What Is Necrotic Ring Spot?


Necrotic Ring Spot is one of the most destructive lawn diseases in Colorado. Necrotic ring spot is a fungus that feeds on soil, thatch, and dead leaves in your yard, killing the roots and crowns of your grass in the process.

Sometimes referred to as “frog-eye,” necrotic ring spot causes individual blades of grass to die from the tip down. Affected grass usually dies in a circular pattern, creating the appearance of yellow rings across your lawn.

What Causes Necrotic Ring Spot to Attack Your Lawn?

When temperatures in Colorado start to drop, you might start to layer your clothes to stay warm. But heavy layers in your lawn can actually put your lawn at greater risk for necrotic ring spot or other fungus diseases like snow mold and brown patch.

Thick layers of thatch combined with compact soil can cause shallow roots and poor drainage, trapping moisture underneath and creating the perfect environment for disease to take hold. Improper mowing and overwatering can also contribute to the spread of this parasite.

This fungus is most active during cool, wet weather. Necrotic ring spot can actually survive winter in infected plant material, waiting to infect your lawn again in spring. The damaged yellow rings are most evident in summer. When the weather gets hot and dry, damaged root systems collapse and the plant can die.

How Can You Prevent Necrotic Ring Spot?

The best preventative measure is to develop good lawn care maintenance habits.

  • Aerate: Liquid aeration is the process of removing plugs of soil from the ground. This breaks up compact layers of soil and thatch build-up, giving your soil and grassroots easier access to air, nutrients, and water. We recommend that you aerate your lawn every Fall, before Necrotic ring spots and other fungus conditions have a chance to impact the roots of your grass.
  • Fertilize: Slow-release fertilizers are specially formulated to combat diseases over time. If areas of your lawn are particularly prone to fungus and disease, fertilizers that are specifically formulated to defend against mold and fungus may protect your lawn even better.
  • Water Wisely: It may be tempting to water your lawn more frequently, especially during the hot summer months! But did you know that the time of day and the frequency with which your water your grass can have a very big impact on your overall lawn health? It is better to saturate your lawn with about 1” of water once a week. Watering multiple times can lead to excess moisture, which can lead to rot and molding at the roots of your grass.
  • Use Fungicides: Most homeowners don’t realize that fungicides cannot be used to cure damaged grass. Preventative fungicide treatments can protect the roots of your grass from further damage. They can be used in the fall, but spring application is the most effective.

How Can You Treat Necrotic Ring Spot?

Unfortunately, once the necrotic ring has taken over your yard, it can be difficult to control. If just a small portion of your lawn has been affected, you can dig rings out with a shovel to get rid of the disease spores. You can then fill the hole with potting soil and a ryegrass seed mixture.

If the area is so infected that removing the rings would be unreasonable, the best course of action is to work with a local team of professionals to take back control of your lawn.

If you need help diagnosing and battling necrotic ring spots in your yard, the trained professionals at American Turf and Tree Care are here to help! Give us a call today!

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