Sudden oak death on larch
16 November 2010
Image: Forestry Commission | © Crown Copyright
New discoveries of sudden oak death (Phytophthora ramorum) outside previously-known sites in both Wales and Northern Ireland suggest that the disease could be more widespread than first thought.
About 60 Larix kaempferi (Japanese larch) were found to be infected by the fungus-like pathogen at the Bwlch Nant yr Arian visitor centre, near Aberystwyth, on the west coast of Wales. All the trees have been felled. There have also been three further cases, also in Japanese larch trees, in Co. Antrim and Co. Down, following the diagnosis of the first known cases in Northern Ireland, at three woodland sites in Co. Antrim, in August. The Forestry Commission is also investigating areas of dying larch in south-west Scotland and the Isle of Man.
Until 2009, few trees had been infected in Britain and the disease was largely confined to Rhododendron species, particularly the naturalised R. ponticum - but testing has confirmed that the disease is present on larch plantations in 58 locations in England and Wales. The only known treatment is to fell diseased trees in a bid to contain the spread, meaning nearly 2000 hectares of forest plantation are having to be destroyed.
What to look for
Concerned owners should look for wilting fresh needle growth, dieback extending along branches from the growing tips and resinous bleeds on branches and main stem. Other symptoms include dead needles retained on the bud and excessive sideshoot growth combined with abnormally high cone production.