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Lawn Diseases to Watch for in Minnesota
Got weird patches in your lawn? It might not be bugs—or neglect. It could be a lawn disease.
Here in Minnesota, hot and humid summers create the perfect conditions for fungal issues like:
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Red Thread
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Dollar Spot
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Necrotic Ring Spot
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Ascochyta Leaf Blight
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Brown Patch
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Summer Patch
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Fairy Ring
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Rust
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Snow Mold
So, what exactly is a lawn disease?
Most are fungal infections that show up as brown spots, bleached patches, or even pinkish threads in your grass. And yes, they’re as annoying as they sound.
The good news?
With the right care, most lawn diseases can be prevented—or at least kept in check. Scroll down to learn how to spot the signs and protect your lawn.
1. Red Thread
How can you spot red thread? This one doesn’t hide very well—it literally looks like red or pink threads growing in your grass.
You’ll notice circular patches in shades of tan, pink, or red, anywhere from a few inches to a couple feet wide.
What You Need to Know About Red Thread
Look closely and you’ll see thin red strands sticking out from the grass blades—that’s where Red Thread gets its name.
The good news? It doesn’t damage the roots, so your lawn usually bounces back on its own once conditions improve.
Red Thread shows up in warm, humid weather and can spread quickly.
We recommend aerating annually and applying a fungicide treatment to help stop the spread of the fungus.
1. Red Thread
How can you spot red thread? This one doesn’t hide very well—it literally looks like red or pink threads growing in your grass.
You’ll notice circular patches in shades of tan, pink, or red, anywhere from a few inches to a couple feet wide.
What You Need to Know About Red Thread
Look closely and you’ll see thin red strands sticking out from the grass blades—that’s where Red Thread gets its name.
The good news? It doesn’t damage the roots, so your lawn usually bounces back on its own once conditions improve.
Red Thread shows up in warm, humid weather and can spread quickly. While fungicide treatments are available, in many cases, patience (and proper lawn care) is all you need—it often clears up without treatment.
2. Dollar Spot
How can you spot dollar spot? This fungus loves humidity and underfed lawns—especially those low in nitrogen.
You’ll see light, bleached-looking patches scattered across your yard, usually a few inches to about a foot wide.
Applying a nitrogen-rich fertilizer can give your lawn the boost it needs to recover.
Aim for a balanced, slow-release fertilizer and follow label instructions to avoid overfeeding.
We recommend aerating annually and applying a fungicide treatment to help stop the spread of the fungus.
3. Ascochyta Leaf Blight
Hot, humid weather is the perfect setup for Ascochyta Leaf Blight.
It shows up fast—creating large, uneven patches of grass that suddenly turn straw-brown and look completely dead.
What makes Ascochyta Leaf Blight stand out? It can pop up almost overnight.
To help prevent it, aerate your lawn yearly to reduce thatch and improve water flow. Keep your mowing height between 2.5 and 3 inches, and try not to mow when the grass is wet.
Even though it may look like your lawn is toast, the fungus doesn’t harm the roots or crowns—so your grass should bounce back within a couple of weeks, depending on the weather.
4. Necrotic Ring Spot
This tricky lawn fungus thrives when cool, wet weather is followed by summer heat and drought.
Got compacted soil or skipped aeration? That’s exactly the kind of environment Necrotic Ring Spot likes to call home.
You’ll notice small, circular patches that look straw-colored—typically under a foot wide. It shows up most often in newer sod but can affect seeded lawns, too.
To fight back, start with core aeration to loosen compacted soil and improve drainage. Staying on top of your fertilizing schedule also helps your lawn recover and stay strong.
We recommend applying a fungicide treatment to help stop the spread of the fungus.
5. Brown Patch
This summer lawn fungus tends to show up in Minnesota during hot, humid stretches in mid to late summer.
What Brown Patch Looks Like
Brown Patch shows up as irregular, circular patches that are brownish-yellow in color. They can range in size from just a few inches to several feet wide.
What Causes It
Your lawn is more likely to get Brown Patch if you’re overwatering, overfertilizing with nitrogen, have poor drainage, compacted soil, or a thick layer of thatch.
How to Prevent It
Skip the heavy nitrogen, avoid watering in the evening, and aim to water early in the day so grass can dry out before nightfall. Annual aeration and dethatching will also help reduce your risk.
We also recommend applying a fungicide treatment to help stop the spread of the fungus.
6. Summer Patch
It might not sound serious, but Summer Patch is no joke. This fungus strikes in the heat of summer, leaving behind dead grass and rotted roots—right when you want to enjoy your lawn the most.
It often starts as small, wilted circles of thinning grass. But don’t be surprised when those spots expand into large, irregular patches with yellow to bronze tones, anywhere from 6 inches to 3 feet wide. Before you know it, big chunks of your lawn can look scorched and lifeless.
What Makes Summer Patch So Tough
Summer Patch thrives in compacted, poorly drained soil—especially during hot, wet weather. It also loves closely mowed grass, so be sure not to cut your lawn too short.
This fungus is often confused with Dollar Spot or Necrotic Ring Spot, but it’s even more damaging because it attacks the roots, not just the grass blades.
Not sure if it’s Summer Patch? Try pulling up a patch of grass. Infected roots will be short, dark brown or black—healthy ones are longer and lighter in color. If the roots are rotting, reseeding will likely be necessary.
We recommend aerating annually and applying a fungicide treatment to help stop the spread of the fungus.
7. Fairy Ring
Unlike Necrotic Ring Spot, which creates small straw-colored circles, Fairy Rings are much larger—often ranging from 3 to 20 feet wide. These big rings can appear as dark green or dead patches in your lawn.
How to Spot Fairy Ring
Fairy Ring stands out by color or texture. You might see rings of grass that grow thicker, greener, and faster—or, on the flip side, look drier and more brown than the rest of your lawn. In wet weather, mushrooms may pop up along the edges of the ring.
To help your lawn fight back, keep up with regular fertilizing in the spring and fall for stronger, healthier turf.
8. Rust In Lawn
Rust is one of the milder lawn diseases, but it can still leave your yard looking tired and patchy. It usually shows up in mid to late summer—especially during warm, humid stretches when grass growth slows down.
You’ll often notice a powdery orange or rust-colored coating on grass blades. Walk across the lawn, and you might even see the telltale dust on your shoes or mower.
To help your lawn recover, mow regularly, improve airflow, and apply a balanced fertilizer to encourage fresh, healthy growth. With a little care, rust usually clears up on its own.
9. Snow Mold
Snow Mold is one of the milder lawn diseases. It typically appears in regions with heavy winter snowfall—like ours—and shows up as the snow melts in early spring.
You’ll often see grayish-white or even pink patches in the lawn as the snow melts—classic signs of Snow Mold.
Once the grass dries out, gently rake the matted areas to loosen them up. The mold usually clears quickly, and a light dose of fertilizer can help the new growth bounce back.
We recommend aerating annually and applying a fungicide treatment to help stop the spread of the fungus.
Think You Might Have Lawn Fungus?
If you're noticing unusual spots, patches, or discoloration in your lawn, it could be a fungal disease. Many lawn fungi can look similar, so a proper diagnosis is key to effective treatment.
Feel free to text (507) 934-5296 or email us photos—we’re happy to take a look and help identify the issue.
If it turns out to be a treatable problem, signing up for a fungus control treatment with Spring Touch can help protect your lawn and prevent future damage.