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Serious new tree disease found in Britain

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Lawson's cypress tree (Chamaecyparis lawsoniana) infected with Phytophthora lateralis at Balloch Castle Country Park, West Dunbartonshire, Scotland

A deadly tree disease never previously found in Britain has been confirmed at a country park on the shores of Loch Lomond, Scotland.

Forestry Commission scientists have confirmed that Phytophthora lateralis (P. lateralis), a fungus-like pathogen that kills trees’ roots, has killed at least one Lawson’s cypress tree at Balloch Castle Country Park. Many of the other 80 Lawson’s cypress in the park also have symptoms consistent with death or decline due to P. lateralis infection. Samples from some of the others are being examined, but the scientists say it is highly likely that P. lateralis is the cause of their condition.

Twenty-seven dead and dying yew trees in the park are also being tested to try to establish the causes of their condition. The park is a popular visitor attraction about 32 kilometres (20 miles) north of Glasgow, but the pathogen is harmless to humans and animals.

Spores that spread the disease can be transmitted in contaminated soil, as well as on pruning equipment and other tools. Biosecurity measures will be put in place, including the installation of disinfectant mats at exit points from the park to reduce the risk of spreading the disease on contaminated footwear.  All visitors and staff will be asked to use them as they leave the park. Notices will be erected to inform visitors of the infection and asking them to take other simple biosecurity measures such as keeping to footpaths, keeping dogs on leads, and refraining from taking cuttings or other plant material from the park.

Until recently, P. lateralis was mostly known in the western states of Canada and the USA, but outbreaks have also been recorded recently in France and The Netherlands. Dr Bob McIntosh, Director of Forestry Commission Scotland, said,

“This is a very worrying development. P. lateralis is a particularly virulent pathogen, and very few trees survive an attack.

“Although its main victim is Lawson’s cypress, it can kill other species, particularly Pacific yew (Taxus brevifolia), a close relative of our native ‘English’ yew (Taxus baccata).

“It could also be serious for the ornamental plant industry if it became established in Britain, because Lawson’s cypress - and its various colourful cultivated varieties - are some of the most important conifers in our ornamental plant trade.

“Scientists in our Forest Research agency are researching the outbreak as quickly as possible to find out as much as they can, although the current poor weather is hampering the investigations.  We are also working closely with West Dunbartonshire Council to fell and destroy the dead and dying trees and to implement biosecurity measures at the park to minimise the risk of spreading the disease.

“Anyone living in the area who has Lawson’s cypress on their property is asked to check them carefully for signs of dying foliage and to report suspicious symptoms to us. We will be carrying out our own surveys in the area as well.”

Councillor Jim McElhill, the council’s spokesperson for Environmental & Economic Development, added,

“The council’s park staff will place disinfectant mats at exit points from the park, and public notices are also being displayed in the park to inform visitors of the infection and encourage them to observe sensible biosecurity measures.

“This soil-borne fungus poses no risk to the public or their pets, but I would ask residents and visitors to please work with our staff and follow the advice in the public notices displayed in the park.”

Symptoms of P. lateralis infection on Lawson’s cypress include the foliage initially appearing slightly lighter in colour than that of healthy trees, then withering and turning reddish-brown. Also, as the infection extends from the roots and root collar up the trunk, tongues of killed inner bark become visible by their darker colour, and the entire trunk can be girdled.

Anyone concerned that their Lawson's cypress trees might have the infection should contact the Forestry Commission’s Disease Diagnostic & Advisory Service on; tel: 0131 445 2176; or by post to Disease Diagnostic & Advisory Service, Forest Research, Northern Research Station, Roslin, Midlothian EH25 9SY. Notifications should include as precise a description of the location as possible – an Ordnance Survey or GIS reference is ideal, otherwise a full postcode is helpful. Photographs clearly showing the symptoms are also welcome to aid diagnosis.

Further information about P. lateralis, including frequently asked questions, is available from the pests and diseases section of the Forestry Commission website at

1. P. lateralis is thought to have originated in Asia before being introduced to North America, where it has caused the collapse of the Lawson’s cypress nursery industry in western states of the USA.
2. ‘English’ yew (Taxus baccata) is a British native species whose timber is prized for uses such as furniture veneer. The Forestry Commission is not aware of any records of P. lateralis infection of English yew, so it is anxious to also identify the cause of the declining yews in Balloch Castle Country Park.

Media contacts:

  • Forestry Commission – for general enquiries: Charlton Clark, 0131 314 6500; for enquiries specifically about P. lateralis in Scotland: Paul Munro, Forestry Commission Scotland, 0131 314 6507;
  • West Dunbartonshire Council – Moira Rodger, 01389 737225.