Question
I don't know if what is going on is a fungus or not but my tree has green blotches from the bottom to the top of it's bark (trunk). I have seen other trees in my town with the same symptoms and the town has cut them down because they were too far gone. Can you please give me some idea of what I am dealing with so I can try to save my tree. By the way i have no idea what the name of my tree is. However, it does not have leaves. It appears to be some type of of pine or fir tree.
Thanks.

Answer
The green blotches are lichens.
Lichens are organisms consisting of a fungus and a green or blue-green alga growing together in a mutually beneficial, symbiotic, relationship. The entire structure, called a thallus, is so different structurally from either of its partners that microscopic examination is necessary to distinguish the fungus and the alga.

The fungus obtains water and minerals from the air and the material it is growing on. The alga provides carbohydrates and vitamins. Some blue-green algae fix nitrogen that is used by both the alga and the fungus. Nitrogen is also obtained from bird excrement, organic debris, or plant leachate.

Lichens may be flat, leafy, or branched and hairlike. All three forms occur on tree bark as well as on rocks, soil, and other substrates. Colors may range from white to gray, red, green, yellow, and black.

Although lichens grow on tree bark, they are not parasitic (disease-causing organisms), and do not harm trees. The fact that lichens grow rapidly when exposed to full sunlight may explain their profusion on dead trees. The one conclusion that may be drawn with certainty from lichens on trees is that the air nearby is relatively pure. Most lichens will not grow in a smoky or polluted atmosphere.

If the foliage is green and healthy looking then the tree is healthy. I would think the other trees that were cut had some major problem--the lichens did not kill them.