A while ago, when trimming off a few lower branches, I noticed sticky stuff dripping from my magnolia tree. Upon closer inspection, I saw blackened leaves, as well as a black residue on my white veranda rails and porch. Next came the swarms of hornet-like bugs attracted to the sugary residue. What a mess! Apparently, my tree is infested with magnolia scale, as described by the University of New Hampshire:
Magnolia scale feed on plant sap with piercing-sucking mouthparts and excrete a sweet, sticky fluid called honeydew. Unsightly black fungus called sooty mold often grows on the honeydew, making the leaves look dirty and reducing photosynthesis. Honeydew also attracts sugar loving insects such as ants and wasps.University of New Hampshire
The Stages of Magnolia Scale
Instead of laying eggs, the adult female magnolia scale insects give birth to young crawlers, which then molt into adults sporting a waxy, outer soft shell that protects their bodies. If you discover whitish patches on the branches of your magnolia tree, that would be the time to treat the tree. Otherwise, the tree will suffer greatly.
Treatment for Magnolia Scale
Treating the scale insects at this stage is easiest. My magnolia tree is not yet fully grown so I can still reach all the branches, especially when standing on my veranda. I used another of my trusty Melaleuca products, a concentrated solution of thyme and lemon, called Solugard. I coated each white patch and sprayed the veranda and railing. I may have to repeat the treatment, will keep you posted.
You can also prune out infected branches and twigs if there are not many involved. Most of my branches are so that was not an option. Another solution is a pesticide specifically for the magnolia scale; you probably know what I think about pesticides.
Also suggested is a late April (before the buds open on the tree) application of dormant horticultural oil such as neem oil. This early treatment will kill the magnolia scale insects that have overwintered on your tree.
A cold winter helps too. Our last few winters here in Ottawa have been unusually mild so more of these insects survived on the branches.
Bring on the cold, just not yet please. We have several more months until I am ready for that weather, hoping for another beautiful autumn first.
Before the Magnolia Scale
I will be heartbroken if this gorgeous tree does not survive. Fingers crossed I caught the scale in time