The aim of this study is to investigate the habituation phenomenon of essential oils as potential feeding deterrents in agricultural practices and their associations with taste receptors. Non-choice tests and contact-fumigation bioassays were conducted to determine the feeding deterrency and insecticidal activity of 30 commercial oils on the third instar larvae of the tobacco cutworm. The results indicated that lemongrass, fennel sweet, and clove bud oils had the highest feeding deterrency in that order, and no direct correlation between insecticidal activity and feeding deterrency was observed. To validate the habituation phenomenon, larvae were exposed to the three abovementioned oils at a 1 mg/g for 48 h, then a choice assay was conducted. It showed a significant reduction in both feeding deterrence and repellency in all cases. Similar reductions in feeding deterrence were observed when individuals exposed to the main components of the three oils: citral&limonene, anethole, and eugenol. Additionally, the oil mixture of fennel sweet and clove bud exhibited the most significant synergistic effect on feeding deterrency, suggesting a relatively slower habituation process. This reduction in feeding deterrence is presumed to be due to desensitization of the larval taste sensory organs, including the maxillary palp, lateral styloconica, and medial styloconica. Further research will be conducted to investigate the specific mechanisms and spike activity associated with these sensory organs using electrophysiological study.

• Hyoeun Jeon(Department of Agricultural Biotechnology, Seoul National University) Corresponding author
• Jun-Hyung Tak(Department of Agricultural Biotechnology, Seoul National University, Research Institute of Agriculture and Life Science, Seoul National University)