Black Rot
Disease · Commonly affects: Cabbage, Broccoli, Cauliflower, Kale, Brussels sprouts, Turnip
Black rot is a bacterial disease of cabbage and its relatives, caused by the bacterium Xanthomonas campestris pv. campestris. It matters to home gardeners because it spreads quickly in warm, wet weather and can ruin an entire planting of cole crops in a single season.
How to identify it
Look for yellow, V-shaped patches along the leaf edges, with the point of each V aimed inward toward the midrib. Inside these areas the leaf veins darken to brown or black, and slicing through an infected stem often reveals a blackened ring of water-conducting tissue. Affected leaves eventually turn brown, dry out, and drop.
Damage
The bacteria clog and blacken the plant's vascular tissue, causing stunting, wilting, and lopsided or one-sided growth. Heads may fail to form or rot from the inside, and soft-rot bacteria frequently invade the damaged tissue and turn it into a foul, slimy mush.
Prevention
Start with certified disease-free seed and transplants, since the pathogen commonly arrives on infected seed, and rotate cole crops so they do not return to the same bed for at least two to three years. Space plants for good air movement and keep the garden clear of cruciferous weeds such as wild mustard and shepherd's purse, which can harbor the bacterium. Clean up and remove all crop debris after harvest, and choose cabbage varieties with some resistance where the disease is a recurring problem.
How to manage it
Pull and destroy infected seedlings and plants as soon as you notice symptoms, and do not add them to the compost pile. Water at the base of the plant instead of overhead, and stay out of the patch while the foliage is wet, because brushing against wet plants carries the bacteria from leaf to leaf. Prune out lower leaves showing early edge lesions and disinfect knives, pruners, and other tools between plants to slow the spread.
General guidance for US home gardens, focused on prevention and non-chemical control. For a confirmed diagnosis and options specific to your area, contact your local Cooperative Extension office. Page updated Aug 4, 2026.