Sudden oak death

Phytophthora ramorum (P. ramorum) is a fungus-like pathogen which causes extensive damage and mortality to a wide range of trees and other plants.
On trees, symptoms include lesions – sometimes known as bleeding cankers - which exude fluid from infected bark, visible as a black exudate which can dry to a crust on the trunk. The inner bark under this bleeding area is usually discoloured and dying. Trees die when the lesions become extensive on the main trunk.