Swede: Pests & Diseases
Swede is a hardy root brassica that develops best in cool weather and can stand in the ground well into winter. Early protection matters because flea beetles and cabbage root fly can check young plants. A roomy bed and steady growth help roots become smooth, solid and flavoursome.
Common pests
Flea beetles are a major early pest, peppering swede seedlings with shot-holes and sometimes destroying tiny plants. Cabbage white caterpillars from large and small white butterflies and cabbage moth caterpillars eat leaves later on. Mealy cabbage aphid and cabbage whitefly can build up on foliage. Cabbage root fly maggots damage roots and cause wilting, while pigeons graze uncovered leaves.
Common diseases
Club root causes enlarged, distorted roots and stunted tops, making it especially serious for a root crop on wet, acidic ground. Downy mildew produces pale areas with grey growth under leaves. White blister creates white pustules, and powdery mildew may coat older foliage. Ringspot forms dark circular lesions. Black rot can yellow leaf edges and blacken the veins, reducing plant vigour.
Prevention
Keep swedes and every other brassica in a long rotation, leaving several years before returning to the same bed. Improve drainage and lime acidic soil to reduce club root, and choose resistant varieties where available. Thin or plant at adequate spacing, remove diseased leaves and clear crop residues. Fine insect-proof mesh is the single most effective early safeguard, excluding flea beetles, butterflies, pigeons and cabbage root fly.
Non-chemical control
Use fine mesh from emergence or planting, ensuring no gaps at the edges. Put brassica collars around transplants to reduce cabbage root fly egg-laying near stems. Hand-pick caterpillars and remove butterfly eggs during routine weeding. Wash small aphid colonies from leaves with water and encourage predators with flower-rich margins. Keep the soil evenly moist during establishment, but lift and discard club-rooted plants rather than composting them.
What to look for
Watch emerging seedlings closely in spring and summer for flea-beetle shot-holes, pigeon grazing and sudden loss of vigour. Check young plants for root-fly wilting. From late spring, inspect leaf undersides weekly for caterpillar eggs, larvae, aphids and whitefly. After wet weather, check for mildew, ringspot and white blister; inspect roots of persistently stunted plants.
Tips
Thin direct-sown plants promptly so roots have room to swell, using the thinnings only if they are healthy. Lift roots before hard ground frost in colder districts, or mulch around them for easier winter harvesting. Avoid damaging skins during lifting.
Swede pests & diseases: frequently asked questions
What are the common pests of swede?
Flea beetles are a major early pest, peppering swede seedlings with shot-holes and sometimes destroying tiny plants.
What diseases affect swede?
Club root causes enlarged, distorted roots and stunted tops, making it especially serious for a root crop on wet, acidic ground.
How do I prevent pests and diseases on swede?
Keep swedes and every other brassica in a long rotation, leaving several years before returning to the same bed.
General guidance for UK home gardens, focused on prevention and non-chemical control. The RHS or a local garden centre can help with tricky cases. Page updated 18 Sep 2026.