LAUSR

Oligonychus coffeae Nietner is cosmopolitan in its distribution and is an important pest of a number of economically important tropical and sub-tropical crops including tea. It is the most damaging acarine pest of tea crops in the sub-Himalayan Terai region of India which is mostly controlled chemically in the conventionally managed tea plantations of the region. Objectives of the present study were to i) investigate the tolerance level of O. coffeae collected from bio-organically managed plantations (BMP) (with no synthetic acaricide application) and conventionally managed plantations (CMP) (with periodic application of synthetic acaricide) to the acaricides, ’ethion’ and ’fenpropathrin’, ii) Quantify the detoxifying enzymes, general esterases (GE) of phase I and glutathione S-transferases (GST) of phase II, in O. coffeae as these are deemed important in acquiring pesticide tolerance, iii) Establish the relation of GE and GST activity levels with acaricide tolerance levels in populations of O. coffeae. The study revealed that i) BMP populations of O. coffeae were susceptible to both of the acaricides whereas CMP populations were tolerant. CMP populations of the pest showed low to medium tolerance to the organophosphate acaricide ’ethion’ whereas tolerance to the synthetic pyrethroid, ’fenpropathrin’ was high; ii) Corresponding GE and GST levels were significantly higher in CMP populations compared to that of BMP population. Electrophoretic analysis of GE isozymes of CMP and BMP populations further corroborated the quantitative study; iii) activity of the detoxifying enzymes, GE and GST were positively correlated with the tolerance level of O. coffeae populations indicating involvement of these enzymes in the development of acaricide tolerance.