The Forestry Commission is investigating a recent outbreak of a disease affecting a number of trees on sites in Devon, Cornwall and Somerset.

The disease, Phytophthora ramorum, has been present in the UK for a number of years but, to date, has been largely associated with Rhododendron ponticum. These new finds are in Japanese larch. This is the first time that conifer species have been found with stem lesions caused by proximity to rhododendron which raises the question of how they have become infected.

Scientists from the Forestry Commission’s Forest Research agency have isolated P. ramorum on these sites and are investigating further. As a priority they are now carrying out more extensive tests and research to determine if P. ramorum is the main cause of the outbreak. Apart from finding a number of Japanese larch and Western hemlock trees, some broadleaf species (beech, birch and some oaks) growing in the same area are also infected.

Roddie Burgess, head of the Forestry Commission’s Plant Health Service said:

“This new find could represent a significant step change in the susceptibility of our trees to this disease so we are very concerned about this development. With our partners in the Food and Environment Research Agency (Fera), as well as scientists in our Forest Research agency, we are working extremely hard to learn as much as we can, as quickly as we can, about what’s happening. We can then consider what we need to do to manage the situation, building on the current programme of work to manage risks from this pathogen.

“It is important to stress at this time that much more research is needed to give us a full a picture and allow us to assess what the potential implications are. Once we have done that we will share our findings with local woodland owners and managers.”

Defra announced they would provide £25 million to fund a five-year programme, which started on 1 April this year, for research and development, and further disease control measures.

Further information about the disease can be found at: www.forestry.gov.uk/pramorum

Affected woodland sites include woodlands managed by the Forestry Commission as well as forests in private ownership.

Download: Guideline and Symptoms Briefing Note

Local forest and woodland managers who wish to be kept informed should contact the Forestry Commission’s South West England regional office at Mamhead Castle, Nr Exeter: Tel: 01626 890666 or E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it