Question
Near Austin, Texas a large post oak had a white growth that looked look a brain coral growing on a dead branch about 15 foot in the air.  The dead branch was about 5 inches in diameter and from the broken off end was a white growth that looked like brain coral that completely covered the end of the branch adn was about two inches in diameter larger than the branch.  What is it and is it harmful to the tree.

Dan

Answer
These are fruiting bodies of a decay fungi. The fungi itself lives in the woody and some tine during the year will put out these conks which are the "flowers" of the fungi that contain spores to spread the fungi. The conks themselves are not a problem and there is no need to break them off.
The decay fungi break down dead woody material so it will decay faster into the soil. If a tree is wounded the fungi can get into the woody trunk or branches and begin decaying the wood and in time hollow out the tree trunk. They will not kill the tree but over many many year could weaken the trunk making it easier for a high winds to blow the tree over or in most cases break the limbs off. The way to help the tree fight these fungi is to keep it healthy by adding 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. Also during dry periods water the tree with 1 inch of water per week--place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop.