The waxy protective coating is what forms the crusty patches or bumps you see.
What Causes Magnolia Scale?
Magnolia trees that experience stress are more likely to suffer from scale infestations.
The Spruce / Brianna Gilmartin
A tree that doesn’t get enough moisture is especially susceptible, as are those suffering from other diseases.
They begin to feed and grow in the spring.
The insects mate in late spring, then the males die and the females continue to enlarge through July.
It’s possible to pick off the insects by hand when you spot them.
you’re able to also pick off crawlers when they emerge in late summer and early fall.
It becomes harder, if not impossible, with large mature trees.
This solution works best if you catch the infestation at a fairly early stage.
Spray With Pesticide
Chemical pesticidescan be used to kill scale insects at the crawler stage.
Drenching the root zone in early May gives the best results for this method.
Prune away diseased or damaged limbs as soon as you notice them.
Avoid over-fertilizing these trees, as it seems to encourage scale insects to attack.
Ladybugs and lacewings are natural predators of scale insects at the beginning of their larval “crawler” stage.
University of Wisconsin Horticulture,
Magnolia Scale.Ohio State University.
