Asparagus: Pests & Diseases
Asparagus is a long-lived perennial vegetable that rewards patient preparation with spring spears for many years. It needs a sunny, well-drained bed kept free from perennial weeds, with crowns planted where they will not be disturbed. Healthy summer fern is essential because it rebuilds the crowns for the following season.
Common pests
Asparagus beetle is the chief pest: striped adults and greyish grubs feed on spears and fern, stripping foliage and weakening crowns. Slugs may scar emerging spears or eat young shoots in wet weather. Aphids can sometimes gather on fern, and birds may peck fresh tips. Damage from beetles is most important after the main picking period, when the fern needs as much healthy leaf area as possible to feed the plant.
Common diseases
Asparagus rust causes orange pustules followed by darker spots on fern, leading to yellowing and early dieback. Violet root rot produces purple fungal growth around roots and can kill plants over time. Crown rot and other root rots occur where soil remains wet, causing weak, sparse shoots and decaying crowns. Grey mould may affect damaged fern in humid conditions. Fusarium-related decline can also weaken old or stressed plants in poorly drained ground.
Prevention
Choose a sunny, open site with excellent drainage and do not plant asparagus where old crowns suffered root disease. Keep crowns widely spaced, remove perennial weeds, and avoid damaging roots when cultivating nearby. Do not overwater established plants. Cut down and clear old fern in autumn once it has yellowed, reducing overwintering beetles and rust spores. Keep harvested spears cleanly cut, and avoid moving soil or plants from beds affected by violet root rot.
Non-chemical control
Hand-pick adult asparagus beetles and their grey grubs from spears and fern, dropping them into soapy water. Inspect plants frequently from spear emergence onwards, as early removal limits egg-laying. Check damp areas after rain and hand-pick slugs or use physical barriers around young shoots. Encourage insect-eating birds and predatory beetles in the garden. Remove rusted or badly diseased fern promptly, then clear all autumn debris from the bed.
What to look for
From the first spears in spring, examine stems and fern twice weekly for striped beetles, dark eggs and grey grubs. Check new spears for slug scarring after wet nights. During summer, inspect fern for orange rust pustules, yellowing and premature dieback. Look for thinning patches, weak shoots or crown decay that may indicate root disease.
Tips
Do not harvest heavily until crowns are well established, usually after their second growing season. Stop cutting when spear size declines, then let all remaining shoots grow into fern. Feed with compost around, rather than over, the crowns and keep the bed weed-free.
Asparagus pests & diseases: frequently asked questions
What are the common pests of asparagus?
Asparagus beetle is the chief pest: striped adults and greyish grubs feed on spears and fern, stripping foliage and weakening crowns.
What diseases affect asparagus?
Asparagus rust causes orange pustules followed by darker spots on fern, leading to yellowing and early dieback.
How do I prevent pests and diseases on asparagus?
Choose a sunny, open site with excellent drainage and do not plant asparagus where old crowns suffered root disease.
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.