Dogwood Tree

Dogwood anthracnose is a disease that affects the flowering and Pacific dogwood (Cornus florida and C. nuttallii). Pacific dogwood infections have been reported in Washington, Oregon, Idaho, and British Columbia. In the eastern states, flowering dogwood infections have been reported in Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, and Delaware. More recently, anthracnose has been detected in Maryland, Virginia, West Virginia, North and South Carolina, Tennessee, and Georgia.

A dogwood in bloom, Georgia. JLM Visuals. Reproduced with permission.

The disease is caused by the anthracnose fungus, Discula sp. Infection most often occurs during cool, wet spring and fall weather, but may occur throughout the growing season. Trees weakened by drought or cold are most likely to suffer severely from the disease. When heavy infection occurs for several years, woodland and ornamental dogwoods frequently die.

The origin of anthracnose disease has not been determined. It may have been introduced, or it may have resulted from an altered host/parasite relationship that transformed an innocuous fungus into a significant pathogen.

Cultivated dogwoods that are well cared for are better able to withstand anthracnose during years of widespread infestation. To build up their resistance, dogwoods should be watered during periods of drought. Mulching may help conserve water, as well as protect trees from physical injury. Overhead watering may contribute to leaf infections.

The only way the disease can be effectively controlled is if the disease is detected before extensive dieback has occurred. The removal of diseased twigs and branches helps to reduce potential sources of infection. It may also help to remove any fallen leaves. Succulent growth, which is encouraged by high nitrogen fertilization, can lead to trunk canker formation. To encourage trees to grow, a balanced fertilizer may be applied in early spring.

Applications of the fungicides chlorothalonil and mancozeb in the spring protect against leaf infections. When conditions favor development of the disease later in the growing season, additional applications of fungicides may be beneficial.