Question
Thank you for responding, it was very helpful.  I have a few more questions:

So basically, there is nothing we can do about the galls?  Do these ever just go away?  What about the wasps that come out of the galls are they dangerous?  (We have little children).  The infected tree is in a clump of several trees, can I expect the other trees to become infected?
Thanks
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Followup To

Question -
We live in New Jersey along the shore. The oak tree in front of our house is loaded with what I guess would be called a gall.  They are growing around the small branches of the tree. They are about the size of a golf ball, but not all are pefectly round. They are the color of the bark  Also many of the leaves have white spots and some areas that have been eaten through.  What is happening to our tree and can it be treated? I have photos I can send if that will help.  Thanks

Answer -
The branches sound like galls.  Galls are irregular plant growths which are stimulated by the reaction between plant hormones and powerful growth regulating chemicals produced by some insects or mites. Galls may occur on leaves, bark, flowers, buds, acorns, or roots. Leaf and twig galls are most noticeable. The inhabitant gains its nutrients from the inner gall tissue. Galls also provide some protection from natural enemies and insecticide sprays. Important details of the life cycles of many gall-makers are not known so specific recommendations to time control measures most effectively are not available.

Gall makers must attack at a particular time in the year to be successful. Otherwise, they may not be able to stimulate the plant to produce the tissue which forms the gall. Generally, initiation of leaf galls occurs around "bud break" or as new leaves begin to unfold in the spring.

Twig and Stem Galls
Twig and stem galls, such as the gouty oak gall and horned oak gall, are solid, woody masses that can girdle branches or make them droop from the sheer weight of the heavy growths. The galls can grow to more than 2 inches in diameter. Horned oak galls can be found on pin, scrub, black, blackjack, and water oaks while gouty oak galls occur on scarlet, red, pin or black oak.

These galls have a long and complex development that takes two or more years to develop. The first stage is a blister-like leaf gall that occurs along larger leaf veins. The second stage is a knotty twig gall that is started in mid-summer and becomes fully mature in 1 to 2 years. Adults emerge in the spring. Gouty oak twig galls are smooth; hormed oak galls have horn-like projections. One female wasp can emerge from each horn.

Generally, insecticidal control is not satisfactory because the wasps are physically protected within the galls. Correctly timing applications to provide effective preventive control is difficult. Where practical, pruning of infested twigs may help to reduce the problem on lightly-infested trees. However, pruning is impractical if large trees are heavily infested.
I would not be too concerned with the galls they really do little to harm the tree. Here is web site that gives more information on oak galls. http://www.ento.psu.edu/extension/factsheets/gallsOnOak.htm

The leaves being eaten is from a different insect. Most insects that feed on the foliage of oaks do so in the early spring and the tree will recover without any need for control. You may check with the NJ State Forestry agency and ask one of their foresters to come take a look to make sure it is not something more serious. Their number should be in your local phone book.


Answer
Since the galls do little damage to the tree there is really very little need to do anything. The population of the insects will vary by year and some years you will be hard pressed to find a gall and other years they will be numerious. No the wasps are not dangerous--these are tiny insects that because of the body structures are in the family with wasps. They "sting" only plant tissue and will not bother animals. The Sting causes the plant tissue to swell --an eggs are layed near the sting site and the plant tissue swells over the eggs covering and protecting them.The vast majority of gall insects attack only oak. In general an insect that lives on one species of plant will not live on another different species (example Oak galls will not bother pines). I would not worry about the galls.