Question
I have a weeping willow in my front yard. The tree it self is doing great, but there looks to be a type of fungus growing on it. The fungus is red and kind of spiky and it is growing in small patches no bigger then a quarter. I have no idea what it is or how to treat it.

Answer
You did not say if the growth was on the trunk or the leaves.
If the growth is on the leaves it is an  insect gall caused by a wasp type insect. The galls will not harm the health of the tree but if they are in great numbers may cause the leaves to drop sooner than normal.
If the growth is on the trunk or bark area then it is either a lichen or the fruiting body of a decay fungus. If it is a fungi then under the growth should be soft. If it is then the wood inside the tree may have decay fungus--but it should not cause the tree any problems except that it will become hollow in 10-20 years and then the trunk can lose some of its strength and possibly break in a wind storm.
I lean toward a lichen--the bark and wood under the lichen in solid not mushy. The lichen is growing on the bark surface and it will not harm the tree. Usually lichens are grey green in color but during the time they "flower' they can become quite colorful.
In any case if the foliage is green and healthy looking then there is no concern for the health of the tree. And there is no treatment needed for any of these above problems.