verticillium

Hello! I have this acer palmatum shishigashira, which is developing a black band in the trunk.. is this verticillium?

I never thought I would write a post like this but now I'm pretty sure my loved Deshojo got Verticillium from an unsealed small pruned branch. I didn't think it was so easy for this fungus to enter a susceptible species. All the leaves of this branch, after leafing out fine this spring, suddenly...