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Potato wart disease

Potato wart disease is caused by the fungus Synchytrium endobioticum.

Also known as:
Black wart, Black scab
Potato tumor, Potato cancer
Warty disease

recognize symptoms of potato wart disease
Potato wart disease, photo: Bildoj - CC0 Public Domain

Potato wart disease is caused by the fungus Synchytrium endobioticum. The origin of the fungus is in the Andes. Meanwhile, the fungus is found all over the world.
Synchytrium endobioticum does not form a fungus phloem but sorals, in which spores are formed. The spores invade the epidermal cells of potatoes in spring and cause growths that swell into warts. The infected cells divide, creating more and more warts. In severe infestations, the warts grow into cauliflower-like lumps
Wet soils with a soil temperature of at least 8°C are required for the development of the potato wart desease. Summers with average temperatures of 18°C or below, winters below 5°C and annual precipitation of 700 mm and more are the conditions under which the fungus develops.

In autumn, the warts rot away and release ‘resting’ spores. These spores rest in the soil and retain their germination capacity for up to forty years. The spores survive 11-12 hours survival at 100°C, composting for 12 days at 60-65°C and pasteurization for 90 minutes at 70°C. The spores also survive the way through the digestive system of animals that have eaten contaminated potatoes.

If wart disease is detected on a plot, that plot is declared infected and no potatoes may be grown for a long time until the plot have been found free of the disease .
Wart disease is a quarantine disease (EU), which is subject to strict legal regulations. Similarly, no other planting material (e.g. bulbs, trees and perennials) may be grown on an infected plots – anything to prevent the spread of the fungus.

Where to find

Control

After infection, recovery is no longer possible.

Prevention

In some countries potatoes are subject to a cultivation regulation to prevent the spread and infection of the potato wart disease: only potato varieties with a certain minimum wart disease resistance are allowed in a large area around infected plots.
Much research is being done on wart disease-resistant potato varieties.