Field evaluations and in vitro sensitivity of Microdochium nivale to succinate dehydrogenase (SDHI) fungicides

Microdochium patch is a destructive disease of amenity turfgrass caused by the fungus nivale (Fries) Samuels & I.C. Hallett. The succinate dehydrogenase (SDHI) class fungicides relatively new and their efficacy against M. remains unclear. Fluxapyroxad (3-(difluoromethyl)-1-methyl-N-[2-(3,4,5-trifluorophenyl)phenyl]pyrazole-4-carboxamide), penthiopyrad (1-methyl-N-[2-(4-methylpentan-2-yl)thiophen-3-yl]-3-(trifluoromethyl)pyrazole-4-carboxamide), pydiflumetofen (3-(difluoromethyl)-N-methoxy-1-methyl-N-[(2R)-1-(2,4,6-trichlorophenyl)propan-2-yl]pyrazole-4-carboxamide) were evaluated for field in vitro during winter 2019–2020 Madison, WI. plots inoculated with following treatment application to encourage fungal infection. each compound was conducted determining radial growth inhibition on potato dextrose agar at two different temperatures (10 20 °C). In study, pressure high none reduced severity relative non-treated control, including positive control fungicide treatment. For consistently colony most regardless incubation temperature least potent. This research indicates that certain SDHI are highly potent vitro, but additional factors such as environmental degradation and/or variable uptake may decrease field.