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The Forestry Commission has introduced a temporary moratorium on issuing new permissions to fell larch trees during the winter in the areas of Britain at greatest risk of having ramorum disease.
Discoloured larch needles are the most visible symptom of infection by the destructive, fungus-like Phytophthora ramorum pathogen, so it is very difficult to identify infected larch trees once they have shed their needles in the autumn.
Dr John Morgan, Head of the Forestry Commission’s Plant Health Service, explained,
“Without knowing whether the trees are infected, we would risk inadvertently spreading the disease during harvesting, transporting and processing operations if infected trees were felled and moved in winter without biosecurity precautions being taken.
“We also do not want to impose the burden of biosecurity precautions on owners, hauliers and processors handling timber that might be disease-free.
“We have agreed with the forestry and timber processing sectors that we should postpone new permissions to fell larch until next spring, when we can be more confident about identifying infected and uninfected trees, before allowing felling to resume in the high-risk areas.
“We fully understand the disruption that this will cause to some forest managers’ plans, but we feel that it is a necessary part of our strategy to bring this highly destructive disease under control.
“I would like to thank all of those forest owners who have co-operated with our control strategy, despite sometimes significant disruption and losses. It is very much appreciated.”
Dr Morgan added that the Commission would process licence applications as quickly as possible once larch felling can resume. The exact date when that can happen will depend on the timing of needle flush next Spring, and is likely to be different in different parts of Britain, but is expected to be no later than the 31st of May 2012.
Further information about the felling licence moratorium in the three countries is available from:
Further information about Phytophthora ramorum, including a map showing the risk zones, is available at www.forestry.gov.uk/pramorum. The moratorium applies in all areas within Risk Zone 1.
NOTES TO EDITOR:
- This is the second year running that a winter moratorium on new permissions to fell larch has applied in England and Wales, and the first in Scotland. It applies in Risk Zone 1 to any stand of trees with a component of larch trees.
- If trees show symptoms of infection during spring and summer, a Statutory Plant Health Notice (SPHN) is issued requiring them to be felled within a specified timescale, and the moratorium would not apply. The produce may then be transported and processed only by hauliers and processors authorised by the Forestry Commission to handle infected material. To be authorised, hauliers and processors must demonstrate that they have put in place and are practising the biosecurity measures required to prevent spread of the disease during operations.
- Phytophthora ramorum (P. ramorum) can infect more than 150 species of plants and trees. It is particularly serious in Japanese larch trees, which produce huge quantities of the infective spores that spread the disease. These can be spread from tall trees by the wind and in moist air currents, and the only available treatment to control the disease is to fell the trees, preferably before they next sporulate (produce spores).
- P. ramorum was first identified in the United Kingdom in a viburnum plant in West Sussex in 2002. It has since been found infecting a wide range of plants and trees throughout the UK. Until recently it had mostly affected shrubs such as rhododendron, camellia and viburnum, but only a limited number of trees. However, since late 2008 infection it has been found in the environmentally important bilberry plant (Vaccinium myrtillus - known as blaeberry in Scotland and winberry in Wales), and in Japanese larch trees since 2009. An estimated 3 million larch trees have been felled in the UK in an effort to bring the disease under control.
- Tree mortality is rapid – P. ramorum appears to be able to kill Japanese larch trees within a single growing season after its presence is first detectable. In Japanese larch, it causes shoot tips to wilt and needles to turn black and fall prematurely. Cankers that bleed resin can appear on the branches and upper trunk.
- The European Commission has adopted emergency measures that regulate P. ramorum as a ‘quarantine’ organism so its presence on trees or woodland plants must be notified to the relevant authorities (Forestry Commission, Fera, Welsh Government or Scottish Government), who must take statutory action to contain or eradicate it.
- P. ramorum does not harm the timber, and logs from infected trees can be sold into the timber market, subject to biosecurity measures to prevent further spread.
- Larch is a durable, versatile timber that tolerates changes between wet and dry conditions very well, resists rotting when used in the ground, and is easily stained, worked and finished. It is therefore in demand for outdoor uses and flooring and chipboard. There are about 134,000 hectares (331,000 acres) of larch woodland in Britain: about 5 per cent of the total woodland area.
- P. ramorum is not harmful to humans or animals, and all public woodlands remain open to visitors, except where felling operations are taking place, which are temporarily closed for safety reasons.
P. ramorum causes the disease known as "sudden oak death" in the USA, where a different mating type has killed millions of North American native oak and tanoak trees in California and Oregon. However, its American common name is a misnomer in Britain, where laboratory tests have shown that our native sessile and pedunculate oaks are much more resistant than their American cousins, with only a tiny few confirmed with P. ramorum infection. Therefore the generic term ‘ramorum disease’ is used in Britain instead of ‘sudden oak death’.
- P. ramorum should not be confused with acute oak decline (AOD), which is a separate condition affecting oak trees in the Midlands and parts of Wales and South East England, and in which newly identified species of bacteria appear to be involved.
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