Ask Mr. Smarty Plants

By the time you see the yellow/orange mushroom (the fruiting body that produces spores) growing on the outside, the health of the tree has been pretty severely compromised by the mycelium of the fungus growing inside the tree.  This particular mushroom causes the heartwood to rot.  Probably the wood of this dead tree is not useful for much except as firewood.  Burning the wood should be a safe way to dispose of it.  The heat of the fire should destroy any spores and the fungus growing in the wood.  It has probably already shed its spores and they will create new growths of the fungus when they encounter the proper conditions. The way to protect other trees from this fungus is to avoid injury to the tree that would allow the fungus to enter.  Aging trees with broken limbs and large open wounds are very susceptible to fungus infection.

Now, that being said, since we can't see it we don't know for sure if this is the mushroom that is growing on your oak tree. If this doesn't look like your fungus, you can send us photos and we will try to identify it.  Please visit Mr. Smarty Plants' Plant Identification page to read instructions for submitting photos.