leaves essential oil at varying concentrations on Aedes aegypti was studied. Essential oil from authenticated fresh samples of Eucalyptus globulus leaves were extracted by steam distillation. Bioactive constituents of the oil were analyzed by gas chromatography. The extracted oil taken as 100% concentration was serially diluted to 20%, 10%, 5%, 2.5%, and 1.25% used for larval bioassays and adult repellency tests. Acetone and Odomos® (12% DEET) served as negative and positive controls, respectively. Aedes aegypti eggs from National Arbovirus and Vector Research Centre Enugu were reared to 4th instar larvae and adults for the study. Log-probit regression produced LC₅₀ and LT₅₀ while two-way ANOVA indicated significant differences (p<0.05) between mortality and repellency regarding concentrations and exposure times. Bioactive components of the essential oil included ephedrine, tannin, flavonones, Pinene, Anthocyanin, Tannin, eucalyptol and decanal. In-vivo, 1.25% concentration caused 43.8% larval mortality (LC₅₀=2.3%; LT₅₀=9hrs) while 20% concentration caused 100% mortality. There was higher mortality and repellency effects at elevated concentrations. The essential oil of Eucalyptus globulus showed larvicidal and adult repellency properties, hence highlighting strong eco-friendly potential for Aedes aegypti control.