Question
Hello,

I live in western Maryland and have a grove of 16 pin oak trees that are approx. 17 years of age.  I realize that we have had a very dry summer and that they may have been planted to close together, however, upon close inspection the damage seems to be caused by something eating and damaging the leaves.  I have not noticed any wasp galls on the branches, however the leaves have brown sections, eaten sections, and a good deal of galls on them.  The galls were small, green and solid about a month ago, resembling peas on the leaf surface.  They seem to have grown and turned tan.  I have not noticed any large groups of aphids, leaf bugs, or worms, but did see a couple small black wasps (?) and a variety of caterpillars, but not of the same type.  We have posted pictures of the samples we collected on 28 August on the following website:

http://www.smugmug.com/gallery/13531701_b3xvN#985864011_QjU9m

Please help us save our trees!  They are losing foliage quickly.  I had an arborist out about a month ago, who took samples which were sent to a lab, but the results indicated everything was nromal and he recommended pruning.  We have these results if you would like to view them.  Thanks in advance for any advice you can provide - the Wares

Answer
I think you have several thing going on with your trees none of which cause much health problems with trees.

The dying of the ends of the leaves with no sign of eating or disease is a sign of the effect from the drought. Not anything that can be or needs to be done--they will recover when they leaf out next spring.

The feeding seems to be either a sawfly--the surface of the leaf is eaten and leaves a skeleton of the leaf. Some leaves are eaten half off--this is a sign of a caterpillar. Since the damage seems to be slight neither one of these insects are causing a health problem. For damage to be a problem would would expect more than 1/2 the foliage to be gone and this would cause some growth loss the first year--IF the defoliation happened two years in a row you would start to get some dieback of the limbs. This does not seem to be the case with your trees.

The galls are not a real health problem. Most galls 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 eggs 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 are a web links to a couple of sites on gall wasp that discuss the wasps and control measures.
http://entomology.unl.edu/ornamentals/pestprofiles/gallwasps.htm
http://www.ces.ncsu.edu/depts/ent/notes/O%26T/trees/note05/note05.html

Some of the lower branches maybe dying from natural pruning. Lower branches are shaded and the tree tends to shed them over time. Some of the lower branches look as if they have died but not sure of the cause. I would check and see if in fact they are dead--scrape a small bit of bark off the end of the branch and the color under the bark will be green if the limb is still alive. If the color is brown the branch is dead at this point on the branch--you can continue down the branch until you find green of reach the trunk. These dead limbs for sure should be pruned off. Other lower green limbs could also be pruned but DO NOT top the trees or prune partially back branches. Prune them back to with in about a 1/4 of an inch of the main trunk. There is a branch collar near the trunk that should be left. This will speed up the healing process. Do not use a wound dressing on the cuts.

I know I have maybe rambled but overall I think from what I saw the trees will be ok. It is also late in the year so anything effecting the leaves will not effect the growth of the trees since the growth processes have started to shut down for the season. I hope this helps.