Identifying diseases that cause bark death and stem bleeding

Horse chestnut trees with bleeding canker disease show symptoms of bark death and stem bleeding, but other Phytophthora diseases can cause similar symptoms.

Many tree species – including horse chestnut – may suffer from Phytophthora root disease, particularly on sites that are liable to be wet. In these instances Phytophthora infects the roots and root collar, but the lesions may extend upwards by as much as 1-3 m and be visible as bleeding areas on the tree trunk. This type of stem lesion is connected to a root infection and is distinct from the isolated aerial lesions that may be caused by other Phytophthora pathogens such as P. cactorum and P. plurivora.

Bleeding canker in other trees

• Although bleeding canker is the common name of a disease affecting horse chestnuts, the symptoms of bleeding cankers are sometimes seen on other trees.
• In the UK, both P. cactorum and P. plurivora have been found to cause bleeding cankers on the trunks of lime (Tilia). In the USA, the same Phytophthora pathogens have also been found to cause bleeding cankers on Acer (maple), Betula (birch), Liquidambar (sweet gum), Quercus (oak) and Salix (willow).