Dollar spot

There is evidence that a fungal mycotoxin produced by the pathogen may cause root damage, including necrosis of the apical meristem in creeping bentgrass (Agrostis stolonifera).

[4] The absence of fruiting bodies made the taxonomic classification of the fungus extremely difficult until the introduction of DNA sequencing and analysis.

In 2018, Salgado-Salazar et al. used DNA sequencing data to analyze the causal agent of dollar spot and a new genus, Clarireedia, was created to accommodate the pathogen within the family Rutstroemiaceae based on their findings.

The pathogen infects most cool and warm-season grasses throughout the world, including creeping bentgrass (Agrostis stolonifera), annual bluegrass (Poa annua), Kentucky bluegrass (Poa pratensis), perennial ryegrass (Lolium perenne), hybrid bermudagrasses (Cynodon dactylon x tranvaalensis), seashore paspalum (Paspalum vaginatum), and zoysiagrass (Zoysia spp.

)[4] On fine textured and close-cut turf, the disease appears as round, brown to straw-colored and somewhat sunken spots approximately the size of a silver dollar.

Dollar spot is readily distinguished from other turf disease by light-tan lesions with a reddish-brown border on the leaf blades of live plants near the edge of the affected area.

During early stages of the disease, affected plants may appear water-soaked and wilted, but spots quickly fade to a characteristic straw color.

When environmental conditions become favorable for pathogen activity (warm, humid, high moisture in canopy), the dormant mycelia and stromata on the infected debris resume growing on the plant tissues.

Dew formation, which is driven by warm temperatures and high humidity levels during the day, followed by cool nights, enhances disease development.

Light, frequent applications of nitrogen enhance the recuperative ability of the plant, allowing the turf to hide the symptoms of dollar spot and recover from any damage sustained.

Quicker growth results in more frequent mowing, which removes necrotic tissue and improved the appearance of turf affected by dollar spot.

There are many fungicides labeled for control of Sclerotinia homoeocarpa, including benzimidazoles, carboxamides, nitriles, dicarboxamides, and demethylation inhibitors (DMIs).

Some common fungicides used include chlorothalonil (nitrile), propiconazole (DMI), boscalid (carboxamide), thiophanate-methyl (benzamidazole), and iprodione (dicarboxamide).

Adequate coverage can be achieved by applying fungicides in 2 gallons of water per 1000 ft2 through an air induction or flat fan nozzle producing fine to medium size droplets.

Dollar spot is the most common turfgrass disease in North America, with the exception of the Pacific Northwestern United States and Western Canada.