Abstract: To obtain a new high\|efficiency acaricide mixture， the joint acaricidal action of propargite and chlorfenapyr against Tetranychus cinnabarinus （Boisduval） and their optimal ratio were investigated by means of co\|toxicity factors and Suns co\|toxicity coefficients （CTC）. At 24 h post\|treatment， the LC50 of propargite and chlorfenapyr against T.cinnabarinus female adults were 43538 and 880 mg·L-1， respectively， and the synergistic mass ratios of propargite and chlorfenapyr ranged from 980∶20 to 954∶46. The best synergistic effect was discovered in the ratio of 965∶35 and 960∶40 （propargite∶chlorfenapyr） with the CTCs of 24026 and 24158， respectively， and LC50 of 11468 and 10837 mg·L-1， respectively， and the toxicities were 380 and 402 times of propargite， respectively. These findings would provide scientific basis for the mixing of propargite and chlorfenapyr against spider mites and for the development of new compounded acaricide.

Key words: Tetranychus cinnabarinus, acaricide, propargite, chlorfenapyr, co\, toxicity coefficient, co\, toxicity factor