Insecticidal and repellent activities of Cymbopogon citratus (Poaceae) essential oil and its terpenoids (citral and geranyl acetate) against Ulomoides dermestoides

Abstract

The peanut beetle, Ulomoides dermestoides Fairmaire (Coleoptera: Tenebrionidae), is a worldwide pest of stored grains. This study evaluated the toxicity and repellency of lemongrass (Cymbopogon citratus) essential oil and its components (citral and geranyl acetate) against U. dermestoides adults. Lethal doses (LD50 and LD90), survival rate, respiration rate, and repellent activity were determined. The major components of lemongrass essential oil were neral (24.6%), citral (18.7%), geranyl acetate (12.4%), geranial (12.3%), and limonene (7.5%). Lemongrass essential oil (LD50 = 5.17 μg insect−1), citral (LD50 = 4.17 μg insect−1), and geranyl acetate (LD50 = 7.21 μg insect−1) caused high contact toxicity in U. dermestoides adults. The survival rate was 99% in control insects, decreasing to 65.7% in insects exposed to the LD50 of lemongrass essential oil, 41.3% in insects treated with geranyl acetate, and 28.5% in those treated with citral. Insects exposed to lemongrass essential oil, geranyl acetate, or citral showed low respiration rates, reduced locomotor activity, and avoidance responses to treated surfaces. These findings demonstrate that lemongrass essential oil and its terpenoid components exhibit insecticidal and repellent activity against U. dermestoides, suggesting their potential for controlling this stored grain pest.