Parsnip canker
Brown, orange or black rot spreading from the shoulder and crown of a parsnip root, often around a crack or a carrot fly tunnel, with the foliage yellowing and thinning above it. It is the reason a parsnip bed that looked fine in October produces unusable roots in January, and almost everything that reduces it is decided at sowing rather than at harvest.
Caused by: Itersonilia perplexans and related fungi · also called parsnip crown rot, black canker, orange canker
What brings it on
Wet autumn soil, a crown left proud of the surface, and any wound the fungus can enter through — frost cracks, splits from irregular watering, carrot fly tunnels. Early-sown, wide-spaced roots that grow large and split are affected far more than later, closer sowings.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Parsnip canker
- Agriculture and Horticulture Development Board — AHDB: Parsnip — canker
Checked 2026-08-13
Usually seen: September, October, November, December, January
Preventing it
Ordered by how much difference each measure actually makes, not by how often it is repeated.
- Sow later and closer for smaller, sounder roots, earth up the shoulders so the crowns are covered, keep watering even enough to avoid splitting, and choose a canker-resistant cultivar — the resistance in cultivars such as 'Gladiator' and 'Avonresister' is the most effective single measure available.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Parsnip canker — control
Checked 2026-08-13
- Rotate away from parsnip, carrot, celery and parsley for at least three years, and control carrot fly, whose tunnels are a main entry route.
source
Horticultural consensusmoderate confidence
- Agriculture and Horticulture Development Board — AHDB: Umbelliferous crop rotation
Checked 2026-08-13
Dealing with it once it is there
- There is no treatment for a cankered root. Lift the crop earlier rather than leaving it in wet winter ground, cut the affected shoulders away, and use what is sound.
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GrowingHQ editorial positionhigh confidence
Recorded as editorial because it is a decision about salvage rather than a control measure.
- GrowingHQ editorial synthesis — GrowingHQ
Checked 2026-08-13
What it affects
On sprays and treatments
GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.