Dollar spot

Dollar spot is a destructive fungal disease affecting turfgrass, caused by fungal pathogens belonging to the genus Clarireedia. This disease is one of the most persistent issues for golf course superintendents and landscape professionals, significantly impacting the quality and health of various turf species globally.

The disease primarily targets cool-season grasses, including Agrostis (bentgrass), Poa pratensis (Kentucky bluegrass), and Festuca (fescue). It is particularly aggressive on lawns mowed at low heights, where the stress of constant cutting and high traffic makes the grass more susceptible to infection by the pathogen.

The diagnostic symptoms include the appearance of small, circular, straw-colored spots on the turf, roughly the size of a dollar coin. During early morning hours, when dew is still present, one can often observe a white, cobweb-like mycelium growing across the affected leaf blades, which serves as a definitive indicator of the active fungal presence.

Environmental conditions play a critical role in the outbreak of Dollar Spot. The fungus thrives in warm, humid weather with daytime temperatures between 15°C and 30°C. Long periods of leaf wetness, often caused by heavy dew, frequent light irrigation, or high humidity, create an optimal microclimate for the fungus to spread and colonize the turf canopy.

Effective management requires an integrated approach. Cultural practices such as light topdressing, increasing airflow, and optimizing nitrogen fertility levels are essential. When cultural methods are insufficient, systemic fungicides are applied to protect the turf. It is also crucial to reduce the duration of leaf wetness by dragging the turf to remove dew and avoiding late-afternoon irrigation to keep the canopy as dry as possible during the night.