parsnip canker

Symptoms

Rough, cracked black-brown cankers develop on the shoulder and crown of the root (the part nearest the surface), sometimes spreading down the side; the rot lets in secondary organisms and the root becomes inedible at the top. Orange-brown and black canker forms also occur. Leaves may show small orange-to-brown spots, often ringed by a pale-green halo.

Plants affected

• parsnip

Easily confused with

• Powdery mildew of parsnip

  How to tell them apart: Erysiphe heraclei (powdery mildew) coats the leaf as a dry, white-to-grey, dusty or floury film that can be wiped off with a finger, sitting on top of otherwise green tissue. Itersonilia perplexans (parsnip canker / leaf spot) instead produces discrete dark brown to black, often angular necrotic spots and blotches with a water-soaked margin that sit within the leaf and cannot be rubbed away, and it also causes the characteristic black-brown cankers on the root shoulder. In short: white removable dust on the surface points to powdery mildew, dark sunken fixed spots plus root canker point to Itersonilia.

Common questions

How do I recognise parsnip canker on parsnip?

Rough, cracked black-brown cankers develop on the shoulder and crown of the root (the part nearest the surface), sometimes spreading down the side; the rot lets in secondary organisms and the root becomes inedible at the top. Orange-brown and black canker forms also occur.

Do I have to report parsnip canker?

No. parsnip canker is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is parsnip canker treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.