Leaf and Sheath Spot (Mini Ring) Fungicides

Leaf and sheath spot, also called mini ring, is caused by heat-loving Rhizoctonia-related fungi and is most often seen on ultradwarf bermudagrass putting greens.

What to Look For

Yellow or bronze rings and patches, usually 3 to 24 inches across, appear in late summer. Lower leaves may bleach, and severe disease darkens sheaths, stolons, and nodes. Rings can persist into spring.

Why It Develops

The pathogen is most active in hot weather. Low nitrogen, drought, very low mowing, aggressive growth regulation, and mechanical injury from summer verticutting or aerification can intensify symptoms.

Reduce Disease Pressure

• Raise mowing height during peak stress and use rolling if green speed is needed.
• Avoid aggressive verticutting in July and August.
• Use regular summer urea applications where agronomically appropriate.
• Avoid chronic drought and excessive growth-regulator stress.

What University Research and Extension Guidance Says

NC State research found that weekly urea supplying about 0.1 to 0.3 pound nitrogen per 1,000 square feet dramatically reduced severity, while ammonium sulfate increased it. Preventive fungicides perform best with adequate urea fertility and should be watered into stolons, nodes, and roots.

Choosing and Using a Fungicide

Use the products below as a starting point, then match the active ingredient, FRAC group, turf species, use site, timing, rate, interval, and watering directions to the current product label. Preventive or very early applications are usually more reliable than rescue treatments after extensive injury. Rotate effective FRAC groups and combine fungicides with the cultural changes above.

Research and label note: University research may identify useful activity even when a current product label does not name this disease. That is research evidence, not a label direction. Apply a product only where the turf or application site and use pattern are permitted, and follow the complete label and applicable state requirements.

University sources: NC State Extension: Leaf and Sheath Spot in Turf; University of Kentucky: Chemical Control of Turfgrass Diseases 2024.