Turf Necrotic Ring Spot Lawn Disease

ring spot

ring spotTurf necrotic ring spot lawn disease is a soil-borne lawn fungus, also known as Ophiosphaerella korrae. It is characterized by circular straw-colored or gray patches that appear in the spring. They can grow over a foot in diameter.

Basic Features of the Disease

This fungus will rot the roots, crowns, and rhizomes of your grass. Such damage renders the grass bed vulnerable to being uprooted easily.

That itself creates a hazard for the overall health of your yard, as foot traffic and pet traffic can easily lift patches of grass and create bald spots.

Turf necrotic ring spot can also lead to a pattern known as “frog eye,” as healthy green grass grows back in within the yellowed rings. This visual pattern can make it difficult to discern necrotic ring from other fungal lawn diseases.

Prime Conditions

While it appears and spreads in the cooler wet weather of the spring and fall, necrotic ring spot continues to grow- less noticeably- in warmer temperatures. It will then re-emerge with the heat and stress from summer drought. This makes it easily confused for a summer fungus.

This type of fungus is often caused by overwatering and poor drainage. Compacted soil can also help the fungus take hold.

Additionally, overwatering can lead to the depletion of beneficial microbes that help battle the fungus. Without these microbes, there is no resistance to the fungus, and it is allowed to flourish.

Necrotic ring can also spread through aerating, and on tools used in affected areas. Cleaning lawn tools well after use is a good practice.

The spores may also be transported on shoes or wheelbarrow wheels. They can also be spread throughout your lawn via wind and moisture.

Preventive Measures

Any resiliency against climatic stress gives your lawn a greater chance of surviving fungal diseases. For this reason, it’s good to a few simple measures for prevention.

Irrigating the lawn midday helps cool the turfgrass during hotter months. It also helps the infected grass survive late afternoon stress.

Early morning or evening watering can also help keep fungus at bay. Night watering actually helps promote the growth of fungus, as water will sometimes sit longer on the soil at night.

A drip or misting irrigation system for the hottest parts of the year may help keep your lawn healthy.


Once it has been noticed and identified, turf necrotic ring spot can be treated. It is a lengthy process, however, and takes patience and proper lawn maintenance.

It may take up to 6-12 months to fully replenish the microbes in your lawn. Overseeding affected areas can help with the regrowth.

The lawn can also be treated with sulfur in the form of sulphur-coated urea. Fungicides may reduce the severity of the disease, but won’t fully control it. Fungicides are usually used as a last resort.

Final Analysis

With most lawn diseases, prevention is the best course. Fungus is the cause of many lawn diseases, and should be treated seriously.

Start by ensuring your soil is well-aerated and not too compact. Fungus attacks some grass varieties more than others, so look for a resistant variety.

Good to know: some new seed blends are engineered to be more resistant to the fungus and other lawn diseases. Also noteworthy: ryegrass is naturally resistant to necrotic ring spot.

Use an adequate fertilizer that contains phosphorus, potassium, and a slow-release nitrogen. Aerate the yard to help establish deep roots. Raising mower blades to 3 inches is also a good idea.

Visit our service page for aeration services to learn how JC’s Landscaping can help.

To prevent this and other diseases from taking hold, plan and research the right type of grass for your area, and take care of your yard.

Janice Nelson

Janice Nelson

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