Toxicity and repellency of origanum essential oil and its components against Tribolium castaneum (Coleoptera: Tenebrionidae) adults

The components of Origanum vulgare L. essential oil showing insecticidal activity and repellency against red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae), adults were analysed by GC-MS. All constituents were identified, and the main components were carvacrol (67.2%), p-cymene (16.2%), gamma-terpinene (5.5%), thymol (4.9%), and linalool (2.1%). In a vapor phase fumigant assay, the origanum oil was more effective in closed conditions (LD(50)=0.055 mg/cm(3)) than in open conditions (LD(50)>0.353 mg/cm(3)). This suggests that toxicity is exerted largely in the vapor phase. Based on 24-h LD(50) values, the toxicity of caryophyllene oxide (0.00018 mg/cm(3)) was comparable with that of dichlorvos (0.00007 mg/cm(3)). In addition, thymol, camphene, alpha-pinene, p-cymene, and gamma-terpinene showed good insecticidal activity (LD(50) = 0.012-0.195 mg/cm(3)). In repellency tests using 9 constituents of origanum oil, caryophyllene oxide showed complete repellency at 0.03 mg/cm(2). Hydrogenated monoterpenoids, such as thymol, a-pinene, carvacrol, and myrcene, elicited strong repellency at 0.03 and 0.006 mg/cm(2). Repellency depended on both time and concentration. These results indicate that origanum oil and its components could be potential candidates as a fumigant and repellent for managing T. castaneum adults. (C) Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2010 Published by Elsevier B.V. All rights reserved.