Parsnip Canker

Canker can be a serious disease of parsnips especially in wet soils or during rainy seasons.

Canker can manifest itself as spots, blotches and lesions that penetrate the crown, shoulder or sides of the parsnip root. Spores that are produced on foliage fall to the ground where they come in touch with the roots.

There are 3 types of canker which can affect parsnips:

 

The cause of black canker is fungal in origin Infection may be by Intersonilia pastinaceae or Phoma sp. Other pathogens may be also be present.  

The cause of orange-brown canker has not been defined and may be physiological in origin.

Brown-black canker is also caused by fungal infection

Black canker is the most frequently occurring form.

On foliage small pale green or water soaked flecks which may have a paler halo.

Lesions on the shoulders of the root, darkbrown/black or purple black in colour, frequently flecked with orange colouration.

Lesion size can vary from a few millimetres to several centimetres. Young lesions are coarse or granular in appearance.

Sunken lesions can occur on the root surface. The underlying tissue can have a rough scrufy appearance when exposed.

Invasion of the lesions by secondary rot bacteria or fungi can cause rapid decay of the whole root.

Intersonilia can remain active after foliage dieback, increasing the risk of canker in late harvested crops.

Crops already weakened or damaged by pests are more readily infected than strongly growing crops.

Crop rotation:-Ideally do not grow on the same land within 4 years and avoid planting other susceptible crops such as beet, celery or carrots. Cereal breaks are the preferred option.

Control carrot fly attack to avoid secondary infection by the pathogen

Ridging up Ridge up just before foliage meets within rows, making sure there is no damage to roots.

Prompt disposal of debris to remove source of infection.

Cleaning of machinery to avoid cross contamination to uninfected land

Good drainage

Regular monitoring of disease levels and appropriate control with fungicides

Short storage where possible

Use resistant varieties