This study evaluated the larvicidal activity, and ovicidal activity of Origanum vulgare EO and its major components against the cotton bollworm, Helicoverpa armigera. The chemical composition of the O. vulgare EO was analyzed by gas chromatography-mass spectroscopy. GC-MS analysis revealed that the O. vulgare EO was composed of ten compounds. The major constituents were carvacrol (78.35%), followed by p-cymene (6.85%) and γ-terpinene (3.70%). In larvicidal activity assay, the O. vulgare EO achieved a LC50 value of 265.51 μg/ml. The three major constituents from the O. vulgare EO were tested individually for toxicity against larvae of H. armigera. Carvacrol, p-cymene, and γ-terpinene appeared to be most effective against H. armigera, with LC50 values of 51.53, 121.32, and 150.15 μg/ml, respectively. Moreover, EC50 values of carvacrol, p-cymene, and γ-terpinene against H. armigera eggs were 33.48, 47.85, and 56.54 μg/ml, respectively. Overall, this study showed that O. vulgare EO and its major constituents have the potential to develop as new eco-friendly insecticides against H. armigera.
Keywords: Botanical insecticides; Carvacrol; Helicoverpa armigera; Larvicidal activity; Origanum vulgare; Ovicidal activity.