Hexane extracts of certain botanicals were evaluated in the laboratory for their oral, contact, fumigant toxicity and repellent activity at 5% concentration against rice weevil Sitophilus oryzae L. at the Natural Pesticide Laboratory, Department of Agricultural Entomology, Agricultural College and Research Institute, Madurai, Tamil Nadu during 2019-2021. The results revealed that all the botanicals were effective. Considering the contact toxicity, 5% hexane extract of Mentha spicata 5% (80.00%) performed better at 72 hr after treatment. M. spicata and Vitex negundo 5% hexane extract exhibited maximum oral toxicity (90.00%). Fumigant effect was maximum in V. negundo (73.33%), M. spicata, Ocimum sanctum and Tagetes erecta flower extracts (70.00%). Ocimum sanctum (70.56%) and M. spicata (67.22%) exhibited maximum repellency. Thus, M. spicata at 5% was the most effective as contact, oral, fumigant toxicant and repellent against S. oryzae in stored maize.

Two spotted spider mite Tetranychus urticae Koch is an economically serious pest posing threat to major vegetable crops. Roving survey in and around Coimbatore region revealed that farmers do not target mites with acaricides instead they use higher dose of insecticides at frequent intervals which results in development of resistance. The bioassay results revealed that fenpropathrin (2.07 to 6.86-folds) and fenazaquin (2.74 to 7.13-folds) exhibit higher susceptibility, whereas diafenthiuron (5.35 to 12.25-folds) revealed a low to moderate level of resistance. The propargite (43.80 to 60.63-folds) and chlorfenapyr (61.01 to 75.10-folds) exhibited high resistance, followed by spiromesifen (222.28 to 300.26-folds) and buprofezin (382.60 to 417.87-folds), with extremely high level of resistance. The higher specific activity of GST (4.54-folds), MFO (10.06-folds) and CarE (15.06-folds) in Puthupalayam population suggested the role of biochemical resistance. A significant positive correlation was observed between diafenthiuron and CarE activity (r = 0.981*), fenpropathrin and MFO activity (r = 0.964*).