Red Thread Fungicides

Red thread is a foliar disease of slow-growing, low-fertility turf. It is common on perennial ryegrass and fine fescues but can affect many cool-season grasses.

What to Look For

Irregular pink or tan patches develop with red or coral threadlike fungal strands projecting from leaf tips. The disease blights leaves but usually does not kill crowns or roots.

Why It Develops

Cool humid weather, long leaf wetness, low nitrogen, slow growth, compaction, and poor rooting favor symptoms.

Reduce Disease Pressure

• Correct nitrogen deficiency with a light, balanced application.
• Water early and improve airflow.
• Mow regularly with sharp blades and remove excessive infected clippings.
• Aerify compacted soil and improve rooting.

What University Research and Extension Guidance Says

University guidance often recommends a small nitrogen correction before fungicide because turf can outgrow the foliar damage. Fungicides are most justified on high-value sites or persistent outbreaks. Kentucky's review also notes that pink patch can occur under similar conditions but does not respond identically to every product.

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.