Parsnip (Pastinaca sativa)-Itersonilia Canker

Cause The fungus, Itersonilia perplexans, is a common saprophyte on umbelliferous crops as well as some weeds and other cultivated plants including brassicas. It overwinters as chlamydospores in soil or plant debris, on living parsnip roots, and can also infest seed. It spreads by wind as ballistospores, which die rapidly once in contact with soil microorganisms. Disease is favored by moist and cool conditions; 68°F is optimum for growth of the fungus.

Symptoms Reddish-brown to blackish cankers develop on the shoulders and crowns of roots; other microbes may subsequently invade and the entire root system collapse from rot. Itersonilia may also invade lateral roots at their base as well infect the aboveground portions of parsnip. Bases of petioles will develop dark lesions and leaves will exhibit brownish lesions with pale green halos, which may coalesce.

Cultural control

  • Plant resistant varieties such as Andover.
  • Hilling up soil over parsnips' shoulders throughout the season will reduce disease.
  • Long rotations will reduce the population of chlamydospores in soil.
  • Select well-drained fields. Avoid fields with excessive soil compaction.
  • Burying infected plant debris will hasten breakdown of plant material and expose the pathogen to antagonistic soil microbes.
  • Control weeds and insect pests that damage roots.

Reference Davis, R.M., and Raid, R.N. 2002. Compendium of Umbelliferous Crop Diseases. St. Paul, MN: APS Press.