How to Spot and Treat Brown Patch Lawn Disease

You’re proud of your home. When you have company, the first thing your visitors see is your house and your lawn. “Curb appeal” means a lot. But a gross stretch of dead or discolored grass wipes out that curb appeal real fast.

While it might look like your grass has dried out or been scorched by the sun, there’s a good chance you’re dealing with brown patch lawn disease, a common fungal problem that affects lawns during warm, humid weather.

Knowing how to spot and treat brown patch lawn disease can make the difference between a temporary setback and long-term damage to your turf. Turn that brown upside down; let’s turn that ugly grass back into lush greenery as soon as possible.

Article Contents

• What Is Brown Patch Fungus?
• How to Identify Brown Patch Lawn Disease
• Common Causes of Brown Patch Fungus
• How to Treat Brown Patch Lawn Disease
• Preventing Brown Patch in The Future
• When to Call The Grounds Guys

What Is Brown Patch Fungus?

Brown patch fungus is a turf disease caused by Rhizoctonia solani, a soil-borne fungus that thrives in hot, humid conditions. Cool-season grasses such as tall fescue, perennial ryegrass, and Kentucky bluegrass are at high risk, but it can also damage warm-season varieties like St. Augustine and zoysia.

The fungus develops when moisture and heat create ideal growing conditions—usually when night temperatures remain above 65°F and daytime highs reach 80°F or more. Lawns that stay wet overnight are at risk, so brown patch outbreaks are most common in late spring through early fall.

How to Identify Brown Patch Lawn Disease

Recognizing brown patch fungus early gives you the best chance to control it. The symptoms can vary by grass type, but here are the most common signs to watch for:

• Circular patches: The disease often appears as roughly circular areas of brown or tan grass ranging from a few inches to several feet in diameter.
• Smoky or grayish ring: In the morning dew, you may see a thin gray ring at the border of the affected area. This is called the “smoke ring,” a telltale sign of active fungal growth.
• Leaf spots or lesions: Individual blades may show irregular tan or brown lesions with darker borders. The blades often wilt and die from the tips downward.
• Patchy or sunken appearance: As the fungus spreads, the infected areas may look slightly sunken or matted compared to the surrounding healthy turf.

Brown patch fungus can resemble drought stress or fertilizer burn, but unlike those issues, it spreads in circular patterns and typically worsens after humid nights or heavy rainfall.

Common Causes of Brown Patch Fungus

Brown patch fungus develops when several environmental and cultural conditions align. Understanding what causes it can help you avoid the problem in the first place.

• Excess moisture: Overwatering or watering late in the day leaves grass damp overnight, creating ideal conditions for fungal growth.
• High humidity and heat: Warm, muggy weather allows the fungus to thrive. Nighttime temperatures above 65°F and heavy dew increase the risk.
• Thick thatch or poor air circulation: Dense thatch or compacted soil traps moisture and limits air movement, which can promote fungal growth.
• Overfertilizing with nitrogen: High nitrogen levels stimulate fast, tender growth that’s more susceptible to infection.
• Mowing too short: Scalping the grass stresses the turf and reduces its ability to recover from disease.

When these factors combine, the fungus can activate quickly and damage large areas of your lawn in just a few days.

How to Treat Brown Patch Lawn Disease

The key to treating brown patch disease is balancing moisture, temperature, and nutrients while stopping the fungus from spreading. Here’s how to approach treatment safely and effectively.

1. Adjust your watering schedule. Water early in the morning—between 5 a.m. and 9 a.m.—to allow grass blades to dry during the day. Avoid watering in the evening or at night, when moisture lingers on the surface.
2. Mow carefully. Keep your mower blades sharp and never remove more than one-third of the grass height at a time. Allowing the grass to grow slightly taller improves root strength and air circulation.
3. Improve soil drainage and air flow. Aerate compacted soil to enhance oxygen exchange and water penetration. Rake out dense thatch layers to reduce trapped moisture that encourages fungal growth.
4. Apply fungicide if needed. For active brown patch infections, use a lawn fungicide labeled for Rhizoctonia solani. Apply early in the disease cycle for best results, and repeat according to product directions. Fungicides should supplement—not replace—good lawn care practices.
5. Manage fertilization. Avoid applying high-nitrogen fertilizers during hot, humid months. Instead, use balanced or slow-release fertilizers to support steady, healthy growth without over-stimulating the grass.
6. Reseed or resod damaged areas. Once the disease has been controlled, reseed thin or dead spots to restore your lawn’s appearance. Choose a grass variety suited to your region’s climate and soil type.

By addressing the environmental factors that fuel brown patch fungus, you can help your lawn recover and prevent future outbreaks. Contact a professional lawn care service near you for expert support in restoring your lawn’s health and appearance.

Preventing Brown Patch Lawn Disease in the Future

The best defense against brown patch lawn disease is a healthy, well-maintained lawn. If you’re in a new home, now’s the perfect time to get sod installation from local professionals who know their stuff. Prevention focuses on long-term care and environmental balance.

• Water deeply and infrequently rather than shallowly and often.
• Mow at the recommended height for your grass type.
• Fertilize appropriately in spring and fall using balanced nutrients.
• Aerate once or twice per year to relieve compaction and improve drainage.
• Overseed in cooler months to thicken the lawn and increase disease resistance.
• Avoid leaving grass clippings on the surface when conditions are hot and humid.

When your lawn has good airflow, proper nutrition, and balanced moisture levels, it becomes far less susceptible to fungal diseases.

When to Call The Grounds Guys

Brown patch fungus spreads fast, so don’t procrastinate! A complete plan to fix the issue includes aeration, dethatching, fertilization, irrigation management, and fungus treatment.

If you’ve tried to manage it on your own without success, or if you’re seeing recurring infections, professional help can make all the difference. The Grounds Guys provide expert lawn care services based on the local climate, soil conditions, and turf types. Our service professionals understand how to diagnose brown patch lawn disease and create a custom plan to restore your turf’s health.

Get professional help treating and preventing brown patch lawn disease. Request a free estimate from your local Grounds Guys team today to restore your lawn’s health and enjoy a lush, green yard all season long.

This article is intended for general guidance only and is not applicable to every situation. You are responsible for determining the proper course of action for your property and situation. The Grounds Guys are not responsible for any damages that occur as a result of advice and/or guidance derived from its blog content. The Grounds Guys services may vary by location. Contact The Grounds Guys franchise nearest you for more information.