This item was published during the term of a previous administration that ended in April 2007
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Ban on river irrigation lifted in parts of Tayside
13/02/2004
Deputy Minister for Rural Development Allan Wilson today announced the partial lifting of the ban on the irrigation of potato crops with water drawn from the Tay river system in Perthshire.
This follows the successful eradication from the Lunan Burn and River Isla of the organism which causes potato brown rot. The organism Ralstonia solanacearum was discovered in autumn 2000 in parts of the Lunan Burn, River Isla and River Tay in Perthshire.
Mr Wilson said:
"Although no infected potatoes have been found in Scotland, I am acutely aware of the danger which potato brown rot poses to Scottish potato production and in particular to Scotland's world renowned seed potatoes.
"This partial lifting of the ban is welcome news for local landowners, potato growers and the Scottish potato industry in general. Our efforts will now focus on eradicating this organism from the lower reaches of the River Tay.
"I am hugely encouraged by its successful eradication from the Lunan Burn and the Isla. The absence of this damaging potato disease will help underpin the high health reputation that Scottish seed potatoes enjoys around the world."
The prohibition on irrigation has not been lifted from the lower stretches of the River Tay (i.e. between the confluence with the Isla and estuarine waters. SEERAD plans to conduct further eradication work along the affected stretch of the Tay in 2004.
The bacterium which causes potato brown rot ( Ralstonia solanacearum) can be spread in contaminated irrigation water. It survives in the wild host plant woody nightshade ( Solanum dulcamara) growing in river water. Among other plants affected are tomatoes which when infected suffer from bacterial wilt. The bacterium is subject to specific controls under EU Council Directive 98/57/EC which is implemented in national legislation by the Plant Health (Amendment) (Scotland) Order 1999.
The only confirmed contamination in a Scottish watercourse was discovered during routine monitoring in August 2000. The contaminated watercourse comprised:
the Lunan Burn from Carsie sewage works until it joins the River Isla
the River Isla from the confluence with the Lunan Burn downstream until it joins the River Tay
the River Tay from the confluence with the River Isla downstream until it meets estuarine waters
A prohibition on the irrigation and spraying of potato (and tomato crops) from the contaminated watercourse came into force on October 13, 2000 and the legislation required this to be maintained for a minimum of 3 growing seasons.
In 2001 SEERAD began work to eradicate Ralstonia solanacearum from the affected river system. The work involved the elimination of the alternative host plant Solanum dulcamara initially along the contaminated stretch of the Lunan Burn. Following the success of this work the programme was extended in 2002 to include the River Isla. All S. dulcamara plants growing with their roots in the river water were killed by spraying with herbicide (Glysophate). The success of the eradication exercise was monitored by sampling and testing the level of R. solanacearum in the river system throughout each growing season. In 2002 and 2003 the bacterium was not recorded in water samples taken from this or any other river in the potato growing areas of Scotland.
All the evidence indicates that R. solanacearum has been successfully eradicated from the Lunan Burn and River Isla.
Further work to identify and eliminate S. dulcamara plants along the River Tay below its confluence with the River Isla will be required in 2004. Although water sample results from the Tay in 2002 and 2003 also proved negative for the organism there were findings in 2000 and 2001.
This suggests that there may be infected S. dulcamara plants growing on the banks of this stretch of the Tay. Eradication of any S. dulcamara plants that are growing along the banks of the contaminated stretch of the River Tay is therefore planned for 2004.
SEERAD routinely monitors rivers in potato growing areas as part of surveillance work required under EU legislation. Since 2001 the survey has included all Scottish rivers used for the irrigation of seed potato crops. Information on watercourses used for the irrigation of potatoes is collected annually during seed potato crop inspections. In 2003 the survey included 22 rivers.
The survey was conducted during August and September when river water temperatures were highest and would have encouraged survival of R. solanacearum. All sample results were negative.