Large Patch Fungicides

Large patch is a Rhizoctonia disease of warm-season grasses, especially zoysiagrass and centipedegrass, during spring and fall transitions.

What to Look For

Orange, yellow, or reddish-brown patches expand from several feet to many yards wide. Leaves at the active margin pull easily from rotted sheaths, while crowns and roots may remain alive.

Why It Develops

Cool, wet soil, excess thatch, poor drainage, low mowing, and nitrogen applied too late in fall or too early in spring favor disease while warm-season turf is growing slowly.

Reduce Disease Pressure

• Avoid late-fall and early-spring nitrogen that stimulates tender growth.
• Improve drainage and irrigation scheduling.
• Reduce excessive thatch and compaction.
• Maintain the recommended mowing height for the grass species.

What University Research and Extension Guidance Says

University trials show preventive applications timed to declining fall soil temperatures are more dependable than spring rescue treatments. Root-zone placement can improve results for some products. Repeated spring-only programs may suppress symptoms without reducing the underlying fall infection cycle.

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: University of Kentucky: Chemical Control of Turfgrass Diseases 2024; Penn State Extension: SDHI Fungicides for Turfgrass Diseases.