Repellent Efficacy of Caraway and Grapefruit Oils for Sitophilus oryzae (Coleoptera: Curculionidae)

This study examined the repellent efficacy of six essential oils extracted from caraway, clary sage, grapefruit, strawberry, thyme white, ylangylang, and their related volatile constituents against the adult rice weevil, Sitophilus oryzae using an olfactometer. The caraway and grapefruit oil showed the highest repellent efficacy against the rice weevil at a dose of 10μl. Gas Chromatography-Mass Spectrophotometer analysis revealed caraway oil to be rich in carvone and limonene, and grapefruit oil to be rich in limonene, β-myrcene and α-pinene. When the monoterpene was mixed in equal parts with the caraway and grapefruit essential oils, carvone with limonene in caraway oil demonstrated the highest repellent efficacy (96.7%). Limonene with α-pinene and β-myrcene in grapefruit showed strong repellent efficacy (86.4%) with synergistic effects on the S. oryzae.A mixture of caraway and grapefruit oils, as well as carvone and limonene, can be potent repellents that may be useful for controlling S. oryzae.