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 Managing fairy ring can be time consuming and costly, and sometimes it can be hard to spot. Photo: Leonard Burkhart It’s not often that a plant disease is associated with dancing fairies, but that’s the case with Fairy Ring.
“The formation of dark green or dead turf rings and the seemingly sudden appearance of a circle of mushrooms gave rise to the lore that fairies danced inside the rings,” says Deborah D. Miller, plant pathologist and senior diagnostician for the Davey Institute.
But there are no fairies dancing in these rings. It’s a much more practical explanation. “Fairy rings are caused by a group of soil-inhabiting fungi in the class Basidiomycetes,” she says.
“These fungi grow in turfgrass where there is an even distribution of nutrients in the soil or thatch and are associated with sandy soils.
“When fairy rings develop, three basic things can be done: excavate the affected turf and soil area, apply fungicides or appreciate their aesthetic beauty.”
Miller says multiple season observations need to be made before a type of fairy ring can be assigned because not all symptoms may be apparent in one year.
Ring shape (i.e. circular patch, wavy-shaped) and size vary according to the fungal species. All turfgrass species are affected and scientists have classified these rings into three visual types based upon symptoms.
Type 1 rings have a dead zone of grass with one or two zones of darker green grass growing adjacent to the circle. Type 1 rings are considered the most serious type of fairy ring.
Type 2 rings form a single ring of dark green, stimulated grass. No dead zone of grass is formed. Basidiocarps may or may not be produced. When the weather is hot and dry, Type 2 rings may develop into Type 1 rings. This may induce locally dry spots and accumulations of toxic levels of ammonium.
Type 3 rings often have no apparent effect on grass growth. Basidiocarps appear in a ring or an arc.
“Most fungi produce basidiocarps in mid-to-late spring or in late summer to early autumn, following periods of rain or heavy irrigation,” Miller says.
Mycelium – threads of the fungus – can penetrate into the soil to a depth of 8 inches. The fungi expand outward until something like a lack of food, a sidewalk, flower bed or another fairy ring impedes its growth, Miller says.
“Multiple fairy rings can become established in the same area,” she says. “However, when the rings intersect, they do not overlap, but produce a scalloped pattern due to an antagonistic effect.”
While you might think fairy ring is easy to spot, Miller says clusters of mushrooms growing in the turf may not be the beginning of a fairy ring, but could be colonizing buried organic debris.
“A ring pattern of damage from winter injury and/or snow molds can mimic fairy rings,” Miller says.
Managing fairy ring can be a time consuming and costly activity, Miller says.
You should remove woody roots and limbs prior to turf site construction.
Avoid using soil mixes containing a high composition of undecomposed organic materials, and reduce thatch accumulation by vertical cutting. Because some species are poisonous, remove basidiocarps where children or pets are present.
Where basidiocarps are considered a nuisance, remove by raking or mowing, Miller says. To mask the dark green rings of some fungal species, apply a light application of nitrogen or iron.
“However, this can increase the incidence of other species, such as Tricholoma sordidum,” she says. “Core aerification and watering can reduce the hydrophobic effects of the mycelium in the root zone. Physically remove turf and soil from affected areas.”
Miller says, fungicides are effective in managing some fairy ring species fungi.
“Soil drenches should penetrate to a minimum depth of 4 inches to reach the mycelium growing in the soil,” she says.
The following active ingredients are currently labeled for fairy ring control: azoxystrobin, flutolanil, hydrogen dioxide, pyraclostrobin, polyoxin D; triadimefon, azoxystrobin + propiconazole.
“Using a surfactant or wetting agent can increase efficacy of the fungicide,” Miller says.
The author is an associate editor at Lawn & Landscape. Send him an e-mail at bhorn@gie.net
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