Inhibitory Effect of Dimethomorph on Phytophthora parasitica var. nicotianae in China

The inhibitory effect of dimethomorph on 20 strains of Phytophthora parasitica var.nicotianae,which isolated from Shandong and Yunnan province,were determined by using mycelium growth rate method.The results showed that EC50 values of 20 strains were ranged from 0.60 to 1.28 μg/mL,Compared with of the sensitive strain EC50 value,the inhibitory factors were ranged from 1.87 to 4.00,which indicated that the 20 strains were sensitive to dimethomorph.Dimethomorph could evidently inhibit the formation of sporangia.The inhibitory rates against the sporangia formation of P.parasitica was 100％ by 8.00 μg/mL dimethomorph.The resistance risk of P.parasitica to dimethomorph was proved by testing on inhibitory activity of dimethomorph to mycelial growth of the sub-culture fungus.