August 30, 2004
From: ProMED-mail<promed@promedmail.org>
Source: European Plant Protection Organization (EPPO), Reporting Service, 2004 No. 6 [edited]

2004/089
Update on the situation of potato bacteria in United Kingdom

The NPPO of United Kingdom has informed the EPPO Secretariat about recent phytosanitary incidents concerning potato bacteria.

_Clavibacter michiganensis_ subsp. _sepedonicus_ (EPPO A2 list)

As reported in EPPO RS 2003/159, potato ring rot, caused by _Clavibacter michiganensis_ subsp. _sepedonicus_ [Cms], was discovered in November 2003 in a sample of seed potatoes (_Solanum tuberosum_ cv. Provento)grown in 1 farm in Wales. In 2004, tracing and testing studies confirmed that the outbreak has been contained and that no other farms have grown or received infected stocks. In total, more than 165 000 potato tubers were tested. On the outbreak farm, 1 stock of cv. Provento and 1 stock of a Provento/Almera admixture were found to be infected. Apart from these 2 stocks, all tests were negative, including for the remaining 20 other seed potato stocks on the outbreak farm.

The testing programme included: all potato stocks on the outbreak farm; other stocks of cvs. Provento and Almera from the UK 2003 harvest; seed potatoes from the UK 2003 harvest grown from 2002 stock from the outbreak farm; seed potatoes from stocks with a clonal link to stocks grown on the outbreak farm in previous years; seed potatoes on farms with a machinery link to the outbreak farm. A substantial testing programme was also carried out in the Netherlands, where the Provento seed potatoes grown on the outbreak farm originated.

The NPPO of UK considers that the outbreak has now been contained. However, some restrictions will remain in place (e.g. disposal of infected or possibly infected stocks, cropping restrictions on the land where the
infected potatoes where grown).

The situation of Cms in United Kingdom can be described as follows: Transient, 1 isolated outbreak was detected in 2003 in 1 farm but was contained in 2004, still under official control.

_Ralstonia solanacearum_ (EPPO A2 list)
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In 2004, during a routine annual survey, a consignment of seed potatoes was found to be infected with brown rot (caused by _Ralstonia solanacearum_ [Rs]). These potatoes (cv. Premiere) were located at 1 farm in Lancashire
(northwest England) and were due to be planted for ware potato production. They had been imported from the Netherlands in 2003. Tracing studies showed that 3 other consignments of cv. Premiere had been delivered to 3 farms in England and Wales, as well as consignments of cv. Wilja originating from the same Dutch supplier. However, all potatoes of cv. Wilja tested negative.

Phytosanitary measures are being taken on the farms concerned (for cv. Premiere which is considered as contaminated and also on cv. Wilja as a precautionary measure). These measures include: holding and disposal of seed potatoes in a manner to eliminate any risk of spread, disinfection of premises and equipment. In UK, surveys on solanaceous crops and weeds, and on watercourses are continuing.

The situation of Rs in United Kingdom can be described as follows: Present, the bacterium has been eradicated from solanaceous crops, but can still be detected in a few watercourses.

[Cms and Rs are 2 of the most serious pathogens of potato. Sanitation is the key to disease management. Only classified seed should be used for planting; all machinery, equipment, vehicles, containers such as potato sacks, storage facilities such as bins, and any other possible source of the pathogen must be identified and rigorously cleaned and thoroughly disinfected. Finally, if possible, dispose of all potato waste at an approved tip (dump) by incineration, which will inactivate these pathogens. See the 2nd link below -- it deals with disposal of water waste.

A continuing problem in some circumstances is infection of solanaceous plants near potato washing and waste operations. Runoff of contaminated water leads to infection of reservoir hosts such as _Solanum dulcamara_
(climbing nightshade) along waterways, thus perpetuating these 2 pathogens.

Useful links:
<http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex1206?opendocument> (Ring rot)
<http://www.potato.org.uk/upload/pdf/researchReports/report191.pdf> (Potato brown rot)
<http://www.potato.org.uk/upload/pdf/researchReports/report190.pdf> (Contaminated irrigation systems)
-Mod.DH]