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.