Lawn Problem Solver

Brown patch Fungal Disease

Rhizoctonia solani

Brown Patch is a common fungal lawn disease that causes circular brown or tan patches in turf, especially during hot, humid weather. It is most common in tall fescue, perennial ryegrass, and other cool-season lawns during summer stress. Brown Patch can make a healthy lawn look thin, scorched, or drought-stressed almost overnight.

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Brown patch

What Brown patch Looks Like

Brown Patch usually appears as circular or irregular brown, tan, or yellowish patches in the lawn. The patches can range from a few inches wide to several feet across.

In tall fescue, individual grass blades may have tan lesions with darker brown borders. In the early morning, you may also notice a smoky gray or dark outer ring around the patch when humidity is high.

Why It Spreads

Brown Patch develops when heat, humidity, and extended leaf wetness create ideal conditions for fungal growth. It is especially common when lawns are watered late in the day, mowed too low, fertilized too heavily with quick-release nitrogen during disease-prone weather, or growing in areas with poor airflow.

Tall fescue and perennial ryegrass are especially susceptible during hot, humid summer conditions.

How to Prevent It

Prevent Brown Patch by reducing leaf wetness and improving overall turf health. Water deeply and early in the morning, avoid evening irrigation, mow at the correct height, improve airflow in shaded or tight areas, and avoid over-applying nitrogen during hot, humid weather.

For tall fescue lawns, choosing or overseeding with improved turf-type tall fescue varieties can help reduce future disease pressure.

Best timing: Late spring through summer before hot, humid disease pressure begins.

How to Control It

Use a lawn fungicide labeled for Brown Patch and safe for your lawn type. Apply preventively or at the first signs of disease during warm, humid weather.

For best results, rotate fungicide groups when repeat applications are needed. Avoid mowing immediately before or after application, and always follow the product label for timing, rate, and reapplication intervals.

Best timing: At the first sign of symptoms during warm, humid weather. Start first application of fungicide in May. Reapply every 28 days.

Recommended Solution

Brown Patch is best managed with a combination of proper lawn care and timely fungicide applications. Start by correcting the conditions that encourage disease, such as evening watering, excessive leaf wetness, poor airflow, and heavy nitrogen during hot, humid weather.

If Brown Patch is active or conditions are favorable, apply a labeled fungicide before the disease spreads across the lawn. Brown Patch often damages the leaf blades more than the crown of the plant, so many lawns can recover once the disease slows down and healthy growth resumes.

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Frequently Asked Questions

What causes Brown Patch in lawns?

Brown Patch is caused by the fungus Rhizoctonia solani. It becomes active during warm, humid weather, especially when the lawn stays wet for long periods.

What grass types get Brown Patch?

Brown Patch can affect many turfgrasses, but it is especially common in tall fescue, perennial ryegrass, and other cool-season grasses during summer stress.

Will Brown Patch kill my lawn?

Brown Patch usually damages the grass blades first, so many lawns can recover when conditions improve. Severe or repeated outbreaks can thin the lawn and may require fungicide treatment, better watering habits, and overseeding in the fall.