Abstract: Eleven chemical pesticides were used to evaluate their selective toxicity to Verticillium dahliae, a pathogen of cotton wilt, and its bio-control strains.
Results showed that carbendazim, benlate, thiophanate methyl and triadimefon had strong inhibitory effects on V. dahliae CV-1 at 100μg/g,
but the concentration of dimethachlone and quintozene to suppress the fungus was higher (5000μg/g). Fungicides with benzimidazolyl had the highest toxicity against Trichoderma viride LTR-2 The EC₅₀ value of carbendazim, benlate and thiophanatemethyl were 0.7395, 1.6784 and 0.7370μg/g, respectively. The minimum inhibitory concentration(MIC) of carbendazim, benlate and thiophanate-methyl for control of V. dahliae were 0.7, 2.3 and 2.6μg/g, and that against T. viride LTR-2 were 1.2, 3.4 and 6.4μg/g, respectively. The toxicity selective ratios (TSR) of carbendazim to LTR-2, 2-②, Tc, Tk7a and GLR, that ranged from 1 to 10, were 4.6, 3.1, 4.7, 1.2 and 7.3 respectively, which had positive regulation. The TSR of Sxb was 27.5, which had moderate positive regulation. The TSR of T9 was 9145.0, which had strong positive regulation. The TSR of benlate to Sxb, 2-②, Tc, Tk7a, GLR, LTR-2 and T9 were 2.8, 3.9, 5.6, 4.5, 4.7, 13.7 and 66.5 respectively, which had no strong positive regulation.