Fungus - Nothing Cute About Fairy Rings

By Dennis Hinkamp

A fungus doesn’t deserve such a cool name, but “fairy ring” refers to a turf disease, not a gang of ex-Disney computer hackers.

Fairy ring is actually a fungal disease that effects many lawns, parks and ball fields, says Jerry Goodspeed, Utah State University Extension horticulturist. Fungal diseases include mushrooms, smuts (also a cool name) and rusts. Many fungi are associated with decaying or rotting organic matter. They are one of Mother Nature’s ways of breaking down dead wood and herbaceous material.

Fairy ring appears as dark green grass growing in a circular pattern, he explains. As the they decompose the dead matter fungi convert the raw material into nitrogen, which greens the lawn up around the fungi. Mushrooms are normally associated with the ring of dark grass. Just outside the dark ring the grass sometimes turns brown and becomes thin. The soil is compacted as the fungi moves through it, making it difficult for water to penetrate the soil.

The life cycle of fairy ring fungus is typical of most fungi, Goodspeed adds. It survives in the thatch and soil throughout the winter. The dormant fungi becomes active in the cool, wet spring and continues to grow outward throughout the summer and into the fall. Mushrooms appear in the area after heavy rains or when the turf is heavily watered.

“Fairy ring mushrooms feed on decaying organic matter,” he says. “They often appear where a tree has been removed, or if there is some decaying wood or an old, thick thatch layer in the turf. These dark green rings vary in size from one to ten feet. They may look like a full circle, a semi-circle or as just fragments of a circle.”

The real trick to controlling fairy ring is simply keeping it out of the yard in the first place, Goodspeed says. Be certain to remove all wood, tree limbs or branches, old trunks and discarded building materials from the turf area before tilling, seeding and sodding. These can be a source for the beginning of fairy ring.

“Keep the lawn’s thatch layer under one-half inch,” he says. “If the thatch becomes too thick, aerating the lawn on a regular basis will help reduce it. Some lawns that are planted in heavy soils need to be core aerated two to three times a year.”

If fairy ring has already attacked your lawn, there are a couple of cultural practices that may help either mask or eliminate the problem, he explains. Applying nitrogen fertilizer around the area and throughout the lawn helps disguise the problem. All the grass is then dark green and lush, not just the area around the fairy ring.

Heavily aerating the affected area reduces the compaction caused by fairy ring and allows more water to penetrate the soil surface, Goodspeed says. After aerating the area, water deeply by soaking, if possible. This helps keep the grass from drying out and turning brown outside the fairy ring.

“Most fairy rings are only present for one to four or five years and eventually outgrow themselves,” he says. “Be patient. The ring should become less of a problem and slowly fade.

“In extreme cases, the affected area can be dug up to a depth of 12 to 18 inches deep, removing at least two feet around the perimeter of the ring. Then, replace the soil and plant new sod or re-seed. This approach is a little extreme and may be more work than it is worth.”

“There are a couple of products on the market that are registered for fairy ring control,” Goodspeed says. “My experience is that they are generally a waste of money. I have never seen good results from a fungicide treatment.”

There are folks who swear by their home remedies, he adds. Some of these treatments that have had limited success include dish soap, soft hand soap, bleach and other cleaning solutions. They probably won’t work; however, you probably will have the cleanest grass in the neighborhood.

For more information, contact your local USU County Extension office.
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Issued in furtherance of Cooperative Extension work, Acts of May 9 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Robert L. Gilliland, Vice-President and Director, Cooperative Extension Service, Utah State University, Logan, Utah. (EP/06-99/DF)