With its four-petaled pink or white flower bracts surrounding a tiny cluster of flowers, the dogwood is an easily identifiable and common landscape tree. Dogwood trees may experience a number of fungal and bacterial diseases that can kill them if not caught. Once identified, many diseases can be treated with fungicide. To keep dogwoods healthy, prune them annually and fertilize regularly with a balanced fertilizer.
Discula destructiva fungus causes dogwood anthracnose. This disease was first discovered in the 1970s. Leaves develop tan or purple blotches initially that may be confused with leaf spot diseases, but unlike leaf spot-infected leaves, these remain on the tree through the season, even into spring. As the infection worsens, trees develop brown cankers on twigs and branches. Homeowners can control this disease with fungicides.
Dogwoods infected with powdery mildew develop white-dusted leaves. Leaves may curl up or become stunted or deformed. This disease strikes younger trees more frequently than older ones and is easily identifiable from the affected foliage. Microsphaera pennicillata causes this disease, which can be controlled with fungicides containing mancozeb or myclobutanil.
Two types of cankers affect dogwoods: dogwood canker and crown canker. Crown canker develops along the trunk of newly transplanted trees and is caused by the fungus Phytophthora cactorum. It commonly occurs when trees are planted in poor-draining soils and have root injuries. Metalaxyl fungicides can treat crown cankers. Dogwood canker produces both sunken and swollen patches along the tree trunk. According to North Carolina State University, this canker has unknown origin and no known control.
Dogwoods planted in poorly draining soil can develop root rot, which is challenging to detect in early stages since initial symptoms occur underground. Dogwoods that develop yellowing or tan leaves and branches that die back have root rot. By the time these symptoms are detectable it's often too late to save the tree. To ward against root rot, plant dogwoods in well-draining soil.