A photo of a diseased lawn

Eight Common Lawn Diseases in Toronto and How to Avoid Them

Lawns can get sick, especially if you don’t follow proper lawn care and maintenance practices. In this article, we’ll discuss eight common lawn diseases in Toronto, their symptoms, and the best ways to avoid them so your lawn stays lush and beautiful.

Most Common Lawn Diseases

1. Dollar Spot

Dollar spot is a fungal disease caused by Sclerotinia homeocarpa that can affect Bermuda grass, fescue, annual bluegrass, and ryegrass. The pathogen thrives when the temperature reaches 60 to 80 degrees Fahrenheit, there’s excess moisture in the soil or no moisture at all, and the thatch is thick. It’s spread by mowers, shoes, water, and wind.

Symptoms include small, circular spots the size of a silver or quarter dollar. The spot may look sunken compared to the rest of your lawn. Affected leaves will appear grayish-white in the morning and then turn brown.

You can protect your lawn from this disease by aerating the soil and dethatching it when needed. You should also practice proper watering and mowing. Do not water at night, and increase your mower height to three inches. If the pathogen has been around for years, you may have to apply fertilizer to restore infected areas.

2. Necrotic Ring Spot

Also known as frog-eye, necrotic ring spot is a lawn disease caused by a root-infecting fungus called Leptosphaeria korrae. It spreads via humans, animals, wind, water, and air, affecting Kentucky bluegrass and annual bluegrass at any time of the year. However, symptoms become more visible during warmer weather.

This disease is common on sodded lawns but can also affect seeded lawns. If your lawn catches this disease, you will see perfectly shaped rings of straw-colored grass with healthy green grass growing inside the ring.

A few practices can help you prevent this disease, such as proper watering, increasing mowing height, and overseeding with perennial ryegrass. Ensuring your lawn soil has enough nitrogen levels by applying nitrogen fertilizer can also help.

3. Leaf Spot

Leaf spot is a lawn disease caused by the Helminthosporium species. It typically affects Bermuda grass, blue grass, fescues, and ryegrasses in the spring and summer when the weather is warm and humid. The disease usually favors lawns that aren’t frequently mowed or cut at low heights and soil with excessive amounts of nitrogen.

Infected grasses develop circular to elongated brownish spots with purple or dark brown borders on stems, sheaths, and leaf blades. Their roots and crowns can also have a dark brown rot.

You can protect your lawn from this disease by mowing at the right height, watering properly, reducing shade, avoiding too much nitrogen fertilizer, and improving water drainage and soil aeration.

4. Fairy Ring

The term fairy ring may sound familiar to you. It refers to a naturally occurring circular ring of mushrooms that some people find magical. But it should be a cause for concern, especially if you want to keep your lawn healthy.

Fairy ring is a disease caused by Basidiomycetes, which feeds on decaying organic matter, like logs, tree stumps, and leaves buried in the soil. So, the risk of your lawn developing this disease increases if the soil has high undecomposed organic matter or thatch.

If your lawn is infected with this disease, you’ll see a dark green band of turf developing in a circle or semicircle. Several rings may appear in one area. Sometimes, mushrooms grow. Behind the dark green band, grass may die, and weeds may invade.

You will need to apply enough nitrogen, aerate the soil, water heavily for several days, and dethatch to prevent the disease. If rings have already appeared, the only way to control them is by removing the lawn and soil in the infected area and reseeding.

5. Anthracnose

Anthracnose is caused by the fungus Colletotrichum graminicola and typically attacks Kentucky bluegrass and annual bluegrass. This disease can develop in the spring through the late summer on poorly drained lawns with compacted soil.

Anthracnose appears in the lawn as irregularly shaped patches of brown grass. You’ll see brown or tan blotches on the infected leaves and black, spiking structures on dead grass.

To prevent this disease, improve your soil’s aeration and implement proper watering techniques. You should also increase your mowing height and avoid applying too much nitrogen. Also, make sure to limit the amount of time that the leaves stay wet after watering.

6. Pink Snow Mold

Pink snow mold is a lawn disease caused by the fungus Fusarium nivale. It happens under snow cover during winter, but symptoms only become visible in late winter or early spring. It affects all types of cool-season grasses.

Affected lawns develop pink, white, or tan patches of matted, dead leaf blades that can reach up to 10 inches in diameter. The white, fluffy residue appears like it’s following the retreating snow line.

You can protect your lawn from this disease by making sure it is well-maintained and fertilized. Make sure you aerate and dethatch the lawn to increase air circulation. If you’ve found infected areas, rake them early in spring and increase sun exposure.

7. Red Thread

Red thread is caused by the fungus Laetisaria fuciformix. This disease typically develops during rainy periods in the spring and fall, but the fungus lives in dead leaves, thatch, and soil year-round. It attacks Bermuda grasses and other perennial grasses that do not receive enough nitrogen and grow in compacted soil with poor drainage and a thick thatch layer.

Symptoms of this disease are ragged patches of pink to red threads on the grass sheath and blade. If you see a lawn suffering from this disease from a distance, it just looks like it lacks enough water.

To protect your lawn from this disease, fertilize with enough nitrogen. Also, try increasing air circulation, dethatching or aerating the soil, and reducing shaded areas. Furthermore, make sure to water your lawn properly.

8. Rust

Rust disease is caused by the Puccinia species, and it typically affects cool-season grasses. The fungi live on dead and living leaf tissue in the thatch layer of your lawn grass or on ornamental plants. The disease is most active when the temperature and humidity are high, which happens in the late summer or fall.

Rust-infected grass develops light yellow flecks on sheaths and leaves and then reddish-brown colored spores. You can easily rub off rust spores. While rust only wilts the blades most of the time, it’s best to take precautionary measures because it may permanently damage the lawn if the disease becomes severe.

Some precautionary measures you can take include mowing at the right height and frequency, adopting proper watering practices, and implementing a balanced fertilizer program. You should also increase air circulation and overseed the patches.

Lawn Diseases FAQ

How Can I Prevent Diseases on My Lawn?

Your lawn’s best defense against diseases is proper care and maintenance. Research lawn care tips from experts and make sure to follow them.

Does Lawn Disease Go Away?

Unfortunately, lawn fungus does not go away on its own. Proper treatment is needed to eliminate fungus.

How Do I Identify Diseases Affecting My Lawn?

You can use a lawn disease identification chart containing comprehensive information on issues plaguing your lawn. These resources can help you determine the issues facing your lawn so you can address them properly.

Prevent Lawn Diseases Today

Brown patches in your lawn can stick out like a sore thumb. Prevent them from appearing through proper lawn care and maintenance.

At LawnMart, you can find reliable lawn care professionals who can treat your lawn disease in no time and prevent fungi from coming back. The team uses all-natural, safe products and methods to keep your lawn healthy and happy.

To learn more about how LawnMart keeps lawns free of illnesses, don’t hesitate to contact the team today.

Michael Schäfer

President – LawnMart Inc.

Years of Experience: 31 Years

  • Land Class 1 and 3 Licenses Since 1993
  • Pest Control Operator License Since 1995
  • PIC Accredited Pest Technician Examiner Since 2004
  • Biting Flies Control License Since 2020

Michael Schäfer is President and Founder of LawnMart Inc. After training privately under Dr. Larry Whiddell of Ohio State University, he became a Lawn Technician at Barefoot Grass Lawn Services (1993) and leveled up to Tree/Shrub Care Manager before taking over all Canadian operations as Area Manager. In 1996, Michael founded LawnMart Inc., which has since grown into a multi-award-winning company that cares for thousands of lawns in the Golden Horseshoe area.