Fairy rings are common in all types of turf or grassland.  They are often associated with ribbons, arcs or rings of stimulated grass growth and may also be associated with zones of dead grass or fruiting bodies (mushrooms) depending on severity and the causal fungus.

Whilst the fungus itself is not thought to have much direct effect on grass growth, secondary effects are visible from the stimulation of grass growth brought about by the degradation of organic matter in the soil by the fungi and the waxy, hydrophobic substances left behind that can affect grass growth at the surface.

Many fungal species can cause fairy rings but growth follows a similar pattern.  Rings start from an infection point and then grow outwards radially sometimes being disrupted into arcs or ribbons of growth over time.  Growth is slow and rings expand over many years and the fungus itself can establish a doughnut like zone of growth in the soil which can penetrate to some depth (30 -60 cm or more) depending on soil type and environmental conditions.

All fairy rings are caused by basidiomycete fungi.  These form a large and variable class of related fungal species, so for practical purposes fairy rings are identified by type

Fairy Rings Type 1:

The disease typically appears as a ring of dead or stressed turf, bordered on both the inner and outer edges by a band of stimulated grass growth.

New rings can appear just as green ‘patches’. The fungus can be identified by taking a soil sample from the leading edge of the ring – it has a characteristic ‘musty’ smell.

Fairy Rings Type 2:

Many different types of fungi are associated with the cause of Type 2 fairy ring, these include: Agaricus spp. and Lycoperdon spp.  Rings of stimulated grass growth are seen normally without fruiting bodies.

It is rare that excessive damage is caused to the turf, although the stimulated growth obviously affects the playing quality of the affected surface.  Lush grass growth can also encourage secondary infection such as Fusarium patch (Microdochium nivale).  Symptoms are normally seen during the summer and autumn.

Fairy Rings Type 3:

Type 3 rings are made by many different types of Basidiomycete – including: Hygrophorus spp. and Psilocybe spp.

There are no distinct effects on the turf surface except when the fruiting bodies are present (normally during the autumn) where these form rings of toadstools or puffballs.  Until this time such rings rarely have any effect on the quality of the sports turf surface. 

Superficial Fairy Rings:

Superficial fairy rings are regularly seen in the summer and autumn.  A large number of non-sporing basidiomycete fungi such as Coprinus spp. are capable of producing superficial fairy rings.  Symptoms include rings, arcs, or ribbons of pale yellow grass.  If the thatch layers of the infected areas are investigated, fungal mycelium is normally present at the turf surface and has a distinct characteristic musty smell.  Turf around the affected area can sometimes show stimulated growth as mycelium breaks down organic matter to release readily available nitrogen.   Apart from stimulated growth, surface conditions are not severely affected, although aesthetically such surfaces are not normally acceptable on golf or bowling greens.  However, annual meadow grass can be severely affected due to the shallow rooted nature of the species.  In this situation the deeper-rooted grasses such as Bent (Agrostis spp.) and Fescue (Festuca spp.) are better able to sustain growth in the hydrophobic conditions due to their more robust root systems.

Control of Fairy Rings:

As fairy rings establish deep within the soil substrate, few if any traditional fungicides offer any useful level of control.  Integrated control measures are essential to manage the impact of  fairy ring fungi.  Complete eradication is difficult so management techniques can be adopted to lessen the impact of the problem.  Consideration can be given to:

• Judicious use of nitrogen to stimulate growth of the surrounding grass so that it will mask the grass ring stimulated by the Fairy ring.
• Sulphate of iron can also be used to darken the sward and mask the ring.  This can be useful where excessive additional growth needs to be avoided to avoid further impact on the playing surface.
•  The use of wetting agents (either as spot treatments or irrigation aids) can help mitigate the effects of the dry zones within the fairy rings and help alleviate symptoms.
• Specialist wetting agents like Clearing are especially formulated to hydrate the waxy deposits created by fairy ring fungi and offer additional benefits to help create conditions to allow the fairy ring to break down naturally.
• As a last resort fairy rings can be dug out and physically removed.  This involves removal and replacement of soil in the vicinity of the ring (and a buffer zone surrounding this area) bearing in mind the ring may extend to some considerable depth.