Sensitivity and fitness analysis of round spot of Panax notoginseng Mycocentrospora acerina to azoxystrobin, prochloraz and difenoconazole

The sensitivities of 34 strains of Mycocentrospora acerina to azoxystrobin, prochloraz and difenoconazole were tested using the mycelium growth rate method, the strains were isolated from 5 major origins of Panax notoginseng in Yunnan Province. The survival fitness was also analyzed. The results showed that those fungicides had high inhibition effect on the mycelium growth of strains. The EC₅₀ values of prochloraz, azoxystrobin and difenoconazole to all tested strains are in the range of 0.03-1.91 mg/L, 0.18-2.36 mg/L and 0.45-2.15 mg/L, respectively. The sensitivities of all strains to prochloraz were higher than that of azoxystrobin and difenoconazole. The difference of mycelial growth for the sensitive and the insensitive strains was not significant, which demonstrated that all strains showed high survival fitness in field.