A potentially devastating fungal disease infects flowering dogwoods throughout the eastern and northwestern U.S. Called dogwood anthracnose. The disease afflicts landscape dogwoods and causes mortality in the majority of infected trees.
The first symptoms of dogwood anthracnose are dark spots on the leaves and flower bracts, which typically develop in May or June. This symptom first develops on lower branches and continues to develop up the tree throughout the growing season. Proper attention and regular maintenance helps dogwood trees thrive and prevents the spread of disease to healthy parts of the tree. It is important for gardeners to prune out dead and dying twigs and rake up fallen leaves to improve the tree's defenses and reduce sources of disease.
Another potential cause of a dying dogwood tree is a pest known as the dogwood borer. Dogwood borers burrow into the main trunk and branches and cause significant structural damage. Trees infested with borers eventually develop seeping cracks in the trunk, which become filled with piles of sawdust.
It is also possible for dogwoods to die as a result of being planted in soil with poor drainage or soil that lacks appropriate amounts of organic matter. Dogwoods also need protection from drought-like conditions and prefer planting sites with moderate amounts of shade.