High efficiency fungicide screening for Phytophthora parasitica var. nicotianae

To screen out the effective fungicides to control tobacco black shank, the inhibition effects of 22 fungicides on Phytophthora parasitica var. nicotianae were tested by the mycelial growth rate method. The EC₅₀ values of 7 fungicides with better inhibiting effects were measured. The control effects of 23.4% mandipropamid suspension on tobacco black shank were investigated by pot experiments in greenhouse with 50% dimethomorph suspension and 25% metalaxyl wettable powder as the control agents. The results showed that among the tested fungicides, 7 fungicides including flumorph, shenqinmycin, metalaxyl, mancozeb, pyrimorph, dimethomorph and mandipropamid had better inhibitory effects with the EC₅₀ values of 2.023 0, 1.923 0, 1.808 2, 1.758 0, 1.400 0, 0.783 0 and 0.018 0 mg/L respectively. The relative control efficiency of 23.4% mandipropamid suspension on tobacco black shank was 80.11%, which was significantly higher than 50% dimethomorph suspension (64.89%)and 25% metalaxyl wettable powder(66.05%)