They are totally harmless and are in no way responsible for the poor health of the tree. The reason they are associated with declining plants is that as woody plants loose vigor and decline, the number and size of leaves decreases. This allows more sunlight, which lichens need to grow, to reach the trunk and branches. An epiphyte is an organism that lives upon a plant, using the plant only for support and protection. Spanish moss does not feed directly on the tree, but obtains its water and nutrients from the air and rain.
Spanish moss is limited to warm, humid areas of the southern and coastal regions of the state.
Each bundle of moss is made up of a mass of long, gray-green filaments, which are its stems and leaves. Since the leaves of Spanish moss require sunlight to produce their own food, it is usually found in trees that are in a state of decline. Heavy infestations of Spanish moss can lead to further tree decline by shading out lower leaves and the weight of large masses of wet Spanish moss can lead to limb breakage. Removal by hand may also be necessary to rid the tree completely. There are at least 750 different galls that have been identified on oak.