Threshold trait analysis was used to estimate realized heritability (h 2) of re sistance to five acaricides (three single acaricide and two mixtures) and resistance risk in Tetranychus cinnabarinus (Boiduval). Tetranychus cinnabarinus collected from the field of Beibei, Chongqing reared more than 60 generations under pesticide free conditions and considered s usceptible. Successively selected for about 30 generations, the strain had a 65.55-, 5.82 - , 1.23-, 5.20- and 1.42-fold increase in resistance to fenpropathrin, abam ectin, pyridaben, pyridab en-abamectin (pyridaben: abamectin=7.4:0.1, m/m) and fenpropathrin-abamectin (fenpropathri n: abamectin=8.9:0.1, m/m), respectively. The realized heritability of resista nce t o fenpropathrin, abamectin, pyridaben, pyridaben-abamectin (pyridaben: abamectin=7.4:0.1, m/m) and fenpropathrin-abamectin (fenpropathrin: abamectin=8.9:0.1, m/m) is 0.2167, 0 .0967, 0.0130, 0.0800 and 0.0172, respectively. Under the selected condition, a 10-fold incr ease in resistance would be expected 15 generations for fenpropathrin, 34 generations for abamectin , 333 generations for pyridaben, 42 generations for pyridaben-abamectin (pyridaben: a bamectin=7.4:0.1, m/m) and 200 generations for fenpropathrin-abametcin (fenpropathrin: abamectin= 8.9:0.1, m/m). The highest resistance risk of the five acaricides in Tetranychus cinnabarinus was fenpropathrin, then abamection, pyridaben-abamectin (pyridaben: abamectin=7.4:0.1, m/m), fen propathrin- abamectin (fenpropathrin: abamectin=8.9:0.1, m/m) and that to py ridaben was the lowest. The mixture of pyridaben and abamectin is not useful in delaying development of resistance in the pest to the two single acaricide while the mixture of fenpropathrin and abamectin could do it.
