Necrotic ring spot appearing on lawns

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

Rings and crescents of dead grass are a telltale sign

 The most serious issue we see in the heat of summer is necrotic ring spot. Caused by the fungus Leptosphaeria korrae, in its advanced stage the damage takes the form of rings or crescents of dead grass.  It’s main host is unfortunately the most common grass on home lawns, Kentucky bluegrass. 

 At early stages, the damage 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 its growth in spring and fall, but the dry hot summer reveals its symptomatic arcs and rings more blatantly. Unchecked over years, the rings of dead grass can grow to over a couple feet in diameter. 

 There is no cure for 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. You CAN make your lawn resistant with good cultural practices.

 If you already have it: 

  •  Clean your lawn mower:  Mycelia tend to attach themselves to the underside of dirty lawn mowers and are carried from lawn to lawn.  We most often see necrotic ring spot 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. 
  • 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.
  • Over-seed with resistant varieties of Kentucky bluegrass and resistant perennial rye-grass. (LawnSavers special overseed blend is very resistant)
  • Let it run it’s course!: any efforts to seed or dig it out will only be met with disappointment as disturbing it helps the fungus spread and new seedlings become infected quickly.


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

  • 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.
  • Over seed, 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.

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  • Coping with Covid Update: (updated 06/01/20)

    Hi Everyone, 

    I’m happy to share some good news during these crazy times. LawnSavers is servicing lawns in all areas as lawn care and pest control services that provide for lawn health are officially on the Provincial list of essential services due to the fact we can provide this service safely and with no personal contact!

    We do not expect any delay in our regular timing of applications (except from the brief wintry weather in May).  We put together an easy to read lawn care service timeline that you can use to know when to expect us for each scheduled service in your package. 

    I want to reassure you that in every decision we make around COVID-19, our number one priority remains the health and safety of our employees and customers.  Safety and honesty are our two most important core values.  We will continue to follow strict safety guidelines that ensure “zero touch”.  We will not let our guard down on exercising our safety protocols!

    Our office is open but with less staff in order to maintain safety protocols like social distancing.   Please note our phones are experiencing a high volume of calls and we know how much everyone hates being left on hold, so please leave us a message or email us at  and we will get back to you in less than 24 hours.
    Please be patient with us, we will get back to you as fast as possible.
    You can also sign up for services on our website by clicking here.

    Thank you all for your understanding and patience during these challenging times. Our team works hard, so if you are met with our exceptional service from our technicians or office team members- please give them a thumbs up to make them smile or let me know through a quick email to

    We thank you for supporting our local, family-owned business of 30 years.
     genuinely appreciate each and every one of you and promise that we will do our part to ensure our mutual safety and be on your lawn as soon as possible.  

    Thank you in advance,
    Kyle Tobin
    Chief Environmental Officer