Clackamas County Oregon arborvitae
Thank you for your question. First, the white spots appear to be lichens, which don’t cause any damage, but are often found on woody plants that have problems. Second, we need to see a photo of the entire plant to spot trends in the problem(s). Third, we cannot diagnose the trunk and branch blackening on a plant without knowing the plant species and seeing the entire plant. I suggest you take these photos, more as described above, and plant samples into one of the 3 metro Extension offices for help. Here are the 3 possible sites: https://extension.oregonstate.edu/mg/metro/have-gardening-question Good luck!