Tree disease outbreaks confirmed in Devon, Cornwall and Somerset

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 P. ramorum. Many of the infected trees are not growing in close 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 whether P. ramorum is the main cause of the outbreak. Apart from 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 & 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 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 it would provide £25 million to fund a five-year programme, which started on 1 April this year, for research, development and further disease control measures. Lord Davies, Defra Plant Health Minister, said:

"This latest find reinforces the need to press ahead with the £25 million of work we’re doing to reduce the disease’s spread through the removal and destruction of rhododendrons from the most at-risk areas across England.

"It’s important that we continue to manage the spread of this disease to ensure our woodlands stay pristine and healthy so that they can be enjoyed by generations to come."

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