Abstract
Phytopathogenic Oomycetes continue to demonstrate their historic dominance as major plant pathogens capable of causing serious epidemics in crops and forest ecosystems. The emergence of Phytophthora ramorum as a devastating non-host-specific pathogen of both ornamentals and forest tree species in North America and Europe has rekindled the continuous battle between man, through his activities that have tremendous impact on the natural ecological balance, and pathogens, which are constantly evolving, causing significant damage to plants. This paper provides a global up-to-date review of the threats of P. ramorum and the progress made in research and management efforts. It also discusses the need for continual vigilance and for serious consideration of new reports of unknown diseases and their associated pathogens, as these become established in our constantly changing ecosystem with severe consequences to man and his way of life.