Necrotic Ring Spot / Summer Patch
Necrotic Ring Spot is also called Summer Patch because of its tendency to strike during hot weather when grass is under stress. Species such as Kentucky Bluegrass that are best suited to cool weather but planted in warm climates are at high risk. When symptoms first develop, the grayish green or tan patches may be donut shaped with a small live patch of grass in the middle. Strands of pink fungus may be seen where the grass stems meet the soil and dark green spots may be apparent on individual blades.
Courtesy of Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org
Shape: Round patterns
Season: Summer – over 75 degrees
- Limiting nitrogen applications
- A morning watering schedule
- Keeping thatch to a minimum
- Lawn aeration
- Improve drainage
Remedy: Fungicides are more effective for prevention than for treatment with this lawn disease.
A number of necrotic ring spot symptoms are mentioned here to help you identify it. A necrotic ring spot symptom includes rings and round spots of lifeless or dying turf grass. It has severe effects on Kentucky bluegrass lawns, seeded in the last 2- 4 years. Fine leaf fescues are also susceptible. Heat and water stressed areas shows symptoms first, as turf grass patches or rings develop in heat and gradually patches coalesce. In mixed turf grass, circular patterns of diseased turf can be easily observed. A root infecting fungi causes both the diseases; the roots and crown of plants will be brown to black and rotted.
The fungus overwinters as mycelia on roots and lower crowns. Mycelium and spores attack the roots in spring but symptoms may appear only 18 months later. Heat and drought stress in summer enhance the symptoms but reduce the fungus. An unfavorable rooting condition brightens the occurrence of necrotic ring spot.
Management practices that reduce stress on turf grass such as more watering, will help to suppress necrotic ring spots. Infrequent watering will cool the grass and allow the infected plants to survive the heat. To initiate recovery, a light application of water is essential, but be careful not to give too much water. Compacted soil isfavorable to the disease and this can be prevented by core- aeration with clean equipment.