Necrotic Ring Spot is Colorado’s most common lawn problem. Here is a little quiz to test your knowledge, if you want! 

1) Cutting out the ring spots and putting in new sod will help NRS.T/F

2) Aeration is very helpful for lawns with NRS.T/F

3) NRS affects all grass types.T/F

4)Watering more will help get rid of NRS. T/F

5) NRS is a perennial soil-based fungus. T/F

(Answers at the bottom)


According to CSU, Necrotic Ring Spot is the most common lawn problem in Colorado. It affects more severely, hardened and poorly drained soil, and that is why aeration helps lawns affected by NRS. We recommend if your lawn has NRS to aerate both in the spring and the fall. 

Cutting out dead patches and replacing with new sod isn’t recommended since this perennial soil-based fungus affects Kentucky Bluegrass. If you are installing “new” Kentucky Bluegrass sod, NRS will return since it is soil based. It is better to do a fall aeration and overseed with grasses resistant to NRS such as fescues.  

Since it is a fungus, overwatering does not help NRS but makes it worse. Water deeply and less often. Talk to us about how to set your sprinklers for each season, since adjustments need to be made. Spring, Summer and Fall timing of watering should be different.

Mowing sporadically and inconsistently stresses a lawn out. Mowing too short is also stressful to the grass plants. When grass is stressed it is more susceptible to flareups of lawn diseases such as Necrotic Ring Spot.

Fungicide applications can be helpful in suppressing NRS when in conjunction with aerations, and a lawn fertilization program designed to boost the natural health of the lawn. Timing is crucial for fungicide applications and based on soil temperatures. I talked to one person, who had applied four fungicide applications, at random times without considering soil temperatures and called us to see if we would apply more fungicide last fall. He didn’t understand that more fungicide isn’t better when dealing with NRS, but timing and a holistic approach is needed. Overapplication of fungicides leads to resistance like overuse of antibiotics in  agriculture and medicine. 

Combined with proper mowing and watering practices, we recommend a fall core mechanical aeration with an overseeding of grass types resistant to NRS for 2-3 years to fill in as the best way to combat this fungus.

Answers: 1) F 2) T 3) F 4) F 5) T

Here is the link to a CSU Extension article : Learn More

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Servicing Northern Colorado including Fort Collins, Loveland, Greeley, Windsor, Eaton, Evans, Johnstown, Severance, Timnath.