Update on conifer hosts of P. ramorum in the UK

This is of interest to Washington because Douglas-fir and western hemlock are important forest species here:

"The 2009 UK sites where Japanese larch (Larix kaempferi) were found with Phytophthora ramorum foliar and stem infections, yet not in close proximity to Rhododendron ponticum, have more recently been found to have a range of other woodland and commercial plantation species affected by the pathogen (primarily bole canker infections). Tests conducted by UK Forest Research have shown that the Japanese larch foliage strongly supports P. ramorum sporulation, possibly even to the extent seen on California bay laurel (Umbellularia californica). Foliar infections on larch appear to be able to generate hundreds and even thousands of sporangia on a single infected needle. This inoculum load high in the crowns of affected Japanese larch has likely lead to widespread local infection on the foliage and boles of nearby susceptible tree and understory species, as well as caused bole infections on the larch.
Affected species of the larch understory include beech (Fagus sylvatica), sweet chestnut (Castanea sativa), and oak species (Quercus spp), all of which are known to suffer from bole cankers, as well as birch (Betula pendula), which has not previously been found as a bole host. Over the past 6 months a number of conifer species have also emerged as bole hosts, including western hemlock (Tsuga heterophylla), Port Orford cedar (Chamaecyparis lawsoniana), and Douglas-fir (Pseudotsuga menziesii); however, only one or two individuals of these conifer hosts have so far been confirmed P. ramorum positive. Western hemlock has also been confirmed as a foliar host of the pathogen.
This upsurge in P. ramorum and the many new hosts that are emerging is strongly correlated with proximity to larch exhibiting crown dieback. The number of sites where this is known to be occurring is limited. Control measures are now underway, which includes felling the larch to prevent further sporulation following budburst in the spring. For more information and details of symptoms, go to http://www.forestry.gov.uk/forestry/INFD-7XVEWH and http://www.forestry.gov.uk/website/forestry.nsf/byunique/infd-5vfmzu "

from the April COMTF newsletter