Bacterial tuber rot

Dickeya spp. (formerly Erwinia chrysanthemi) and Pectobacterium spp.

Symptoms

• The symptoms of the bacterial disease in the potato tuber are strongly influenced by the potato variety, temperature and moisture. This makes it very difficult to determine a clear distinction between the various types of bacteria based on the symptoms of the infection
• Laboratory analysis is required for an exact identification

All the Dickeya and Pectobacterium species occurring in potatoes are listed below with a number of distinguishing characteristics.

Vaguely outlined wet rot with jelly-like texture, odourless

• Dickeya solani, Dickeya dianthicola

Often darkly outlined wet rot with mushy structure, rather odourless

• Pectobacterium atrosepticum, Pectobacterium carotovorum ssp. brasiliense

Indistinct outlined rot, smelly (fish odour)

• Pectobacterium carotovorum spp. carotovorum

Indistinct outlined rot with fish odour and CO₂ bubbles when tuber is pressed. Tubers leak moisture

• Pectobacterium wasabiae

Symptoms

• Humid and low-oxygen soil conditions are important for all species (wet anaerobic conditions)
• Infection via the stolon end and lenticels
• Infection via the lenticels starts with small brown spots around the lenticels
• Infection spreads very rapidly

Infection and spread

• Bacteria can be latent on the seed tubers
• In the field the plants are usually infected via the root system. Bacteria in the infected tuber are released into the soil and enter the plant via the roots
• Bacterial rot is usually spread by machinery, hygiene is very important (insects, contact, damage and haulm destruction)

Possible confusion with

• Pink rot (Phytophthora erythroseptica)
• Water rot (Pythium spp.)