Bacterial Blackleg Stem Rot

Plants that grow from infected seed often die shortly after emergence. Symptoms include: inky black stem below ground, sometimes extended far above ground; and wilting of leaves or entire stems.

Causal Agent:

Pectobacterium atrosepticum, Dickeya spp.


Blackleg begins with planting infected seed. Seed can be infected during seed production, handling, cutting, and planting. Infected seed pieces sometimes rot before emergence — this is called seed piece decay. Not all infected plants produce symptoms, but can still pass the infection to progeny tubers and therefore into storage.


Blackleg occurs everywhere potatoes are grown.


  1. Prevention is key.
  2. Know your seed source — healthy seed is critical.
  3. Sanitize seed cutting equipment between lots by cleaning all soil and debris from cutting equipment and applying a disinfestant.
  4. Plant well-suberized seed into well-drained soil of 50-58 degrees F.

Further Reading:

Pacific Northwest Pest Management Handbooks

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