Gray Snow Mold (Typhula incarnata)

Gray snow mold is also known as Typhula incarnata, Typhula rot, or white snow mold. It is a common winter lawn disease that occurs primarily during periods of prolonged snow cover.

When does gray snow mold occur?

The disease tends to develop in:

– a cool, humid climate
– Temperatures between 0 and 8 °C
– a prolonged, continuous snow cover
– Snow on unfrozen ground

The longer the snow remains on the lawn, the higher the risk of infestation.

Symptoms and Identification Characteristics

Gray snow mold can be identified by the following characteristics:

– brownish to light green, irregular spots
– Infestation often begins at the tips of the leaves
– no distinct ring-shaped structures, as seen in pink snow mold
– Grasses feel dry, papery, and brittle
– High humidity causes a grayish-white fungal mycelium to form
– brownish-orange sclerotia on the leaves and at the root collar
– Affected areas often have a musty or moldy odor

Factors That Promote Infestation

The following conditions promote the growth of gray snow mold:

– long snow covers
– Snow on unfrozen ground
– poor lighting conditions
– high humidity and condensation
– Temperatures ranging from 0 to 8 °C
– soft tissue
– late replanting
– heavy shading of the grasses
– Cut the grass high before winter
– Waterlogging and soil compaction
– thick thatch
– high nitrogen applications in the fall
– Small amounts of potassium in the fall
– Dull blades when mowing the lawn

Preventive Measures

Targeted prevention is the most important defense against gray snow mold:

– a balanced and consistent supply of nutrients
– Potassium-rich fertilization in the fall
– an adequate intake of magnesium and manganese
– Light application of iron in late fall
– No high nitrogen applications in the fall
– Mowing with sharp blades
– Reduce the cutting height before winter
– Remove thatch (scarifying, aerating, topdressing)
– Avoid waterlogging and keep the soil well-drained
– Regularly remove dew from the blades of grass
– No late replanting
– Remove snow from the lawn, provided the ground is not frozen
– Mow the lawn in winter when it's growing rapidly and no frost or snow is forecast

What should you do in the event of an acute infestation?

If you notice an infestation, you can help support the recovery process:

– Carefully comb through the affected areas with a lawn rake
– Loosen clumps of grass so that air and light can reach the plants
– Let the surface dry faster
– Scarify in the spring (2–3 weeks after the first fertilization)
– Resow any bare spots as needed

In most cases, the lawn recovers on its own as temperatures rise.