Parsnips: Pests & Diseases
Parsnips are long-season roots valued for their sweet flavour after cool autumn weather. They need deeply worked, stone-free ground and patience, as germination can be slow. Their foliage resembles carrot foliage, and several carrot-family pests can affect them, so protective growing methods are useful from sowing onwards.
Common pests
Carrot fly can attack parsnips as well as carrots, with larvae tunnelling roots and encouraging decay. Celery leaf miner creates pale, blistered mines in leaves, reducing vigour when infestations are heavy. Aphids may cluster on tender foliage and stems. Slugs can graze germinating seedlings, and wireworms may mark roots in plots recently converted from grass. Damage is often most noticeable when roots are lifted.
Common diseases
Parsnip canker is the principal disease, causing dark, sunken lesions around the shoulder or lower root and worsening in wet, cold soil. Powdery mildew produces white patches on older leaves late in the season. Cavity spot and sclerotinia can also affect roots, especially in poorly drained ground or storage. Forking is usually a soil problem, not a disease, and follows stones or compaction.
Prevention
Sow fresh seed into a deep, stone-free bed with good drainage, avoiding freshly manured soil. Rotate parsnips away from carrots, celery and previous parsnip beds for several years where canker has occurred. Use fine mesh or fleece to exclude carrot fly, and remove weeds that restrict airflow. Choose canker-tolerant varieties where available, thin carefully and avoid damaging crowns during cultivation.
Non-chemical control
Keep mesh or fleece in place from emergence to exclude carrot fly, sealing the edges securely. Remove and destroy mined leaves containing celery leaf miner larvae before they pupate. Pick off slugs at dusk and encourage beetles, birds and other natural predators around the plot. Lift badly cankered roots and dispose of them rather than storing them. Store only clean, unbruised roots in cool, dry conditions.
What to look for
Check germinating rows frequently for slug loss, then inspect foliage from early summer for aphids and celery leaf miner blotches. During thinning, look for carrot-fly symptoms and keep disturbed foliage away from the bed. From autumn onwards, test-lift roots for canker lesions, tunnels and signs of rot before harvesting the main crop.
Tips
Parsnips tolerate frost and often taste sweeter after cold weather, but lift them before soil becomes too hard to dig. Mark rows clearly, as seedlings are slow to establish. Water during prolonged dry periods to help roots grow evenly and reduce toughness.
Parsnips pests & diseases: frequently asked questions
What are the common pests of parsnips?
Carrot fly can attack parsnips as well as carrots, with larvae tunnelling roots and encouraging decay.
What diseases affect parsnips?
Parsnip canker is the principal disease, causing dark, sunken lesions around the shoulder or lower root and worsening in wet, cold soil.
How do I prevent pests and diseases on parsnips?
Sow fresh seed into a deep, stone-free bed with good drainage, avoiding freshly manured soil.
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.