Brown Patches on Grass? 7 Reasons Your Grass Isn’t Greener (and How to Fix It)

Mariel Loveland
Written by Mariel Loveland
Updated March 22, 2022
freshly cut grass in backyard of house
Photo: SVproduction / iStock / Getty Images

Highlights

  • Fungal diseases are the most common cause of brown patches.

  • Your pet, lawn mower, or lawn maintenance may also be to blame.

  • If you see birds, you may have insects.

  • Proper lawn care usually solves most lawn problems.

  • Consider a soil test to ensure your grass is getting the right nutrients.

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So, your grass is looking less than green. Don’t panic. A certain amount of dead grass on your lawn is inevitable. In fact, brown patches are normal for grasses that go dormant during cold weather (lthink: Bermudagrass). Sometimes, though, brown patches are indicative of a very real problem.

Though there are general lawn care tips that can help you grow the greenest grass possible, you may have to take special measures. What is causing the brown patches of grass on your lawn? Let’s take a look.

1. Fungal Diseases

Brown patch fungus, also known as brown patch disease, is exactly what it sounds like—a fungus that causes brown spots of dead grass across your lawn. The technical name is Rhizoctonia. It’s one of the most common lawn diseases, but it’s far from the only fungus that will kill your grass. Aside from brown patch fungus, you may have one of the following:

  • Pythium blight: you’ll notice dead spots and a material that looks like cobwebs

  • Pink snow mold: You’ll see brown patches surrounded by a white or pink ring

  • Gray snow mold: You’ll notice white patches like cobwebs instead of brown patches

  • Summer patch: Grass dies from the tip down, causing brown spots

  • Necrotic ring spot: You’ll notice a brown ring

  • Rust disease: You’ll find a light-yellow powder

  • Red thread: You’ll see brown patches with a reddish hue

  • Dollar spots: You’ll notice tiny clusters of brown spots

How to Treat Lawn Diseases

You can treat some fungi (like brown patch fungus) with a lawn fungicide. This isn’t effective for all lawn diseases. Sometimes, all you can do is ramp up your lawn care (this lawn maintenance checklist can help). You can try aerating your soil, applying fertilizer, and only watering in the morning before 10 a.m. to ensure that the lawn dries out before the sun goes down.

2. Thatch

Thatch happens when dead and decomposing material line the grass and suffocate the root system. This can happen if you mow your lawn frequently and don’t remove the debris. Thatch doesn’t just cause brown spots—it makes your lawn vulnerable to lawn diseases and pest infestations. The problems can compound.

How to Treat Thatch

Getting rid of thatch is simple. Use a dethatching rake to break up the debris and aerate your lawn.

3. Insect Infestations

Grubs (beetle larvae) and leatherjackets (a type of fly larvae) feed on the roots of your grass and cause brown patches. You may also notice yellow patches on your grass from these pests. If insects are to blame, the dead spots should look uniform rather than irregular. You may even notice birds feeding on your lawn, since larvae are an excellent meal. 

How to Treat a Grub Infestation

You can hire a local lawn care service to apply insecticide. If you don’t like the idea of spraying chemicals, you can introduce beneficial nematodes (that kill the grubs) or milky spore disease (a natural pathogen that will kill larvae without harming your grass). You can also make a DIY bug spray with dish soap and water, though too much dish soap will make your brown patches worse. Overall, proper lawn maintenance deters bugs since they prefer damp conditions.

4. Too Much Fertilizer or Weedkiller

man using a fertilizer spreader on lawn
Photo: groveb / iStock / Getty Images

Your lawn might be killing your grass. Two common causes of brown patches on grass are excessive nitrogen from over-fertilization and weed killer overdoses. While there’s not much you can do to bring dead grass back from the grave, you can prevent the problem from persisting.

Always make sure you’re using the correct dose of fertilizer or weedkiller. Avoid fertilizing on hot days and water directly after fertilization. Never walk across your grass after spraying weeds, as you can easily trail herbicide into your lawn with your shoes.

5. Lack of Moisture or Poor Soil Quality

If your lawn isn’t getting the water and nutrients it needs, it will start to die. Hello, brown spots. If you live in a drought-prone area, it might be inevitable. Otherwise, a sprinkler system can make watering easier.

To address poor soil quality, enlist a local soil testing company to test your soil. If the soil is lacking, you may need to add fertilizer, organic matter (like compost), or another soil amendment.

6. Your Pet’s Bathroom Habits

cute dog walking around backyard
Photo: wombatzaa / iStock / Getty Images

If you have a dog and notice circular brown patches, your four-legged friend may be to blame. Female dog urine is particularly damaging to grass and causes brown patches. The best way to stop the problem is to immediately rinse the area and train your pup to go elsewhere. You may want to consider:

7. Your Lawnmower

Did you know improper mowing can actually kill your grass? Dull blades will shred and damage your lawn. So will cutting the grass too short. Similarly, a leaky lawn mower is a one-way ticket to a chemical burn. Gasoline and oil leaks can cause brown patches overnight. 

To prevent the problem, tune up your lawn mower. Try sharpening the blades and readjusting your lawn mower to the correct height. Make sure you never overfill the fuel or oil tank and don’t refill the tank on your lawn.

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