Erwinia carotovora subsp. carotovora has recently been renamed Pectobacterium carotovora. It is one of the pectolytic bacteria causing extensive bacterial rots (bacterial soft rot, bacterial stem rot).
Life cycle and appearance of Bacterial soft rot, bacterial stem rot
Erwinia carotovora subsp. carotovora or Pectobacterium carovora is very common, but does not often reach epidemic population densities. It can survive as epiphytic bacteria on various plants or in the soil in low densities. It has also been found in the gut of insects, possibly spreading from decaying vegetation to the growing crop that way. Erwinia carotovora subsp. carotovora or Pectobacterium carovora infects plants through fresh wounds, for example pruning wounds. It cannot infect healthy green leaves, but can grow in senescent leaves and from there grow through the petiole to the main stem through the xylem vessels. High humidity is required for disease development. Erwinia carotovora subsp. carotovora or Pectobacterium carovora can also be found as secondary pathogen in plants that are infected by other pathogens. The bacteria that causes black leg in potato is a different subspecies.
In tomato, Erwinia carotovora subsp. carotovoraor Pectobacterium carovora causes bacterial stem rot as well as soft rot. Stem rot is first noticed when plants wilt at the time of first harvest or after that. The pith disintegrates and the stem becomes hollow. Because of the bacterial growth in the pith, the stem seems wet and slimy. Above or below the hollow stem the vascular tissue keeps its normal colour.
On the fruits, lesions first are small and sunken, water-soaked and light to dark brown. They are adjacent to wounds and natural openings at the stem end. Later the fruit becomes soft and lesion contents become liquid.