Chemical composition and toxic activity of essential oil of <i>Caryopteris incana</i> against <i>Sitophilus zeamais</i>

Abstract

During our screening program for new agrochemicals from Chinese medicinal herbs, essential oil of Caryopteris incana aerial parts was found to possess strong insecticidal activities against the maize weevil, Sitophilus zeamais. A total of 37 components of the essential oil were identified by GC and GC/MS. Estragole (24.8%) and linalool (14.0%) are the two main components of the essential oil followed by 1,8-cineol (5.2%) and δ-guaiene (4.1%). The essential oil possesses strong fumigant toxicity against S. zeamais adults with an LC₅₀ value of 10.05 mg/L air. The essential oil of C. incana also showed contact toxicity against S. zeamais adults with an LD₅₀ value of 122.65 μg/adult. The essential oil C. incana may have potential to be developed as a new natural fumigant/insecticide for the control of stored product insects.

Key words: Caryopteris incana, Sitophilus zeamais, fumigant, contact toxicity, essential oil composition, estragole, linalool.