Fairy ring is the common term used to describe circles of mushrooms, green circular bands of turf, or rings and arcs of dead plants in a turfgrass stand. Fairy ring symptoms are caused by numerous species of soil and thatch inhabiting fungi of the Basidiomycetes family. Many of these fungi produce mushrooms or puffballs (basidiocarps). They reside in the thatch or deep in the soil and decompose organic matter as a food source. These fungi may produce a dense network of mycelia which repels water, making the soil hydrophobic (water repelling) and causing localized dry spot. Fairy ring fungi grow radially outward from their point of initiation and release nitrogen from the degradation of thatch or other organic matter. Fairy ring symptoms may be observed at any time of the year, but are often observed in hot, dry weather, especially in nutrient deficient turf.
Three types of Fairy ring have been described based upon symptoms. Type 1 symptoms are fungi that cause a ring of necrotic or dead turf, with an inner or outer ring of dark green grass stimulated by nitrogen release. Type 2 appears as rings of dark, lush grass which may or may not produce fruiting bodies. Hydrophobic conditions of the soil and/or localized dry spot may be associated with both Type 1 and Type 2 fairy rings. Symptoms of Type 3 are limited to rings of basidiocarps, with no visible effect on turfgrass growth. Fairy ring symptoms have been treated with a combination of cultural practices and chemical applications (fungicides, wetting agents) in various configurations; consistent and reliable control has not been achieved.
- Provide a steady and consistent water supply, avoiding regular cycles of moist/dry soil.
- Keep affected area very moist by frequent injection of water into and through the rings in dry weather. Deep punctures through the soil surface and addition of wetting agents enhance this approach.
- Prevent the accumulation of thatch as this deprives the fungi of a food source and slows their growth.
- Symptoms can often be masked by a combination of deep irrigation and carefully timed nitrogen applications. This promotes turf growth around and within the rings to match the growth of the stimulated rings. Iron applications can also be used to promote dark, green growth.
- Cultivation or mixing of soil can be effective. Soil must be thoroughly cultivated and soaked with water, then left unplanted for a period of time. Turf may be removed and restored as sod.
- Rapid eradication by soil replacement is an extreme but sometimes effective technique. The sod and underlying soil is removed to a depth of 8-30 inches, the soil replaced with clean, preferably sterilized topsoil, before turf is reestablished.
Management with Fungicides
Applications of fungicides or wetting agents produce limited and inconsistent results. Numerous species of fungi produce fairy rings; some are not sensitive to registered fungicides or are too deep in the soil to be reached. Success requires that the fungicides and/or wetting agents be well distributed throughout the soil by a combination of thorough irrigation and physical disruption of the soil surface.
For a listing of fungicides currently labeled to manage this disease, refer to the Disease Management chapter of UMass Extension's Professional Guide for IPM in Turf for Massachusetts.
Written by: M. Bess Dicklow