Dollar spot is a serious disease of creeping bentgrass, Kentucky bluegrass, fine-leaved fescue, ryegrass, zoysia, and bermudagrass.
On closely cut bentgrass and bermudagrass putting greens, the disease appears as sunken, round, tan to straw-colored spots roughly the size of a silver dollar. On Kentucky bluegrass, fine-leaf fescue, higher cut bentgrass, ryegrass, zoysia, and bermudagrass, the spots may reach 3 to 8 inches in diameter. If uncontrolled, the spots may become so numerous that they merge to produce large, irregular, sunken areas of straw-colored turf. Characteristic light-tan lesions with dark-brown to reddish brown borders girdle the leaf blades of Kentucky bluegrass and fine-leaved fescue at the margins of the affected areas. On coarser grasses, such as tall fescue, the lesions tend to occur along the margins of the leaves. White cobweb-like fungalgrowth (mycelium) may be visiblewhen the air is saturated with moisture.
By 2010,the name of the fungus responsible for dollar spot was changed to Rutstroemia floccosum syn. Sclerotinia homoeocarpa.
The fungus attacks when grass is actively growing during warm, humid days, cool nights, and heavy dew in the spring, early summer, and autumn.
Dollar spot is more severe on dry soils deficient in nitrogen. Follow good cultural practices for the turfgrass species you are growing to reduce stress and promote steady growth. In particular, the following practices are most beneficial: 1) water deeply and infrequently, 2) maintain balanced and adequate fertility using light and frequent applications, 3) core aerify to reduce compaction and thatch, and 4) remove dew and guttation fluids from the leaf surfaces in the early morning by mowing, brushing the grass with a long limber pole, or by dragging a mat, hose, or rope across the turf. There are many turfgrass varieties available that are resistant to dollar spot. Dollar spot usually develops slowly at first, allowing the turf manager time to respond with fungicide applications if needed. However, applying fungicides preventively may be justified where dollar spot has been prevalent and difficult to control once the symptoms appear. Repeat applications are needed at 7- to 21-day intervals during moist weather in spring, summer and autumn, when temperatures are between 60 and 90 F.