Forsythia Crown Gall: Pruning Out Bacterial Disease

Knotty swellings on forsythia stems are crown gall (Agrobacterium tumefaciens)—a bacterial disease with no chemical cure.

Management

• Prune affected branches 6+ inches below visible galls
• Disinfect pruners between cuts (1:10 bleach solution)
• Destroy infected material—don't compost

The bacterium persists in soil, so avoid replanting susceptible species in the same spot. Crown gall affects many woody plants; euonymus, rose, and willow are also vulnerable.