How to Manage Pests

UC Pest Management Guidelines

Fairy rings are circular or semi-cirular and can range in size from a few centimeters up to many meters in diameter. Symptoms can be variable, depending on the species of fungi, and include: 1) dark green rings with no dead turf; 2) dark green rings with a thin ring of dying or dead turf inside or outside the green ring; 3) rings of dying and dead turf with a hardened hydrophobic layer of soil that is difficult to irrigate; and 4) rings of mushrooms without a visible effect on the turf. Weeds commonly invade infested areas.

There are two types of fairy rings, edaphic (non-superficial) or lectophilic (superficial). Edaphic rings are generally formed by fungi that inhabit the soil underneath the turf. These frequently cause a hardened hydrophobic layer of soil above the areas of their active growth that prevents water penetration into the soil and often causes plant death. Rings of dead turf are frequently associated with this type.

Lectophillic rings are caused by fungi that inhabit the thatch layer and decomposed plant debris, litter, and old thatch. These rings are characterized by a slight depression of the affected areas surrounded by dark green rings of turfgrass where the fungi are breaking down plant material and releasing nitrogen. A hard hydrophobic soil layer is not associated with this type of fairy ring.

The fungus survives as a white mass of mycelia in the soil or thatch layer, or can be spread by spores dispersed by the mushrooms produced by the rings. In some cases, rings or mushrooms can appear in the turfgrass and cause no apparent damage.

SUSCEPTIBLE TURFGRASSES
All grasses are susceptible to fairy ring.

CONDITIONS FAVORING DISEASE
A dense thatch layer contributes to the availability of undecomposed matter, as does the addition of composts or other organic material that have not been fully decomposed. Also, turfgrass growing in low fertility soils with insufficient irrigation appears to suffer more damage from fairy rings than turfgrass with adequate fertility and irrigation.

MANAGEMENT
A turfgrass management program that provides proper fertilization and irrigation along with regular dethatching of the turfgrass will help prevent the development of this disease. Fungicide treatment or soil removal may be necessary if fairy ring becomes a problem.

Cultural Control
To avoid or reduce symptoms, apply adequate nitrogen and water. Symptoms of superficial rings can be masked by nitrogen applications. If fairy rings are present, aeration followed by heavy watering for several weeks may help reduce symptoms; soil wetting agents may improve water penetration. Proper thatch management and regular dethatching can contribute to a reduction in the disease. Fairy ring can be eliminated by removing the turf and root zone with the soil containing the white, cottony, mycelial mass. If fairy ring symptoms consist only of mushrooms and there is no zone of dark green grass, the mushrooms can be raked off and disposed of. While this will not weaken or control the fungus, it will improve the turf's appearance.

Treatment Decisions
Fungicide applications of azoxystrobin appear to provide good control of the disease when used properly. Flutolanil applications provide some suppression but may aid if used in conjunction with cultural practices. In extreme cases, sod removal and fumigation with methyl bromide can be performed to eradicate the fungus, but this is generally not recommended.

Common name	Chemical class
Many of these products are available for use by licensed applicators only and cannot be used by home gardeners.
A.	AZOXYSTROBIN	QoI (strobilurins)
B.	FLUTOLANIL	Oxathiin/Carboxin
C.	METHYL BROMIDE*	Fumigant (multi-site)
	COMMENTS: Complete soil sterilization. Use 400 lb/acre, 1 lb/100 sq ft, or 10 lb/1000 sq ft. California is currently phasing-out methyl bromide use.
*	Permit required from county agricultural commissioner for purchase or use.

PUBLICATION

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
Diseases
F. Wong, Plant Pathology, UC Riverside
M. A. Harivandi, UC Cooperative Extension, Alameda Co.
J. Hartin, UC Cooperative Extension, San Bernardino Co.
Acknowledgment for contributions to the disease section:
M. E. Grebus, Plant Pathology, UC Davis

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