Question
I live in GA and have a Pin oak that has swollen bubbles all over the stems.  The bubbles break off easy and appear to have sawdust in side.  I do not see holes in the stem but some times see a Little bug.  Do you know what this is and how to treat?  Thank you.

Answer
They are called galls and are caused by an insect (small wasp) The wasp lays its eggs on the surface of the leaf or twig and secretes a chemical that causes the tissue of the leaf or twig to swell and cover the egg. the egg hatches and moves on. The galls themselves will not harm the overall health of the tree although they can look bad. Leaf galls may cause the leaves to drop prematurely. There are many types of these wasps some attack the twigs and others the leaves. Control is not usually needed and has to be timed with the wasp presence and not the galls themselves. Here is a web link to more information on gall wasps that discuss the wasps and control measures.
http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note05/note05.html