On horse chestnuts with leaf miner, is bleeding canker terminal and infectious?
Leaf miner can continue for many years and, on its own, is unlikely to kill the tree, however it does weaken the tree which makes it susceptible to other diseases and Canker is the most likely. Chondrostereum (Silver Leaf) is also able to attack weak trees, but I would suggest following canker infection. In terms of infection this is not conclusive, it may require wounds to infect (which may include naturally occurring lenticels, or pores, in the bark) or might exist on plant surfaces and be spread by wind-blown rain. It is much like Phytophthora, which would make any tree within the area susceptible and is terminal if infection girdles the whole tree in the lower stem. See link below to Forestry Commission where a recent page has been set up for all the main tree pests and diseases with links to detailed information. This is a great resource and should be on every Tree Wardens favourites.