Frequently, just behind the dark green band is an area of sparse, brown, dying grass caused by lack of water penetration and by hydrogen cyanide secreted by the fairy ring fungus. Often a circle of mushrooms will develop around the edge of the infected area after wet weather or heavy watering. The ring of dark green grass is caused by a release of nitrogen in the soil, as the fungus breaks down organic matter. Weed invasion is common. All turfgrasses can be affected by fairy ring, but the effects may be fewer on grass species with long stolons.
Symptoms are most obvious on nitrogen-starved turf.
Fairy ring develops most frequently in soil high in organic matter such as undecomposed thatch. Apply adequate nitrogen, but do not overfertilize. Remove thatch periodically. Aerate soil to improve water penetration, and apply water heavily in holes every day for 3 to 10 days. Removing the turf, digging out and discarding the infested soil, and replacing it with fresh soil may be possible for small-infected areas.