Microdochium Patch (Pink Snow Mold)

Microdochium nivale

Cool-Season Grasses Severe Fungus

Symptoms

Circular salmon-pink to orange-brown patches ranging from 2–12 inches in diameter. Pink mycelium may be visible at the margin. Does not require snow cover — active throughout the cool, wet season.

Circular patches 2–12 inches in diameter with a salmon-pink to copper-brown color
Pink to white mycelium may be visible at the advancing margin of active patches
Individual leaf blades show water-soaked lesions that turn tan with a pink to reddish border
Crown tissue is frequently killed, requiring re-establishment in severe cases
Most damaging under snow cover, but significant damage occurs without snow in the Pacific Northwest and UK

Signs

Salmon-pink to white cottony mycelium visible at the advancing patch margin under moist, cool conditions
Mycelium is finer and more delicate than that of gray snow mold (Typhula spp.)
Salmon-pink coloration of mycelium is the key distinguishing sign from other cool-season diseases
Sporodochia (spore-producing structures) may be visible on infected leaves under magnification as white to pink cushions

Biology

M. nivale is active at temperatures just above freezing and does not require snow cover. It spreads via conidia in cool, wet conditions. Fall nitrogen applications that produce lush, succulent tissue dramatically increase susceptibility. The pathogen can kill crowns, requiring reseeding.

Favorable Conditions

Temperature range: 32–60°F (does not require snow cover)

Cool, wet weather from 32–60°F
Extended periods of cloud cover and leaf wetness
Snow cover on unfrozen ground (accelerates disease)
Lush, succulent growth from excessive fall nitrogen
Poor air circulation and shade
Alkaline soil pH

Cultural Practices

Avoid high nitrogen applications after mid-fall — nitrogen timing is the single most important factor
Apply potassium in fall to harden turf before winter
Improve drainage and air circulation
Remove leaves and debris that trap moisture
Mow turf at normal height going into dormancy — avoid excess growth
Avoid late-season irrigation that extends leaf wetness

Related Reports

No published reports yet for this disease.

Reports will appear here as they are peer-reviewed and published.