The killing or dark-green reaction sometimes results from hydrogen cyanide (HCN) production, which in high concentrations is lethal to grass. Mushrooms may appear periodically. The soil is permeated by a white fungus growth (mycelium) and is usually very dry.
Fairy rings spread outward a few inches to a few feet per year. Where the grass cover is not uniform, the rings may not be completely circular. As the fungus spreads, it consumes a portion of the organic matter in the soil. The fungus prevents the penetration of water into the soil, and the grass is damaged or killed from drought.
In developing your lawn, do not bury roots, stumps, branches, and other large pieces of organic debris. These provide a food source for these fungi. If the only effect of the fairy ring is a stimulation of growth in rings, fertilization usually takes care of the problem. Removing cores of soil (aerification) aids in water penetration.
Topdress holes with fresh soil free of organic matter. Some experts recommend removing the soil 18 inches on each side of the outer stimulated area 1 foot deep. In removing infested soil, do not spill it on adjacent healthy grass. Fill trench with fresh soil and reseed or resod. Chemical control is generally not very effective because the fungus grows so deeply into the soil.
For more information on this turf disease please use this link to the University of Arkansas Turf Website: