🥬 Cabbage How hard it is to control: ★★★☆☆ 3/5

Alternaria leaf spot on cabbage

A fungal leaf disease caused by Alternaria brassicae and A. brassicicola. It attacks brassicas from the seedbed through to storage, producing characteristically zoned spots on older leaves.

Symptom photos

Alternaria leaf spot — Leaf — brown spots zoned in concentric rings, with holes where dead tissue has dropped out — Leaf — brown spots zoned in concentric rings, with holes where dead tissue has dropped out Photo: Jochen Kreiselmaier, Pflanzenschutzberatung DLR Rheinpfalz, licence CC BY-SA 4.0

Alternaria leaf spot — Leaf — early stage, small dark specks scattered over the blade — Leaf — early stage, small dark specks scattered over the blade Photo: Jochen Kreiselmaier, Pflanzenschutzberatung DLR Rheinpfalz, licence CC BY-SA 4.0

Symptoms

Round, brown spots with darker concentric rings
A black, velvety bloom of spores on the surface of the spots
Spots first on the oldest, lowest leaves
Dark, sunken specks on the wrapper leaves of the head
Affected leaves dying back and drying up

What it does to the crop

Loss of working leaves and smaller heads
Spots on the outer leaves reducing market value
Heads rotting in store
Seed infection carrying the disease into the next season

What encourages it

Leaves staying wet for a long time (more than 12 hours)
Temperature 20-25°C
Brassicas grown after brassicas
A dense crop with poor air movement

Prevention

Use healthy, treated seed
Rotate with a 3-4 year break from brassicas
Destroy crop debris straight after harvest
Water in the morning and avoid wetting the leaves in the evening
Feed nitrogen in a balanced way, without overdoing it

⚠️ 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

In the app you can identify a disease from photos, work out the spray dose for your own bed and log the treatment in your task calendar. Free, no sign-up, works offline.

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