Question
I have a fungas (I think) at the base of my magnolia tree.
It is a white mass with the texture of a large mushroom.
The tree is approximately 26 years old.  Is it possible to save the tree?  The leaves are falling and look pretty bad, however, the new leaves look pretty strong.

Answer
This is a fruiting body of a decay fungus. They grow during periods of high moisture. Heart rot in living trees is caused by fungi which have the ability to decay wood. These fungi gain entrance to the wood of the tree through wounds, branch stubs, etc., which expose the bare wood. The fruiting bodies, mushrooms or "conks," are common on trunks of decaying trees. Production of fruiting bodies on a living tree is a sign of extensive decay in the stem at that point. A useful rule of thumb might be that a cubic foot of wood has been decayed for each conk produced. Heart rot fungi do not invade living wood of healthy trees. As long as the tree is growing vigorously the rot will be confined to a small central core of the trunk and the structural integrity of the tree will be maintained. If the tree is weakened for any other reason or fresh wood exposed by severe pruning or storm damage, then the decay fungi can advance to more and more wood


I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. This will help the health of the tree.