It looks like
Fomitopsis pinicola to me. Another possibility is a
Gandoderma species. Both of these are
medicinal fungi, used in alternative (Chinese) medicine.
Ganoderma have brown spores,
Fomitopsis have yellow/white. What part of the country is this growing in? What kind of tree is it growing on?
There is no "getting rid of" this type of fungus. It will be living in the tree until the tree dies, and will continue to live in the dead tree, slowly digesting it and turning it back into soil. While the US Forest service might consider these to be parasites, it is highly debatable whether these fungi are actually harmful. There is some evidence that infection with certain types of fungus protect the trees against other types of more harmful infection.