Options to control scale on magnolia
Q: I noticed scale on the underside of my magnolia trees leaves. Is this something I can treat now or do I have to wait until the spring?
A: The most advantageous time to treat for scale is in the spring when young crawlers emerge from under the protective cover a female scale provides. Scale can be suffocated with a horticultural oil spray but it is almost impossible to get the spray under the heavy leaves of a magnolia.
Dinotefuran (Safari) is a systemic insecticide that controls armored scale reasonably well.
A third option is to simply monitor the scale population. Beneficial insects attack scale naturally and you might do more harm than good if you use an insecticide.