Necrotic ring spot appearing on lawns

lawnsavers necrotic ring in grass

What To Do With Brown Circles on Your Lawn?

Jump To: What To Do If You Have Necrotic Ring Spots On Your Lawn, How To Prevent Necrotic Ring Spots, Contact Us, Other Lawn Care Tips

The hot weather and frequent rain are creating ideal conditions for fungus to thrive.

The most serious issue we see in the heat of summer is necrotic ring spot, some would call it dead circles in their lawn or brown rings in their lawn. This is different than another issue that causes dead patches of your grass in your lawn known as bentgrass.

Caused by the fungus Leptosphaeria korrae, in its advanced stage, the damage takes the form of brown rings of dead grass.  Its main host is unfortunately the most common grass on home lawns, Kentucky bluegrass.

At early stages, the damage of these dead rings in the grass appears as scattered patches that coalesce and pull out easily. The roots and crowns have been killed, so nothing holds the grass in the soil anymore. The fungus spreads outwards in an arc form by spores and mycelia. New grass can grow back in the region the fungus has abandoned, resulting in the characteristic ring shape. Cool wet weather promotes the fungus’s growth in spring and fall, but the dry hot summer reveals its symptomatic arcs and circles of dead grass more blatantly. Unchecked over years, the rings of dead grass can grow to over a couple feet in diameter.

There is no cure for dead circles in your lawn caused by necrotic ring spot. There is no product registered for use in Ontario or North America for that matter which will kill the fungus or stop it from infecting grass and causing these brown rings in your lawn. You CAN make your lawn resistant with good cultural practices.

What To Do If You Have Dead Circles of Necrotic Ring Spots On Your Lawn:

  •  Clean your lawnmower:  Mycelia tend to attach themselves to the underside of dirty lawnmowers and are carried from lawn to lawn.  We most often see the brown circles of necrotic ring spots on lawns that have a mowing service.
  • Sharpen your mower blade: Torn grass blades are more easily infected because they have larger surface areas to become infected by most lawn diseases.
  • Fertilize with Nitrogen: LawnSavers professional fertilizer contains a high amount of slow-release nitrogen which helps the lawn grow through this disease quicker reducing the spread of dead circles in your lawn.
  • Syringing: (only recommended to help reduce an identified Necrotic ring spot problem)  Water very lightly during the high heat of the day, essentially to activate the fungus and expose it to the sun, therefore decreasing its life expectancy.
  • Aerate: Aerating the lawn reduces compaction thereby reducing the amount of infection and amount of circles of dead grass.
  • Overseed with resistant varieties of Kentucky bluegrass and resistant perennial rye-grass. (LawnSavers special overseed blend is very resistant)
  • Let it run its course!: any efforts to seed or dig it out will only be met with disappointment as new dead circles of grass appear as disturbing it helps the fungus spread and new seedlings become infected quickly.

dead rings in grass lawnsavers torontoHow To Prevent The Brown Circles of Necrotic Ring Spot

Strong roots and resistant strains of grass will both help shield your lawn from this attack of dead circles in your lawn.

  • Water deeply, once or twice a week. Grass will grow roots to where the water is. Creating a deep reservoir and allowing the surface to stay drier will encourage the roots to grow long.
  • Mow frequently and high, to prevent thatch build-up which can snarl root growth.
  • Core aerate every year to break up excess thatch and reduce soil compaction, so the roots have a better base to grow into.
  • Overseed, not only to replace any grass damaged by fungus but to introduce new, stronger varietals which resist necrotic ring spot better.

We can over-seed starting at $59.95 + tax and core aerate starting at $60.00 + tax, and both services can be bundled together for bigger savings.

Contact The Best Lawn Care Company Near You

If you’re looking for help with your lawn care or weed problems, look no further than the lawn experts at LawnSavers. We have over 30 years of experience helping people achieve their very best and beautiful lawns. Our effective weed control treatments can help your lawn remain lush, green, and weed-free, while we offer multiple packages to suit any budget. LawnSavers currently services the GTA including Toronto, Newmarket, Milton, and Barrie. Contact us today for your FREE estimate.


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  • Let’s Grow Healthy Lawns and Trees together. updated: 07/21/22

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    Summer is officially here!
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    2020-21 important turf and tree high (and low) lights:

      • Nine days of snow, ice and wintry weather in May 2020,
        2021 was the driest April, May, and June in 51 years See Actual GTA daily weather records by clicking here.
      • One of the hottest, driest summers on record in 2020 with long spells of grass-killing heat and drought. Read more here in our 2020 summary blog.
        2021 carried on this trend with only a few days of rain in July and August, with extreme dryness and heat.
      • A bumper crop of crabgrass that germinated in the perfect (rainless) storm. As expected, even more arrived this past summer in 2021!
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