🥬 Cabbage How hard it is to control: ★★★★☆ 4/5

Cabbage root fly

Larvae of the fly Delia radicum feed in the roots and stem base of brassicas. The damage is invisible from above — the plant simply wilts in the sun and stops growing.

Symptom photos

Cabbage root fly — Kohlrabi root — white root fly maggots in the tunnelled tissue — Kohlrabi root — white root fly maggots in the tunnelled tissue Photo: Schlaghecken Josef, licence CC BY 4.0

Cabbage root fly — Cauliflower root collar — maggots and blackened, rotting tissue — Cauliflower root collar — maggots and blackened, rotting tissue Photo: Rasbak at Dutch Wikipedia, licence CC BY-SA 3.0

Symptoms

Plants wilting during the day even though the soil is moist
Dull, blue-green discoloration of the leaves
White, legless larvae in tunnels in the roots
The root collar eaten away and blackened
Plants lifting easily out of the soil

What it does to the crop

Young transplants dying after planting
Plants dwarfed and failing to form a head
Secondary root rots
An uneven, thin stand

What encourages it

First fly flight in May, further ones in July and August
Light soils that have dried out
Brassicas planted after brassicas
Bare soil around the root collar

Prevention

Fit cardboard or felt collars around the stem after planting
Cover with fleece from planting day for the first 6 weeks
Plant earlier or later, either side of peak flight
Rotate crops and plough deeply in autumn
Water and earth up plants to encourage new roots

⚠️ 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.

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📅 When to Sow Cabbage? →