P-130 - Regional Sensitivity of Microdochium nivale to Common Fungicides for Snow Mold Control

Pink snow mold, caused by Microdochium nivale, poses a significant threat to turfgrass under cool, wet conditions. Effective snow mold management primarily relies on preventative fungicide applications in late fall. Previous research has indicated that M. nivale isolates from the Pacific Northwestern regions of the U.S. can exhibit resistance to various fungicide classes, but research on other regions is limited. This study assessed the sensitivity of nine M. nivale isolates from Wisconsin, Michigan, Massachusetts, Oregon, Idaho, and Norway to three fungicide classes: dicarboximides (iprodione), triazoles (propiconazole) and strobilurins (azoxystrobin). The median effective dose (ED50) values were determined for each isolate against each fungicide using the growth inhibition on fungicide-amended vs. non-amended media. All isolates demonstrated sensitivity to propiconazole. However, individual isolates from Oregon and Wisconsin showed significantly high ED50 values indicating decreased sensitivity to iprodione. The Oregon isolate (AG) showed a notably high ED50 value for azoxystrobin, suggesting potential resistance. Isolates from Norway and other U.S. isolates were sensitive to all three fungicides. This study highlights the varying sensitivity of M. nivale isolates to different fungicides across multiple regions, underscoring the importance of regional monitoring and location-specific integrated disease management strategies to effectively control pink snow mold and minimize the risk of fungicide resistance.