Lawn Disease – Necrotic Ring Spot

(Ophiosphaerella korrae)

Necrotic Ring Spot is a serious turfgrass diseases caused by Ophiosphaerella korrae. Necrotic Ring Spot is common on high maintenance lawns around the northern United States and is particularly destructive on Kentucky bluegrass. Damage usually occurs in spring and again in late fall through early winter.

Identifying Necrotic Ring Spot -

Necrotic Ring Spot produces circular patches with thinning turf that are yellow to light-green in color and 3 to 15 inches in diameter. The patches can grow up to 3 feet in diameter, eventually turning brown and dying. The roots of the infected turfgrass also become thin and weakened, turning from brown to black. The patches often form a “frog-eye” where less susceptible turfgrass species survive inside the patch ring.

Necrotic Ring Spot is often found in areas with a shallow layer of top soil and a hard, rocky layer of sub-soil. Damaged areas of turf will pull-up easily.

Conditions for Necrotic Ring Spot Infection -

Necrotic Ring Spot can only lead to an infection in your lawn if all of the following conditions are present:

1. Pathogen – Ophiosphaerella korrae

2. Host – Various bluegrass species and fine fescue

3. Environment – Compact, high nitrogen soils with temperatures up to 80 degrees Fahrenheit

Necrotic Ring Spot Control -

Cultural disease control practices create favorable conditions for a healthy lawn, and often create unfavorable conditions for the growth of Necrotic Ring Spot. Environmental conditions cannot be changed, but cultural practices performed by the homeowner can be modified to lessen the chance of extensive damage from Necrotic Ring Spot. Scotts LawnService can help determine a plan for preventing and controlling Necrotic Ring Spot in your lawn.

For Necrotic Ring Spot control and treatment, Scotts LawnService recommends the following cultural control tips:

  • Raise lawn mowing height
  • Reduce soil compaction and thatch with lawn aeration
  • Use fertilizers with moderate to high amounts of phosphorous and potash
  • Maintain adequate nitrogen levels using a balanced fertility program
  • Reduce the amount of shade in your lawn
  • Lightly irrigate in the mid-afternoon to cool plants and avoid drought stress

Scotts LawnService has professional products that can prevent and control lawn diseases when cultural control practices are not effective.

Scotts LawnService is the trusted industry leader for professional quality lawn care. Our exclusive lawn care products include premium grass seeds and professional-grade fertilizers; our lawn service teams are comprised of highly trained, industry-certified professionals. Contact a representative today for Necrotic Ring Spot control options available in your area and to learn how you can enjoy a lush, thicker lawn that only Scotts LawnService can deliver.