Biscogniauxia, (formerly Hypoxylon), Canker
Biscogniauxia, a common genus of fungi found throughout the United States, causes canker, dieback, and death of stressed oaks (Quercus spp.), pecan (Carya illinoinensis), hickory (Carya spp.), sycamore (Plantanus spp.), maple (Acer spp.), elm (Ulmus spp.), and other hardwoods.
Biscogniauxia are endophytic fungi meaning that they live within healthy plant tissue but cause no damage in/to the healthy plant tissue. However, stress (such as drought; heat; root, chemical, insect, mechanical damage; nutrient deficiencies; overcrowded planting conditions; soil compaction; another disease; or something else not listed here) can reduce a tree’s natural defenses and disease resistance, allowing Biscogniauxia to become pathogenic.
There is no known control for Biscogniauxia canker other than maintaining healthy, vigorous trees. Implement good horticultural practices and provide the best growing conditions possible to maintain robust plants with strong natural defenses and disease resistance. Correct adverse conditions that may lead to stress before the fungus can become pathogenic.
Remedial pruning of the tree may be a management option if 15 percent (%) or less of the canopy is showing signs of dieback. Remove infected branches 8 to 12 inches below the visible canker. Sanitize pruning equipment between each cut to avoid spreading the pathogen. For information on tools, timing, and technique, see HGIC 1003, Priciples &. Practices for Pruning Trees.
Tree removal should be seriously considered if more than 15% of the canopy is exhibiting dieback as trees can quickly become hazardous.
For more information on Biscogniauxia, see HGIC 2006, Oak Diseases & Insect Pests.