Holding a tree securely in place is an important job of tree roots. Anything interfering with a root system's structural support can cause a tree to become unstable. Root rot, also known as root decay, can hinder the ability of a root system to support a tree, notes the University of California. Root rot can occur when microorganisms, such as soil-borne fungi, attack tree roots. Usually these microorganisms infect roots through wounds, although some can directly infiltrate a root.
Cortical root rots occur when microorganisms attack the cortex, which is the outer, succulent tissue of young tree roots, says Forest Pathology. Many nursery diseases are due to cortical root rots.
Vascular wilts are root rot diseases where a pathogen moves into a root's active xylem, which hinders xylem sap from flowing. This results in wilting and other drought-like symptoms. Trees affected with this type of root rot include various western conifers, ponderosa pines, Douglas firs and pinons, which are small pines.
Root Rot Diseases
Littleleaf disease is a cortical root rot disease that affects shortleaf pine trees. Loblolly trees are also affected, but on a lesser scale. Symptoms are shorter needles and thinning crowns. It causes a tree to die in roughly six year from the time of infection. Port-Orford cedar root rot is cortical root rot that only infects Port-Orford cedars. The fungus can enter through either soil or water. Annosum root rot occurs primarily in temperate areas of the Northern Hemisphere. Most conifer trees are vulnerable. Pines infected with this root rot disease usually die quickly.
Decline on the top of a tree is the initial sign of a root problem, says the University of Illinois. Fungi resembling mushrooms that grow at the base of a tree can also suggest a root rot problem. Corks, also known as fruiting bodies or shelf fungi, that are found growing on a trunk or main branches, can be symptoms of wood rot fungi. In Gandoderma root rot a fungal structure can be seen at the base of a tree, such as seen in trees as the honey locust.
Fallen trees with an exceptionally small root system, showing several decayed roots, are most likely victims of root rot, although sometimes tree failure is simply because a tree's root system is too shallow to support its weight. Because there are usually no above-ground signs that suggest a tree might have a shallow root system, the problem can be extremely deceptive, notes the University of California.
There aren't any chemicals that can help trees declining from root rot, warns the University of California. Practice preventative measures for improving tree vitality, such as watering weekly, cutting off dead branches and fertilizing a tree in late fall or early spring. Fertilizing extremely large or old trees may not have any effect.