Identify bug, worm, or pest?

I began to see these linear white things on trunk and branches of a mature trident maple this winter. In spring/summer tree has produced leaves well, and seemed in good health. The white things now appear to have pumped up a bit, and are more numerous. They don't move while watching them, and don't have visible legs. They measure 2-3mm in length. I have picked off a couple classic appearing scale insects from this tree, which look much different from these things and are in different locations. Again tree appears very healthy. Most of these can be brushed off with wet tooth brush. Any idea what they are? Any serious concern?







Identity, level of concern and potential treatment would be appreciated. Thanks, Josh