Vol. 11, Special Issue 9 (2022)

Author(s):
K Aarthi, M Shanthi, G Srinivasan, S Vellaikumar and G Hemalatha

Abstract:
Four species of mint essential oils were tested in the laboratory for their repellent toxicity against rice weevil Sitophilus oryzae L. at different concentrations in the Insectary, Department of Agricultural Entomology, Agricultural College and Research Institute, Madurai, Tamil Nadu during 2021-22. In comparison with other mint oils, the spearmint essential oil (Mentha spicata) possessed the highest repellency effect against S. oryzae at 12 nL/cm² (66.66%) after 24 hours of exposure, which comes under class IV repellency. Next in order of repellency was M. piperita, which displayed 53.33 percent repellency with class III at 40 nL/cm² concentration after 24 hours of exposure. Whereas, M. arvensis and M. citrata exhibited 66.66 and 53.33 percent repellency towards S. oryzae at 173 nL/cm² concentration after 24 hours of exposure, which comes under class IV and III categories, respectively. The Median Repellent concentration (RC₅₀) of the mint oils were 5.9 nL/cm² (M. spicata), 36.3 nL/cm² (M. piperita), 70.7 nL/cm² (M. arvensis) and 128.3 nL/cm² (M. citrata), and the time taken for 50 per cent repellency (RT₅₀) were 2.30 h, 3.00 h, 4.50 h and 5.30 h, respectively. Thus, it is concluded that though all the mint essential oils exhibited repellent action against rice weevil, S. oryzae, in stored rice, the spearmint oil, M. spicata exhibited the maximum repellency effect within a short period against rice weevil.