Fairy ring is a fungal disease of turfgrass caused by Marasmius oreades that grows outward in a radial pattern. The disease is characterized by a ring of lush green grass bordered by a ring of brown dying grass. The lush grass is the result of increased plant nutrients made available by the fungus. The dry grass ring occurs when the underground fungal mass grows so thick that water is prevented from penetrating down to plant roots.
“Spike and Soak” is a technique used to mask the visible signs of fairy ring. A garden fork is used to poke aeration holes through the mycelial mass followed by a heavy watering. Regular applications of lawn fertilizer will also help mask the problem.
If you wish to eliminate the disease totally, all infected soil must be removed and replaced.