Fairy rings

Name: Fairy rings

Alias: Fairy ring disease.

Distribution: Found throughout the country.

Hosts: All turfgrass species.

Characteristics: In spring and early summer, on moist lawns, rings or arcs of dark green grass or rapidly growing (overgrown) grass may appear, with concentric circles of weak, dormant, or dead grass occasionally appearing inside. Sometimes secondary rings of overgrown grass appear within the ring formed by dead grass.

When the soil is dry, especially in autumn, the outermost ring of overgrown grass may disappear, causing the grass in the outermost ring to die while the grass in the inner rings grows vigorously. In mild weather, after rainfall or heavy irrigation, mushrooms may grow on the outer ring of overgrown grass. Fairy rings appear suddenly.

Based on symptom expression, fairy rings can be divided into 3 types: Type one has 1 ring of dead grass and 1 or 2 rings of dark green overgrown grass. Type two has only a ring of dark overgrown grass, with mushrooms growing within the ring. Type three has 1 ring of mushrooms, with essentially no obvious effect on turfgrass growth. In any case, the mushrooms are only temporary.

Pathogen: Fungi. More than 50 species of fungi in over 20 genera of Basidiomycetes. The most common include Leiota, Lycoperdon, Marasmius, Scleroderma, and Tricholoma. Among them, the fairy ring caused by M. oreades is the most common.

Occurrence characteristics: Initially, diseased grass generally forms a small circle or a cluster of mushrooms appears. The diameter of the fairy ring increases by several cm each year, sometimes reaching 0.5 m. As the fairy ring fungus grows rapidly outward from the ring, the old fungus inside the ring gradually dies, and consequently the grass in the inner ring grows vigorously. In type two fairy rings, vigorous growth of both inner and outer ring grass occurs simultaneously, with no dead grass band. Generally, the disease is most severe on sandy loam soil, low-fertility soil, and soil with insufficient moisture. Shallow irrigation, shallow fertilization, thick thatch layer, and drought all favor the occurrence of the disease.

Control methods:

1. Ensure adequate soil moisture and maintain the soil in a very moist state.

2. Soil fumigation, which should be carried out after removing the diseased turf. Replacing diseased soil is a method to rapidly eliminate the pathogen. Soil cultivation and mixing involves cutting out the entire piece of turf and removing it, then using a heavy rotary tiller to cultivate and mix the soil. After cultivation, the area is best soaked with water to promote the growth of antagonistic microorganisms against the fairy ring fungus.

3. Remove the thatch layer promptly, irrigate deeply and thoroughly, and pull out mushrooms.

4. When necessary, methyl bromide or formaldehyde can be used to fumigate the soil, or holes can be punched and chlorothalonil etc. can be applied by irrigation.