Fairy Rings

Encyclopedia Article

Image of dead grass rings resulting from fairy ring mushrooms
Dead grass rings resulting from fairy ring mushrooms 

Overview   

This fairy rings common in summer and fall in lawns and other grassy places. Patches can be up to 12 inches in diameter. There are several mushrooms associated with fairy ring formation in lawns.

They first appear as a cluster of mushrooms or stimulated grass. The rings enlarge each year from a few inches to several feet. Some rings disappear for a year or more and then reappear. Fairy rings may be produced by 50 or more species of soil-inhabiting fungi.

Signs and symptoms

Fairy rings are found in three general patterns:

  • Mushrooms appearing in circles or arcs and lasting only for a brief time, without the presence of a dark green ring
  • Stimulated grass growth producing a dark green ring, along with the presence of mushrooms
  • Circular patterns of dead grass developing in the center of the dark green ring, along with the presence of mushrooms

The dark green grass is largely due to the increased amount of nitrogen that is made available to the grass roots by the fungus as it breaks down organic matter in the thatch and soil. The ring of brown or thin grass develops largely as a result of drought stress caused by the dense growth of fungal material. This weakened grass is more susceptible to environmental stresses, disease, and weed invasion.

Image of fairy ring mushrooms
Fairy ring mushrooms 

Fairy rings are usually most severe in light-textured, low fertility soils low in moisture. The mushrooms grow on decaying organic matter and are most likely to form in turfs with a thick thatch or in areas where trees have been removed.

Type of Sample Needed for Diagnosis and Confirmation

The Iowa State University Plant & Insect Diagnostic Clinic can help you to investigate and confirm if you plant has this disease. Please see our website for current forms, fees, and instructions on collecting and packing samples. Contact information for each states diagnostic laboratory for U.S. residents.  If your sample is from outside of Iowa please do not submit it to the Plant & Insect Diagnostic Clinic without contacting us

Management of fairy rings

Prevention of fairy ring is to balance the thatch formation in the lawn. Thatch is a source of nutrients or the mushrooms that form fairy rings.

Control of fairy rings can be difficult and be depending on the case. In most cases damage to the lawn is minimal.  Once the mushrooms have appeared is recommend to reduce the amount of thatch. In extreme cases,  Fairy rings can be physically removed by digging out the sod on either side of the dark green ring of grass and replacing it with new soil. Alternatively, soil cultivation, and mixing grass reseeding may help. For example, the area may be killed with a herbicide and rototilled in different directions. The area can then be reseeded. Certain fungicides are labeled for use for fairy ring control, but may only be effective for one of the fungal/mushroom species. In most cases, suppression may only be temporary.

 

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