Chemical composition and insecticidal activity of Aloysia citrodora essential oil against Aphis fabae (Hemiptera: Aphididae), Rhopalosiphum maidis (Hemiptera: Aphididae) and Tribolium castaneum (Coleoptera: Tenebrionidae)

The black bean aphid Aphis fabae (Hemiptera: Aphididae), the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae) and the corn leaf aphid Rhopalosiphum maidis (Hemiptera: Aphididae) are three pests that causes significant economic losses, to several crops, in particular faba bean (Vicia faba), stored products, and maize (Zea mays) respectively. In order to search for readily biodegradable and eco-friendly insecticides, this study aimed to evaluate the efficacy of Lemon verbena Aloysia citrodora (Verbenaceae) essential oil fumigant toxicity against these three pests and identify its chemical composition by gas chromatography-mass spectrometry (GC-MS). The major compounds were Citral (13.80%), D- limonene, (12.16%), Neral (10.67%), Bicyclogermacrene (10.03%), Isospathulenol (6.06%), caryophyllene oxide (5.63%) and p-cymene (4.5%). Significant differences in insect mortality to essential oil vapor were identified in the fumigant toxicity at 48 h exposure time; A. citrodora oil showed higher toxicity on A. fabae (LC50 = 0.011 mu l/l air), compared to R. maidis (LC50 = 0.021 mu l/l air), followed by T. castaneum (LC50 = 1.149 mu l/l air). The present study indicates that A. citrodora essential oil could be employed as a potential insecticide against aphis fabae, Rhopalosiphum maidis and Tribolium castaneum.