UCONN IPM Turf:Diseases:Dollar Spot

Dollar Spot

Dollar spot is caused by fungi in the species Lanzia and Moellerodiscus, which were once known as Sclerotinia homeocarpa. This disease is a common problem on golf courses, but rarely causes extensive damage to other turfs. It occurs on most turfgrass species, and is especially destructive on creeping bentgrass. The disease is favored by warm, humid (but not wet) weather; especially when nights are cool enough to cause heavy dew formation. This disease is worse when the soil is dry and of low fertility. It is usually seen in late spring or late fall. It is not often seen in the summer. This fungus is quite persistent and patches often reappear in the same areas year after year.

Symptoms. On grasses that are mowed short, such as golf greens, this disease causes small, circular, sunken patches in the turf. These are generally smaller than 2" in diameter, about the size of a silver dollar. When the disease is severe, these patches can grow together to form irregular patches. The spots are first brown, and then become bleached or straw-colored.

On grasses that are mowed longer, such as home lawns, the patches are irregularly shaped. They are bleached or tan in color, and can be 1" to 6" in diameter. The patches may grow together to become quite large.

On individual blades of grass, regardless of how the turf is managed, the symptoms start as a yellowish spot. This spot then becomes watersoaked, and later bleached or straw-colored. The edges of the spots are generally tan to reddish-brown. On most grasses, the spots usually reach across the entire leaf blade, so that they look like a band across the blade. There can be several spots on one blade and they may cause the entire blade to shrivel and die. Spots can start at the cut end of the blade and grow down.

In the early morning, when the grass is moist from dew, the fungus may be visible. A white cottony, cobweb-like growth is present until the grass dries. Other fungi (Pythium and Nigrospora) produce similar fungal growths.

Similar Diseases. The early spots may look similar to those caused by red thread. Some red fungal growth is always visible when the red thread fungus is present.

Prevention.

Maintain adequate to high nitrogen and potassium levels in the soil.
Avoid high levels of fertilizer in the fall.
Mow regularly.
Avoid drought conditions, but avoid allowing the plants to be wet for long periods of time.
Water deeply and as infrequently as possible.
Water early in the day to allow the leaves to dry quickly.
Remove dew from the turf in the early morning by poling or dragging a hose or mat over the turf.

Resistance is available to this disease. See current recommendations for chemical control measures.

By Pamela S. Mercure, IPM Program Assistant, University of Connecticut, 1998.

References.

Smiley, R.W. 1983. Compendium of Turfgrass Diseases. APS Press, St Paul, MN.

Smith, J.D., N. Jackson, and A.R. Woolhouse. 1989. Fungal Diseases of Amenity Turfgrasses, Third Edition. E. & F.N. Spon, London.

Turgeon, A.J. 1996. Turfgrass Management, Fourth Edition. Prentice Hall, Upper Saddle River, New Jersey.

This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

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