How to treat Japanese maple disease: white spots on bark and bark cankers on Bloodgood Japanese maple?

Question

It’s a mature tree that has been on that same spot for about 5 years.

Answer 1

These articles may help you assess the issue.

https://www.gardeningknowhow.com/ornamental/trees/japanese-maple/japanese-maple-problems.htm
https://www.gardeningknowhow.com/ornamental/trees/maple/maple-tree-bark-disease.htm