Resistance status and activity of detoxifying enzymes in Oligonychus coffeae (Nietner)(Acari:Tetranychidae) on tea

Abstract

Regular monitoring of acaricide resistance in economically important plant feeding mites is important for effective management. Oligonychus coffeae is one of the most important mite pests of tea and acaricides are frequently used to manage this pest, yet control failures sometimes occur at recommended doses. Hence, bioassay experiments were conducted to confirm whether such control failures were caused by resistance development in populations collected from major tea growing areas of Sub-Himalayan West Bengal, India. The adult females of O. coffeae were bio-assayed with commonly used six acaricides viz., dicofol, ethion, fenpropathrin, fenpyroximate, fenazaquin and propargite. Moreover, we estimated the activity of general esterase (GE), glutathione S-transferase (GST) and cytochrome P450 monooxygenase in the field collected samples as well as laboratory reared susceptible population. Based on the LC50 values, the resistance ratio of the field collected populations compared to the laboratory reared susceptible population varied from 3.29 to 5.85-fold,4.13–11.21-fold,12.07–28.28-fold,1.19–1.67-fold,1.12–1.77-fold, 2.73–5.34-fold for dicofol, ethion, fenpropathrin, fenpyroximate, fenazaquin and propargite, respectively. General esterase, GST and MFO activities of the tested populations were in the ranges of 5.69–16.54 mOD/min/mg protein, 91.51–319.91 μM/min/mg protein and 0.040–0.071 mOD/min/mg protein, respectively. The highest enzyme activity was detected in the Naxalbari population which was one of the most resistant populations to all the tested acaricides. The findings will be useful to the tea industry for selection of most effective chemical for successful management of this pest. Use of fenpropathrin and ethion should be discontinued for tea pest management and use of other chemicals having different mode of actions may be continued with rotation.