Potato Ring Rot

Identification and reduction of risks posed by potato ring rot disease to the Scottish potato industry

Project start and end date: 05/12/2005 – 31/03/2009

Project collaborators: Fera, York, UK; James Hutton Institute, Dundee, UK; SASA

Funding from: Scottish Government’s Flexible Fund (now called Contract Research Fund)

Clavibacter michiganensis subsp. sepedonicus (Cms), potato ring rot has never been detected in Scottish potatoes. This project focused on identifying risks to Scotland’s potato industry should the pathogen ever be introduced.

A postal survey of all Scottish potato growers revealed that although infrequent, some growers exercised poor or inadequate cleaning of harvesters, graders, etc. and re-used bags and boxes returned to their farms without adequate cleaning and disinfection. All such practices were judged to be risky and could facilitate the spread of ring rot within Scotland should it ever be introduced at some future date. Controlled greenhouse experiments have shown that the most commonly grown cultivars in Scotland can be infected by Cms even at low inoculum levels but some varieties, such as cv. Desiree, show limited if any symptoms. This highlights the need to test for ring rot by laboratory testing as field symptoms are unlikely to be observed in all varieties currently grown in Scotland.

Materials commonly used in the potato trade that represent surfaces that could come into contact with Cms were collected. The persistence of the ring rot organism on these trade materials has been monitored as was the efficacy of washing and disinfecting these surfaces.  It is clear that some substrates currently in use by Scottish growers are ineffective at killing Cms and also that care must be taken to ensure a reasonable contact time with effective disinfectants to ensure an effective kill.

Optimisation of sampling strategies has been evaluated and a statistical model developed which will be applied to develop a sampling strategy during an outbreak situation.

This project was instrumental in shaping Scotland’s contingency plan for a future ring rot outbreak. 

Further details can be obtained from Gerry Saddler on 0131 244 8925 or by email.