What Causes Brown Spots on My Grass?

Posted on May 20, 2025

Revealed: The Reasons Why Your Lawn Is Discolored

We’ve all been there. You look out at your lawn and…surprise! The sea of gorgeous green on your Midwest lawn suddenly has an ugly brown patch. Of course, you immediately want to know: What are these brown spots on my lawn? And how do I fix them?

These discolored areas can be caused by several factors:

Fungal diseases
Environmental stress (drought or heat stress)
Improper lawn care
Insect infestations

Want to restore your yard to a green oasis? The expert technicians at Kapp’s Green Lawn can help identify the root cause and treat the issue quickly.

Common Causes of Brown Spots

1. Fungal Diseases

Fungi thrive in warm, moist conditions and can quickly spread across your lawn. The visible result? Dead or discolored patches. Some of the most common fungal infections include:

Brown Patch & Large Patch
- These diseases create circular brown areas that can expand rapidly, especially in humid weather.
Dollar Spot
- Remember the silver dollar? This disease creates small, silver-dollar-sized spots that merge into larger patches if untreated.
Gray Leaf Spot & Leaf Spot
- These can turn grass blades brown or add a smattering of dark spots. Common in St Augustine in early summer
Spring Dead Spot
- Common in warm-season grasses, this fungus appears as circular dead patches after winter dormancy.
Fairy Rings
- Sounds magical, right? In reality, these dark-hued rings are caused by fungi breaking down organic matter in the soil.

It’s important to remember that fungal spores can survive winter in the thatch layer, reactivating when conditions become favorable. Proper lawn maintenance (balanced fertilization, aeration, and correct watering) can help prevent outbreaks.

2. Environmental & Maintenance Issues

Even without disease, your lawn can develop brown spots due to:

Compacted Soil
- Heavy foot traffic or clay soil restricts root growth and water absorption, leading to stressed, brown grass.
Excess Thatch
- A thick layer of dead grass and roots prevents water, air, and nutrients from reaching the soil.
Drought & Dormancy
- Heat can really hurt your lawn. During hot, dry periods, grass may go dormant and turn brown until moisture returns. Prolonged drought will cause permanent damage
Non-Uniform Irrigation
- Clogged, misaligned, or broken sprinkler heads or uneven water pressure can lead to dry spots that never get water.
Animal Urine
- Sorry, dog owners. Your canine friend’s urine contains high nitrogen levels, which can create small, circular dead spots.

3. Insect Damage

Certain lawn pests feed on grass roots or blades, weakening the turf and creating brown areas. Common culprits include:

Grubs: These beetle larvae eat grass roots, causing large dead patches that lift easily.
Chinch Bugs: They suck moisture from grass blades, leaving straw-like, discolored turf in their wake.
Caterpillars: These pests also damage grass by feeding on stems and roots.

How to Treat & Prevent Brown Spots

1. Apply Fungicides When Necessary

If a fungal disease is confirmed, fungicides can stop its spread. Early treatment is key. Once the disease progresses, recovery becomes harder. Damaged areas will take weeks to recover. For the best results, follow label instructions carefully and reapply as needed.

2. Water Wisely

Overwatering encourages fungal growth, while underwatering stresses the grass. The best practice is:

Water deeply but infrequently (about 1 inch per week in winter months, 2 inches in summer growing season, including rainfall).
Avoid watering in the evening, as prolonged moisture can promote disease. Instead, water early in the morning to ensure the grass dries by evening, reducing the risk of fungal growth.

3. Aerate

If thatch is thicker than ½ inch, it’s best to remove it. Aeration also helps by reducing compaction and improving nutrient absorption.

4. Mow Correctly

Keep grass at the recommended height for your turf type (never cut more than 1/3 of the blade at once).
Use sharp mower blades to avoid ragged cuts that stress the grass.
Leave grass clippings (unless diseased) to return nutrients to the soil.

5. Fertilize Properly

A balanced fertilizer schedule strengthens grass against disease and stress. Avoid high-nitrogen fertilizers in summer, as they can promote fungal growth.

Bye-Bye Brown Spots

You can finally stop wondering, “What causes brown spots on my grass?” Get in touch with the lawn care experts at Kapp’s Green Lawn. We proudly serve communities in the Midwest, ensuring high-quality lawn care and pest control services in these areas: