Potato diseases
Six major diseases in depth, and short entries on zebra chip, ring rot and wart. The pages are written for growers, seed buyers and analysts who need the cause, the risk and the control in one place.
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How these pages work
Each disease page covers the cause, symptoms, how it spreads, where the risk is highest, management (cultural, resistant varieties and chemical, with regulatory notes), the seed certification angle and key sources. Regulatory notes name the instrument, but approvals change by country and year, so check the current national register before using a product.
Seed health runs through all of it. Most potato diseases of consequence travel in the seed tuber, which is why certification classes set maximum tolerances for disease and zero for regulated bacteria.
Disease guides
Zebra chip
Zebra chip is caused by the bacterium Candidatus Liberibacter solanacearum, carried by the tomato potato psyllid (Bactericera cockerelli). It stains the tuber's internal carbohydrate structure in dark stripes that show up when the tuber is fried. The psyllid was first recorded in New Zealand in March 2006, and the bacterium was identified in New Zealand potato crops in 2008 (Potatoes New Zealand and journal literature, as summarised in the Potatopedia corpus). Control is based on psyllid monitoring and insecticide timing.
Bacterial ring rot
Ring rot, caused by Clavibacter sepedonicus, is a regulated bacterial disease that rots the vascular ring of the tuber. It has zero tolerance in seed in every certified class, and Germany requires testing of all seed lots under the Plant Protection Act. It spreads through infected seed and on equipment and crates, which can carry the bacterium for long periods. The standard defence is certified seed and cleaning and disinfecting everything that touches seed (EPPO Global Database; Bundessortenamt).
Potato wart
Potato wart disease, caused by Synchytrium endobioticum, produces cauliflower-like outgrowths on tubers and is a quarantine pest in most potato-producing countries. Its resting spores persist in soil for many years, so affected fields are placed under movement restrictions. Detections in Prince Edward Island have at times interrupted exports to the United States, and Canada's CFIA enforces quarantine zones and movement controls. Resistant varieties are the practical defence, and variety lists show resistance to the pathotypes present (CFIA; EPPO Global Database).