TPMR
Dollar Spot
Photo: J.E. Kaminski
Disease Profile

Dollar Spot

Clarireedia jacksonii (formerly Sclerotinia homoeocarpa)

All Turfgrasses Severe Fungus

Symptoms

Straw-colored spots the size of a silver dollar on closely mowed turf. White mycelium may be visible in the early morning.

  • Individual spots are tan to straw-colored, 1–3 inches in diameter on short-cut turf
  • On higher-cut turf (lawns), spots can merge into large irregular blighted areas
  • Characteristic hourglass-shaped lesions with a reddish-brown border on individual leaf blades
  • Cottony white mycelium may be visible in early morning dew — evaporates as the day warms
  • Spots may coalesce under heavy pressure into large patches

Signs

  • Cottony white mycelium visible across leaf surfaces and between plants in early morning dew — evaporates quickly as temperatures rise
  • Stromata (tan to reddish-brown hardened masses of mycelium) may be visible in thatch with close inspection
  • No visible spore-producing structures (conidiophores) without magnification

Biology

Pathogen overwinters in infected thatch and plant debris as stromata. Spores are spread by water, wind, mowing equipment, and foot traffic. Infection occurs during periods of prolonged leaf wetness at moderate temperatures. Multiple generations occur throughout the growing season.

Favorable Conditions

Temperature range: 59–86°F (15–30°C)

  • Extended leaf wetness (dew, irrigation, rain) for 10+ hours
  • Moderate temperatures between 60–85°F
  • Low nitrogen fertility
  • Drought stress followed by humid periods
  • Thatch accumulation promoting surface moisture retention

Cultural Practices

  • Maintain adequate nitrogen fertility — low N greatly increases susceptibility
  • Irrigate in the early morning to minimize leaf wetness duration
  • Raise mowing height to reduce stress and improve airflow
  • Core aerate and dethatch to reduce surface moisture retention
  • Avoid drought stress, which predisposes turf to infection
  • Clean mowers and equipment between areas to limit spread
  • Use fans or syringe turf to break dew on high-value surfaces

Related Reports

No published reports yet for this disease.

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