Q: My saucer magnolia is covered in wasps and dirt daubers. Also there seems to be some nodule type growths on the stems that I can pick off with a fingernail. Are these two events related?
A: If you have scale insects (which release a sweet liquid that attracts wasps) on the magnolia, the two could very well be related. There are many types of scales. Tea scale on camellia and euonymus scale on its eponymous host are common in Georgia landscapes.
An adult scale secretes a hard, waxy coating over their body to protect it. They happily suck sap from a stem or leaf and ooze honeydew, which coats nearby leaves. These leaves may turn black as sooty mold sets up housekeeping on the honeydew.
The best time to attempt control measures is when baby scale (crawlers) are moving about the plant in spring. In early April, wrap double-sided tape around stems near where you notice the nodule growths on the branches. Inspect the tape every few days. When yellow crawlers hatch they will be caught on the tape, signaling you to begin spraying with horticultural oil at weekly intervals. The oil will not only kill the young scale but it will suffocate the adults, which have been weakened by the stress of winter.