Disease
Parsnip canker
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Watch for | Watch for in January | Watch for in February | Watch for in August | Watch for in September | Watch for in October | Watch for in November | Watch for in December |
What it is
Parsnip canker is a common and frustrating problem: a fine-looking row of foliage hides roots with ugly, rotten shoulders. Several fungi can be involved, but the most frequent in Britain is Itersonilia pastinacae. Damage is often worse in wet autumns and on large, older roots.
Symptoms
Patches of orange-brown, reddish brown or black, rough or cracked skin develop on the top of the root, usually around the crown where it meets the soil surface. The patches may spread down the root and lead to soft rot. On the foliage you may see small brown spots with a pale halo, as spores splash from leaves to roots. Carrot fly tunnels are narrower and rust coloured, running into the flesh rather than across the surface.
Cause
Spores are produced on infected leaves and washed into the soil by rain, where they infect the roots, especially through wounds. Damage from carrot fly larvae, hoes and cracks after heavy rain following drought all give the fungus a way in. Acidic soil, very rich soil and early sowings that produce big roots by late summer are all linked with heavier canker.
Control
There is no treatment once roots are affected. Lift cankered roots, cut away the damaged areas and use them soon, as they will not store well in the ground. Clear old foliage after harvest. Do not leave rotting roots in the bed over winter.
Prevention
Choose a canker-resistant variety such as 'Gladiator' or the older 'Tender and True'. Sow from April into May rather than February; later sowings give smaller roots that suffer less. Space plants about 10 cm apart, keep soil close to neutral with lime if needed, and draw a little soil over the shoulders. Hand-weed close to the row rather than hoeing, and protect the crop from carrot fly.
Plants often affected
Could it be something else?
These problems share some of the same symptoms. Compare them, or run the symptom checker with these signs ticked.
Months to keep an eye out: January, February, August, September, October, November and December.
Sources
Identification and life-cycle details were checked against the references below. Text and advice are our own. See our editorial policy.