Broccoli: Pests & Diseases
Broccoli, including calabrese and sprouting types, is a productive brassica for British gardens when given rich soil and regular water. Its developing florets are easily spoiled by hidden caterpillars, while overwintering plants need protection from hungry pigeons and good airflow to stay healthy.
Common pests
Large and small white butterfly caterpillars are frequent in broccoli heads, where they are hard to spot until harvest. Cabbage moth caterpillars, mealy cabbage aphid and cabbage whitefly can also inhabit leaves and florets. Cabbage root fly maggots weaken young plants and cause wilting. Flea beetles pepper seedlings with shot-holes, and pigeons may remove leaves and tender shoots from unnetted plants.
Common diseases
Club root causes swollen, misshapen roots and poor growth, and is most severe in acidic, poorly drained soil. Downy mildew creates yellowish patches with grey mould-like growth underneath. White blister forms conspicuous pale pustules. Powdery mildew can cover ageing foliage in dry spells. Ringspot produces dark circular lesions, while black rot causes yellowing from leaf margins and darkened veins.
Prevention
Keep broccoli in a long brassica rotation, avoiding affected ground for several years. Improve drainage and lime acidic soil to make conditions less favourable for club root. Use club-root-resistant varieties if necessary. Set plants at their recommended spacing, firm them well and remove old leaves and crop remains. Cover immediately with fine insect-proof mesh; this is the most reliable protection against brassica pests and pigeons.
Non-chemical control
Keep mesh over the crop, lifting it only to weed, water and inspect. Remove clusters of yellow butterfly eggs and hand-pick caterpillars, including those tucked among florets. Use brassica collars around newly planted stems to deter cabbage root fly. Encourage hoverflies, lacewings and small wasps with nearby nectar-rich flowers. Wash aphids from small infestations with a firm water spray, then recheck plants.
What to look for
Inspect young plants soon after planting for wilting, flea-beetle holes and signs of cabbage root fly. From late spring, examine leaf undersides and forming heads weekly for eggs, caterpillars, aphids and whitefly. After wet periods, look for mildew, and pull up severely stunted plants to confirm club root before replanting.
Tips
Harvest calabrese while buds are tight and before yellow flowers show. Check each head carefully in the kitchen, as caterpillars can hide deep in florets. Pick side shoots regularly from sprouting broccoli to prolong cropping.
Broccoli pests & diseases: frequently asked questions
What are the common pests of broccoli?
Large and small white butterfly caterpillars are frequent in broccoli heads, where they are hard to spot until harvest.
What diseases affect broccoli?
Club root causes swollen, misshapen roots and poor growth, and is most severe in acidic, poorly drained soil.
How do I prevent pests and diseases on broccoli?
Keep broccoli in a long brassica rotation, avoiding affected ground for several years.
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 19 Sep 2026.