Leaf Spot Fungicides

Leaf spot diseases begin as infections of turfgrass leaves and are commonly associated with Bipolaris and Drechslera species. Kentucky bluegrass, ryegrass, fescues, and several warm-season grasses can be affected.

What to Look For

Individual blades develop brown, purple, or tan spots with darker margins. Spots may enlarge and join, giving the canopy a thin, dull, or scorched appearance while crowns and roots are still alive.

Why It Develops

Cool, wet weather and long leaf-wetness periods favor initial infection. Shade, low airflow, excessive or deficient nitrogen, thatch, low mowing, and drought stress can increase injury and allow the disease to progress.

Reduce Disease Pressure

• Use resistant cultivars and adapted seed mixtures.
• Maintain balanced fertility and an appropriate mowing height.
• Water deeply and early so leaves dry quickly.
• Reduce shade, improve airflow, and manage thatch.

What University Research and Extension Guidance Says

NC State recommends treating at the earliest leaf-spot stage when chemical control is warranted. University efficacy tables also show meaningful differences among active ingredients, so a product that controls other turf diseases should not be assumed effective on leaf spot.

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: Leaf Spot in Turf; University of Kentucky: Chemical Control of Turfgrass Diseases 2024.