Powdery Mildew Fungicides

Powdery mildew is primarily a shade and airflow problem on Kentucky bluegrass and other susceptible cool-season turf.

What to Look For

A white or gray powder coats leaf surfaces, beginning in shaded patches. Infected leaves may yellow, thin, and decline when disease is chronic.

Why It Develops

Dense shade, poor air movement, cool humid weather, excessive nitrogen, and susceptible cultivars favor infection. Unlike many foliar diseases, free water on the leaf is not required.

Reduce Disease Pressure

• Prune or thin vegetation to improve light and airflow.
• Raise mowing height and reduce traffic in shaded areas.
• Avoid excessive nitrogen.
• Renovate chronic sites with shade-tolerant turf or a non-turf groundcover.

What University Research and Extension Guidance Says

University guidance treats site correction as the long-term solution. Fungicides can suppress symptoms on high-value turf, but repeated treatment will not make a deeply shaded site suitable for a sun-loving cultivar.

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.