General: Fairy Ring is a disease which causes dark, green, circular patterns in the lawn. Rings may vary in size, from a few feet to many yards in diameter. They are most noticeable in early spring and fall. As the disease progresses, these rings may get larger.
Causes: Many fungi cause Fairy Ring. These fungi occur naturally in the soil and live by decomposing organic matter (thatch). They grow radically outward from the point of the original infection. The dark green of the outer zone occurs because the fungi release nitrogen as they decompose organic material, and the nitrogen stimulates the turf. As the fungi mature, a hard layer is formed and turf growth becomes difficult, resulting in thin areas inside the green ring.
What to do: There are no fungicide controls. The best approach is to disrupt the ring by mechanical means, such as aerating and fertilizing. Aerating with stimulate more uniform turf growth by allowing downward movement of nutrients and water in damaged areas. Fertilizing will enhance the green color of grass surrounding the ring. Grass growth will become more uniform in the damaged areas and the ring will not be as noticeable.