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Surprise! It's snow mold!

Michelle Grabowski, UMN Extension Educator

M. Grabowski

Many Minnesotans have anxiously awaited snow melt this spring. The joy of seeing green grass again may be coupled with the disappointment of snow mold. Lawns affected by snow mold have round to irregular patches of matted down tan to gray turf grass. If a light drizzly rain is present or humidity is high at low temperatures, cobweb like fungal mycelia may be seen growing across the infected turf grass.

This winter's heavy wet snow layer has provided ideal conditions for the fungal pathogens that cause snow mold. These fungi thrive at temperatures just around freezing. Persistent snow or cool rainy weather provides the humidity and temperatures needed by the fungi to thrive.

M. Grabowski

Photo 2: Fluffy fungal growth on a snow mold patch on a cool rainy day

In spring the best management strategies for dealing with snow mold of a home lawn include removing heavy snow from valuable turf areas, raking up matted down turf grass to improve air circulation and drying of infected patches, and removing any leaf litter or other plant debris that may have accumulated on the lawn. Sunny weather and warming temperatures will favor growth of the turf grass and most lawns recover. In severe cases, the center of the snow mold patch may need to be reseeded.
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