Fairy rings appear in any lawn, golf course or other turf areas during
spring and summer months. The rings appear as either dark green or brown
circular bands ranging in size from a few inches to 50 feet in diameter.
The fairy ring fungus grows outward from a central point at a rate varying
from a few inches to as much as several feet a year. Where several distinct
rings converge, fungus activity stops at the points of contact. As a result,
the circular shape of the original rings is replaced by a scalloped effect.
Mushrooms frequently develop in a circle outside of the dark green or brown ring during spring and fall after a period of heavy rainfall or irrigation. Centuries ago people thought that the mushrooms appeared where "fairies" had danced the night before-hence, the name, fairy ring.
Disease Cycle. The disease is caused by any one of a number of soil-inhabiting fungi. Development of the fairy rings starts with a germinating spore or a strand of mycleium and grows outward in all directions. The fungus feeds on organic matter in the soil. Fungal strands (mycelium) spread throughout the soil to a depth of 10 to 12 inches. As the fungus grows, the first visible evidence of a new fairy ring is a cluster of mushrooms (the fruiting structure of the fungus) or a tuft of stimulated dark green grass. Later, as the fungi spread outward from the point of origin, the ring-like pattern develops.
The initial tuft of dark green grass and the ring of stimulated grass that develops later result from the nitrogen released after the fungus breaks down the organic matter in the soil. Ae ring of brown or dead grass may also develop, caused by the depletion of soil moisture in the area where the fungus is concentrated. If you dig into the area of brown or dead grass, you will find a dense growth of white mycelium. Water will not penetrate this zone of dense mycelial growth.
During periods of unfavorable conditions, low temperatures and drought, mushroom production and fungal activity stops and may not be resumed for months or years.
Control. Fairy rings are very difficult to control with fungicides since the soil in the infected area is almost impervious to water. Some success has been achieved by aerating the soil and drenching the infected area with fungicide. A new fungicide, Prostar from AgrEvo USA Company, has shown good control of fairy ring.
Masking the symptoms of fairy rings is most effective. Aerating and drenching the soil with a wetting agent will help prevent the development of the zone of brown or dead grass in the area of dense mycelial growth. Keeping the fertility level of the turf high will also help to mask the appearance of the ring of stimulated, or dark green growth. Also, regular mowing removes the mushrooms, the other symptom of the fairy ring disease.