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Is the UK prepared for Sudden Oak Death?

27 April 2009 Imperial College London

Britain’s ability to stop the spread of so-called ‘Sudden Oak Death’, a disease threatening the country’s trees, woods and heathland, will be assessed in a new review by Imperial College London researchers announced today.

The review, which has been commissioned by the Government’s Department for the Environment, Food and Rural Affairs (DEFRA), will be carried out as part of the UK Research Council’s Rural Economy and Land Use Programme. It will look at the effectiveness of current strategies being used to keep this burgeoning disease under control.

Despite its name, Sudden Oak Death does not affect just oak trees. The disease is caused by two pathogens, Phytophthora ramorum and Phytophthora kernoviae, which can infect a wide range of trees and shrubs found in the UK including beech, ash, yew, rhododendron, magnolia and heathers.  

The pathogens kill trees and shrubs by creating cankers which girdle the trunk or stem, and clog up their water-carrying ‘veins’. Since the 1990s, Sudden Oak Death has wiped out millions of trees in the forests of California and Oregon in the USA. Experts in the UK fear that if the disease took hold and spread rapidly throughout the UK, the impact on ecosystems, biodiversity and the national landscape could be severe.

In the last five years, outbreaks of this disease have been identified in the West Country, as well as in Wales, Staffordshire, and Scotland. The Government has responded to these outbreaks, recently announcing additional spending of £25 million that will be dedicated to preventing it spreading further, and to eradicate it where it is found.

The controls to date have included setting up a ‘plant passport’ system in the nursery trade, which requires consignments of at-risk species like rhododendrons to have their health certified before they can be moved around the EU. In the UK, Government inspectors have been sent into nurseries, woodland gardens and other high-risk locations to identify diseased plants and recommend that they be safely cleared. 

The scientists conducting the new review, led by Dr Clive Potter from Imperial’s Centre for Environmental Policy (CEP), will evaluate how effective these and other measures have been to control recent outbreaks in Cornwall and elswhere, and will recommend improvements to be made when the new control programme is rolled out nationally later this year.  

Dr Potter and his CEP colleagues Dr Isobel Tomlinson and Dr Tom Harwood are already carrying out a major analysis of the science and policy of tree disease epidemics as part of the UK Research Council’s Rural Economy and Land Use Programme. They are investigating how lessons learnt during the 1970s Dutch elm disease epidemic can be applied to this new threat.

Dr Potter said: “We are well placed to take an independent look at Government policy in this area as it fits well with the work we’re already doing on Phytophthora ramorum and Phytophthora kernoviae.

“We know that some of the policies pursued in the 1970s inadvertently promoted the spread of Dutch elm disease. For example, felling diseased trees but then transporting the timber without removing the bark enabled the pathogen to survive and move around the country very rapidly.

“So a review of the strategies being employed against these new woodland diseases is timely. It will enable us to bring experience from the past to bear, and to evaluate the effectiveness of current policies.”  

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