The heads from these plants deteriorate rapidly after harvest. Although the distribution of diseased plants in the field may be quite uniform, the disease may be more common and severe in low and shaded areas. If a few infected seedlings were set in the field, scattered pockets of diseased plants will appear in the field early in the growing season. Diseased plants often appear in the same rows as a result of spread during cultural operations. Seedling infection is often very difficult to detect.
Infected seedlings tend to be stunted and often exhibit one-sided growth.
The leaves may be light green, and lower leaves may drop prematurely. Vascular elements in the stems will be black. However, infected seedlings may show no symptoms at all. The recognition of infected seedlings is very important in the control of the disease. Cause Black rot of cabbage is caused by the bacterium Xanthomonas campestris .