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Gray snow mold; why this winter allowed it to thrive

A long lasting snowpack and unfrozen ground have created the perfect conditions for this unique mold to form in local yards

MOLINE, Ill. — With the snowpack finally disappearing from our yards, a unique type of mold is now popping up amongst the dormant grass. Snow mold, named after the snowy conditions that support its growth, is taking aim on several local yards.

The overall weather pattern this winter made for ripe conditions to support this type of spider web-looking mold. 

The snowpack has remained on the ground for a number of weeks. Despite record-breaking cold in February, that snow acted as an insulator keeping the ground in an unfrozen state. 

According to the University of Illinois Extension, the particular type of snow mold that we are seeing here is commonly named Gray Snow Mold, or Typhula. 

It is common in areas where snow cover is present throughout much of the winter season. All cool-season turfgrasses are vulnerable, with bentgrasses, annual bluegrass, and ryegrass being most vulnerable. Kentucky bluegrass varieties can differ. 

Credit: WQAD - Andrew Stutzke
Snow mold is seen in a yard after the snow had completely melted. It has a spiderweb-like appearance.

During and after snow-melt, gray snow mold appears in almost circular patches from 1 to 3 feet in diameter. Wet grass can be matted together or covered with a fluffy white mold. 

The pathogen responsible for mold growth lies dormant during warm, dry weather. Once temperatures cool, it becomes active and thrives in an environment that features a prolonged snow cover on unfrozen soil. 

The Extension recommends raking matted grass, fertilizing, and re-seeding or sodding as necessary to repair the damage. 

You should only apply fungicides preventatively to areas that have had a history of gray snow mold. One to three fungicide applications during cold, wet weather from mid to late autumn through early spring will usually do the trick. 


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