This circular pattern of mushrooms is a Type III fairy ring.
Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org
Yes, this ring of mushrooms is called a fairy ring.
Fairy ring is caused by numerous species of basidiomycetes, mushroom- and puffball-producing fungi that naturally occur in forest soil. These fungi break down tree stumps, dead tree roots and other organic matter for their food. They are not known to infect or parasitize grass. However, when present in the soil of a turf situation, their growth can affect the surrounding grass, sometimes killing it.
Fairy ring affects all cool- and warm-season lawn grasses. Three types of symptoms are possible. The symptoms of Type I fairy ring include the development of hydrophobic (repels water) soil and thatch that can damage or kill turf in patches, rings or arcs. With Type II fairy ring, symptoms include rings or arcs of dark green turf that grow more quickly than nearby turf because of the release of nutrients by the fungi as they break down organic matter. Symptoms of Type III fairy ring include the production of mushrooms/puffballs in a ring or arc, often with no other visible effect on the grass. The type of symptom that is expressed varies with time of year and weather.
Type 1 fairy ring in turf
Lester E. Dickens, www.insectimages.org
Type II fairy ring in turf
William M. Brown Jr., www.insectimages.org
As with many gardening problems, it is easier to prevent this problem then it is to control after it becomes established. Before planting turf, it is important that large pieces of woody material (stumps, waste lumber, dead tree roots) be removed from the soil. Once the lawn is established, dethatch and aerify as needed. Maintain soil fertility as per soil test recommendations.
Treatment of fairy ring depends on which symptoms are present. With Type I symptoms, the water-repellent thatch and soil must be broken up and re-wetted. This can be accomplished by aerifying the affected area as well as using soil surfactants and hand watering. The symptoms of Type II fairy ring are usually more obvious in grass that is growing in low-fertility soil, especially when nitrogen and iron are low. The symptoms can be masked by adding iron or fertilizer as per a soil test to green up the surrounding grass. Note: Applying nitrogen to a cool-season turf during summer is not recommended because of the potential for development of serious disease problems. Mushrooms and puffballs can be broken off and removed to minimize Type III symptoms.
The good news is that fairy rings tend to disappear over time. The bad news is that it may take years. Other management options include removing/replacing the infested soil, renovating the lawn, and using fungicides. These choices can be very expensive and typically provide only temporary results, and as such, are not recommended for home lawn situations.
For additional information on fairy rings, see HGIC 2355, Mushrooms in Lawns.
J. McLeod Scott
Home & Garden Information Center
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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.