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Phytophthora ramorum

Phytophthora ramorum is a fungus-like pathogen first discovered in the UK on a viburnum plant in Sussex in 2002.

What is Phytophthora ramorum?

In 2009 Phytophthora ramorum was found to be infecting and killing larch trees in south west England and subsequently spread to many western parts of the UK, leading to widespread felling. It has also been found to infect rhododendron, and native bilberry.


  • Wilted, withered shoot tips with blackened needles
  • Infected shoots shedding their needles
  • Prematurely bleeding cankers exuding resin on the upper trunk and branches


  • Phytophthora ramorum spreads easily in moisture and water such as moist air currents, mists, fog and watercourses
  • Contaminating spores can also be spread by animals and on footwear, vehicle wheels, machinery and equipment


  • The ability of the organism to switch host plants is worrying. In the USA, the disease earned the name “sudden oak death” because of its impact on native oak and tan oak species there
  • Globally it has more than 150 host species. Further significant areas of infection have been found in south west Scotland and south Wales over the past two years
  • Wentwood forest, near Newport in south Wales, has been the worst affected Woodland Trust site. Whilst the larch trees were earmarked for felling within our programme of ancient woodland restoration, this would have been a very gradual removal to protect the delicate ground flora
  • Having no choice but to clear fell these areas means we need to change our approach and restock very quickly with a broad range of native species in order to preserve the associated flora and soil conditions associated with ancient woodland

Report it

If you think you’ve spotted this disease please inform the Forestry Commission using the Tree Alert reporting tool. Three good-quality digital photographs are required to aid identification.

For more information visit the Forestry Commission.