Fairy Rings - fungal lawn disease

A Fairy Ring is a lawn disease that is caused by certain types of fungus. The effect and appearance of a fairy ring can vary depending on what type of fungus is causing the problem but they generally form one or more of the following:

  • A ring of toadstools on the lawn when there is sufficient moisture
  • One or more rings of deep green, lush looking grass
  • Areas of dead / yellowed grass or bare soil between the lush rings.

Some may find the appearance of the toadstool only fairy rings attractive, especially in a grassy woodland environment. They can however cause serious problems on a more formal lawn where the effects of dead grass, bare patches and uneven colouring and grass growth can significantly impact on a lawns appearance.

What causes fairy rings to appear?

Fairy rings are the result of certain types of fungi forming fungal threads in the soil that the turf is laid on. The most common fungus to cause fairy rings is Marasmius Oreades. The threads that form are very densely packed and normally reach down so soil depths of around 20cm although they have been known to reach up to about 40cm. The effect of these tightly packed threads on the lawn is to effectively starve the grass roots of both water and nutrients by inhibiting root growth and preventing water uptake. The resulting lack of water will effectively kill the grass in badly effected areas of the lawn and so yellow / brown patches can appear. Bare patches of soil may appear on the lawn where the grass has been dead a long time.

How can a Fairy Ring be treated?

Once a fairy ring is established on your lawn they can be very hard to remove. To try and prevent the spreading of the fairy ring you can carefully cut any of the toadstools off at their base and place them in a container. Once you have collected all the toadstools burn them. Do not put them on the compost heap or redistribute them over the lawn or soil as they contain spores that will further the growth of the fungi. Burning the toadstools will destroy the spores.

Another tip for preventing the spread of a fairy ring is to mow the fungal infected area independently of the rest of the lawn. That is make sure to collect the grass clippings seperately and again burn them rather than adding them to the compost heap as they can contain the fungal spores. After mowing the infected section of the lawn you can use a fungicide to clean down the mower to kill any spores on the mower that might be transferred to a healthy section of the lawn.

Getting rid of fairy rings can be tricky. You may be able to use a fungicide containing dichlorophen that is suited for applying to lawns. Make sure to check with the manufacturers instructions for application and usage guidelines. You don't want to kill off all flora and fauna!

One labour intensive way to restore your lawn is to literally replace the infected part of the lawn by digging up the turf from the centre to 18 inches outside the infected area. Once the turf is up discard it and then dig up the infected soil that contains the fungal threads to a spades depth. Discard this soil (not on the lawn and preferably at a waste disposal site) and then fill the area with fresh uninfected soil and re-sow or re-turf the now bare area of lawn.