Ganoderma root rot (caused by Ganoderma spp.) is a fungal disease that primarily impacts maple, oak, honeylocust, but also ash and other deciduous trees. A conspicuous sign of this disease is red to brown shelf-like fungi that appear each summer and fall, often at the base of the tree.
white and gold colored fungal growths at the base of a tree

Curtis E. Young, The Ohio State University,