Gray Leaf Spot

What is Gray Leaf Spot?

Gray leaf spot is a fungal disease caused by Pyricularia grisea. It primarily affects St. Augustine but is also found in Bermudagrass, centipedegrass, and zoysia.

When & How Does it Occur?

🌡 Ideal Conditions:

• Daytime temperatures between 75-95°F and nighttime temperatures above 65°F.

• Most severe during humid, rainy periods.

🌿 How it Spreads:

• The fungus survives in thatch and dead foliage during dry conditions.

• Spores spread via wind, rainfall, irrigation, and lawn equipment when moisture levels rise.

What to Look For

🔍 Early Symptoms:

• Small, brown leaf spots that quickly expand.

• Spots become oval, tan, and gray with brown or purple borders.

• Some may have a yellow halo or cause general leaf yellowing.

⚠️ Advanced Disease Symptoms:

• In humid conditions, a grayish fungal growth appears on dying foliage.

• Grass blades wither and die if too many spots form.

• Large turf areas may look scorched, resembling drought stress.

Management Strategies

✅ Mowing & Lawn Care:

• Mow at the correct height and only when the grass is dry.

• Sharpen mower blades to prevent additional stress.

• Bag & dispose of clippings if the disease is present.

✅ Improving Lawn Health:

• Reduce thatch buildup.

• Aerate to improve airflow and soil circulation.

• Limb up overhanging trees and prune shrubs to increase sunlight.

✅ Irrigation Best Practices:

• Water deeply but infrequently (max 3x per week, totaling 1 inch of water).

• Irrigate in the morning to allow quick drying and prevent fungal growth.

✅ Avoid These During Disease Activity:

• Post-emergent weed killers (can stress the lawn further).

• High nitrogen fertilizers (can fuel fungal growth).

📢 Early identification and proper lawn care are key to preventing severe outbreaks of Gray Leaf Spot!