Hydrangea Leaf Spots: Cercospora vs. Anthracnose Identification

Distinguishing Two Common Hydrangea Leaf Spots

Hydrangeas with brown spots—small scattered vs. large edge spots—likely have one of two fungal diseases requiring different management.

Disease 1: Cercospora Leaf Spot

• Symptoms: Many small (1/8–1/4"), circular, purple-brown spots with gray centers. Scattered randomly. Coalesce in wet years.
• Timing: Mid-late summer.
• Management: Sanitation (remove fallen leaves), avoid overhead water, fungicides (chlorothalonil, myclobutanil) if severe.

Disease 2: Anthracnose

• Symptoms: Larger, irregular, often target-ringed spots. Concentrated on leaf edges/tips. Can cause distortion.
• Timing: Spring-early summer (cool, wet).
• Management: Same cultural practices. Fungicides: copper, mancozeb, chlorothalonil.

Diagnostic Resource

Alabama Extension Guide: Photos + management for both diseases

Action Plan

1. Compare your spots to guide photos.
2. Remove/destroy affected leaves (sanitation).
3. Switch to drip irrigation / base watering.
4. Mulch to reduce splash.
5. Fungicide only if severe and correctly identified.

Both diseases are manageable. Correct ID ensures the right fungicide timing.