January 7, 2003
From: EPPO Reporting Service 2003, No. 11 [edited]

2003/166

Survey on Ralstonia solanacearum in United Kingdom: 2003 results

In United Kingdom [U.K.], there have been 5 confirmed outbreaks of _Ralstonia solanacearum_ [Rs] (EPPO A2 list) in potato crops: 2 in the Thames Valley (in 1992 and 1995), 2 in Northamptonshire (in 1999), and 1 in Kent (in 2000). The bacterium has also caused 2 outbreaks in tomato crops grown at one locality in Bedfordshire (in 1997 and 1998).

All these cases were apparently caused by irrigating crops with water from contaminated rivers, where the bacterium persists by infecting _Solanum dulcamara_ (bitter nightshade) with roots in the water.

Monitoring programmes and eradication measures are being applied in U.K. Since the last outbreak in 2000, Rs has not been detected on crops but only in watercourses. Results of the 2003 action and survey are presented in
detail on the web site of DEFRA. Numerous herbicide spot treatments were applied against _S. dulcamara_ along watercourses (4000 in June/July 2003, and 2000 treatments in September 2003).

Rs was absent in 41 of the 65 sites sampled (63 percent). The bacterium was found in water samples from 12 water courses (essentially located in the south and south-east of England).

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.

Source: Web site of Department for Environment, Food and Rural Affairs (DEFRA), United Kingdom: Potato brown rot: 2003 monitoring programme: Final results. <http://www.defra.gov.uk/planth/pbr2.htm>

[In February 2003, Rs race 3, biovar 2, not known to occur in the USA, was detected and confirmed in geraniums imported from Kenya and eradicated. Subsequently it occurred again in late December 2003 in geranium imported from Guatemala. The pathogen causes a wilt disease in several important agricultural crops such as potato, tomato, pepper, and eggplant. Some control actions have already taken place, and importations into the United States have ceased. Primary symptoms of Rs race 3, biovar 2 infection in geranium are wilting of leaves and/or abnormal yellowing of lower leaves. Rs can be transmitted through soil, contaminated irrigation water,
equipment, or personnel. Rs does not readily spread from plant to plant via splashing water, casual contact, or aerially. Spread can be controlled in greenhouses by application of sound sanitation practices. Rs is thought to
have originated in the temperate highland regions of Peru but has subsequently spread to Europe, Asia, South and Central America, and Australia. It has been classified into a number of races and biovars. Most races of the bacterium, and their associated diseases, appear to be limited to tropical, sub-tropical and warm temperate climates, and thus pose no long-term threat to agriculture in cool temperate climates. However, Rs race 3, biovar 2A, which has a very wide host range, is now considered to be a quarantine pest in Europe, Canada, and the United States.

Additional references: <http://www.aphis.usda.gov/ppq/ep/ralstonia>
<http://www.inspection.gc.ca/english/sci/surv/data/ralsole.shtml> - Mod.DH]