Black Rot of Cabbage and Related Crops
Vegetable Disease Information Note 16 (VDIN-0016)
Charles W Averre, Extension Plant Pathologist
of cabbage has a long history in North Carolina where cabbage and related
crops are grown. Although the disease is usually of minor importance,
when conditions are suitable it may become serious and many growers sustain
severe economic loss. In some cases, the crop may be a total loss.
In the field, the disease is easily recognized by the presence of large yellow to yellow-orange "V"-shaped areas extending inward from the margin of a leaf, and by black veins in the infected area. Usually only a few of the outer leaves are involved.
If infection occurred in a young seedling, the disease is usually much more severe since the main stem becomes infected and the disease becomes systemic in the plant. These plants remain stunted and the veins in the stems are black. 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.
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 seedling infection is made more difficult since
only a few (less than 1%) of the seedlings in a lot may have the disease.
The recognition of infected seedlings is very important in the control
of the disease.
Black rot of cabbage is caused by the bacterium Xanthomonas campestris. The bacterium enters the plant principally through the hydathodes, stomates, and injuries on the leaves. In time, the bacterium spreads in the vascular system of the leaf and stem. The seed stalk and seed eventually become infected. Plants growing from infected seed will have the disease.
The bacteria spread and cause most damage in wet, warm weather. It does not usually spread in dry weather and is inactive at temperatures below 50 degrees F. The bacteria can survive in the soil for a year and may be spread in surface water or through irrigation.
cause a similar disease in most members of the crucifer family, such as
mustard, collards, wild mustard, cauliflower, Brussel sprouts, kohlrabbi,
rutabaga, kale, rape, and chinese cabbage. The disease is apparently restricted
to this family of plants.
of this disease is based on sanitation. There are no commercially acceptable
varieties resistant to the disease at this time. Spraying with copper
fungicides could be expected to reduce spread in the field, however, copper
sprays cause black spots on the outer leaves and are not recommended.
The following steps will reduce the changes of the disease occurring,
the spread in the field, and resulting economic loss:
North Carolina Cooperative Extension Service
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Recommendations of specific chemicals are based upon information on the
manufacturer's label and performance in a limited number of trials. Because
environmental conditions and methods of application by growers may vary
widely, performance of the chemical will not always conform to the safety
and pest control standards indicated by experimental data. All recommendations
for pesticide use were legal at the time of publication, but the status
of registration and use patterns are subject to change by actions of state
and federal regulatory agencies.