Cankers are characterized by the growth of small areas of dead tissue over several years. They can be caused by a wide range of fungi or bacteria and vary in degrees of severity.
Horse Chestnut Bleeding Canker can be caused by two pathogens, the fungi, Phytophthora; and the bacterium, Pseudomonas syringae pv. aesculi. Both target Horse Chestnut and Red Horse Chestnut. Interestingly, recent data has found a rise in cases caused by Pseudomonas.
As the name suggests, the main symptom of Bleeding Canker is lesions which exude a red-brown liquid. This liquid stain trees rusty red-brown in the summer.
Horse Chestnut trees respond to the bacteria by bleeding. The liquid is what damages the inner bark, cambium and outer layers of wood, disrupting the movement of water and nutrients.
Ultimately, Bleeding Canker disease leads to tree death. But sometimes, trees show periods of improvement, with some reaching full recovery. More research is needed to understand the life cycle of the disease better.