Fairy ring in a lawn
Fairy rings are visible as rings of green, vigorous grass, often with dead patches, that sometimes produce small brown mushrooms as well. The ring is caused by a fungus in the soil. Fairy rings are usually only a problem on good, long-established lawns. Control is difficult. Applying fertiliser, except on the ring itself, masks the problem, and is the best solution in a domestic garden.
Inkcaps and other toadstools arise from bits of rotten timber and other organic material in the soil. When this material finally rots away the toadstools no longer appear. Toadstools are not, strictly speaking, a lawn disease and can be crushed or simply brushed away.
Other diseases sometimes cause yellow, brown or dead patches in the lawn. These are most serious on fine grass mixture and damp, starved lawns. If there is a reddish tinge, caused by red thread disease, on the dying grass, or white growth caused by fusarium, when examined closely, a spray with a systemic fungicide will help.