Southern Blight Fungicides

Southern blight is a hot-weather crown and stem disease caused by Sclerotium rolfsii. It can damage several turf species and is most likely in warm, humid regions or unusually hot wet periods.

What to Look For

Circular or irregular yellow-brown patches expand rapidly. White fanlike mycelium may grow at the soil surface, followed by small round sclerotia that change from white to tan or brown.

Why It Develops

High soil temperature, humidity, thatch, moist organic debris, dense turf, and poor airflow favor the pathogen.

Reduce Disease Pressure

• Remove heavy clippings and organic debris from active areas.
• Improve airflow and drainage and avoid over-irrigation.
• Manage excessive thatch.
• Confirm the disease because symptoms can resemble brown patch or Pythium.

What University Research and Extension Guidance Says

Published turf trials are less extensive than for brown patch or dollar spot. Kentucky and Penn State identify activity from flutolanil and several broad-spectrum combinations, but performance should be judged against local conditions and the current label. Early treatment is more realistic than trying to recover severely rotted crowns.

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.