Phytophthora ramorum is an aggressive fungus-like pathogen that causes extensive damage to a wide range of trees and shrubs. The disease affects the foliage and bark of a number of both broadleaved and conifer trees and is particularly prevalent on the western side of the UK where climatic conditions favour its growth and spread. When multiple hosts occur on infected sites, symptoms of P. ramorum are likely to occur in a variety of species. The disease is often fatal to the trees it affects and it has had a major impact on forestry in the UK.
