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.

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.