Mysteriously cropping up on residential lawns and golf courses, fairy rings can be unsightly and persistent. This fungal damage affects all varieties of turfgrass and is difficult to control once visible, so prevention is key.
What is a fairy ring?
Varying in size from a few inches to several feet in diameter, fairy rings originate from one of more than 50 different species of fungi in the class Basidiomycetes. Evidence of the fungus appears as brown or green circles or rings of mushroom.
The fungus doesn’t attack turfgrass directly, but causes damage by affecting the soil as it feeds on decaying organic matter in the thatch layer or in the soil from rotting tree roots, stumps and buried lumber scraps.
What causes fairy rings?
The fungi spread through spores carried by wind or water. Fairy rings often develop in poor soils or in heavy thatch, proving particularly troublesome in sandy soils. In manicured commercial lawns and golf courses, the fungus may infiltrate from native grasses nearby.
Dark Green Rings
Rings of dark green grass are a side effect of nitrogen being released as the fungi break down organic matter in the soil. The nitrogen feeds the grass, encouraging it to grow faster and darker in color.
The brown rings occur when the fungi become dense, repelling water from the soil, depleting nutrients, and emitting toxic levels of hydrogen cyanide, ammonium nitrogen and other compounds. The turfgrass roots can’t get the water and nutrients they need, leaving a circle of dead grass.
Mushroom or Puffball Rings
Fairy rings reproduce through a circle of mushrooms or puffballs, which often appear after extended rain. They should be removed manually to minimize spread of the fairy ring fungi.
Fairy Ring Prevention
- Aerate in the fall for cool season grasses, spring for warm season.
- Dethatch warm season turfgrasses in late spring or early summer if the brown layer reaches half an inch or more.
- Avoid over or under watering grass, which causes stress and may invite fungi.
- Test soil regularly for balanced fertility. More robust turfgrass leads to fewer issues.
- Remove stumps and roots from fallen trees. Remove lumber waste, roots and other organic matter before installing new sod.
- Apply preventative fungicide to commercial properties and golf courses, twice in spring when temperatures consistently remain above 55°. Fungicides have been shown to be more effective with higher water application rates of four gallons per 1,000 square feet
Fairy Ring Control
Because they are caused by such a wide variety of fungal species, fairy rings are difficult to control chemically. Course superintendents and grounds managers may need to experiment to find an effective treatment. Fungicides may offer temporary results, but the circles tend to recur as long as the decaying material remains in the soil or thatch.
These cultural tips will help remedy fairy rings.
- Grow healthy turfgrass. Follow all preventative measures above to help strengthen turfgrass.
- Topdress area with high quality sand, especially on golf course greens.
- Aerate and apply soil surfactants for brown rings. Apply heavy irrigation to affected areas without overwatering surrounding grass.
- Add nitrogen fertilizer to mask green rings during the turfgrass variety’s main growing season—spring and fall for cool season grasses, late spring and early summer for warm season.
- Remove mushrooms or puffballs carefully by hand to avoid spreading spores. Protective clothing and a mask are recommended.
- Remove turf from the affected area. This is an extreme and labor intense option, but may be necessary if rings return year after year.