Brussels Sprouts: Pests & Diseases
Brussels sprouts are a long-season brassica, planted in spring and harvested from autumn into winter. They need deep, firm ground and patient attention because their foliage remains exposed to pests for months. Strong plants with protected leaves make tighter, more even sprouts along the stem.
Common pests
Cabbage white caterpillars from large and small white butterflies and cabbage moth caterpillars can defoliate plants over summer. Mealy cabbage aphid may infest the developing sprouts, while cabbage whitefly shelters beneath leaves. Cabbage root fly maggots affect young plants, causing wilting. Flea beetles perforate seedlings, and pigeons can strip foliage or peck at exposed sprouts during winter.
Common diseases
Club root produces swollen, distorted roots, stunted growth and wilting, particularly in poorly drained acidic beds. Downy mildew forms pale patches and grey growth beneath leaves. White blister causes raised white pustules. Powdery mildew sometimes affects older foliage. Ringspot creates dark, circular markings, while black rot causes yellow leaf edges and characteristic dark veins that can spread through the plant.
Prevention
Follow a rotation that leaves several years between brassica crops in each bed. For club-root-prone ground, improve drainage, lime acidic soil and choose resistant varieties. Prepare deep, fertile soil, plant firmly and give each plant enough space. Remove yellow leaves and crop debris promptly. Cover from planting with fine insect-proof mesh, which is the single most effective way to exclude butterflies, pigeons and cabbage root fly.
Non-chemical control
Use securely weighted fine mesh throughout the vulnerable season, with brassica collars around the stem bases of new plants. Inspect leaves and sprout buttons regularly, hand-removing eggs and caterpillars before they enter tight growth. Prune off heavily aphid-infested leaves and encourage hoverflies, ladybirds and parasitoid wasps with nearby flowers. Hand-pick visible pests during harvest, and avoid composting club-rooted roots.
What to look for
Check transplants for flea beetle holes and root-fly wilting during their first weeks. From late spring onwards, inspect leaf undersides weekly for whitefly, aphids, eggs and caterpillars. As sprouts form, part leaves to check hidden buttons. In wet weather, watch for mildew and ringspot; investigate persistent stunting by examining roots.
Tips
Harvest sprouts from the bottom of the stem upwards once they are firm and closed. Do not rush picking after mild weather; a touch of cold often improves their flavour. Remove loose yellow leaves to improve airflow and reduce hiding places.
Brussels Sprouts pests & diseases: frequently asked questions
What are the common pests of brussels sprouts?
Cabbage white caterpillars from large and small white butterflies and cabbage moth caterpillars can defoliate plants over summer.
What diseases affect brussels sprouts?
Club root produces swollen, distorted roots, stunted growth and wilting, particularly in poorly drained acidic beds.
How do I prevent pests and diseases on brussels sprouts?
Follow a rotation that leaves several years between brassica crops in each 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.