You can see sooty mold growing on the bark of this  maple. Sooty mold grows on the sugary sap that is leaking from woodpecker holes in the tree. Notice the holes arranged in lines on the bark.Maples, beech trees, hollies, crape myrtles and many other plants can get covered in a black fungus. Although this 'sooty mold' can look bad, it is harmless to the tree. Sooty mold fungus grows on sugary liquids that leak from a tree, shrub or other plant. The sooty mold is harmless to the tree.

Above you can see a beech tree covered in sooty mold. In fact, so much fungus has accumulated that the fungus looks like sponges on the tree. This is caused by beech blight aphid insects. These insects suck the juice from the tree. The black stuff is mold growing on their sugary droppings. These insects are harmless to the tree. There is no need to treat these insects as they do not hurt the plant. Learn more here: https://ag.umass.edu/landscape/fact-sheets/beech-blight-aphid