Pak Choi: Pests & Diseases
Pak choi is a quick, tender brassica for spring and late-summer sowing in UK gardens. Its succulent stems and leaves grow best in moist, fertile soil and cool conditions. Protect seedlings early, as rapid pest damage can check growth and make plants bolt before useful hearts form.
Common pests
Flea beetles pepper young leaves with tiny holes, especially in dry spring weather. Cabbage white caterpillars can strip foliage, while slugs and snails damage seedlings and lower leaves. Cabbage root fly maggots may weaken roots and cause plants to wilt. Mealy cabbage aphid and greenhouse whitefly can gather in leaf folds, leaving sticky honeydew and distorted growth.
Common diseases
Club root causes swollen, distorted roots and stunted, wilting plants, particularly on acidic or repeatedly cropped brassica ground. Downy mildew produces yellow patches above and greyish mould beneath leaves in cool, damp weather. Damping off can kill crowded seedlings. Grey mould may affect damaged leaves during prolonged wet spells, especially where plants are closely packed.
Prevention
Use a four-year brassica rotation and avoid sites with known club root. Improve drainage, keep soil near neutral, and choose club-root-resistant varieties where risk is high. Sow thinly, allow good spacing and water at soil level. Cover crops immediately with fine mesh to exclude cabbage root fly, butterflies and whitefly. Clear old brassica debris and keep seed trays clean.
Non-chemical control
Pick cabbage white caterpillars and egg clusters from leaves regularly. Use fine insect mesh, securely weighted at the edges, from planting onwards. Hand-pick slugs and snails on damp evenings, use barriers around young plants, and encourage frogs, ground beetles and birds. Water stressed plants thoroughly in the morning. Remove badly aphid-infested leaves and wash small colonies away with a firm water spray.
What to look for
Inspect seedlings every few days from emergence, looking for flea-beetle shot holes, slug grazing and wilting. Check leaf undersides weekly for butterfly eggs, caterpillars, aphids and whitefly. After wet, cool weather, examine foliage for yellow patches and grey downy growth. Lift any persistently stunted plant to check roots for club root.
Tips
Sow little and often rather than raising a large batch at once. Pak choi is happiest in cool weather, so provide shade and reliable moisture during warm spells. Harvest whole plants young, or take outer leaves, before flowering stems lengthen.
Pak Choi pests & diseases: frequently asked questions
What are the common pests of pak choi?
Flea beetles pepper young leaves with tiny holes, especially in dry spring weather.
What diseases affect pak choi?
Club root causes swollen, distorted roots and stunted, wilting plants, particularly on acidic or repeatedly cropped brassica ground.
How do I prevent pests and diseases on pak choi?
Use a four-year brassica rotation and avoid sites with known club root.
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.