The article on cytospora canker says the only solution is to prune the affected area, but I have amber sap coming out of the trunk of my weeping cherry tree, about 4 feet up, so I think the cause isn't a boring insect. Any idea of how I can protect my tree given I can't prune out the trunk? Thank you! Bruce
Cytospora Canker on Trunk of Weeping Cherry
Certified GKH Gardening Expert
Usually by the time you have this issue on the trunk the disease has progressed in the tree.
There is no treatment but you can try bacericide products containing fixed copper.
You could also have the tree looked at by an professional arborist.
Best of luck.