Chemical composition, insecticidal effect and repellent activity of essential oils of three aromatic plants, alone and in combination, towards Sitophilus oryzae L. (Coleoptera: Curculionidae)

Essential oils of aromatic plants with insecticidal properties are nowadays considered as alternative insecticides to protect stored products from attack by insect pests. A combination of some of these plants in the granaries is a current practice in certain localities of northern Cameroon. The aim of the present work was to analyze the impact of the combinations of the essential oils of Vepris heterophylla (Rutaceae), Ocimum canum, and Hyptis spicigera (both Lamiaceae), the three most used local aromatic plants because of their insecticidal activity and their repellent effect on Sitophilus oryzae. The present work revealed that these plants are rich in monoterpenoids. The GC/MS analyses have shown that monoterpenoids represented 65.5% for H. spicigera, 92.1% for O. canum and 47.0% for V. heterophylla. The crude essential oil of O. canum was the most insecticidal with a LD50 of 42.9 ppm. The most repellent effect was obtained by a combination of the essential oils of H. spicigera and O. canum, with a repellent percentage at 77.5%. These results suggest a suitable strategy for pest management of stored products.