Mountain bikers urged to help beat deadly tree disease in Afan Forest Park

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18 JUNE 2010NEWS RELEASE No: 13715

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Mountain bikers are being asked to do their bit to avoid spreading a fatal tree disease in South Wales.

Phytophthora ramorum is a fungus-like pathogen that kills many of the trees and plants that it infects. An outbreak has been found in Japanese larch trees in the Afan Forest Park near Port Talbot which is managed by Forestry Commission Wales on behalf of the Welsh Assembly Government and is home to some of the best mountain bike routes in Wales.

Forestry Commission Wales’s MTB Ranger, Carl Denham, is appealing to mountain bikers to help contain the outbreak and keep the routes in Afan Forest Park open by following some simple biosecurity measures.

Carl said, "Forestry Commission Wales is working hard to minimise the impacts of this serious disease on our woodlands and the support of the mountain bike community is vital.

"Everyone who works in or visits the affected woodlands here in South Wales is being asked to observe some simple biosecurity measures so that they don’t inadvertently spread this pathogen.

"For mountain bikers, this means washing their bikes and kit thoroughly to remove all dirt and plant material before they leave the forest after their ride.

"Bike washes are available at both Afan Forest Park visitor centre opposite the car park and Glyncorrwg Mountain Bike Centre opposite the bike shop."

One of the five mountain bike trails at the Afan Forest Park, the Penhydd Trail, had already closed in April for Forestry Commission Wales to carry out tree thinning work. This area of woodland is now one of the worst affected so far by the Phytophthora ramorum outbreak and, in order to contain the outbreak, extensive felling of infected larch trees is about to begin there.

Carl said, "When we shut the Penhydd Trail in April, we anticipated that it would be closed for a year before being redesigned and reopened.

"The Phytophthora ramorum outbreak in the woodlands around the Penhydd Trail means that more trees will have to be cut down there now but we still hope the route will reopen in mid 2011."

Japanese larch trees infected by Phytophthora 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. The outbreak in South Wales, which has affected the Afan Valley, near Port Talbot, Garw Valley, near Bridgend, and the Vale of Glamorgan, is the first time it has been encountered on larch elsewhere in Great Britain.


Phytophthora ramorum

  • Phytophthora ramorum (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, Welsh Assembly Goverment, Scottish Government). It was first found in Britain on a viburnum plant in a nursery in 2002.
  • 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. However, its American nickname is a misnomer in Britain, where laboratory tests have shown that our two native species of oak, sessile and pedunculate oak, are much more resistant to P. ramorum than their American cousins. Fewer than five native oak trees have been confirmed with P. ramorum infection in Britain.
  • It 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.
  • P. ramorum kills most trees that it infects, but symptoms vary according to the type of tree or shrub. On Japanese larch (Larix kaempferi) trees, it causes shoot tips to wilt and needles to turn black and fall prematurely. Numerous cankers that bleed resin can appear on branches and the upper trunk. Infected Japanese larch trees produce particularly high numbers of the spores that spread the disease – five times the level produced on rhododendron - meaning the disease can quickly affect a large number of trees and shrubs.
  • P. ramorum has not been found infecting any European larch (Larix decidua) or hybrid larch (Larix x eurolepsis) trees, which are the other two species of larch grown in Britain, but these species are being kept under close surveillance.
  • P. ramorum can be spread on footwear, vehicle wheels, tools and machinery that have been used in infected forests, or by the movement of infected plants. It can also be spread in rain, mists and air currents, and scientists at Forest Research, the Forestry Commission’s scientific research arm, believe this is the likely pathway for the Japanese larch infections from South West England to South Wales.
  • In South West England, P. ramorum has affected a mix of Forestry Commission and privately owned forests.
  • P. ramorum has not been found on any trees in Scotland.
  • P. ramorum is not harmful to humans or animals.

Japanese larch

  • Complete figures are not available for Japanese larch numbers 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 – 43,000ha / 4.3 per cent;

· Scotland – 65,000 ha / 5.1 per cent.

(To convert hectares to acres, multiply by 2.47)

  • 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.

Advice to woodland owners or managers

Woodland owners or managers who suspect infection in their trees should report it in Wales to Forestry Commission Wales’ Grants & Regulations office at Clawdd Newydd, Ruthin, Denbighshire, LL15 2NL Tel: 0300 068 0300, e-mail:

Mountain biking in South Wales

For information on mountain biking in sites managed by Forestry Commission Wales, please contact Carl Denham, Mountain Bike Ranger, on 0300 068 0300 or 07833 237133,


For information about P. ramorum: