This is on a European hornbeam (carpinus betulus) cultivated for bonsai.
I cut off part of a branch that I wanted to shorten and noticed weird black and brown bumps along a line on the branch. When I looked at the cross-section, there was a darkened segment that looked like the wood was rotting.
Does anyone have any idea what it might be? Could it be harmful? If so, what should I do to remedy this? A person on reddit said it might be damage from beetle larvae.
I am reluctant to cut off that entire branch as it’s pivotal to the design of the tree, but I could cut a little lower and carve out the part that looks dead/diseased. Would that be enough to stop the possible pathogen from spreading, or is cutting off the entire branch the only option?
Thank you in advance for your help!