Bacterial Ring Rot of Potato

Bacterial ring rot disease of potato is not known to occur in British Columbia. Occasional outbreaks in home gardens and table stock fields over the years have been detected and eradicated. The disease can be prevented by planting only "BC Certified" seed potatoes and not using table potatoes for seed or bringing in seed potatoes from outside the province. All potato growers in BC are asked to be aware of the symptoms of the disease and report any suspicious tubers to the British Columbia Ministry of Agriculture and Lands.

Regulations: Bacterial ring rot is a regulated disease in British Columbia. All potatoes grown in British Columbia are covered under Domestic Bacterial Ring Rot Regulation 93/59. Under this regulation, if symptoms of bacterial ring rot are found in any potato crop grown in British Columbia, the occurrence must be reported to the provincial Ministry of Agriculture and Lands, and the crop must be detained until inspected. Bacterial Ring Rot Regulation 92/59 provides for inspection of all potatoes imported to British Columbia.

Bacterial ring rot infected tubers

Symptoms: The disease is called " rot" because the rot appears in the vascular ring of the potato tuber. In severely affected tubers, the vascular ring is brown to black in colour, often with a cheesy or creamy ooze and many hollow spaces where the flesh has disintegrated. Dry cracks can usually be found on the surface of the tubers. In milder cases, the vascular ring may show only broken, black lines or a yellowish discolouration. Leaves of infected plants may show interveinal yellowing, wilting, or no symptoms.

Cause: Ring rot is caused by a bacterium called Clavibacter michiganense subsp. sepedonicus. It causes disease only on potatoes.

Survival and Spread: Once a crop or farm is infested with the bacteria, the disease will carry over from year to year and spread quickly. The bacteria can survive for 2 to 5 years in dried slime on the surface of machinery, crates, bins or burlap sacking, even if frozen. Volunteer potato plants and plant debris, including infected cull tubers will also carry the bacteria overwinter. The bacteria can be spread in rain and irrigation water and by insects, but wounds are needed for infection. Thus, the most important means of infection is cutting seed potatoes with contaminated knives.

Management:

Control: If symptoms are seen or the disease is suspected, please notify the BC Ministry of Agriculture and Lands as soon as possible. Samples will be tested in the laboratory to confirm the disease and trace the source of the outbreak to prevent further spread. Ministry staff will advise on clean-up and disposal and will do follow-up testing to ensure that the disease has been eradicated. Please help protect our BC potatoes.

Further Information:

BC Plant Protection Act, Bacterial Ring-Rot Regulation (unofficial version)

Bacterial Ring Rot of Potato – The Facts (British Potato Council) (pdf format)

Understanding Bacterial Ring Rot in Potatoes (Alberta Agriculture, Food & Rural Development)