Hello, Thank you for contacting Ask Extension. In order to be able to give you a better assessment of the tree, I need a few more pictures from you. Could you send a couple of pictures of only the trunk area, especially the ones that you state have black and white spots on them. Also, could you send a picture of a close of the leaves. 
Once I receive those, I will be able to better look at the whole picture. 

Thank you,

I am sending three pictures!  Thank you for your quick reply.

Not sure if you received the new pictures

I did. I will look them over and get back to you by tomorrow.

Thank you for contacting Ask Extension. Thank you for sending the additional pictures because it really helped in determining your problem. You have Magnolia Scale, which are the white spots and some of the black spots that are older scale. The black spots on leaves are called honeydew, which is the secreted sap that the scale eliminates on the branches. The honeydew attracts bees, flies and wasps.

So here is how to take care of the Magnolia Scale. There are two methods in dealing with a heavily infested tree. The first is to buy a product with the active ingredient imidacloprid or dinoterfuran. You will mix these up, according to the label instructions, to make a drench to pour around the tree. The second method is to spray your tree when Magnolia scale is in the crawler stage. You will want to look for small reddish crawlers that emerge in the middle of September and early October. You will use a horticultural oil, sometimes called Neem oil, to spray over the crawlers which will suffocate them. You will want to do another spraying in early spring after the last frost, but before the buds have opened.

I have included several publications to help you with what to spray and when.

Magnolia scale is having a good year - MSU Extension

Magnolia Scale | Ohioline (osu.edu)

Magnolia Scale (psu.edu)

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