ABSTRACT:

Purpose: To investigate the chemical composition and insecticidal activity of the essential oil of the aerial parts of Ainsliaea fragrans against maize weevils (Sitophilus zeamais). Methods: The essential oil of A. fragrans aerial parts was obtained by hydrodistillation and analyzed by gas chromatography (GC) and gas chromaotography-mass spectrometry (GC-MS). Contact toxicity of the essential oil and its major constituents was determined by topical application against S. zeamais. Results: A total of 30 components of the essential oil were identified. The major constituents were myristicin (41.3 %), elemicine (11.9 %), cis-isosafrole (11.5 %), borneol (9.1 %) and caryophyllene (8.8 %). The essential oil of A. fragrans exhibited contact toxicity against S. zeamais with LC50 value of 50.7 µg/adult. Elemicine possessed the strongest contact toxicity (LC50 = 13.5 µg/adult) while cis-isosafrole, myristicin, caryophyllene and borneol had LC50 values of 31.2 µg/adult, 43.4 µg/adult, 57.9 µg/adult, and 98.4 µg/adult, respectively.     Conclusion: The study indicates that the essential oil of A. fragrans aerial parts and its major constituents have a potential for development into natural insecticides for the control of grain storage insects.