Habitat: Roots, trunks and stumps of most tree species. Several fungal diseases, sometimes called heart rots, sap rots, or canker rots, decay wood in tree trunks and limbs. Armillaria Root Rot: Rhizomorphs or bootlaces (see photo) can be found year round under infected bark, on roots and in the soil. It grows on tree trunks and fallen logs in the wild but can be cultivated as well . Black knot is caused by an infection of the fungus Apiosporina morbosa. These are thick black thread like bundles of hyphae that can give means for the fungi to travel fairly large distances through the soil. This tree bark fungus causes tarry, black swellings on branches that can slowly kill tree limbs. Generally, these insects excrete this substance on the leaves of trees. It is a type of mold that grows in the honeydew or secretion of many common plant pests, such as aphids or scale. However, the substance can drip down onto the bark of the tree as well, allowing mold to grow on the tree's outer skin. If these don’t resolve the issue, please respond. Sooty mold is a type of plant mold. The pests cover the leaves of your plant in honeydew and the sooty mold spore lands on the honeydew and begins to reproduce. The spots on your leaves are probably a common fungus, marssonina. Root Rot Diseases: Root rot diseases are caused by fungi that are found in the soil and attack the roots of plants. Common Tree Fungi. Include pictures of the whole tree and area, as well as up-close pictures of what you might find on the tree trunk, branches or leaves. Moreover, lichens, composite organisms composed of algae and fungi, grow on the trunks of unhealthy trees and resemble mold. It is now widespread throughout Canada, and infections can rip through fruit tree populations like cherry, plum, and apricot. Symptoms of Sooty Plant Mold Growth. Diseases caused by a tree fungus are separated into four categories, root and butt rot, canker, foliar/shoot, and wilts. Under conditions favoring growth of specific rot fungi, extensive portions of the wood of living trees can decay in a relatively short time (i.e., months to years).