Host: all varieties of wood-gymnosperms, woody dicots, palms. Oaks, maples, and honeylocusts are especially susceptible, although elms, ashes, and other deciduous trees and even some conifers may be attacked.
Scientific name of causal agent: Ganoderma spp. (G. zonatum, G. lucidum, G. applanatum)
Disease Description and Symptoms:
Trees affected by this fungus may exhibit yellowing, wilting, undersized leaves, dead branches, stunted growth, and a higher than normal incidence of dead lower leaves. During rainstorms or windy periods trees are easily blown-down. Trees may exhibit decay ranging from a few inches to several feet into the lower (butt) part of the tree, this dependent upon the particular species of Ganoderma.
Fungus spreading occurs when spores form on the outside, or conks of the tree. New spores release from the conks and disperse with ease by wind and water during periods of humidity. Spores then germinate and an infection spreads, attacking the sapwood of major roots and the lower tree trunk. As years progress, the amount of wood decay increases. This leads to soft, spongy wood in the area of the tree which functions as the tree’s anchor. Conks occur annually–new ones produced every summer and fall, after which they die and decay.
There is no known control for this type of disease. Good practices to help maintain the health of any tree include planting, fertilizing, watering, and pruning. Avoid damage and infection by decay fungi by safeguarding tree trunks and roots. Even the smallest wounds caused by mowers or trimmers can make trees susceptible. Monitor trees and their stumps for conks. If one is discovered, a trained professional should inspect the tree for safety and structural integrity.
Texas Plant Disease Handbook – Texas A&M Agrilife Extension https://plantdiseasehandbook.tamu.edu/landscaping/trees/maple/
Root and Butt Rot of Oaks- NCSU Plant Pathology Extension https://www.ces.ncsu.edu/depts/pp/notes/Ornamental/odin30/od30.htm