Potato ring rot : Q & A
What is potato ring rot?
Potato ring rot (pdf) is caused by the bacterium Clavibacter michiganensis sepedonicus and is a serious non-established disease of potatoes. It is a quarantine disease listed in the EC Plant Health Directive and is notifiable in the UK. The disease causes significant yield losses, which can be as high as 50%.
How is it spread?
The disease is largely spread by vascular infection of daughter tubers derived from infected seed. The disease is thought to be unable to overwinter in the soil but will do so in groundkeepers (unharvested potatoes from the previous crop) and debris from infected crops. Infected groundkeepers lifted at the same time as an otherwise clean seed crop can infect that crop.
What are the symptoms?
The initial symptom is a soft cheese-like rotting of the vascular ring. In severe cases this rots completely and the skin of the potato may crack. However, latent infection is common with this disease and often its presence can only be detected by laboratory testing.
What controls are in place?
The EC Plant Health Directive (2000/29/EC) prohibits the import of material carrying the bacterium. In addition, a specific control Directive (93/85/EEC) is in place laying down measures to prevent spread and facilitate the eradication of any outbreaks. Defra’s Plant Health and Seeds Inspectors (PHSI) and their equivalents in Scotland and Northern Ireland carry out an annual survey of seed and ware crops including those grown from UK and non-UK stocks. Consignments of imported ware potatoes are also inspected. Samples are tested for latent infection at the Central Science Laboratory. A contingency plan (pdf) is in place which outlines measures to be taken in the event of an outbreak.
Can the disease be treated?
There are no recognised chemical treatments available for disease control in plants.
Can other crops catch this disease?
No.
Is compensation paid for crops destroyed?
There is no scheme for paying farmers/growers compensation for losses (either stock value or consequential) sustained as a result of action to eradicate and contain quarantine plant diseases.
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Page last modified:
7 Nov 2006
Page published: 17 Oct 2003