Clavibacter michiganensis sp.

Bacterial canker of tomato


Clavibacter is a quarantine organism in Europe, which means that strong efforts are used to prevent the bacterium from entering. When the occasional infection is found, strict measures are taken to eradicate the infection. In tomato, growers must either destroy the infected crop entirely or, if the crop is old, only the plants in the infected area, with a substantial buffer zone. Replanting can only take place after thorough disinfection has been proven to the authorities. Potato growers lose their entire crop of the affected field and potatoes from other fields on the farm, are labelled as ‘suspect’ that year. On the infected field no potatoes or other Solaneceaous crops can be planted for five years. On other fields on the same farm, no seed potatoes can be grown for one year after infection.

Life cycle and appearance of Bacterial canker of tomato

Clavibacter is seed-borne and tuber-borne and primary infection is mostly from infected propagation material. It spreads to other seedlings by touching the plants in greenhouse crops and by water in field crops, for example through splashes of rain or irrigation. Both in greenhouses and in the field, spraying may also spread the bacteria. The bacteria can also be dispersed by machinery, crates and tools. The bacteria infect the new plants by entering through wounds and then growing into the vessels of the plant. Plant growth is inhibited and the plant wilts because the xylem vessels become blocked. The bacterium can survive some time in crop residues like volunteer tubers and potato crop residues. Infected tubers can infect healthy tubers during post-harvest storage.

How to prevent Bacterial canker of tomato

  • Use clean propagation material:
    • Use only tested and disinfected seed
    • Use only tested and certified seed potatoes
  • Apply strict hygiene measures in greenhouse crops: remove infected plants in closed plastic bags, destroy crop residues, use protective clothing and gloves, disinfect tools and greenhouse structures
  • Use a crop rotation in field crops of at least two years and alternate with a non-host crop
  • Apply deep-ploughing to stimulate the decay of crop residues

Prevent plant diseases by optimizing plant potential and crop resilience.