Beginner

Scientific Name
Pectobacterium carotovorum subsp. carotovorum

Identification
Stems

• A clear rot starts on wounds or lesions on stems caused by hail, wind-blown sand or farm equipment
• The decay is soft and slimy in wet weather. Under dry conditions, infected tissues may become dry and shriveled. Eventually the rotten tissue turns black.
• The rot extends up and down the stem from the point of infection. Infection can spread through the stems and stolons to daughter tubers, causing symptoms similar to blackleg.
• Tubers
• The aerial stem rot bacteria penetrate tubers through the tuber stem end. By contrast, blackleg infections are seed-borne and move up the stem.

Often Confused With
Blackleg 
Late blight

Period of Activity
More common after heavy rainfall on plants growing in rows damaged by farm equipment or after hail damage.

Scouting Notes

• Scouting should start at row closing.
• Fields should be monitored at least twice a week. 
• When walking fields, stop at many sites as possible and check plants at random.
• Always check low spots and areas of poor drainage

Thresholds
No thresholds established.

Advanced

Scientific Name
Pectobacterium carotovorum subsp. carotovorum

Identification
Stems

• A clear rot starts on wounds or lesions on stems caused by hail, wind-blown sand or farm equipment
• The decay is soft and slimy in wet weather. Under dry conditions, infected tissues may become dry and shriveled. Eventually the rotten tissue turns black.
• The rot extends up and down the stem from the point of infection. Infection can spread through the stems and stolons to daughter tubers, causing symptoms similar to blackleg.
• Tubers
• The aerial stem rot bacteria penetrate tubers through the tuber stem end. By contrast, blackleg infections are seed-borne and move up the stem.

Often Confused With
Blackleg 
Late blight

Biology
The aerial stem rot bacterium is soil borne. Contaminated surface water is an important source of infection.

The bacterium requires wounds or bruises to penetrate stems. Lesions often develop in rows that are damaged by farm equipment.

Aerial stem rot infections often develop in wet seasons. The bacterium spread rapidly by rain splashes. Potato varieties that develop big canopies are more susceptible to aerial stem rot.

Period of Activity
More common after heavy rainfall on plants growing in rows damaged by farm equipment or after hail damage.

Scouting Notes

• Scouting should start at row closing.
• Fields should be monitored at least twice a week. 
• When walking fields, stop at many sites as possible and check plants at random.
• Always check low spots and areas of poor drainage

Thresholds
No thresholds established.

Management Notes

• Use healthy seed
• Select well-drained fields.
• Avoid crop stress:
• Provide adequate levels of nutrients
• Manage other pests
• Match irrigation with crop needs. Do not over-irrigate
• Harvest tubers when the skin is set and avoid mechanical injury.