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Brown patch lawn disease
Brown patch appears as irregular circular patches of brown, tan, or yellow grass, usually 6 inches to several feet in diameter. These patches of dead and dying grass can enlarge and join together.
Key identifier: lesions on the grass blade
Individual grass leaves will remain upright and have lesions on the grass blades. Lesions appear irregularly shaped and are tan in color with dark brown edges.
Main lookalike: drought
Brown patch is often confused with drought based on the lawn's appearance, which can lead to applying water to resolve “drought”, and exacerbating the disease. To avoid this issue, make sure to look for lesions first.
Susceptible grass species
All major grass types, but especially prevalent in bentgrass, ryegrass, bluegrass, and St. Augustine. In St. Augustine, brown patch may be brownish in the interior with a yellow outer border ring.
What causes brown patch?
Brown patch is caused by the presence of the fungus, Rhizoctonia solani. This fungus occurs naturally in soils, and only causes damage when favorable conditions are present in the lawn.
Favorable conditions for brown patch
- High humidity
- Wet soil that drains poorly
- Excessive thatch
- Soil temperatures above 60°F
- Ambient temperatures between 60°–90°F, particularly 80°–90°F
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What's the difference between brown patch and patches of brown grass?
Brown patch is a type of lawn disease caused by a specific type of fungus, whereas brown or yellow patches in the lawn can be caused by a number of issues, not just fungus. In order to determine whether you have brown patch fungus, you’ll need to pay close attention to the grass blades, and characteristics of the patch(es). Although it’s great to know if you’re dealing with a fungus, most brown patches in your lawn can be resolved the same way: by improving basic lawn care practices.
How to treat brown patch fungus
Allow your lawn to dry out
Fix your overwatered lawn, then adopt a deep and infrequent watering schedule in the morning hours when you’re ready to water again.
Audit watering system
Evaluate watering practices to ensure your lawn is getting the right amount of water.
Resolve issues in shaded areas of lawn
Prune trees and shrubs to encourage air movement and increase light, or water less in shady areas. If issues don’t resolve, consider alternative plantings or mulch.
Seed in grass types with greater disease tolerance
First, reseed or resod affected areas as needed. Then continue to overseed with disease-resistant grass types.
Dethatch as needed
If your thatch levels reach over 1” you may occasionally need to lightly rake away thatch to reduce opportunities for high moisture and fungus to move in.
Delay nitrogen applications
When your lawn is experiencing a fungal episode, like a brown patch, we recommend avoiding nitrogen-based fertilizer applications until the issue resolves.
More severe cases of brown patch can lie dormant in the soil over winter, then reappear once temperatures warm up. If brown patch continues to persist in your lawn year to year, you may need to resort to using a fungicide treatment to resolve the lawn disease issue.
Will Sunday nutrients help brown patch?
When your lawn is ready for nutrients again, Sunday can help reduce future opportunities for lawn disease in your lawn. Many of the ingredients in our nutrient blends can help remedy soil, promote turf resiliency, and support grass growth — but they won’t grow new grass on their own and even healthy grass can be slow to fill in patches. Consider introducing Sunday’s grass seed to help fill in dead or bare spots, prevent weeds from coming in, and maintain proper moisture levels in your lawn.
Cited sources
Brown Patch. NC State Extension.
Lawn Diseases: Prevention and Management Guidelines. UC IPM.
Turf: Brown Patch. UMass Amherst Extension.
Turfgrass Diseases: Brown Patch. PennState Extension.
