Dollar spot

Dollar spot, caused by the fungal pathogen Clarireedia homoeocarpa, is a devastating disease affecting turfgrass species such as bentgrass, Kentucky bluegrass, and fescue. It is widely recognized as the most persistent and economically damaging disease on managed turf, causing significant disruption to the uniformity and quality of golf courses and residential lawns.

The characteristic symptoms of the disease include the appearance of small, circular, straw-colored spots roughly the size of a silver dollar. During the early morning hours, particularly when dew is present, you may observe a distinct, white, cobweb-like mycelium growing across the surface of the infected grass blades. As the infection progresses, the leaves within these spots die, turning a bleached or tan color.

The development of Clarireedia homoeocarpa is highly favored by warm, humid weather conditions, specifically daytime temperatures between 15°C and 30°C and extended periods of leaf wetness. The pathogen thrives when night temperatures are warm and dew formation is heavy, while its spread is often exacerbated by turf under nitrogen stress, making deficient lawns particularly vulnerable to rapid infection.

The damage caused by dollar spot is severe because it results in foliar death and, in extreme cases, can penetrate the crown of the plant. If left untreated, these small lesions coalesce, leading to large patches of blighted turf that require significant restoration work, reseeding, and prolonged maintenance to restore the aesthetic and functional value of the surface.

Effective management requires an integrated approach that combines proper cultural practices with chemical interventions. Key strategies include:

• implementing a balanced nitrogen fertilization program;
• removing dew in the morning via mowing or dragging;
• improving drainage to reduce humidity;
• applying site-specific systemic fungicides when disease pressure is high.