Hypoxylon Canker (Hypoxylon tinctor) - "Hypoxylon canker is a fungus that causes cankers and death\r\nof oak and other hardwood trees. The disease is common\r\nin East Texas and all across the southern United States.\r\nRelatively healthy trees are not invaded by the fungus, but\r\nthe hypoxylon fungus will readily infect the sapwood of a\r\ntree that has been damaged, stressed, or weakened. Natural and man-caused factors that can weaken a tree include\r\ndefoliation by insects or leaf fungi, saturated soil, fill dirt,\r\nsoil compaction, excavation in the root zone of the tree, removal of top soil under the tree, disease, herbicide injury,\r\ndrought, heat, nutrient deficiencies, competition or overcrowding, and other factors. The hypoxylon fungus is considered a weak pathogen in that it is not aggressive enough\r\nto invade healthy trees. In addition to the hypoxylon fungus, weakened and stressed trees may become susceptible\r\nto a host of other insect and disease pests."