| discovery of a fourth evolutionary lineage of phytophthora ramorum: eu2. | phytophthora ramorum is a recently introduced, aggressive phytophthora species that has caused extensive mortality of oak and tanoak trees in the western usa and japanese larch trees in the uk. p. ramorum is also present on rhododendron, camellia, and viburnum in the nursery industry, which is thought to have been the pathway for its spread into new geographic regions including forests and natural ecosystems. three lineages of p. ramorum have been described, informally designated eu1, na1, and n ... | 2012 | 23153808 |