What are these white spots on my Magnolia tree?
Regarding your question about your Magnolia, the white spots that you are seeing are called Scale and it is an insect. The white is actually a waxy protective coating and the insect is underneath feeding on the leaves of the plants. With Scale on your Magnolia, you will probably also notice black sooty mold on the leaves of the plants. The black sooty mold is the result of the insects honeydew like excrement that when reacts with the air, it molds, kind of like when bread is left out.
To treat the insect you are going to want to use a horticultural oil and spray the top and undersides of the leaves to the point of run off. This may take a few applications but will smother the insect. We sell this horticultural oil at are garden center and it is $7.49.
If you would like more information on scale, we have a great article posted on our website that goes into more detail. The link to it is: http://verdego.com/10/scale-insects-mealybugs-on-ornamental-plants/