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Historical Significance

Dollar spot was initially described as a disease in the 1920s when the causative agent was first thought to be a species of Rhizoctonia. The disease was initially referred to as “small brown patch” to distinguish it from “large brown patch” which is caused by R. solani. It was not until the 1930s that the causal agent was reclassified as Sclerotinia homoeocarpa. The disease is called dollar spot because spots of diseased turf are approximately the size of a silver dollar.

Dollar spot is a worldwide problem and affects almost all cultivated turfgrasses. The disease is most important in the northern areas of the U.S. on golf putting greens and fairways composed of creeping bentgrass and annual bluegrass. However, dollar spot is also damaging to other turfgrasses in home lawns, athletic fields, and other turfgrass areas. In the southeastern U.S., warm-season turfgrasses may be severely affected, but the disease occurs infrequently in the northwest and southwest U.S. In Great Britain, the disease is confined to fine-leaf fescues (Festuca spp.).

Worldwide, more money is spent on the chemical control of dollar spot than any other turfgrass disease. However, over the years, the repeated use of some fungicides has selected for fungicide-resistant populations of S. homoeocarpa. Resistance to benzimidazole and dicarboximides fungicides was reported in 1973 and 1983, respectively. Resistance to sterol demethylation inhibitor fungicides, a class commonly referred to as DMIs, was initially detected in the U.S. in 1992.