Sensitivityof<italic>Fusariumgraminearum</italic>topydiflumetofenanditsfieldefficacyonfusariumheadblight

The fungicide pydiflumetofen 3-(difluoromethyl)-N-methyl-N-1-methyl-2-(2,4,6-trichlorophenyl) ethyl-1H-pyrazole-4-carboxamide, is a novel succinate dehydrogenase inhibitor (SDHI) . In order to determine thepotential application of this novel fungicide for the control of wheat head blight in China, the baseline sensitivities of Fusarium graminearum to pydiflumetofen cross-resistance analysis and the field trail were determined. Toxicities of the pydiflumetofen on mycelium growth, conidial germination of 106 strains form six regions in Hubei Province were determined, the cross-resistance between carbendazim and phenamacril fungicides and the control efficacy was evaluated. The EC₅₀ value of pydiflumetofen against the mycelial growth of 106 strains of F. graminearum was 0.018 0-0.209 0 mg/mL and the average value was (0.072 8 ± 0.025 9) mg/mL. The EC₅₀ value of pydiflumetofen against conidium germination was 0.052 7-0.473 2 mg/mL and the average value was (0.176 0 ± 0.059 6) mg/mL. The EC₅₀ values distribution of 106 strains measured by mycelial growth assay or by conidium germination assay exhibited as a unimodal curve and could be used for detecting any sensitivity changes of F. graminearum to pydiflumetofen in the future. The results of cross-resistance analysis indicated that there was no positive or negative cross-resistance between pydiflumetofen and carbendazim or phenamacril. In field trials, pydiflumetofen at 200 g a.i./hm² provided > 90% control efficacy which was significantly higher than that of phenamacril at 600 g a.i./hm² and significantly raised the plot yield by 127%-135% (P < 0.05) compared with the untreated controls. In conclusion, pydiflumetofen had very high activity against F. graminearum in vitro and excellent efficacy for the control of fusarium head blight (FHB) . Therefore it could be used to manage carbendazim-resistant F. graminearum population in the field.