Thank you for reaching out to ask2.extension.

If you go to mortonarb.org and search for magnolia scale, you will come to a screen with different magnolia trees listed.  Scroll down u til you see magnolia scale and click on the title. 
You will find information and pictures.  On the left hand side you will see management.  Click on that and it will tell you how to take care of the scale.

Good luck!