Dollar spot

Clarireedia monteithiana is a fungal pathogen responsible for the turfgrass disease commonly known as Dollar Spot. It was formerly grouped within the Sclerotinia genus but was reclassified due to specific morphological and genetic traits. This disease is arguably the most common and damaging turfgrass issue worldwide, particularly affecting golf course fairways and high-maintenance residential lawns.

The host range of this fungus is extensive, including common lawn grasses such as Kentucky bluegrass, fescues, and bentgrass. The fungus survives as mycelium within infected plant debris and soil during periods of unfavorable conditions. When temperatures and humidity align, it emerges to infect healthy leaf tissue, disrupting the plant's nutrient uptake and leading to localized tissue death.

The primary symptom is the emergence of small, circular, bleached-out patches, typically the size of a silver dollar coin. In the early morning, especially under high humidity, a fine, cobweb-like white mycelium may be visible across the affected areas. Over time, these spots can coalesce into larger, irregular zones of dead, straw-colored turf, significantly diminishing the aesthetic quality of the grass.

Disease development is heavily influenced by environmental factors, most notably air temperature and leaf wetness. Warm, humid weather with cool nights that promote dew formation creates the ideal environment for Clarireedia monteithiana to spread. Furthermore, nitrogen-deficient turf is significantly more susceptible to infection, making nutrient management a critical component of the overall strategy.

Integrated Pest Management (IPM) is essential for controlling this disease. While chemical intervention with targeted fungicides can stop an active outbreak, long-term success relies on maintaining turf vigor through proper cultural practices. Recommended strategies include:

• Maintaining adequate nitrogen levels to promote rapid tissue recovery.
• Reducing leaf wetness duration by improving air circulation and surface drainage.
• Irrigating early in the morning to allow foliage to dry before nightfall.
• Removing dew from turf surfaces by mowing or dragging.
• Regular dethatching to reduce the accumulation of organic matter where the fungus thrives.