Dollar Spot

Disease

Dollar Spot

Sclerotinia homoeocarpa

Rutstroemiaceae: Helotiales


Dollar spot is characterized by round, bleached-out or straw-colored spots, ranging from the size of a quarter to the size of a silver dollar. Spots appear as sunken areas in the turf, especially low mown turfgrass (0.5 inches or less). Fluffy white mycelia can be seen when fungus is actively growing during morning periods of heavy dew. Symptoms on individual grass blades appear as bleached-out or tan lesions that are often accompanied by reddish brown bands present at the outer edge of the leaf lesion (except on annual bluegrass).

Dollar spot occurs when daytime temperatures are between 59-88° F (15-31° C) and disease development is favored by warm, humid weather followed by cool nights that produce heavy dews.

  • Crops Affected: Turfgrass

    Damage

    The location of this disease is home lawns and golf courses. General symptoms are spotting. Foliar symptoms are spots and water-soaked grass. This can occur during the months of May, June, July, August, September, and October. Hosts of the disease are Kentucky Bluegrass, Perennial Ryegrass, Fine Fescue, Creeping Bentgrass, and Annual Bluegrass.

    Management

    Adequate nitrogen fertility is important in managing dollar spot disease (Variations exist among turfgrass species in nitrogen fertilizer recommendations). Light and frequent applications of nitrogen fertilizer can be used to achieve the optimal growth and adequate soil nitrogen levels. Low soil moisture appears to be important in the development of dollar spot, and dollar spot is more severe in dry soils. Therefore, moisture level of the turfgrass area should be kept near field capacity. This most often can be achieved by light, daily irrigation regimens.

    Removing dew and guttational fluid is a common practice on golf courses, and serves to reduce the leaf wetness duration, thus inhibiting pathogen proliferation. Recent research has confirmed rolling as a method of disease reduction if implemented on a daily basis on golf course putting greens.

    Many newer turfgrass varieties display moderate to high levels of resistance to dollar spot, and can be used in golf course, home lawn, and athletic field settings. Visit NTEP.org to view disease susceptibility ratings for current cultivars. Biological control of the disease has been achieved at moderate levels with a Pseudomonas bacterium applied on a daily basis.

    Dollar spot can be managed with the use of many systemic fungicides like myclobutanil, fenarimol, propiconazole, boscalid, and triadimefon applied every two to three weeks, or with contact fungicides like chlorothalonil applied every 7-10 days. Many products containing combinations of contact and systemic fungicides can also be effective in controlling the disease.

    The dollar spot pathogen can develop resistance to fungicides, and most golf courses are unable to use systemic fungicides such as thiophanate products due to their use over many years.