Pseudomonas marginalis is caused by a bacterium that lives underground.
Bacterial soft rot
Pseudomonas marginalis or Bacterium marginale is caused by a bacterium that lives underground. High levels of nitrogen in the soil and warm, humid weather increase the likelihood of infection. Splashing rain water from infected soil gets onto the leaf and then the bacteria enter the leaf through the stomata. The leaf edges turn brown to black after which the entire leaf is affected and then the plant itself.
In addition to Pseudomonas marginalis, Erwinia carotovora and E. chrysanthemi can also cause soft rots. The latter two bacteria can also occasionally cause wet rot (wilting) during storage. Once affected, the bacteria multiply explosively.
Where to find
Damage to plants is unfortunately irreversible.
Avoid over-fertilization and harvest chicory when the weather is dry.
Pseudomonas marginalis can still strike even when the chicory is stored. Good aeration of the room helps prevent deterioration.