Brown patch is a damaging fungal disease that specifically targets cool-season grasses, such as Kentucky bluegrass, perennial ryegrass, and tall fescue. Caused by the fungus Rhizoctonia solani, this disease can rapidly damage large areas of a lawn, creating unsightly discolored patches. Thankfully, it is possible to prevent and treat brown patch if you can identify it early, which is exactly why we have put together this guide.
Come read all about brown patch and what you can do to keep it out of your lawn. Be sure to check out our lawn care services for the Vancouver, WA area that will help keep your turf healthy and free from disease!
Brown patch in cool-season grasses manifests as circular or irregular areas of discolored grass, often tan or brown. These patches can range from a few inches to several feet in diameter. One of the most distinctive features is a yellow or light brown "smoke ring" around the edges of the patches, particularly noticeable in the morning when dew is present. This ring indicates active fungal growth and is a reliable sign of brown patch in lawns.
On closer inspection, grass blades in the affected areas may exhibit tan or light brown lesions bordered by a dark, water-soaked margin. These lesions weaken the grass, causing it to thin out and die back, leaving behind patchy, unhealthy areas. Brown patch is most common in lawns with poor drainage, high humidity, or excessive nitrogen fertilization, making these conditions key factors to address.
How To Identify Brown Patch:
The Rhizoctonia solani fungus responsible for brown patch is also responsible for the lawn disease called “large patch,” which affects only warm-season turf. Once thought to be caused by different fungi, large patch and brown patch are now known to come from the same invasive species.
Brown patch exclusively affects cool-season grass types and thrives during hot, humid weather, particularly when nighttime temperatures stay above 65°F and daytime temperatures exceed 80°F. These conditions are especially common in the summer, even in regions where cool-season grasses typically thrive.
Prolonged wetness from heavy dew, frequent rainfall, or overwatering creates the perfect environment for the fungus to spread. Over-fertilization with nitrogen during the summer also makes turfgrasses more susceptible, as the lush, fast-growing blades become more vulnerable to fungal infections. Most importantly, poor soil drainage and compacted areas largely contribute to the development of brown patch by trapping moisture and reducing airflow.
Common Causes Of Brown Patch:
Brown patch poses a significant threat to the health and appearance of lawns. The disease weakens grass blades, reducing their ability to photosynthesize and grow. While brown patch typically doesn’t kill the roots or crowns of grasses, it can severely thin the lawn, creating unsightly patches that are vulnerable to weeds, pests, and more. The damage caused by brown patch can necessitate reseeding or resodding your lawn if the grass is not properly cared for and can not easily recover from the stress.
Brown patch primarily affects the grass blades of cool-season grasses, rather than the roots or crowns. This means that, with proper care, the grass has the potential to recover. However, severe infections can cause significant thinning, leaving large bare patches that may struggle to fill in naturally.
Cool-season grasses like Kentucky bluegrass and tall fescue can usually survive brown patch if it is addressed quickly. However, delayed treatment or continued unfavorable conditions can lead to lasting damage, requiring reseeding or additional interventions to restore the lawn.
Prevention is key when it comes to brown patch in your lawn. The fungus responsible for this lawn disease can only develop under certain conditions, so maintaining a lawn that avoids such situations is the most effective way to deter brown patch.
If brown patch has already appeared in your lawn, immediate action is essential to prevent further damage. Thankfully, foliar diseases like brown patch are reversible if you catch them early. While fungicides can be effective, they should be a last resort and should only be applied by a professional lawn care provider. Keep the following tips in mind if you want to prevent brown patch from taking over your turf!
