Forestry Commission Wales (FCW) have reported on a outbreak of Phytophthora ramorum in South Wales. Currently the outbreak has only been found in Welsh Assembly Government woodlands managed by FCW.

The disease Phytophthora ramorum was first found in the UK in 2002. In the wider environment it has largely been associated with Rhododendron species that act as a host from which spores are produced. When produced in sufficient quantity these can infect trees and other plants generally in the immediate vicinity. Control efforts in woodlands had focused primarily on removing Rhododendron.

In August 2009 Phytophthora ramorum was confirmed on Rhododendron ponticum in the understorey of mature Japanese larch, and also on the foliage of thicket stage Japanese larch in Cornwall.  Since then infected sites have been found in Devon and Somerset and it has also been confirmed that infected Japanese larch produces spores at about five times the level of Rhododendron and that these can be dispersed considerable distances, probably some tens of kilometres.

Aerial surveys of woodland in South Wales in May 2010 identified symptoms that indicated that Phytophthora ramorum might be present. Subsequent inspections and testing have confirmed that there is widespread infection in the lower Afan Valley, Garw Valley and Vale of Glamorgan, in south Wales, in all ages of larch. The situation is changing rapidly as we undertake more surveys and it is likely that the infection has spread more widely.

On Japanese larch, shoots and foliage can be affected and are visible as wilted, withered shoot tips with blackened needles. The infected shoots shed their needles prematurely. Trees with branch dieback may have numerous cankers on their branches and upper trunk that can bleed resin.

FCW has implemented biosecurity measures on all infected sites.  Look on the Forestry Commission website www.forestry.gov.uk/pramorum for more information and keep an eye on the larches in your area.