This species was named as one of the newly defined species within the P. citricola complex in 2003, but has probably been present in Britain for decades and may even be a native. It has a much lower temperature optimum for growth compared with its ‘sister’ species P. plurivora.
Also like P. plurivora it often attacks the roots and root collar of beech, but it can also infect the aerial parts of trees. Phytophthora pseudosyringae has proved to be a very damaging pathogen to Nothofagus trees, particularly Nothofagus obliqua, causing trunk and branch lesions on this tree species and sporulating abundantly on the leaves. Its distribution in Britain is similar that of P. ramorum and it is found throughout much of western Britain.