Causal Agent:
Microdochium nivale
Susceptible Turfgrasses:
Cool-season turfgrasses, including but not limited to annual bluegrass, perennial ryegrass, creeping bentgrass, and fine fescues.
Identification:
Microdochium patch typically appears from late fall to early spring, particularly during cold, wet, and overcast conditions. This disease presents in two phases based on the presence of snow:
Fusarium Patch Phase (No Snow Cover):
Patches appear as small, circular spots ranging from 1–3 inches (2.5–7.5 cm) in diameter.
Spots exhibit reddish-brown, pink, or tan coloration.
Grayish smoke rings (foliar mycelium) may form around the edges.
In immature turf, these patches can expand to over 1 foot (30 cm) in diameter.
Pink Snow Mold Phase (Under Melting Snow):
Patches have tan centers with pinkish-red edges.
Patches can grow between 6 inches and 2 feet (15 cm to 60 cm) across.
This phase occurs when snow cover melts after lingering for extended periods.
Favorable Conditions:
Microdochium patch thrives under the following conditions:
Temperature Range: Between 32°F to 60°F (0°C to 15°C).
Weather: Wet, overcast, and cold conditions.
Fusarium Patch Phase
Most common from late fall to early spring.
Severe in immature fall-seeded turf, especially during persistent cool and wet weather.
Pink Snow Mold Phase
Occurs when snow cover lasts more than 10 days.
Leads to extensive leaf blight and slow recovery once the snow melts.
Persistent snow cover can result in significant turf damage.
Management Tips:
Manage Moisture: Improve drainage and avoid overwatering.
Snow Management: Minimize prolonged snow cover when possible.
Turf Health: Avoid late-season nitrogen applications that promote lush growth before winter.
Mow turf regularly throughout fall until dormancy.
Check seedling turf frequently, especially when blankets are used.
Avoid heavy applications of water-soluble nitrogen sources in late fall prior to dormancy.
