Fairy Rings - Lawn Disease

A fairy ring is a circular ring seen most often on lawns or grassland. They appear as a ring shaped brown or dead patch often with a bright green strip of grass at the inner and outer edges of the ring. They are caused by a fungus growing and feeding just below the surface of the lawn. Often a fairy will start producing mushrooms above ground any time from July onwards which will confirm its presence.

They start small and grow outwards at a variable rate depending on temperature, situation and local conditions, they can grow at several inches to several feet per year.

They are unsightly, but not not a terminal problem for your lawn, how much of a problem they are of course depends on how unsightly you find them. They acquired their common name because they were thought to be the result of fairy-folk dancing in a circle overnight

The fungus does not directly attack the grass plants. Its mycelia (threads of fungal growth) penetrate the soil to 3 to 12 inches. The mycelia are hydrophobic (they shed water) and grow very densely. The grass immediately above this mycelial mat eventually dies from lack of moisture.

The good news about fairy rings is that the mushrooms produced are often of an edible type, any one of three species (this applies to the UK - but check with a fungus ID book before you try them!). The bad news about fairy rings is that they are very difficult to remove.

How do I get rid of a fairy ring?

The short answer is - with great difficulty.

You could dig up and replace the soil to 12-18" depth and 12" either side of the ring (throw the old soil away - down the tip). - If any of fairy ring fungus contaminated soil or sod is spilled on healthy grass it could start the fungus off again in that location.

You could try to sterilize the soil with Armillatox - after digging and burning the turf and soil to a depth of 9". I'd wait to see the mushrooms first though to confirm that you do have a fairy ring before you begin this.

Fairy rings can be controlled with a copper based fungicide or one based on benomyl, eradication by this means is unlikely - a wetting agent added to the fungicide (a little washing up liquid) and / or holes made with a fork or aerator will help the water penetrate as it has a tendency to just run off. Remove the mushrooms as they appear whether you eat them or not, to prevent the problem spreading. Feeding the lawn also helps to disguise the problem which is usually more obvious on an underfed lawn.

It is possible to fumigate fairy rings. This is a major process and requires turf to be removed two feet on the inside and outside of the ring. The soil is then loosened to a depth of 6 to 9 inches and a soil fumigant applied. The treated area is covered with a plastic sheet and left for 2 weeks or more depending on the temperature. Fumigants are powerful chemicals and can burn through clothing, skin and lungs, needless to say they should be used with extreme care or a professional contractor hired. They are not exactly an environmentally friendly approach as just about everything else in the soil is killed as well.

Kill off or dig up the turf and then rotavate the fairy ring infected area in several directions until the soil is thoroughly mixed. This uses the self-inhibiting metabolites produced by the fungi. Mixing these materials together will prevent the regrowth of the fairy ring, it also works for several rings that meet together as the chemicals from each inhibit the others.

How can I avoid getting fairy rings

Fairy rings form most often in soils with high organic matter, or in lawns with a thick layer of thatch (dead grass, moss and clippings between the grass blades and the soil). Scarifying to remove thatch and core aerating to help its breakdown are helpful as they deny the fungus its foodstuff.

When preparing soil for seeding or turf, any large sources of non-composted organic matter such as tree stumps, wood building materials, etc. should be removed as they provide a food from which fairy ring fungi can spread.

Good turf management goes a long way to avoiding fairy rings

How to spot a fairy ring

Fairy rings most often put in an appearance once spring is under way about May time. They may initially be egg shaped and not meet to form a ring. As time goes by they expand outwards but the same thickness (around 15cm, 6 inches) like a smoke-ring. You may see it as a double ring of dark green grass that produces a crop of toadstools.

Sometimes fairy rings may meet up, but they never overlap, chemicals produced by the fungi inhibit the growth of the others, so they touch and stop.

Chemical fungicides

Rose clear combined fungicide and insecticide Make sure you shake the bottle well before use as the active ingredients often settle to the bottom - take it from me I learned the hard way!

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