Ornamental, deciduous, fruit and evergreen trees are susceptible to a variety of fungal diseases that ruin their appearance and health, and in extreme cases cause the tree to die. Tree fungus diseases spread through spores carried by wind, rain or irrigated water, insects or exposure to infected pruning equipment. The disease spreads to different parts of the same tree or from one tree to another. Tree fungi broadly fall into four groups.
The most common tree diseases, foliage fungi affects leaves of trees of all varieties, sizes and ages. Brown spot is a common foliage fungal disease in evergreens such as fir and pine. Also called needle blight, the disease affects the needles of these trees, causing them to turn brown or discolor and eventually fall off. Dogwood anthracnose features blotches and tiny spots with purple rims on infected leaves that spread to the branches if untreated, causing the dogwood tree to die. Leaf blister, a disease common in foliage of oak trees, causes blisters on the leaves in spring. Another common disease that occurs on foliage of most trees is powdery mildew, a white growth on the surface.
Cankers arise on trees with exposed wounds caused due to trimming or pruning. It resembles a sunken purple or brown patch of bark on stems or branches, and often emit a heavy resin. Phomopsis kills evergreen junipers and other healthy trees. Thyronectria is a fungal canker that affects woody ornamental trees and plants, fruit trees and forest trees. Seiridium canker causes infected twigs to turn brown, forming a sharp contrast against the healthy green foliage of the tree. Hardwood trees such as aspen and oak are susceptible to hypoxylon canker. Some cankers cause the bark to split, exposing the cambium tissue, which gets decayed.
Vascular wilts, fungal tree diseases that affects the vascular system, cause leaves to fade or wilt. The vascular system carries moisture and nutrients to and from the roots to the leaves, and trees infected with this serious fungal disease usually die. Leaf curl, a common type of vascular wilt that affects fruit and ornamental trees, causes leaves to curl around the center. Verticillium wilt causes leaves of infected trees to fade in early summer before falling off.
Root rot is a common fungal disease that affects roots of otherwise healthy trees. Armillaria is a common fungal root disease in maple, oak and ornamental trees. Phytophthora root rot affects smaller nursery and landscape deciduous trees in areas with poor soil drainage. Annosus root rot occurs on freshly exposed stumps of conifers. Trees infected with different root diseases exhibit symptoms of the infection that can be treated if noticed early. Once the disease establishes itself, the owner has no choice but to fell the infected tree.