Question
Our oak tree is about 5 years old and we have noticed some of the branches have lost their leaves.  Upon closer inspection, we found "knots" in many of the branches, and upon cracking open some of these found evidence of insects (a white web like substance was presence).  And the inside of the knots had holes, obviously some kind of insect (catapillar?) damage

Can you help?  we are in houston, texas

Answer
It sounds like one of the gall making insects. These normally do not harm the tree unless they are numerious. I would suggest you call or email the Urban Forester in Houston--
Mickey Merritt
(713) 688-8931
[email protected]

Dallas Singleton
(713) 688-8932
[email protected]

They both work for the State Texas Forestry Service and should be able to help you to indentify the problem and tell you if it needs any controls.. This is a free servcie in most states.