Magnolia scale, a small but but numerous insect. Read more here: https://www.canr.msu.edu/news/check_magnolias_for_magnolia_scale_now
There is a small window for treatment after hatchout and before the crawlers
encase themselves. That window is close right now. This could be well handled by a Certified Arborist, one who specializes in everything woody. Find one or more Certified Arborists in your zip code at www.treesaregood.org
Click on the Find an Arborist tab. Arborist evaluations are not expensive and where you can learn much about keeping your plants healthy.