Black-Eyed Susan Leaf Spots: Fungal Disease Management

Long-established black-eyed Susans (Rudbeckia) develop black spots on leaves, progressing to entirely black, curled foliage.

Diagnosis: Fungal Leaf Spot

Common in humid, crowded conditions with poor air circulation and overhead watering.

Treatment Plan

1. Sanitation: Remove and destroy all infected leaves and severely affected plants. Do not compost.
2. Watering: Irrigate at soil level only; avoid wetting foliage.
3. Spacing: Thin plants to improve airflow.
4. Fungicide: Apply a labeled fungicide (e.g., chlorothalonil, copper) per package directions.

Prevention

• Rotate planting locations if possible.
• Choose resistant cultivars.
• Mulch to reduce soil splash.

Prompt action can save the planting and prevent spread to other perennials.