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.

Biology:

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.

Dispersal:

Blackleg occurs everywhere potatoes are grown.

Management:

  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