Occurrence: Rings or arcs of deep green grass as well as unhealthy or dead grass. Rings may vary in size from a few inches to 200 feet or more indiameter with an annual radial growth of 3 inches to 19 inches depending on grass, soil and weather conditions. Mushrooms may appear in the rings or arcs. Mycelium in the soil is evidence that the fungus is present, but does not mean the fungus is active.
Under certain conditions and with certain fairy ring fungi, a ring of dead grass develops. Some fungi kills root cells other fungi create a water-impervious layer resulting in drought-stress. Once the soil under the mycelium layer becomes dry it is very difficult to wet and the roots of the grass plant die. Several years may pass without the production of mushrooms or evidence of rings. Lawns subjected to drought stress are more susceptible to problems from fairy ring.
Conditions Favoring Disease Development: Fairy ring develops mostly in soils high in organic matter, or in lawns with thick thatch. Soil with presence of mycelium have the potential to develop the disease.
Control:Core aerate to encourage thatch breakdown and allow better water penetration. When rings appear, poke holes with aerator or pitchfork 6” deep along rings and soak the areas with water. Spraying dish soap and water mix on rings can also help loosen the bound-up soil caused by the fungus allowing better water penetration.
A second option involves removing the soil one foot deep and wide enough to extend at least two feet on either side of the fairy ring. Replace this soil with non-infected soil. NOTE: If any of the fairy ring contaminated soil or sod is spilled on healthy grass during this process, the fungus may start over in that location.
A third option involves killing the sod and then rototilling the fairy ring infected area in in several directions until the soil is thoroughly mixed. Mixing the soil may prevent the regrowth of the fairy ring. Some success has been reported with this method.
When preparing soil for seeding or sodding, remove any large sources of non-composted organic matter such as tree stumps, wood building materials, etc. These provide a food base from which fairy ring fungi can spread.