Oyster Scale on Magnolia

[WillClimb]

How do you get rid of Osyter Scale on a Magnolia? With oil?
I'm almost 100% sure that this is oyster scale. Looks like white spots of ash on the leaves.

One thing to note: this is next to a road and sidewalk, both of which have heavy traffic. If I climb the tree and spray it with anything, I can see potential overspray problems.

 

[John Paul Sanborn]

Oil or soap after the crawlers emerge.

Soil injection of Metasystox if you are near an economic level of infestation

then try to figure out waht is stressing the plant so much that it cannot fight off the pest.