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Necrotic Ring Spot in Lawns: A Primer

Lawns across Utah are under siege from a challenging disease that is spreading across the state. Known as necrotic ring spot, this fungus requires professional diagnosis and quick action in order to stem its growth. Learn more about necrotic ring spot and how to treat it.

What is Necrotic Ring Spot?

According to Utah State University Extension and Utah Plant Pest Diagnostic Laboratory, necrotic ring spot is a fungus that most often affects turfgrass roots. Many turfgrasses can host this fungal disease and it’s found around the world. Annual bluegrass and Kentucky turf are the primary victims in Utah.

Because there are other diseases that can mimic necrotic ring spot, a thorough inspection by a trained professional is necessary for an accurate diagnosis. An effective plan for disease management can then be created.

What Causes a Necrotic Ring Spot?

Necrotic ring spot occurs most often during periods of cool and wet weather. It can also develop if a lawn is over watered. Although this fungus flourishes during cool and damp weather, its symptoms might not become noticeable until drought stress and/or heat hits the area.

One of the first signs of necrotic ring spot is the development of infected turf in circular patches. These are usually small and light green in color. Over time, these patches become larger.

During drought conditions, necrotic ring spot can extend to two or three feet. Left untreated, the fungus can both increase in severity and size. It’s a fall and spring patch disease because these seasons in Utah provide the best environment for it to develop.

How Do You Treat a Necrotic Ring Spot?

Once your lawn has been positively identified as having necrotic ring spot, it’s crucial to treat it as quickly as possible. When the disease spreads, the roots, leaves and stems eventually develop discolorations that are either into brown or black.

There are a number of treatments available including:


By aerating the lawn, the grass can breathe more easily and fight off the fungus. It’s crucial that the aeration equipment is sanitized after each use so that necrotic ring spot is not spread.


Contrary to what it looks like, necrotic ring spot is actually present in the soil — not in the grass itself. Removing the old lawn and placing fresh sod in its place won’t solve the problem. The rings of dead grass will infest the new lawn.

Instead, consider overseeding bare patches with perennial ryegrasses. Necrotic ring spot doesn’t infect perennial ryegrass so planting it can help hide the symptoms.

Specialized Lawn Supplements

Specialized supplements can strengthen the lawn’s root system so the grass is able to grow up through the rings. While the fungus naturally goes away, the new grass helps hide the bare spots.

Is Your Lawn Under Attack from Necrotic Ring Spot? Call the Lawn Care Experts at Big League Lawns

If your lawn is showing signs of distress, such as bare patches and/or rings of dirt, call in the experts for a professional diagnosis. At Big League Lawns, we have more than 40 years of combined experience with Utah lawns. Contact us today at (801) 773-9999 to schedule a fast and free lawn analysis.

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