I'm not sure about what the stuff inside the red circle is.
Otherwise, it all is just lichen, IMO.
Lichens are not harmful. They are a symbiotic fungal-algal organism (a fungi that discovered farming!) and a good sign of an unpolluted environment. I like the look of age they add to my trees.
I agree with the above^^^. There is quite a bit of lichen starting up, but the circled in red area could be scale. See if it scraps off with your fingernail. If it is live scale, it may be a bit gooey inside. If it is scale, I would rub it off with a q tip dipped in alcohol.
There is definately some lichen there. What concerns me is that there may be some fungal infection, or maybe fungus growing on dead wood. The tree bark seems rather dark in that area.