Dollar spot is a disease of turfgrass caused by the fungus Sclerotinia homoeocarpa. Kentucky bluegrass, annual bluegrass, bentgrass, fescue, perennial ryegrass, and zoysiagrass are some of the grasses affected.
Warm days and cool nights are prime conditions for dollar spot development. Symptoms may begin to appear late spring through the summer months. Patches in lawns can be up to six inches in diameter, but in closely mowed bentgrass golf course greens the spots are usually the size of a silver dollar. Straw-colored spots on the blades are usually bordered by a reddish margin and normally span the width of the blade. In the morning, look for the white cobweb-like fungus growing on dew covered blades. This threadlike material, mycelium, can be spread by foot traffic and mowers.
Dollar spot tends to be most serious in under-nourished lawns. Maintenance of a healthy lawn by such practices as core aeration, balanced fertilization, and proper irrigation may help reduce dollar spot. Mowing when the grass is dry can reduce the spread of the fungus. If necessary, fungicides are available and can be applied at the first appearance of the disease. Accurate diagnosis is the first step in successful disease management.
This article originally appeared in the June 8, 2001 issue, p. 65.