Snow Mold on Minnesota Lawns

The long season of snow cover can take its toll on Minnesota lawns, and fungal diseases can often afflict turf in the early spring. The common names for two of these diseases are Gray Snow Mold and Pink Snow Mold. Both of these diseases are most severe when early snow covers wet, unfrozen ground in the fall.

The symptoms of Gray Snow Mold (aka Typhula Blight) are apparent as circular areas of light straw-colored to grayish-white turf. The spots can vary widely in size. The damaged turf is often covered with a grayish-white mold, or mycelium, with speckled dark flecks. The mycelia are usually most noticed on the outer edge of the spots.

The symptoms of Pink Snow Mold are similar to those of Gray Snow Mold except that there aren't as many speckled dark flecks and the mycelia are a pinkish to reddish-brown coloring (hence the name). Also, unlike Gray Snow Mold, snow cover is not necessary for this disease to develop. When not associated with snow cover, the disease is called Fusarium Patch. As this disease progresses, the spots enlarge and eventually turn light-gray in color.

As mentioned, these diseases are most severe in years when snow covers wet, unfrozen ground. The greatest disease activity occurs within a ground surface temperature range of 30 to 40 degrees F. Also, turf with tree leaves or other debris on it prior to snow cover is very susceptible.

While these diseases can kill large areas of turf, in most cases only the leaves of the plants are damaged. If the turf was and is being maintained at an appropriate level (proper mowing, watering, and fertilization) the plants normally can recover on their own, through re-growth from the crown and the root system. In severe cases, properly timed fungicide applications are effective in controlling these diseases.

Good landscape hygiene is also very important. Leaves and other debris should be thoroughly picked up and removed from all areas of your landscape. Many disease pathogens depend on this organic trash for their very survival. Removing this debris will go a long way in preventing these types of diseases from becoming a problem.

Snow mold is a disease afflicting turf in the early spring.   Close up view of snow mold on turf grass.