I suspect your cabbage have bacterial soft rot. Bacterial soft rot is a group of diseases that affect various crops worldwide. These rots damage succulent plant parts like fruits, tubers, stems, and bulbs. Commonly affected vegetables include potato, carrot, tomato, cucurbits (such as cucumbers, melons, squash, and pumpkins), and cruciferous crops (like cabbage, cauliflower, and bok choy).

Bacterial soft rot is caused by several bacteria, including the species of Pectobacterium, Dickeya, Pseudomonas, Bacillus, and Clostridium. These bacteria can enter plants through wounds caused by tools, insects, hail, or natural openings. Wet weather exacerbates the problem, especially when plants lack sufficient calcium in the soil.

Avoid wet conditions by planting in well-drained soil, controlling watering, and spacing plants adequately so they can dry out between watering and decrease humidity.

Once soft rot bacteria infect plant tissue, there are no treatments. Remove and discard infected plants or plant parts promptly. Do not bury or compost the material.