Rudbeckia (Black-Eyed Susan) Foliage Decline: Multiple Culprits

Why Black-Eyed Susan Leaves Brown and Die by Summer’s End

Rudbeckia foliage starts strong but develops brown spots, dries, and dies while flowers persist. Common issues:

Diseases

• Downy mildew (yellow mottling, wilting seedlings)
• Powdery mildew (white coating late summer)
• Leaf spots (several fungi, usually cosmetic)
• Verticillium wilt (sudden collapse, vascular discoloration)

Insects

• Aphids (honeydew, sooty mold)
• Goldenglow sawfly larvae (defoliation)
• Four-lined plant bug (round brown sunken spots)

Management

1. Remove/destroy infected leaves promptly.
2. Fall cleanup: remove all plant debris to reduce overwintering inoculum.
3. If verticillium confirmed, rotate to non-susceptible plants.

Since roots survive and flowers bloom, plants aren’t severely threatened. Annual sanitation is the best long-term strategy.