Fairy rings are a group of diseases in lawns that are caused by fungi. There are thousands of fungi that can cause fairy rings. The most common type of fairy ring can be recognised in turf, because it causes the turf to grow dark green, in a ring or arc. These measure about 75-200mm wide as an arc, and up to a metre in diameter as a ring. Fairy rings can be many years old, and will grow as long as there is turf in which to grow. There are other types of fairy rings that cause the grass to turn yellow, others that can cause a patch of stunted, reddish turf, and still others that can cause the grass to wilt and die. You may notice that fairy rings do not grow together when they meet in a lawn. This is how arcs or pieces of fairy rings are formed.
Fairy rings begin when a fungus starts growing in your turf. What causes a fungus to start growing in turf is not clear, but often grass that has a thatch layer and is growing on natural soils that receive ample moisture, will develop fairy rings. Fairy rings will grow in finely manicured turfs, sports turfs, golf greens, and unmown swards. In general, they grow at a rate of about 75-150mm per year.
The most common type of fairy ring will cause a circle of grass to turn brown and die off. There may also be toadstools growing within it. If you take a soil sample from the dead area you will find it contains the white fungus mycelium, the same as dry patch. As this soil is water repellent it is important to keep the area spiked and to apply a wetting agent to help the affected area retain moisture. Alternative remedies to deal with Type 1 are to apply a fungicide to the area or attempt to dig the fairy ring out to remove affected soil. Unfortunately, none of the recommended remedies are guaranteed to work.
This fairy ring is seen as a lush ring of very actively growing grass with or without toadstools. These rings are little understood with no known remedies. They can be masked to a certain degree by maintaining a good fertiliser and iron content.
Type three fairy rings are the simplest of them all. This is just a ring of mushrooms or toadstools that tend to be more obvious in spring, autumn or wet conditions. There is no known remedy for this type of fairy ring. However, picking, brushing, or mowing the fungi can help prevent spore production to keep further crops under control.