There are hundreds of native trees in the United States. Some of these native trees include white oak, scarlet oak, giant sequoia, American elm, white pine, sugar maple and flowering dogwood. These deciduous and evergreen trees carry a wide assortment of characteristics, and some bloom with an array of colorful hues. As diverse as these trees are, many of them share the same susceptibility to some native tree diseases.
Anthracnose is a leaf disease caused by a collection of fungi. These collective fungi develop on dead debris and twigs that lie around the tree. The fungal spores are then swept by wind and rain onto the infected tree. This unsightly disease targets most foliage trees, both evergreen and deciduous, as well as fruits and vegetables. Infected trees develop spotted foliage. These brown-colored spots enlarge and become necrotic as they age. The infected foliage also experiences curling and becomes distorted. During severe infections, the infected tree’s branches and twigs may die while the tree takes on a blighted appearance and experiences premature defoliation. Anthracnose can be treated with a series of fungicidal applications, along with the removal of the deadened areas.
Purdue University reports that more than 300 species of trees and plants are susceptible to verticillium wilt. This destructive, soil-borne disease infects the tree through the root system and attacks its vascular system. As the disease progresses, the vascular system is destroyed and becomes unable to transport water and nutrients throughout the tree. The starving and infected tree begins to display symptoms such as yellowing and drying of its foliage, wilting, droop and premature defoliation. The deadened and dying foliage often occurs in patches throughout the tree until the entire tree dies. There is no cure for verticillium wilt, and the infected tree must be removed and destroyed. This disease can live in the soil for long periods without a host. Therefore, it is important that only resistant trees are replanted in the infected area. Some native trees that are resistant to verticillium wilt include the oak tree, dogwood tree and hackberry tree.
Powdery mildew is a common disease among the native trees. On most trees, it is a mild, nonfatal disease that infects only the foliage. However, severe and repeated cases of powdery mildew can cause dieback, growth stunt, and even death of the infected tree. Leaves infected with powdery mildew develop small, white spots or patches. These spots come from fungal spores that are transported by wind and rain during the cool wet spring months. As the disease progresses, the white spots coalesce and a white fungal coating develops across the service of the foliage. The leaves often become distorted and stunted. The tree may experience a loss of vigor. You can treat powdery mildew with a fungicidal spray designed for the disease. Repeat treatments may be required.