February 23, 2021
It might sound pretty, but fairy rings of mushrooms in your lawn is a red flag for fungal disease! This particular disease is caused by a basidiomycotous fungus. The fungus is saprophytic and can only survive by feeding on dead or decaying plant matter. Doesn’t sound so magical now, does it?
Fair Rings Life Cycle
Early on in the life cycle of the fungus, you might not see much damage to your lawn. In fact, the fungus can be present for a few years before there are any outward signs or symptoms. During this time, the fungus is developing from a tiny particle in your soil into an entire mass that spreads outward in a circular pattern. The first obvious sign that fairy ring is present in your lawn is a ring of mushrooms that pop up, seemingly overnight. These ‘fruiting bodies’ are actually the edge of the fungal mass – and the most active portion of the fungus which is underneath the soil. Fairy rings can range in size from 3’ in diameter to 20’, depending on how much organic matter is present to feed & spread the fungus.
In addition to the mushrooms, the edge of the ring may also show as a deep, dark green ring of grass. Because the fungus is actively breaking down plant material, it is producing nitrogen, which essentially is fertilizing the grass.
Fairy rings are common on golf courses & sports fields due to the high organic matter content (thatch build up due to high fertilizer & frequent mowing), but they also pop up in locations where trees & stumps used to reside – feeding off of the decaying organic matter.
After mushrooms or dark green rings have developed, the often most distressing symptom will appear: a ring of dying, wilted, and brown grass. As the fungus grows, it produces a fungal mat of mycelium – which hardens and becomes hydrophobic. As water is not able to pass through this mycelium layer, the grass dies on the outer edges of the ring due to no water penetration.
Treatment and Control
As always, a healthy lawn is the best defense against soil-borne fungal diseases. If fairy rings have already popped up in your lawn, control can prove to be difficult. But, here are some ways to counteract the effects of fairy rings:
- To mask the dark green ring, apply fertilizer to the rest of the lawn to help even out the color. (This is a cosmetic fix, and will not reverse the fungal effects.)
- If grass has already died, water penetration needs to be improved. Aeration can help, followed by drenching the affected soil with a wetting agent.
- Remove excessive thatch and aerate in order to eliminate the excess organic matter that the fungus needs to survive.
- If fairy rings & grass death are pretty severe, the area may need to be stripped and re-sodded. But, be sure to remove the source of food for the fungus, like decaying tree stumps or roots.
If you are concerned that you might have fairy rings in your lawn, contact our lawn health care team for help.
Posted: February 23, 2021