Dogwood Anthracnose

Dogwood anthracnose is a disease of eastern flowering dogwood (Cornus florida) caused by a fungus, Discula destructiva. Infection is favored by cool, moist conditions, especially in spring and early summer. Although all eastern flowering dogwoods are considered to be susceptible, trees that have suffered winter injury and/or drought stress tend to be more likely to experience greater disease severity.

Disease Symptoms

The disease symptoms first appear as tan spots surrounded by purple rimmed margins. Necrotic blotches, that may cover the entire leaf area, can develop later, and these leaves may cling onto the twigs throughout the autumn and into the winter. Lower branch dieback is typically noticeable on diseased trees. Infected watersprouts or epicormic shoots along the main stem of the tree can serve as a direct route for development of trunk canker. Multiple cankers can girdle the trunk and eventually kill the tree.

Signs of the Causal Agent

The presence of the fungus (signs) can be detected by looking at the underside of the infected dogwood leaf or infected twig. Fungal fruiting structures (conidiomata) will be evident as small brownish bumps, that are associated with dogwood leaf hairs. When these structures are ruptured and viewed under a microscope, abundant spores or reproductive structuring of the fungus will be evident.