Fairy ring is caused by a number of mushroom fungi that live in the soil and thatch layer.
Early symptoms of infection appear as circular or partial ring-bands of stimulated grass that vary from less than 1 foot to many feet in diameter. To control an established fairy ring, aerate the entire diseased area every 4 inches plus an additional 2 feet. Areas of dark green grass often can be masked with light applications of nitrogen fertilizers that stimulate adjacent turf growth. Fairy ring is a common disease of Kentucky bluegrass and most other turfgrass species. It is caused by many mushroom fungi that live in the soil and thatch layer.