Forestry Commission experts are working to contain the spread of Phytophthora ramorum infection to Japanese larch trees in South Wales.
Phytophthora ramorum (P. ramorum) is a fungus-like pathogen that kills many of the trees and plants that it infects. Japanese larch trees infected by P. ramorum were first found in South West England last year, the only place in the world where it has attacked large numbers of a commercially grown species of conifer tree.
This development was a step change in the pathogen’s behaviour. Since first being identified in Britain in 2002, on a viburnum plant in a garden centre, it had affected mostly shrub and ground-cover plants such as rhododendron, viburnum and bilberry. Fewer than 100 infected trees – mostly beech - had been found, and most of those were standing close to infected rhododendron bushes.
Although it has been confirmed in only one area of larch forest in Wales so far, Forestry Commission Wales expects to find more as ground inspections follow up the aerial surveys that have pinpointed suspect areas of woodland. Scientists at the Commission’s Forest Research arm believe it likely that the spores that spread the disease have been spread to the larch forests in rain, mists and air currents carried across the Bristol Channel from the South-west, where it was confirmed in Japanese larch last September.
Roddie Burgess, Head of the Forestry Commission’s Plant Health Service, said the Commission and its partners are taking the development very seriously, but hope to be able to contain it.
“Given the damage it has caused elsewhere, we were very concerned when P. ramorum turned up in Britain in 2002, and we and our partner organisations have moved quickly to deal with it and prevent it from spreading wherever it has appeared. We managed to fell most of the infected trees in the south-west before this year’s new needles formed and therefore before new spores could be produced. This appearance and spread into larch trees in Wales adds to our concern.
“However, based on our scientists’ knowledge of local weather patterns and how it spreads, we remain hopeful that by taking quick action now in Wales as well we might still prevent the infection from the larch trees from spreading further north and east outside South Wales and South West England.
“Working with our partners in Forest Research, Defra, Fera and the Welsh Assembly Government, we have set up a programme of action to enhance our survey effort, both in the air and on the ground, and to fell infected trees and destroy other infected plants as fast as we can.
“We are also appealing for the help and support of forest owners, forestry workers and woodland visitors. Woodland owners and managers should be vigilant for and report signs of the disease to us.
“Forestry workers and the visiting public are being asked to take some simple biosecurity measures, such as washing their boots, equipment and wheels, to reduce the risk of inadvertently spreading the disease. Signs have been erected at forest entrances advising visitors what to do to.”
To minimise the economic impact on the forest and timber industries, the Commission is permitting logs from felled infected trees to be moved to specially licensed sawmills, provided certain biosecurity measures are taken. These include stacking the logs on bearers to keep them off the ground while awaiting removal from the forest, and pressure washing timber trucks before they return to the road. Sawmill residues are also being destroyed or used as woodfuel.
Further information about P. ramorum is available in a question and answer factsheet available from a link on the Forestry Commission’s website at www.forestry.gov.uk/pramorum.
NOTES TO EDITOR:
1. Pictures are available from the media contacts below.
2. Suspected infections should be reported to:
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in Wales - Forestry Commission Wales, Clawdd Newydd, Ruthin, Denbighshire, LL15 2NL; tel: 0300 068 0300, e-mail:
bww.ts@forestry.gsi.gov.uk;
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in South West England - Forestry Commission England, Mamhead Castle, Mamhead, Nr Exeter, Devon EX6 8HD; tel: 01626 890666; e-mail:
fc.sweng.cons@forestry.gsi.gov.uk;
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in non-woodland trees such as those in gardens, parks, streets and farmland - Forest Research’s Disease Diagnostic Advisory Service on
ddas@forestry.gsi.gov.uk; telephone 01420 23000.
3. P. ramorum infection has been confirmed in Japanese larch trees (Larix kaempferi) in woodland managed by Forestry Commission Wales in the Afan Valley near Port Talbot, in Garw Valley near Bridgend, and the Vale of Glamorgan. In South West England it has been confirmed in a mix of Forestry Commission England and privately owned forests, including the Commission’s Largin Wood in Cornwall, Plym Woods east of Plymouth, and Canonteign Woods near Exeter.
4. P. ramorum has not been found on any trees in Scotland.
5. P. ramorum can be spread on footwear, vehicle wheels, tools and machinery, by the movement of infected plants, and in rain, mists and air currents.
6. Infected plants such as rhododendron are usually destroyed by burning or deep burial. Infected trees are usually felled to kill the living plant tissue on which the pathogen depends.
7. Bilberry (Vaccinium myrtillus) is an ecologically important ground-cover plant of British woodland and heathland, and known as winberry in Wales and blaeberry in Scotland. Heather has also been shown in laboratory tests to be susceptible to P. ramorum, raising concerns about the ecological consequences if it were to damage large areas of bilberry and heather. Bilberry is grown commercially and the disease could have a serious economic impact on growers.
8. P. ramorum is a ‘quarantine’ organism under European Union law and its presence on trees or woodland plants must be notified to the relevant authorities (Forestry Commission, Fera, Scottish Government, and the Welsh Assembly Government).
9. Infected Japanese larch trees produce particularly high numbers of the inoculum that spreads the disease – five times the level produced on rhododendron - meaning the disease can quickly affect a large number of trees and shrubs.
10. P. ramorum has not been found infecting any European larch (Larix decidua) or hybrid larch (Larix x eurolepsis) trees, but these species are being kept under close surveillance.
11. Complete figures are not available for Japanese larch alone, but all three larch species together cover an estimated 134,000 hectares in Britain, or about 5 per cent of total woodland. Individual country figures are:
- Wales – 23,000ha / 8 per cent;
- England – 47,000ha / 4.3 per cent;
- Scotland – 65,000 ha / 5.1 per cent.
(To convert hectares to acres, multiply by 2.47)
12. Larch is a durable, versatile timber that tolerates changes between wet and dry conditions very well, and resists rotting when used in the ground. It is therefore in demand for outdoor uses such as fence posts, fence panels, exterior wall cladding, boats, sheds and furniture, as well as indoor uses such as flooring and chipboard. It is easily stained, worked and finished.
13. P. ramorum causes the disease known as “sudden oak death” in the USA, where it has killed millions of American native oak and tanoak trees in California and Oregon. However, laboratory tests have shown that Britain’s two native species of oak, sessile and pedunculate (or ‘English’) oak, are much more resistant to it than their American cousins. Fewer than five native oak trees haves been confirmed with P. ramorum infection in Britain.
14. P. ramorum should not be confused with acute oak decline (AOD), which is a separate disease affecting oak trees in the Midlands and parts of Wales and South East England, and in which a newly discovered bacterium species appears to be involved.
MEDIA CONTACTS:
For pictures, and information about P. ramorum in:
- Great Britain overall – Charlton Clark, 0131 314 6500;
- Wales - Mary Galliers or Clive Davies, 0300 068 0300;
- England – Stuart Burgess, 0117 372 1073;
- Scotland – Steve Williams or Paul Munro, 0131 314 6508/7.