Hello, happy to help.

It probably is magnolia scale since they've been present in Hennepin county for years. Here information about Magnolia Scale (scroll down to Scales on deciduous trees/Soft scales on deciduous trees/Magnolia scale) where you can compare your tree's symptoms with those described in the link. It also contains options for management and treatment. Pay close attention to the timing of treatments. If not timed correctly, you'll be wasting money. Also, know that a cure has proven elusive.

Please pay attention to the warning in the link about using insecticides. The label on the product will indicate which insects the product targets. The label also has information about how to safely apply their product and in what amount. More is never better.

I recommend having a certified arborist treat your tree since they can best determine the right timing for whatever insecticide they use. Here is a link to information about how to find and hire a professional.

Sorry, forgot to add the link to finding an arborist. Here is the link.