Phytophthora ramorum is a plant pathogen known for causing Sudden Oak Death, a disease that affects various tree species, particularly oaks. It thrives in moist environments and spreads through water, soil, and infected plant material. The pathogen can lead to significant tree mortality and has serious ecological and economic impacts. This organism is a type of water mold and belongs to the group of pathogens called oomycetes. It can infect a wide range of host plants, including ornamental species, which complicates management efforts. Early detection and proper sanitation practices are essential to control its spread and protect affected ecosystems.