Sclerotinia homoeocarpa
| Dollar Spot | |
|---|---|
| Scientific classification | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Ascomycetes |
| Order: | Helotiales |
| Family: | Sclerotiniaceae |
| Genus: | Sclerotinia |
| Species: | S. homoeocarpa |
| Binomial name | |
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Sclerotinia homoeocarpa F.T.Benn. (1937) |
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Dollar spot is caused by the fungal pathogen Sclerotinia homoeocarpa, in the Sclerotiniaceae family. The pathogen blights leaf tissues but does not affect turf grass roots or crowns. The disease is a common concern on golf course turf, but is rare in sports turf and professional landscapes. Disease symptoms commonly result in poor turf quality and appearance. The disease occurs from early spring through late fall, but is most active under conditions of high humidity and warm daytime temperatures 59–86 °F (15–30 °C) and cool nights in the spring, early summer and fall. The disease infects by producing a mycelium, which can be spread mechanically from one area to another.
Dollar spot is most commonly found on closely mowed turfgrasses. 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.)
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. In coarse textured grasses maintained at taller cutting heights, the dead spots are larger and more diffuse. Spots are often seen in clusters. 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. On fine bladed grasses, the lesions usually girdle the leaf blade. Early in the day or in periods of extended dew, cobweb-like mycelium of the fungus can be seen growing on affected areas. During early stages of the disease, affected plants may appear water-soaked and wilted, but spots quickly fade to a characteristic straw color. The mycelium found on foliage is often confused with that of Pythium, Nigrospora, and Rhizoctonia.
The pathogen overwinters and survives unfavorable periods as dormant mycelium on infected plants and plant debris. In addition to mycelium, dollar spot survives harsh environments in stromata on leaf surfaces. Apothecia occasionally are formed by the pathogen, but are sterile. Sexual spores have not yet been discovered in North America.
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Wikipedia