Acute Toxicity and Sublethal Effects of Lemongrass Essential Oil and Their Components against the Granary Weevil, Sitophilus granarius

Abstract

In the present work, we evaluate the toxic and repellent properties of lemongrass (<i>Cymbopogon citratus</i> (DC. ex Nees) Stapf.) essential oil and its components against <i>Sitophilus granarius</i> Linnaeus as an alternative to insecticide use. The lethal dose (LD₅₀ and LD₉₀), survivorship, respiration rate, and repellency on adults of <i>S. granarius</i> exposed to different doses of lemongrass oil and some of its components were evaluated. The chemical composition of the essential oil was found to have the major components of neral (24.6%), citral (18.7%), geranyl acetate (12.4%), geranial (12.3%), and limonene (7.55%). Lemongrass essential oil (LD₅₀ = 4.03 µg·insect^-1), citral (LD₅₀ = 6.92 µg·insect^-1), and geranyl acetate (LD₅₀ = 3.93 µg·insect^-1) were toxic to <i>S. granarius</i> adults. Survivorship was 99.9% in insects not exposed to lemongrass essential oil, decreasing to 57.6%, 43.1%, and 25.9% in insects exposed to LD₅₀ of essential oil, citral, and geranyl acetate, respectively. The insects had low respiratory rates and locomotion after exposure to the essential oil, geranyl acetate, and citral. Our data show that lemongrass essential oils and their components have insecticidal and repellent activity against <i>S. granarius</i> and, therefore, have the potential for application in stored grain pest management schemes.