Hello Jacquline,

Once Magnolia scale reaches the stage that yours is at is difficult. In addition, the scale excretes a honeydew which is mainly sap that attracts a sooty mold that turns the tops of branches and leaves black. I’m attaching an MSU Extension bulletin that describes the insect.

https://www.canr.msu.edu/news/check_magnolias_for_magnolia_scale_now

As you know, controlling the scale depends on the stage of the insect. June to early July is the time to apply systemic insecticide which is absorbed by the roots and will move from the roots into the branches.

The next stage in the insect’s life is the active crawler stage which occurs in Michigan in August through September when you can spray with a contact insecticide. You should not need to use the second application if you do the first.

MSU’s Enviro-weather site has a tool which states when the crawlers are active.

http://msue.anr.msu.edu/news/magnolia_scale_is_starting_to_appear_on_magnolias

A smaller tree can be managed by hitting the scale with a hard spray of water. However, since your tree is too large for you to treat, consult a certified arborist. Go to: www.treesaregood.org, the website of the International Society of Arborists to find one in your area.

Thank you for contacting Ask Extension.