Question
We have a small stand of birch trees. Trees are approx. 40-50 years old. Lately, we have noticed white fungus or mushrooms growing on the trunk and a few areas of upper branches. I've been told that the mushrooms indicate that the tree is dying and that they are feeding on the dead wood. What can you suggest? Must we cut down the tree?

Answer
The are then fruiting bodies of decay fungi. It means the tree more than likely is hollow or at least has decay in the woody part. The living layer of cells in a tree are just under the bark called the cambium layer. The woody part is dead cells and if there is a wound fungi can get into the wood and start the decay process. It does not mean the tree is dying. As long as the foliage looks green and healthy the tree is OK. The woody part give the tree strength and if the tree becomes hollow it could break during a strong wind storm. I would not cut the trees. They can live being hollow and grow just fine. If you start to see large limbs break off and they become a hazard to people or buildings then you might think about replace the ones that are breaking up. Keep an eye on the foliage and if it starts to thin out and die back this would be signs of health problems for the tree.