Fungicides for Centipede Grass and Fairy Rings

Causal Agent

• Fairy ring is a fungal disease likely caused by over 50 different fungi species, including Agricus campestris, Lycoperdon spp., Marasmius oreades and Scleroderms spp. The fungi interact with the organic matter in the soil and thatch, producing disease symptoms. This interaction causes excessive production of nitrogen in the form of ammonia and other toxic chemicals in the affected grass areas, leading to grass decline.

Symptoms

• The infection of centipede grass with fairy ring fungi results in declining grass. The disease starts with the appearance of large circles or rings of dead or green grass that measure 3 to 20 feet in diameter. Mushrooms often sprout at the outer edges of the ring and continue to grow throughout the year. Though disease symptoms may persist for several years, mushrooms usually do not appear immediately.

Recommended Fungicides

• Fairy ring is considered a poor cultural management problem for centipede grass that is easy to correct by controlling the triggering factors. Turf pathologists at the Colorado State University Extension do not consider the use of fungicides necessary or required for the control of fairy ring. The causal fungi persist 2 to 3 feet below the soil surface, and this makes the penetration of chemicals impossible. However, drilling holes to counteract this issue has also proven ineffective.

Cultural Requirements

• Reduce applications of nitrogen-based fertilizers in the soil. De-thatch grass frequently by core-aeration as the infection is most common in grasses with thick, undecomposed thatch. In lawns where fairy rings are a persistent problem, remove the entire affected grass areas to a depth of a foot and 2 feet beyond the outer edges. Replace the soil and reseed or sod the area with new grass. Keeping the affected area soaked continually for up to six weeks often helps eliminate the problem.