Resistance to the DMI fungicide propiconazole in Canadian populations of Microdochium nivale

Turfgrass managers have anecdotally reported decreased efficacy of DMI fungicides for the control Microdochium patch and pink snow mold at golf courses in British Columbia, Canada. Isolates nivale from these locations, along with isolates collected Ontario, Canada, were tested their sensitivity to fungicide propiconazole [1-([2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl)-1,2,4-triazole]. Ontario (47) had values effective concentration causing 50% growth inhibition (EC50) ranging <0.001 0.89 µg ml–1. In comparison, Columbia (50) an EC50 range 0.02 8.7 Sensitivity testing a discriminatory (0.1 ml–1) larger set revealed that 24% (43 181) 77% (55 71) exhibited resistance (>50% on 0.1 ml–1 compared non-amended media). Because cool, wet climate coastal turfgrass use more applications annually, including propiconazole, diseases caused by M. nivale, this has resulted greater proportion being resistant propiconazole. contrast, less favorable diseases, accordingly fewer directed toward pathogen hence risk developing.