Quick Tips for Avoiding Brown Patch

Brown patch in fescue lawn

Brown Patch (Rhizoctonia solani) is one of the most common and destructive fungal diseases affecting cool-season grasses like tall fescue and perennial ryegrass, as well as warm-season lawns such as bermudagrass and zoysiagrass. It thrives when high humidity combines with warm days (above 80°F) and mild nights (above 65°F)—a common weather pattern in late spring through early fall across the Southeast.

Left unchecked, Brown Patch can quickly cause large, unsightly areas of turf damage. However, with proper cultural practices and an understanding of the conditions that promote disease development, you can significantly reduce the risk.

Fertilize Strategically

Avoid applying fast-acting, high-nitrogen fertilizers between March 15 and September 15. Excess nitrogen encourages soft, lush growth that’s more prone to fungal infection.

Mow at the Right Height—Consistently

Improper mowing is a major contributor to turf stress and disease.

• Fescue: Maintain at 3" or higher

• Bermudagrass: Keep around 2.5"

Cutting too short limits the plant’s ability to photosynthesize, weakening its defense system. Letting grass grow too long increases humidity near the soil—prime conditions for Brown Patch.

• Pro Tip: Never remove more than 1/3 of the blade height in one mowing.

Water Smart

Fungal diseases thrive on wet leaf surfaces. Watering at the wrong time of day can make things worse.

• Water early in the morning (5–9 AM) so grass dries out by midday.

• Avoid watering in late afternoon or evening when water sits on blades overnight.

You can’t prevent dew or rain, but avoiding nighttime irrigation reduces risk.

Aerate to Improve Airflow

Core aeration alleviates soil compaction and increases airflow—critical for lowering humidity at the base of your lawn.

• Aerate at least once annually, ideally in both spring and fall for high-traffic lawns.

When to Watch Closely

Brown Patch is most likely to appear:

• After summer rainstorms

• During stretches of hot, humid nights

• Following heavy nitrogen application

Look for irregular, yellowish patches with a darker, possibly gray or purplish “smoke ring” border. If Brown Patch does develop, early treatment with a fungicide can limit damage, but long-term prevention starts with healthy maintenance.

Learn More

• NC State Extension: Brown Patch in Turf

• University of Kentucky Plant Pathology: Brown Patch

• Penn State Extension: Turfgrass Diseases: Brown Patch