Dollar spot

Dollar spot, caused by the fungus Clarireedia jacksonii, is a destructive disease affecting turfgrass worldwide. Historically identified as Sclerotinia homoeocarpa, it is recognized as a major challenge for golf course superintendents and residential lawn care professionals alike.

This pathogen targets a broad variety of turfgrass species, including creeping bentgrass, Kentucky bluegrass, and fine fescues. The fungus persists in the thatch layer and soil, waiting for the right environmental triggers to initiate infection and spread across the canopy.

The primary symptom is the appearance of small, circular, straw-colored spots that are typically 2–5 centimeters in diameter. Under high humidity, you may observe a fluffy white mycelium on the leaves, which gives the infected area a web-like appearance. If left unchecked, these spots may coalesce, leading to severe thinning of the turf.

Environmental conditions that favor the development of Clarireedia jacksonii include extended periods of high humidity, heavy dew, and daytime temperatures between 15°C and 30°C. Nitrogen-deficient turf is significantly more susceptible to the disease, as is grass that remains wet for long durations due to poor irrigation management.

Control measures rely heavily on integrated pest management (IPM) techniques. Cultural practices such as regular aerification, dethatching, and appropriate fertilization are crucial for reducing disease pressure. When cultural control is insufficient, chemical management involving the timely application of fungicides remains the most effective strategy to stop the progression of the fungus.