How To Identify & Eliminate Lawn Fungus For Good – Follow These Tips For Fungus-Free Grass

A lush green lawn is a joy to behold – and nobody knows better than you the work it took to get it that way. So when lawn fungus appears, with its unsightly brown patches, it’s like your worst nightmare has come true.

Before treating lawn diseases, you want to figure out what kind of grass fungus is involved. “Lawn fungus” is a catch-all term for several grass fungi, but different types often require different lawn fungus treatment options.

I’ll walk you through how to determine which type of fungus is affecting your lawn and how to treat each one. Then I’ll share my top tips for preventing this common lawn problem in the first place.

What Is Lawn Fungus?

Fungal diseases are not rare in the garden. They happen when harmful microbes attack susceptible plants. Grasses are usually tough plants, but almost all are susceptible to fungal issues. They develop problems when exposed to disease pathogens in wet weather. But stress is also a contributing factor.

So how do you know if your grass has a lawn fungus? Look for one or more of these signs:

• Discolored grass
• Yellowing grass
• Browning grass
• Off-color spots on grass
• Dead or dying patches of grass
• Red strands in your grass
• Dull-looking grass
• Mushrooms in your lawn
• Powdery coating on grass blades
• Fuzzy or slimy growth on grass

Common Types of Lawn Fungus

The most common lawn fungus problems are leaf spot or melting out, brown spot, dollar spots, and necrotic ring spot. Here's how to identify each one.

1. Leaf Spot & Melting Out

Many different grasses are susceptible to leaf spot and melting out. Leaf spot is caused by Bipolaris sorokiniana, while melting-out is caused by Drechslera poae. These two fungal diseases appear together.

Leaf spot is the first to appear. Look for purple and brown spots on the grass blades. These enlarge and turn the grass yellow. In the melting out phase, the fungus travels to the roots, causing dieback. At that point, grass tissues rot and turn black.

These fungal diseases are associated with thatch buildup, mowing your grass too short, excessive nitrogen fertilizer, and too much water from either irrigation or rainy weather.

2. Brown Spot

Brown spot results from the grass fungus Rhizoctonia solani. The entire spot can be brown, but sometimes the grass inside the brown spot recovers leaving only a “donut” of brown grass. You can recognize it by browning spots on the lawn and irregular circles of brown grass, ranging from small to several feet in diameter.

Confirm that your lawn has brown spot by looking for a white, web-like substance (white mycelium) that forms between leaf blades. You’re most likely to see it in the early morning.

Conditions that cause brown spot include the usual suspects: too much water, too much rain or humidity, inadequate airflow, high nitrogen fertilizer, and high temperatures.

3. Dollar Spot

Caused by Clarireedia jacksonii, dollar spot can attack any species of turfgrass. This fungal disease looks like brown spots on the lawn, but the patches are smaller, often the size of a silver dollar. This disease is active during the growing season.

To confirm the identity of this fungal disease, inspect the grass blades closely. They will develop hourglass-shaped lesions with pale centers and dark borders. Like with brown spot, cobweb-like mycelium can coat the grass when dollar spot attacks. The spots can eventually merge to form large regions of dead grass.

While humid weather can be a factor in this disease, drought, high temperatures, and dry soil are also causes. However, don’t worry about too much nitrogen here. Low nitrogen levels are more likely to be a factor.

4. Necrotic Ring Spot

This grass fungus is caused by Leptosphaeria korrae. This fungus is most likely to appear in the spring or fall. The lawn will start to get reddish brown rings and you will be able to see black “threads” on the crown of the grass.

The best necrotic ring spot grass fungus treatment is to dethatch your lawn vigorously. As with melting out, the thatch is how the fungus spreads. You can try using a fungicide as well, but it will not help without dethatching regularly. Also, lower the amount of nitrogen fertilizer that you give the lawn.

Unfortunately, even with dethatching and proper care, it may take up to two years for this lawn disease to come under control.

How to Treat Lawn Fungus

To get rid of lawn fungus and keep your grass healthy, you’ll have to walk through all of these steps. It’s important to diagnose the fungal disease before treating it.

Although many lawn fungus have the same causes, that is not always the case. Particular diseases can respond better to individual treatment options. The steps below work for most common lawn fungus.

1. Dethatch Your Lawn

Thatch is a buildup of dead matter between the grass blades. It keeps air and nutrients from getting to the plant's roots. It also holds in water, increasing the humidity of the lawn and giving fungal diseases a leg up.

If you have a small lawn, it may take only an hour of hard work with a rake, but larger lawns are harder to do manually. Rent equipment from a plant store or home service store or buy an at-home dethatcher on Amazon for bigger lawns.

You can also hire a professional to take on the job. It’s often not that much more expensive than renting. Dethatching is not a once-in-a-lifetime activity – you have to do it annually.

2. Apply a Fungicide

To apply or not to apply, that is the question. Fungicide marketers may say it’s always needed as part of lawn fungus treatment. But that just isn’t true. The odds are quite high that your grass will recover from fungal issues without spraying chemicals on it.

However, if you planted an expensive lawn grass, like a bentgrass turf blend, you may think it is appropriate. If you decide in favor of using a fungicide, bring in a professional to help plot your course. They can advise about the type of lawn fungus involved and the best treatment. Or do a little research about your particular disease, then shop lawn fungicides on Amazon.

3. Fill in Bare Spots

Can you grow more grass in the bare spots caused by the fungus? If you treat the problem but the grass doesn’t grow back on its own, you can overseed your lawn it to fill in empty spots.

To prevent more problems, choose a type of grass that is resistant to the fungus that affected your lawn. This popular grass seed mix from Jonathan Green is resistant to both disease and heat, so it's a good choice for lawns that have had problems in the past.

How to Prevent Lawn Fungus

It’s always easier to prevent a problem than to fix it, and this is true of lawn fungus. If you want to keep fungus from attacking your lawn, you can do so by changing your cultural practices. The key is to do less, not more. It will save you time, money, and prevent future problems.

Let’s face it, many of us fertilize our lawns too much and often overwater our grass as well. Fungal lawn diseases thrive in wet, fertile conditions – exactly what you create when you dump on too much fertilizer and water.

Yes, the fertilizer instructions might suggest multiple applications, but this may be better for the fertilizer manufacturers than for your lawn. One or two light feedings a year is usually sufficient for a lawn.

When it comes to watering your lawn, keep your eye on the rainfall. Any week in which an inch (2.5 cm) or more rain falls, no irrigation is necessary. And if you see dew on your grass each morning, don’t water. If you do irrigate your lawn, act early in the morning to let the lawn dry out before dusk.

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