Some of the branches of my azaleas have a barnacle-like growth that is a light gray-blue-green color. I see the the same growth on a nearby young dogwood tree.
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This is lichen and is not harmful to the plants. However, if you want to get rid of it or simply more info, here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/fungus-lichen/treatment-tree-lichen.htm