Snow Mold

Symptoms:

Damage from snow mold fungi usually becomes apparent as the snow melts and exposes the grass in late winter. Snow mold symptoms consist of roughly circular patches (at least 3 to 12 inches) of dead and matted grass blades. In severe cases, these patches coalesce and may not be recognizable as individual circles. Just after snow melt and while the grass remains moist, it may be possible to differentiate between the two common types of snow mold by their color. The web-like mycelium of pink snow mold  may initially look white and mature to a faint pink to salmon color. Gray snow mold  is white to gray in color. The mycelium of both types of fungi will disappear quickly as the grass dries. A useful identifying characteristic of gray snow mold is the presence of tiny brown to black mycelial masses  on the blades and in the leaf sheaths of infected plants. These survival structures vary in size and color, becoming smaller and darker as they dry. The pink snow mold fungus does not produce sclerotia.

It is useful to determine whether the disease is pink or gray snow mold because gray snow mold rarely damages more than the blades of the grass. Lawns with gray snow mold can be expected to recover fairly quickly even when damage appears extensive. Pink snow mold, in contrast, may invade the crowns and roots causing more serious injury. It is not unusual for both types of snow mold to be found in the same area. All common lawn grasses may be infected, but Kentucky bluegrass-fescue lawns are the least susceptible to severe damage.

Gray snow mold on turfgrass and close-up of mycelium
Characteristic pink snow mold symptoms on turfgrass and close-up of mycelium

 If your lawn appears to be affected by snow mold don't panic.  In most cases it will go away as soil temperatures increase and the turf begins to grow.  You should lightly rake the affected areas to allow the areas to dry out and let some air get to the soil surface.

 

Comments

[Lawn Care]

Very informative post. Good job including pictures too. Most people are unaware that patches of dead grass (like in the pictures displayed above) are actually caused by mold. They are usually just dismissed as dead grass. Keep up the good work.