Dogwood trees are extremely popular landscaping trees, but they are fairly susceptible to disease if not properly maintained. While a healthy dogwood may live for decades, if you are not aware of the signs and symptoms of diseases of the red dogwood, then you could be saying "goodbye" to your beautiful tree and lovely pink blossoms much sooner than you expected. Most diseases can be prevented or cured if they are caught in time, so make sure that you monitor your red dogwood closely to avoid complications from infections.
Dogwood trees can suffer from cankers that stunt their growth, kill branches, and may become infected with molds and mildews. These cankers start out as discolored areas on the trunk at the base of a branch, so if you see a branch that appears to be experiencing early leaf fall or actual die-off, then check its base for a depressed discoloration. Over time, these depressions become hard, cork-like tumors on the tree. You will need to remove these cankers from the tree during a dry period and treat the area with a fungicide to prevent infections while the tree heals. If the branches are completely dead, then remove them, too.
Anthracnose Dogwood Disease
Anthracnose infections tend to occur during cool, wet periods during the fall and spring. Anthracnose will cause leaves to turn brown and fall off along with small branches and, eventually, larger ones. Leaves may develop large brown or purple blotches. You should remove any branches that are infected--they will be bare of leaves and appear to be dying anyway--and fertilize the tree with a nitrogen-rich fertilizer. In most cases, unless the tree has already been weakened by drought or several years of the infection, this will enable it to fight off the anthracnose fungus and make a recovery.
Powdery mildew infects red dogwoods that are living in an environment that is too humid. This can be due to poor soil drainage, frequent watering in the late morning and early afternoon, or just too much shade around the tree. Powdery mildew leaves a chalky, dusty powder on affected leaves and branches that may be white, black, gray or pinkish. You should remove affected branches and water your dogwood only when the soil is dry in the early morning. If the area around the tree is overgrown, try pruning back some of the bushes and taller trees around the red dogwood to allow for a little more sun. Powdery mildew can be treated with a fungicide, but in most cases, removal and disposal of affected parts of the tree and monitoring will do the trick and help your dogwood fight off the disease naturally.