Phytophthora lateralis is an aggressive, fungallike pathogen of Lawson cypress trees. It mainly attacks the roots of trees and can spread up through the trunk resulting in the rapid decline and death of the tree. Thought to originate in Asia, the disease is the main cause of mortality in Lawson cypress in its native range in the west coast of North America, and outbreaks have now been recorded in France and the Netherlands. The pathogen was first reported in the UK in 2010, most likely having been imported from mainland Europe, and it has since been found on sites across England, Scotland, Wales and Northern Ireland. It is important that suspected cases of the disease are reported.