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Fairy rings

Maramius oreades

Fairy rings can be caused by many different species of fungi but the mushroom fungus, Maramius oreades, is the most common organism responsible for fairy rings in both turf grass and pasture. This fungus is usually present in most soils but the rings it causes seem to be more noticeable and damaging in drier locations, with lighter soils and lower fertility.

Signs and Symptoms

The first sign of fairy rings may be a ring of mushrooms followed by rings of darker green grass with an inside border of dead grass. The bands of affected grass can be 2-4 inches {5-10 cm) wide and can form circles or arcs measuring 1-6 feet {0.3 - 2 meters) in diameter. Small tan­ coloured mushrooms usually develop on the outer border of the ring or arc especially during rainy weather or later in the season. The mushrooms are the fruiting body structures of the fungus

These mushrooms should not be confused with the cluster of mushrooms that commonly appear in the lawn after heavy rains. They should also not be confused with mushrooms that reappear in the same spot since these mushrooms are usually associated with decaying organic matter, like that of an old tree stump or root system that may be present below the lawn area.

Control

The best method of control for fairy rings in the lawn is to begin with proper care and maintenance of the lawn so that it will be less susceptible to the fairy ring fungus, along with a plethora of other diseases and weeds that can be combated with a healthy lawn.

A simple method of control is to use a garden fork, a screwdriver, a piece of rebar or any other tool that will be able to make a hole about 10 inches (25 cm) deep which will allow water and fertilizer to infiltrate past the white mycelium growth which occurs anywhere from 1-8 inches (2-20 cm) below the soil surface. These holes should be spaced about 4-6 inches {10-15 cm) apart and should run throughout the infected ring and throughout the centre of the ring or arc.

A teaspoon of liquid dish detergent in a gallon of water should be sprayed on the surface before watering which will act as a wetting agent against the hydrophobic mycelium, helping the water soak into the infected soil. This area should then be soaked every day to every second day for at least a month, especially if the fairy ring has progressed to the dried grass stage.  Nitrogen fertilizer should also be applied to the area at the recommended rate to improve the condition of the grass and reduce the growth of the mycelium.
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