Necrotic Ring Spot (NRS) is a disease problem of Kentucky bluegrass lawns. NRS is a root rotting fungus most common in Kentucky bluegrass and other bluegrass bends. It can also be found on other turf types though not often.
Necrotic Ring Spot commonly develops due to cool, wet weather in spring along with
excessive amounts of nitrogen fertilizers and compacted soils. This disease is seen more often on established turf and is more severe on sites with little to no soil preparation on heavy clay soils. Circular dead spots start to appear when weather turns hot and dry. These donut shaped patches are most noticeable in July, August and September. NRS can kill turf.
Proper turf management is the best defense against Necrotic Ring Spot. Adjust irrigation to keep turf drier during the wetter months of spring. Lower the amount of Nitrogen fertilizer applied. Consider fall fertilization with Iron.
Options to fix lost areas is to tear out what is affected and dispose, prepare the soil prior to replanting new sod. Best fix would be to replace bluegrass with a more disease resistant option like Turf Masters’ Enviro Turf™, Natures Prairie Turf™, Canadian Blue Fescue™ or Cowboy turf™ none of which have shown signs of Necrotic Ring Spot.