Resistance of Two Spotted Spider Mite, Tetranychus urticae Koch to Major Acaricides and its Consequences on Biological Characteristics of Mites

摘要

Two Spotted Spider Mite, Tetranychus urticae Koch collected from Vadagur of Kolar district in April 2016 was reared in the laboratory for more than 60 generations and its susceptibility to major acaricides was determined after every 10 generations. The lowest LC_(50) values of different acaricides in the 60th generation viz., dicofol -0.29 ppm; fenazaquin - 0.23 ppm; propargite - 0.32 ppm and spiromesifen - 0.29 ppm were used as the baseline data for determining the level of resistance in the field populations of T. urticae from different locations. Mites sampled from tomato crop in Hassan (TwHSN), Kolar (7mKLR), Chickballapur (7wCKB) and Chitradurga (7mCTD) districts were subjected to bioassay with four major acaricides namely, dicofol, fenazaquin,propargite and spiromesifen to determine the level of acaricide resistance. The level of resistance to dicofol was high at all the four locations (143 to 1038 folds) and resistance to fenazaquin was found to be high in T. urticae population from Hassan(71/HSN). Resistance to propargite was moderate (15.65 to 32.83 folds), while resistance to spiromesifen was high in all the four districts. The consequence of acaricide resistance on the development of male mites was apparent as the mean duration of development of males in the resistant Kolar population (7wKLR) was significantly more (10.4 days versus 10.0 days) than the laboratory susceptible population. Male biased sex ratio was also evident in the acaricide resistant population (male: female ratio of 1.22:1.00 versus 0.98:1.00)