Question
We have a very large and very old oak tree.  It has one
formation of an orange mushroom like growth which we have removed once manually, and it has returned.  Is this a threat to our tree, and how should it be treated???

Answer
Fungi growths on the tree trunk are a sign of the fungi growing on the inside of the tree. The "mushrooms" or conks are the fruiting phase of the fungi (similar to the flower on a plant). The fungi itself is growing inside the tree trunk. Over time the tree will become hollow with these decay fungi. It does not mean the tree is not healthy or that it will dies from the disease. Decay fungi do not kill trees but can cause them to lose the strength of the trunk and be blown down in a high wind. BEFORE this happens you will see large limbs breaking off that are hollow. There is not anything that can be done as far as treating the decay in the tree. The best treatment is to fertilize the tree keeping it healthy. Fertilize with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good.