How to Treat and Prevent Large Brown Patch Disease in St Augustine and Bermuda Grass

Large Brown Patch Disease is a common issue that affects St Augustine and Bermuda grasses, two popular varieties of turfgrass. This disease can cause significant damage to lawns, resulting in unsightly brown patches and weakened grass. This article will explore the symptoms of Large Brown Patch Disease, as well as its causes, prevention, and control measures. You can maintain a healthy and vibrant lawn by understanding this disease and implementing the right strategies.

Understanding St. Augustine and Bermuda Grass

Before delving into Large Brown Patch Disease, it’s important to understand the grass varieties it affects: St. Augustine and Bermuda grass. St. Augustine grass is a warm-season grass known for its dense and lush appearance. It thrives in warm and humid climates, making it popular in southern regions. Bermuda grass, on the other hand, is a versatile warm-season grass that can tolerate different soil types and climates. Both grasses are widely used for lawns due to their durability and aesthetic appeal.

What is Large Patch Disease

Large patch disease, also known as Rhizoctonia large patch, is characterized by the formation of large circles or patches of damaged grass. These patches can range from a few inches to several yards in diameter. During its active season, large patch disease produces bronze-colored borders where the affected grass meets the healthy turf. The patches are perennial and tend to grow larger each year, necessitating proper treatment to avoid extensive damage to your lawn.

Causes of Large Patch Disease

Large patch disease is often a result of improper lawn maintenance practices. Factors such as excessive nitrogen application, over-irrigation, poor soil drainage, thatch buildup, and low mowing heights can contribute to the development of large patches. It typically occurs when soil temperatures drop to around 70 degrees Fahrenheit during the autumn. It’s important to note that a large patch is caused by the same pathogen, Rhizoctonia solani, that causes brown patch disease in cool-season turfgrasses.

Symptoms of Large Brown Patch Disease

Large Brown Patch Disease is characterized by distinct symptoms that are evident on the affected grass. Recognizing these symptoms is essential for early detection and effective management. Here are the main signs to look for:

  1. Circular or irregular brown patches: Infected lawn areas will develop brown patches, which can vary in shape and size. These patches may expand over time if not addressed.
  2. Yellowish halo: Surrounding the brown patches, you may notice a yellowish halo. This halo results from the grass attempting to defend itself against the disease.
  3. Thinning and weakening of grass blades: The grass within the affected patches may become thin and weak, leading to a less vibrant and healthy appearance.
  4. Visible signs of fungus: In some cases, you may observe white, cotton-like fungal growth on the blades of grass within the brown patches. This is a clear indication of Large Brown Patch Disease.

Differentiating Large Patch and Brown Patch

Large patch disease can sometimes be confused with brown patch disease due to their similar symptoms. However, the key difference lies in the grass types they affect. Brown patch primarily affects cool season grasses like bluegrass or fescue, while large patch specifically targets warm season turfgrasses such as zoysia, St. Augustine, and centipede grass. Additionally, large patch disease is most active during the spring or when soil temperatures drop to 70 degrees Fahrenheit in autumn, whereas brown patch is predominant during late spring and summer.

When Does Large Patch Appear in Lawns?

Large patch disease typically emerges in the fall but may not be noticeable until early spring. The symptoms become more evident as the turfgrass begins to green up from winter dormancy during the transition to the spring season. It’s worth mentioning that large patches remain inactive during very cold winters.

Prevention and Control Measures

Preventing Large Brown Patch Disease is always preferable to treating it once it has taken hold. By implementing the following prevention and control measures, you can reduce the risk of this disease affecting your St. Augustine or Bermuda grass:

  1. Proper watering: Avoid over-irrigation and ensure proper drainage to prevent waterlogged conditions. Water deeply and infrequently, allowing the grass to dry out between watering sessions.
  2. Balanced fertilization: Maintain a balanced fertilization schedule, avoiding excessive nitrogen applications. Consider a soil test to determine the specific nutrient needs of your lawn.
  3. Mowing techniques: Follow the recommended mowing practices for St. Augustine and Bermuda grass. Avoid cutting the grass too short, as this weakens the turf. Regularly sharpen your mower blades to minimize damage to the grass.
  4. Aeration and dethatching: Regularly aerate your lawn to alleviate soil compaction and improve root health. Dethatching, if necessary, helps to remove excessive thatch that can harbor disease-causing fungi.

Fungicide Treatments for Large Brown Patch Disease

In severe cases of Large Brown Patch Disease, fungicide treatments may be necessary to control the spread of the disease. Fungicides can help suppress the growth of pathogens and protect grass from further damage. However, it’s important to note that fungicides should be used as a last resort and in conjunction with proper cultural practices. Consult with a professional or local extension office to determine the most appropriate fungicide and application method for your specific situation.

Identifying and Diagnosing Large Brown Patch Disease

Identifying Large Brown Patch Disease correctly is crucial for implementing the appropriate management strategies. If you suspect your St. Augustine or Bermuda grass is affected by this disease, here’s how you can identify and diagnose it:

  1. Visual inspection: Examine your lawn for circular or irregular brown patches with a yellowish halo. Look closely for signs of white, cotton-like fungal growth on the grass blades.
  2. Consult an expert: If you’re unsure about the presence of Large Brown Patch Disease, consult with a professional horticulturist or contact your local extension office. They have the capability to offer expert guidance and assist you in accurately diagnosing the issue.

Best Practices for Lawn Care and Maintenance

Maintaining a healthy lawn goes beyond managing Large Brown Patch Disease. By following these best practices for lawn care and maintenance, you can ensure the overall health and vitality of your St. Augustine or Bermuda grass:

  1. Regular mowing: Set your mower blades to the appropriate height for your grass variety and maintain regular mowing intervals. This helps to promote healthy growth and reduce the risk of disease.
  2. Proper irrigation: Water your lawn deeply and infrequently, allowing the grass to dry out between watering sessions. Adjust the watering schedule based on weather conditions to avoid over-irrigation.
  3. Weed control: Regularly inspect your lawn for weeds and implement appropriate weed control measures. Weeds can compete with the grass for nutrients and water, weakening its overall health.
  4. Soil testing: Conduct regular soil tests to determine the specific nutrient needs of your lawn. Adjust your fertilization program accordingly to ensure optimal growth and health.


Large Brown Patch Disease can significantly challenge St. Augustine and Bermuda grasses. However, with proper understanding, prevention, and control measures, you can mitigate the impact of this disease on your lawn. You can enjoy a vibrant and healthy lawn throughout the year by implementing cultural practices, maintaining proper irrigation and fertilization, and promptly addressing any signs of disease. Remember to consult with professionals to ensure the best care for your grass variety. With diligence and care, you can keep your St. Augustine or Bermuda grass looking its best.

For expert assistance in maintaining a lush and disease-free lawn, visit ECOLawn Florida. Our team at EcoLawn specializes in St. Augustine and Bermuda grass care, offering personalized solutions to keep your lawn thriving. Contact us today for a healthier, greener yard!