Dollar Spot on Lawns

Dr. John F. Baniecki
WVU Extension Service
Plant Pathology and
Entomology Specialist
August 2000

Dollar spot, caused by the fungus Sclerotinia homoeocarpa although occurring on many grass species, is particularly severe on bentgrasses. This disease is prevalent in April, May, and June and again in September and October when the weather is cool and wet. Damage is greatest on lawns that are deficient in nitrogen.

The characteristic symptom on the bentgrass turf is the appearance of dark, water-soaked spots about the size of silver dollars. These turn brown, but later are bleached to a light tan. As the disease develops, the spots merge and large irregular areas cover the lawn. In the early morning, when dew is on the grass, a fine white cobwebby growth can be seen on the grass blades. This is the fungus mycelium. Closer examination of the grass blades will sometimes reveal light tan or bleached hourglass-shaped areas with red to brown borders. On bluegrass, because of the higher mowing practice, the spots on the turf are irregular in shape.