- Volume 28 Issue 4
These studies were conducted to investigate the development of chemical resistance in two-spotted spider mite (Tetranychus urticae Koch) through alternate selection for a given period of time with four acaricides including ethion of organophophours compound, dicofol of organo-chlorine compound, cyhexatin of organo-tin compound, and biphenthrin of synthetic pyrethroid compound; and to examine multiple-resistance among the acaricides to the selected populations. The development levels of chemical resistance in the two-spotted spider mite were greatly varied under alternate selection with the different chemical-group combination of four acaricides. Resistant levels of the ethion/dicofol-selected population at 13th-13th generation showed 49.4-fold resistance to ethion and 18.1-fold to dicofol; the ethion/cyhexatin-selected population at 9th-9th generation exhibited 28.1-fold to ethion and 5-fold to cyhexatin; the ethion/biphenthrin-selectd population at 10th-10th generation revealed 39.8-fold to ethion and 19.2-fold to biphenthrin. However, the dicofol/cyhexatin-selected population at 9th-9th generation showed 11.3-fold to dicofol and 4.9-fold to cyhexatin, and the dicofol/biphenthrin-selected population at 12th-12th generation exhibited 11.2-fold to dicofol and 9.4- fold to biphenthrin, while the cyhexatin/biphenthrin-selected population at 9th-9th generation revealed 3.7-fold to cyhexatin and 7.7-fold to biphenthrin. In case of alternate selection, the ehtion/dicofol-selected population revealed moderate multiple-resistance level to biphenthrin. The ethion/cyhexatin-selected and the ethion/biphenthrin-selected populations showed low mutiple-resistance level to biphenthrin and dicofol, respectively. However, the dicofol/cyhexatin-selected, the dicofol/biphenthrin-selected and the cyhexatin/biphenthrin-selected populations exhibited high multiple-resistance level to ethion.