One day your Northern lawn is lush and green, and the next it’s dotted with yellow patches that quickly turn brown. What’s going on? If this happens seemingly overnight during a stretch of hot, humid weather, you’re likely dealing with a common lawn fungus called brown patch.

Don’t worry. We’ll show you how to identify it, treat it, and prevent it from coming back.

How to Identify Brown Patch in the Lawn

If your lawn is yellowing quickly, get a closer look to confirm it's brown patch. Here are the tell-tale signs:

• Circular Patches: You’ll notice roughly circular, though sometimes irregular, spots in your lawn. These can range from a few inches to several feet across.
• Discolored Blades: Grass blades may have irregular tan spots with a dark brown or purplish border. At the base of the blade, you might see signs of rot.
• Cobweb-like Growth: In the early morning, you may spot a white, cobweb-like fungus (mycelium) around the grass blades before the dew dries. 

What Causes Brown Patch in Lawns

Brown patch is a fungal disease that thrives in heat and humidity and typically appears in late spring, summer, or early fall. The ideal conditions for it are daytime temperatures above 80°F and nighttime temperatures above 65°F, combined with prolonged wetness.

This excess moisture can come from summer rain, evening watering, or poor drainage. Lawns that have been overfertilized with nitrogen right before or during hot, humid weather are also more likely to develop brown patch.

Grass Types Commonly Affected by Brown Patch

This lawn fungus typically attacks cool-season grasses like:

• Tall fescue
• Perennial ryegrass
• Bentgrass

However, some warm-season grasses–St. Augustinegrass and zoysiagrass–are also susceptible.

Your Best Defense: How to Prevent Brown Patch

A healthy lawn is the best defense against any disease, including brown patch.

• Water in the Morning. Water early in the day so the grass blades have plenty of time to dry. Avoid watering between 7 PM and 3 AM, as grass that stays wet overnight is more susceptible to disease.
• Feed Regularly. A well-fed lawn is a strong lawn. Feed your lawn four times a year to keep it healthy. To take the guesswork out of it, get a personalized Scotts® Lawn Care Plan. Just be careful not to overapply nitrogen fertilizer before a hot, humid spell, as this can encourage brown patch.
• Improve Airflow and Drainage. Good air circulation and drainage help grass dry faster. Prune overgrown trees to let more sunlight and air in. You should also aerate and dethatch your lawn every 1 to 3 years to reduce compaction and allow air, water, and nutrients to reach the soil and roots. 

How to Treat Brown Patch When It Appears

If you know your lawn is prone to brown patch, or if you’ve had a forecast calling for hot, humid weather, it’s time to act.

• Treat at the First Sign. To stop the disease from spreading, apply Scotts® DiseaseEX™ Lawn Fungicide. It provides broad-spectrum control for up to 4 weeks and is highly effective at stopping brown patch. Be sure to follow all label directions.
• Feed and Prevent. For a 2-in-1 solution, use Scotts® Turf Builder® Healthy Plus Lawn Food. It prevents and controls brown patch while feeding your lawn to build it up, making it thicker, greener, and better able to handle stress. Apply at the first sign of disease, and always follow the product label instructions.

How to Repair Lawn Damage

After you’ve stopped the brown patch, it’s time to repair the damage.

• For Bare Spots: Use a 3-in-1 mix like EZ Seed® to fix bare spots. Just choose the formula that matches your grass type and apply in early spring or fall for the best results.
• For Thin Areas: To thicken up a lawn thinned out by brown patch use Thick'R Lawn® Sun & Shade or Thick'R Lawn® Tall Fescue Mix (depending on your grass type) in late summer or early fall. Thick’R Lawn® combines seed, fertilizer, and a soil improver to help make your lawn fuller.

With a little care and Scotts by your side, your problems with brown patch will be a thing of the past.