Origanum essential oil [Origanum acutidens (Hand.-Mazz.)] showing insecticidal activity and repellency against red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae) adults was analysed by GC-MS. All constituents of the oil were identified, and the main components were carvacrol (67.2%), p-cymene (16.2%), γ-terpinene (5.5%), thymol (4.9%),and linalool(2.1%). In vapor phase fumigant assay, the origanum oil was more effective in closed condition (LD50 = 0.555 mg/cm3) than in open one (LD50 = 0.353 mg/cm3).This result suggests that the toxicity of the oil to red flour beetle is exerted largely by vapor phase. Based on 24-h LD50 values, the toxicity of caryophyllene oxide (0.00018 mg/cm3) was comparable with that of dichlorvos (0.00007mg/cm3) as a positive insecticide. In addition, thymol, camphene, α-pinene, p-cymene, and γ-terpinene gave good insecticidal activity (LD50 = 0.012 - 0.195 mg/cm3). In repellent test using 9 constituents of origanum oil, caryophyllene oxide showed 100% repellent activity at 0.0158 and 0.0032 mg/cm2. These results indicate that the origanum oil and its some components could be potential candidates as a fumigant and repellent for managing T. castaneum adults. Potential molecular target of repellents will be discussed.

• Soon-Il Kim(WCU Biomodulation major, Department of Agricultural Biotechnology, College of Agriculture & Life Sciences, Seoul National University)
• Je-Won Jung(WCU Biomodulation major, Department of Agricultural Biotechnology, College of Agriculture & Life Sciences, Seoul National University)
• Young-Joon Ahn(WCU Biomodulation major, Department of Agricultural Biotechnology, College of Agriculture & Life Sciences, Seoul National University)
• Hyung-Wook Kwon(WCU Biomodulation major, Department of Agricultural Biotechnology, College of Agriculture & Life Sciences, Seoul National University)