Summer for fairy ring

Fairy ring is a persistent and problematic problem on turf. Symptoms are often most prevalent from spring through fall with symptom severity high in the summer.  Symptoms appear as circular or arc shaped rings where the outer edges or rings are darker green than the surrounding turf. Sixty fungi are associated with causing fairy ring. These fungi are known asbasidiomycetes that produce mushrooms or puffballs as their fruiting structure. Fairy ring for the most part does not attack or parasitize the turfgrass plant directly, but indirectly injures or kills the turf through their growth through the soil.

Fairy ring is a dynamic problem in that the rings continue to grow in diameter from year to year. The growth rate of the fairy ring approaches 1.2 meters a year. A ring is classified, based on symptoms, as Type I, Type II, or Type III fairy ring. Type I rings exhibit a zone of dead grass, one or two zones of darker green stimulated grass and basidiocarps (i.e. mushroom, puffball). Type II fairy rings exhibit a single ring of darker green stimulated turfgrass and basidiocarps. Type III fairy ring appears as a circular arrangement of the basidiocarps.

Symptoms of fairy ring may change over the course of the year. Type III symptoms are most often associated with cool wet conditions found in spring, while Type I and Type II are most often associated with hot dry conditions of summer. With Type II symptoms, inspect the outer margins of the rings for any signs of Type I, because the turf can rapidly wilt and die once Type I symptoms appear.

Upon closer examination of the soil or thatch under the rings will often reveal the presence of white mycelia caused by the fairy ring fungus. The white mycelia are the major cause of the hydrophobicity (water-repellent) of the soil and/or thatch associated with Type I fairy ring symptoms. The location of the white mycelium characterizes the fairy ring as either edaphic or lectophilic. Edaphic describes the fairy ring fungi that mainly inhabit the soil; and lectophilic describes fungi that mainly inhabit thatch and leaf litter.

In addition to the hydrophobic soil conditions that develop underlying the rings, detrimental ammonium levels can accumulate causing severe stress to the root system of the plant. The combination of hydrophobic soil conditions and excessive ammonium levels account for the indirect injury that occurs to the turf from the basidiomycete fungi.

Cultural Control:

Cultural control measures vary depending on whether the symptoms are Type I or Type II. Type II symptoms can be masked with applications of nitrogen or iron. Care needs to be taken not to over-fertilize, especially during summer stress months, resulting in the occurrence of more severe diseases. Reducing or managing the thatch level should be part of a regular management program.

Type I practices are more intensive when compared to Type II. Practices should be targeted to reduce the hydrophobic thatch/soil condition and reduce ammonium levels in the soil. Hollow-tine coring, water-injection, applications of wetting agents (ex. Qualibra) and heavy irrigation are some practices that are effective. Regarding heavy irrigation, target the fairy rings specifically with hand-watering so not to overwater the surrounding turf.

Chemical Control

Preventative applications are the most effective control measures for fairy ring. One recommendation is to make two applications 21 to 28 days apart with Heritage^® fungicide in the spring when soil temperatures reach an average of 13 °C. As part of the program, regular applications of wetting agents throughout the season should minimize the appearance of Type II and Type III fairy ring symptoms.

Syngenta recently launched updated recommendations as part of their Fairy Ring Prevention Assurance. 

Curative treatments of Type I and Type II are more challenging and the results may vary. The steps for controlling Type I and II fairy ring are

1. Hollow-tine core the fairy ring infected area to facilitate the release of ammonium gas and aid in water penetration into the soil
2. Apply a wetting agent to aid water and fungicide penetration down into the soil
3. Apply the recommended fungicide in at least 2 gallons but preferably 4 gallons per 1000 square feet. Irrigate following treatment to wash the fungicide off the leaves down into the soil.​​​​​​​