Geography
Affected Grass Types
Dollar Spot
Clarireedia spp.
Dollar spot is one of the most widespread and economically significant turfgrass diseases in North America, affecting lawns, sports turf, and golf course surfaces from late spring through fall. Caused by fungi in the genus Clarireedia, dollar spot develops when warm days, cool nights, and prolonged leaf wetness create ideal conditions for infection. Though the disease rarely kills turf outright, it produces unsightly bleached patches, weakens turf density, and reduces aesthetic quality. Under conducive conditions, dollar spot can spread rapidly across a lawn or fairway, making it a core management concern for professional turf managers and homeowners alike.
Identification
Dollar spot is typically recognized by its small, straw-colored patches—roughly the size of a silver dollar in low-cut turf, but often larger and more irregular in taller home lawns. Individual blades exhibit hourglass-shaped lesions with tan centers and reddish-brown borders, a key diagnostic marker. In early morning or humid conditions, infected leaves may also show thin, cobweb-like white mycelium at the patch margins. Grasses may appear bleached or straw-colored, and patches tend to coalesce into larger irregular areas when conditions remain favorable. Diagnosis is easiest when lesions are inspected closely on individual leaf blades.
Life Cycle
The dollar spot fungi survive year-round in thatch and soil organic matter as dormant mycelium or sclerotia-like structures. Infection begins when nighttime temperatures remain above 50°F, daytime temperatures reach 70–85°F, and leaf surfaces stay wet for 8–12 hours. Spores are not the primary dispersal mechanism; instead, the fungus spreads through mechanical movement, mowing, water splash, thatch, and wind-blown fragments. During warm, humid periods, the pathogen repeatedly infects new leaves, producing lesions that weaken turf. As temperatures cool in fall or environmental conditions dry out, the disease becomes inactive but remains viable to reemerge the next season.
Damage Notes
While dollar spot rarely causes deep crown or root injury, repeated infections significantly weaken turf by thinning the canopy and reducing the plant’s ability to photosynthesize. Damaged leaves turn white or tan, creating a speckled or patchy appearance that can persist for weeks. In intensively managed turf—such as fairways or golf greens—dollar spot reduces playability, increases mowing debris, and accelerates thatch buildup. In residential lawns, the disease creates an unattractive mottled appearance and predisposes turf to drought stress and secondary pathogens. Chronic pressure can force more frequent overseeding or nutrient inputs to maintain uniform turf density.
Control
Effective control of dollar spot requires a combination of proper cultural practices and, when needed, targeted fungicide applications. Maintaining adequate nitrogen fertility is the most important cultural tool, as dollar spot thrives in nutrient-deficient turf; balanced, light, and timely nitrogen applications help the plant outgrow lesions and resist infection. Irrigation timing is also critical—watering deeply but infrequently, and always early in the morning, reduces the duration of leaf wetness that the pathogen relies on. Improving air movement, reducing thatch, and avoiding overly low mowing heights further limit disease development by reducing moisture retention and turf stress. When conditions are highly favorable or outbreaks are persistent, preventive fungicides—such as DMI, SDHI, QoI, and multi-site compounds—may be required, particularly on susceptible grasses like creeping bentgrass or perennial ryegrass. Rotating chemical classes and applying them before peak pressure periods greatly enhances performance. A well-balanced program combining cultural and chemical strategies provides the most reliable suppression of dollar spot throughout the season.
Regional Notes
Dollar spot pressure follows a consistent seasonal pattern across the U.S. In cooler northern regions, it is active from late spring until early fall. Transitional regions, such as the Mid-Atlantic and lower Midwest, see two seasonal peaks: one in late spring and another in early fall when humidity is high but temperatures moderate. Southern states experience activity mainly during mild, wet periods when warm-season grasses are growing vigorously. Coastal and high-humidity zones experience prolonged pressure due to nightly dew formation. Altitude, shade, and irrigation practices strongly influence local severity regardless of geographic region.