I am unable to confirm that this is the exact type of gall that you mention. But it is a gall. Once the gall has formed there is really nothing to do. The foliage may look disfigured but they do not seriously affect the health of the trees.  Small holes in the gall will indicate that the insects have emerged.  Unless you are getting yearly dieback control is not warranted. If needed, you could spray the tree with horticultural oil in spring just as new growth begins. Here is an article that in general talks about galls
http://bugoftheweek.com/blog/2013/1/27/gall-darn-it-gall-insects-on-hickory-oak-and-elm-iphylloxera-...