Fairy ring may occur in any area where turfgrass is grown.
Fairy rings usually appear during spring and early summer as circles or arcs of dark-green, fast-growing grass. A ring of thin or dead grass may develop outside this circle. Fairy rings vary from a few inches to more than 50 feet in diameter, but most are 2 to 15 feet in diameter. After rain, mushrooms or puffballs (the fruiting bodies of the fairy ring fungi) may suddenly appear on the perimeter of the fairy ring.
Commonly, several distinct rings or arcs develop in the same general area. Where the rings meet, fungal activity ceases and the rings appear scalloped. Generally, fairy rings are first seen as a tuft of stimulated turf or a cluster of mushrooms. Some rings disappear unexpectedly for a year or more and then reappear, usually a foot larger in diameter.
The lush, dark-green grass of a fairy ring results from the increased amount of nitrogen made available to the grass roots by the fungus as it breaks down organic matter in the soil. If this lush growth persists into the autumn, the chances of pink snow mold infection increase. The ring of brown "dormant' grass is caused primarily by the dense, subsurface layer of white mycelia that impedes water movement into the soil, depletes nutrients, and may produce toxic levels of hydrogen cyanide.
Managing fairy rings is no easy task, but there are several tactics which can be used individually or in combination.
Prevention. Before planting a new turf area, remove tree stumps, large roots, construction lumber and other large pieces of organic matter from which these fungi obtain nutrients.
Suppression. Since fairy rings are usually less common and conspicuous on watered and fertilized turf, apply nitrogen fertilizer to the turf several times during the year. Follow local recommendations based on a soil test and the turfgrass being grown. Avoid excessive applications of nitrogen and organic matter (manures or mulches), as they tend to stimulate the development of fairy rings and encourage other turf diseases. The symptoms may be masked by core aerifying and then pumping large quantities of water (including a turf-wetting agent) 10 to 24 inches deep into the soil. A tree feeding lance or root-feeder attachment on a garden hose may he used at 1-foot intervals for a distance of 18 to 24 inches on either side of the stimulated zone of dark-green grass. Maintain the soil in a near-watersoaked condition for 4 to 6 weeks by watering every 2 or 3 days. Repeat the treatment several months to a year or more later when the rings reappear. Certain fungicides are registered as drench treatments for the suppression of fairy rings. To improve fungicide reliability and effectiveness, core aerify and irrigate the site before drenching the turf. The use of a turf-wetting agent may further aid in distributing the fungicide uniformly through the infested soil profile.
Removing the sod over multiple fairy rings, then removing soil containing the fungi from the different rings; thoroughly mixing the soil from these rings; replacing the soil; relaying the sod and watering to help re-establish the sod may help mask fairy ring symptoms for years.
Eradication. Fairy rings can be eradicated by soil fumigation. However, this method is costly and not always successful. In addition, in order to use pre-plant soil fumigants in Illinois, a Turfgrass Applicator must also be certified in the Soil Fumigation Pest Control category.