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Xanthomonas campestris pv. campestris Xanthomonas campestris pv. campestris (Pammel, 1895) Dowson, 1939 · formerly or also: Xcc
Black rot is the most important bacterial disease of cabbage, cauliflower, broccoli and other crucifers worldwide. The bacteria enter through pores at the leaf edges and spread through the veins, causing yellow, V-shaped lesions that point toward the midrib, with blackened veins inside. Infected seed and transplants carry the disease into new fields, and warm, wet weather spreads it quickly.
Black rot of crucifers is caused by Xanthomonas campestris pv. campestris Xanthomonas campestris pv. campestris (Pammel, 1895) Dowson, 1939, a bacterium (Gram-negative) (order Lysobacterales (formerly Xanthomonadales), family Lysobacteraceae).
Older or alternative scientific names: Xcc.
Found worldwide, most damaging in warm, humid regions and in wet seasons.
| Region | Status |
|---|---|
| Asia | Widespread |
| Africa | Widespread; major on cabbage |
| Americas | Widespread |
| Europe and Oceania | Present |
Rod-shaped bacteria that produce yellow, slimy colonies and a gum (xanthan). Several races exist, of which races 1 and 4 are the most common worldwide. The bacteria survive in seed, crop debris and cruciferous weeds. In cool, wet conditions guttation drops at the leaf margins carry bacteria into the hydathodes, which is why infections start at the leaf edges.
| Crop stage | What you see |
|---|---|
| Seedlings and transplants | Seed leaves yellow, blacken and drop; small dark lesions at leaf margins. |
| Leaves | Yellow, V-shaped lesions starting at the leaf edge with the point toward the midrib; veins inside turn black; leaves wilt and drop. |
| Stems and heads | Black ring in the vascular tissue when the stem is cut across; heads stunted, often rotted by secondary soft-rot bacteria. |
Infected seed and transplants introduce the bacteria; debris and weeds carry them over between seasons. Bacteria enter through hydathodes (water pores) at leaf margins, through wounds and through insect damage, and move through the veins. They spread in rain splash, overhead irrigation and on hands and tools during transplanting and clipping of seedlings. Even a very small share of infected seed can start an epidemic in transplant beds, where crowded, wet seedlings allow rapid spread.
| Stage | Duration | Notes |
|---|---|---|
| Seed and transplant infection | At planting | Main introduction route. |
| Entry through leaf margins and wounds | In wet weather | Guttation drops help entry. |
| Spread in the veins | Days to weeks | V-shaped lesions. |
| Survival in debris and weeds | Months to about two years | Until debris decomposes. |
Most severe at about 25-30 °C with rain, high humidity and heavy dew.
Continuous spread in warm, wet weather.
Infected seed and transplants, warm and wet weather, overhead irrigation, clipping of transplants, insect damage, and short rotations with crucifers. Planting fields next to older infected brassica crops, or reusing trays and tools without cleaning, also increases spread.
There is no economic threshold; management is preventive, based on clean seed and transplants, rotation and sanitation.
Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.
Losses range from small to total crop loss in warm, wet seasons, especially when infected transplants are planted; heads may rot in the field and in storage. Infected heads often break down into a slimy rot when soft-rot bacteria invade.
Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.
Copper sprays may slow spread in nurseries and fields but give limited control; they do not cure infected plants. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.
| Scheme | Group | Mode of action | Notes |
|---|---|---|---|
| FRAC | M01 | Inorganic (copper) - multi-site | Limited effect; protectant. |
Cabbage, cauliflower, broccoli, kale, Brussels sprouts, kohlrabi, Chinese cabbage, turnip, radish, oilseed rape, mustards and cruciferous weeds.
How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:
Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.