Does it work to just pick off the scales? I can reach most of them.
Hennepin County Minnesota magnolia scale
Not exactly but if you can remove them it would be good. You need to get rid of all of the insects. The problem is the life cycle of the insect. Here is a link that explains what it is and what it does as well as how to deal with it. https://hort.uwex.edu/articles/magnolia-scale/