Controlling Black Spot on Peonies in St. Louis Gardens

Fungal/Bacterial Leaf Spot on Peonies

Four disease-prone peonies in Zone 5 develop black leaf spots that cause premature defoliation. Neighboring peonies stay clean, suggesting a localized inoculum source.

Management Steps

1. Sanitation: Remove and destroy all spotted leaves now. In fall, cut all stems to ground and dispose of debris.
2. Fungicide: Apply Hi-Yield Copper Fungicide (copper octanoate) per label at first sign of spots. Reapply in 7–10 days. Copper covers both fungal and bacterial pathogens.
3. Early prevention: Next spring, spray as new shoots emerge and repeat per label through bloom.
4. Cultural: Improve air circulation; avoid overhead watering; mulch to reduce splash.

Consistent sanitation and early copper sprays should break the disease cycle and keep foliage attractive all season.