Necrotic Ring Spot Disease

Grasses Susceptible to Necrotic Ring Spot

• Annual Bluegrass
• Rough Bluegrass
• Fine fescue
• Kentucky Bluegrass

Symptoms of Necrotic Ring Spot

Necrotic Ring Spot first appears as thinned, circular patches that are yellow to light green and approximately 3-15 inches wide.  The patches can expand up to 3 feet wide and eventually turn brown and straw colored and die.  The roots and rhizomes of the affected turf turn brown to black.  The disease sometimes causes a symptom known as “frog eye”, in which some grass survives inside the dead patch, creating of damaged turf.

Favorable Conditions for Necrotic Ring Spot

Necrotic Ring Spot initiates in moist soil, thrives in temperatures up to 80 degrees and becomes more severe in higher temperatures and drought conditions.  Newly seeded or sodded areas are susceptible to the disease.  It is also found in areas with compacted soil and high nitrogen levels during the spring and summer.

Necrotic Ring Spot Management

• Raise mower height
• Reduce soil compaction and thatch via core aeration
• Maintain adequate nutrients in soil through proper fertilization
• Minimize shade
• Avoid drought stress through proper irrigation practices