Causal Fungi: Over sixty different species of basidiomycete fungi
Host Grass: All turfgrass species
Cause and Symptoms: Fairy ring is a common and chronic problem of turfgrass in Texas appearing in many turfs including home lawns, golf courses, and sports fields during spring, summer, or fall. Three characteristic symptoms identify fairy ring from other diseases: (Figure 1) Stimulated growth and dark greening, (Figure 2) Necrotic rings or arcs, and (Figure 3) Mushrooms.
There are certainly varying degrees of these symptoms. Fairy ring flourishes in the thatch layer containing a high level of organic matter. As mycelia advances in the soil, they release digestive enzymes, which decompose organic matter into nutrients. These nutrient molecules are taken up by the fungus and by adjacent plant roots; this often leads to the grass next to the ring being dark green because of extra nitrogen released from decomposed organic matter. Brown and necrotic rings develop when fungal mycelium forms a hydrophobic layer, preventing water from reaching turfgrass roots and resulting in drought stress. Often after rainfalls, mushrooms can appear overnight. Particularly on highly maintained turfgrasses, fairy ring can cause severe symptoms of wilting or plant death in ring or arcs that range 4-12 inches wide and up to 30 feet in diameter.
Control and Management: Key cultural practices that reduce the occurrence and severity of the disease include the following:
- Vertical Mowing
- Extra watering
The best cultural practices manage thatch and reduce organic matter in the soil. Dead tree stumps and roots under the ground should be removed. Otherwise, this organic matter will keep promoting the fungus to thrive and produce fairy ring symptoms for years. If a big tree is removed from a lawn but its root is left underground, fairy ring can show up in certain favorable environment conditions for more than 10 years.
Mushrooms can be readily removed by mowing off for the safety of pets or small children. Do not consume mushrooms. Fertilization can mask dark green fairy ring symptoms by balancing growth and color in the rest of the turf. Aeration, drenching with extra water, and using a wetting agent will prevent and remediate development of the zone of brown or dead grass in the area of dense mycelial growth.
Fairy ring control with fungicides is difficult and only recommended for highly managed turfgrass. Fungicide applications have been shown to be unreliable due to difficulty of chemicals in penetrating into the soil and contacting the mycelium to be effective. Better success has been achieved by drenching with fungicide followed by aeration. Preventive application with a rotation of multiple fungicides is recommended in areas with a history of infection.
Content edited by:
Young-Ki Jo (email@example.com, Professor and Extension Specialist)
Raleigh Darnell and Paul Goetze (Extension Assistant)
Department of Plant Pathology & Microbiology, Texas A&M AgriLife Extension Service
September 31, 2021