Yellow Tuft (Downy Mildew) Fungicides

Yellow tuft, or downy mildew, is a water-mold disease most common on creeping bentgrass and annual bluegrass putting greens in persistently wet areas.

What to Look For

Small raised yellow spots contain dense clusters of yellow tillers growing from a single crown, creating a witches'-broom appearance. Spots may follow drainage patterns, and affected plants pull easily from the canopy.

Why It Develops

Cool wet weather, poor drainage, over-irrigation, compaction, and excessive thatch favor infection.

Reduce Disease Pressure

• Correct surface and subsurface drainage.
• Reduce over-irrigation and avoid chronic saturation.
• Aerify and topdress to reduce compaction and thatch.
• Avoid establishing high-value turf in low areas that cannot be drained.

What University Research and Extension Guidance Says

NC State reports that mefenoxam and metalaxyl are very effective, while curative control is difficult and other product efficacy is less certain. Preventive treatment during cool, wet periods is the preferred chemical strategy on chronic sites.

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: Yellow Tuft in Turf; Penn State Extension: SDHI Fungicides for Turfgrass Diseases.