Black leg and stem rot

Pectobacterium spp., Dickeya spp.

Symptoms

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

All Dickeya and Pectobacterium species occurring in potato are listed with some distinguishing characteristics. The first symptoms are wilting of the upper leaves (initially this can be reversed) and a pale green discolouration.

Black leg (black leg stems, yellow stunted growth)

Pectobacterium atrosepticum

• Mainly in cool temperatures (18-21°C) and anaerobic conditions

Wilting followed by stem rot

Pectobacterium wasabiae
Pectobacterium carotovorum ssp. brasiliense
Dickeya solani

• Wet rot with fishy odour
• Mainly in higher temperatures (> 25°C) and anaerobic conditions

Wilting followed by stem necrosis

Dickeya dianthicola
Pectobacterium carotovorum spp.carotovorum

• No smell
• Mainly in higher temperatures (> 25°C) and anaerobic conditions

Wilting followed by stem necrosis

• Bacteria can be latent on seed tubers
• Infection in the field is via the roots
• Bacteria are mainly spread by machinery. Hygiene is very important
• Insects, damage and haulm destruction

Possible confusion with

• Pink rot (Phytophthora erythroseptica)