If you’ve ever noticed mysterious brown circles or patches creeping across your once-lush lawn, you’re not alone. Brown patch is one of the most common and most frustrating lawn diseases faced by homeowners across the country. Left unchecked, it can quickly turn a healthy yard into a patchwork of dead grass and bare soil. But with the right knowledge and a DIY approach, you can protect your lawn and keep it looking its best.
What Is Large/Brown Patch?
Large/Brown patch is a fungal disease caused by the pathogen Rhizoctonia. It affects both cool season and warm season grasses. In cool season grasses like Turf Type Tall Fescue, Kentucky Bluegrass, and Perennial Rye it is referred to as Brown Patch. In warm season grasses like St. Augustine, Centipede, Bermuda, Zoysia and Bahia, the same pathogen is called Large Patch. Same villain, different name.
Understand Your Enemy
- Loves prolonged leaf wetness (heavy dew is enough)
- Lives dormant in your soil as sclerotia (masses of fungal tissue, essentially a compact survival structure) year after year
- Rhizoctonia does not move through spores so it does not blow in on the wind.
How to Identify Large/Brown Patch
Early signs include:
- Circular or irregular patches of brown, tan, or yellow grass
- Patches ranging from a few inches to several feet in diameter
- A “smoke ring” or dark border around the affected area (most visible in the morning)
- Thinning grass and weakened roots/crowns
Brown patch thrives in warm, humid conditions—especially in areas with poor air circulation, heavy thatch, or excessive moisture.
Curative Attack When You See Active Patches
Use the proven “Bulletproof Combo” that professionals and serious DIYers rely on:
1. Spray the affected zones with azoxystrobin at the curative rate
Granular Product: Scott’s DiseaseEx
- 0.31% azoxystrobin
- Curative rate = 4 lb per 1,000 sq ft (twice the preventative rate)
- A single 10-lb bag only covers 2,500 sq ft at this rate
- Identical to the professional product Heritage G with the same exact percentage of azoxystrobin
Liquid Product: Azoxystrobin (Azoxy) 2SC Select
- 22.9% azoxystrobin
- Curative rate = 0.77 oz per 1,000 sq ft
- A pint covers 20,000 sq ft at this rate
- Dilute in 2-4 gallons of water per 1,000 square feet
B. Spray the affected zones with propiconazole at the curative rate
Big-Box Store Product: BioAdvanced Fungus Control for Lawns
- 2.42% propiconazole
- Comes in convenient hose-end sprayer bottle
- A quart covers 5,000 sq ft
Professional Grade Product: Propiconazole 14.3% Select
- 14.3% propiconazole
- Curative rate = 2 oz per 1,000 sq ft
- A pint covers up 8,000 sq ft
- Dilute in a minimum of 1 gallon of water per 1,000 sq ft.
Result: You hit the fungus with two completely different modes of action at the same time so it has nowhere to hide.
Immediate Follow-Up Care
- Apply 5-0-15 Life Support fertilizer. This is a very low Nitrogen product with high potassium for stress recovery. Apply at 3 lbs/1,000 sq ft.
- Water in the fungicides and fertilizer with ½ inch of water
- Do NOT mow for 48 hours minimum
- When you do mow, bag clippings and remove them (don’t spread the fungus)
Prevention - The Real Long-Term Win
Because the pathogen lives in your soil, switch to a preventative program starting the following season:
Warm-season grasses (St. Augustine, Zoysia, Bermuda, Centipede)
- Early–mid March (before spring warm-up)
- Early–mid October (before fall cool-down)
- Apply both Azoxystrobin and Propiconazole at the preventative rates
Cool-season grasses (Tall Fescue, Kentucky Bluegrass, Ryegrass)
- Late spring (before summer heat & humidity)
- Typically in May
- Again in early fall if needed
- Apply both Azoxystrobin and Propiconazole at the preventative rates
Preventative rates
- Scotts DiseaseEx = 2 lbs per 1,000 sq ft (10 lb bag covers 5,000 sq ft)
- Azoxystrobin (Azoxy) 2SC Select = 0.38 oz per 1,000 sq ft (1 pint covers 42,000 sq ft)
- BioAdvanced Fungus Control = 1 quart covers 5,000 sq ft
-
Propiconazole 14.3% Select = 1 oz per 1,000 sq ft (1 pint covers 16,000 sq ft)
Two applications per year at the low rate is cheaper and far more effective than fighting outbreaks every transition period.
Why Some Lawns Get It and Others Don’t
Even with perfect conditions, these factors dramatically increase risk:
- Poor air circulation / constant shade
- Thick thatch layer
- Low mowing height
- Nighttime watering or heavy dew that never dries
- Seasonal transitions
Improve Lawn Conditions:
- Increase airflow by trimming trees and shrubs.
- Water early in the morning to allow grass to dry during the day.
Monitor High-Risk Areas:
Pay special attention to shady spots or areas with poor drainage, these are prime targets for disease.
Recovery Timeline - Be Patient
Even after the fungus is dead, the brown scars can linger for weeks to months, especially if you are heading into slower growth. Healthy runners will eventually fill in, but you can speed it up slightly with light, frequent nitrogen once the disease is under control.
DIY Lawn Care Made Easy
At Yard Mastery, we believe every homeowner can take control of their lawn’s health. With the right products and a little know-how, you can prevent and treat Large/Brown Patch before it becomes a major problem.
Here is our free Fungicide Guide with even more information and tips: Fungicide Guide
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