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Black rot on cabbage

A serious bacterial disease (Xanthomonas campestris pv. campestris). The bacterium enters through leaf margins and wounds, then grows into the veins, turning them black and dry. There is no effective curative treatment.

Symptom photos

Black rot — Young plant — wedge-shaped, yellow-brown lesions spreading in from the leaf margins — Young plant — wedge-shaped, yellow-brown lesions spreading in from the leaf margins Photo: Scot Nelson, licence CC0

Black rot — Leaf — dry, light-brown necrosis with a yellow halo, spreading in from the margin — Leaf — dry, light-brown necrosis with a yellow halo, spreading in from the margin Photo: Scot Nelson, licence CC0

Black rot — Head — extensive dry, grey-brown rot of the wrapper leaves — Head — extensive dry, grey-brown rot of the wrapper leaves Photo: Scot Nelson, licence CC0

Black rot — Young leaf — dying, grey-brown tissue along the margin — Young leaf — dying, grey-brown tissue along the margin Photo: Scot Nelson, licence CC0

Black rot — Field — dying plants and withering outer leaves — Field — dying plants and withering outer leaves Photo: Scot Nelson, licence CC0

Black rot — Dying plant — dried-up leaves after severe infection — Dying plant — dried-up leaves after severe infection Photo: Scot Nelson, licence CC0

Symptoms

Wedge-shaped yellowing patches spreading in from the leaf edge
Blackened veins visible in a cut through the leaf or stem
A sharp, clear boundary between diseased and healthy tissue
One-sided yellowing and dieback of the leaf
Plants dwarfed and leaning to one side

What it does to the crop

Growth checked and no head formed
Young plants dying in the seedbed
Secondary soft rots at the site of infection
Crop losses running into tens of percent

What encourages it

Warm, humid weather at 25-30°C
Wind-driven rain and overhead irrigation
Infected seed and transplants
Leaf damage from pests, hail and routine work

Prevention

Use seed from a reliable source, hot-water treated
Inspect transplants and discard diseased seedlings before planting
Rotate with a minimum 3-year break
Drip-irrigate instead of watering overhead
Do not work among the plants while they are wet

⚠️ Before you reach for a spray

This atlas is informational and still growing — different diseases can look almost identical. Confirm the diagnosis and read the product label before applying any plant protection product. If you are unsure, ask your local extension or advisory service.

Keep the disease atlas with you in the garden

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