Question
QUESTION: We live in Md.and have a tulip tree that has bloomed successfully for @ 5 years. This spring it showed some dead branches and the base of the tree has holes and looks like some fungus/mushroom like growth. also insects have penetrated the tree on the inside. Not sure what they are.What should we do to treat the tree? What has happened to it? and Why? Can it be saved? We love it!

ANSWER: If the foliage is green and full the tree is healthy. It sounds like the wood in the center of the tree is decaying and the tree may have some hollow places in the trunk. The living part of a tree is just under the bark and the bark protects the cells from decay fungi. When there is a wound to the bark decay fungi can get into the woody cells and start the eat away at the cells. Insects more than likely borers take advantage of the wood being softer and borer into the woody cells. The  woody cells are dead cells and not associated with the healthy of the tree except for strength.
Trees can and do live many many years with their trunks completely hollow. Trees have the capability to seal off the decay fungi and slow the growth of the decay. IF the large limbs start to break off and the end near the trunk is decayed or hollow then the tree may have reached a point that it could be a hazard. And then it is only a hazard if it is locates near a structure that could be hit by a falling limb. Yours sounds a long way from that stage.

I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter and water it in  good, or wait just before a rain storm and fertilize and you will not have to water. This will increase the health of the tree and help slow the decay fungi. I would do this now and again after the leaves fall in the Fall.

I would spray the area with an insecticide called Merit or one called Onyx. These will be absorbed into the wood and kill the insects and prevent others form entering.

Should the tree be cut--Certainly some hollow trees may have so little healthy tissue surrounding the hollow area that they must be regarded as dangerous, but this is by no means the norm.  Trees do not become hollow overnight - it can take decades - and while the center of the tree (the heartwood) may be decaying, the tree continues to lay down healthy wood (sapwood) around the outside of its trunk.  This results in the formation of a cylinder, the strength of which depends upon the percentage of healthy to unhealthy tissue.

The first sign of the tree being a danger is large limbs breaking off and these are hollow. This means the decay has reach the limbs and is fairly extensive.  

I would not cut the tree but treat for the borers and fertilize.



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QUESTION: Should we cut off the branches that are dead (no foliage at all)?

Answer
Yes Prune the dead branch off about 1/4 inch from the trunk. This will leave a branch collar and the wound will heal over by itself. If the wound is more than 6 inches across after the cut I would paint the area with a wound dressing. This will keep water from getting into the wound. On wound less than 6 inches across I would leave natural and not paint.

On large trees it is best to make the first cut about a foot from the trunk on the under side then cut the branch off from the top leaving a stub about a foot long. Then you can prune off the stub and the heavy limb will not split the bark on the trunk.
Here is a web link to how to prune trees with a drawing of the large limb pruning method.
http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/trees-new/text/pruning.ht.