Flowering dogwoods are a valuable addition to landscapes, providing beautiful blooms as well as shade and greenery. Given proper care, they can usually fend off most diseases and pests, but accidents, such as nicking the bark with a lawnmower, or improper care, such as under- or overwatering or pruning at the wrong time of year, can invite problems, most of which will result in the loss of the tree if not treated right away.
A fungus that will eventually kill the tree, dogwood anthracnose was responsible for wiping out much of the wild flowering dogwood trees in the United States. It is still uncontrolled in the wild, but it can be stopped and the tree saved if recognized early. The first sign of dogwood anthracnose is brown spots or patches on leaves, which is also a sign of other dogwood problems. Due to this similarity, TreeHelp says, "It is important, therefore, to consult a tree care specialist to verify a diagnosis." Fungicides are available that can stop the infection and salvage the tree. If not stopped, dogwood anthracnose will continue to destroy the tree, traveling up branches to the trunk, where it causes large canker-like lesions until the tree dies. TreeHelp says prevention of dogwood anthracnose begins with purchasing only certified disease-free nursery stock, not transplanting flowering dogwood from the wild and planting in a spot that is not continuously wet.
A moth that likes to feed on the inside of trees during its larval stage, especially dogwood trees, the dogwood borer can both damage and kill flowering dogwood. Most infestations begin at the sight of a wound or damage to the tree. Preventing such an infestation often begins with treating any wounds immediately and sealing off cuts after pruning. Avoid pruning in May and June, when borers lay their eggs, and provide the tree with proper care so that it is less susceptible to breakage or infestation. Signs of infestation include brown, sawdust-like material around the base of the tree, new shoots or leaves that die off quickly and die-back or damage at the crown. If caught early, insecticides may be effective, but prevention is the best cure for dogwood borers.
Although it does not usually kill a flowering dogwood tree, powdery mildew can have serious consequences, including failure to flower and greatly increasing susceptibility to other diseases and infestations that are fatal. Caused by a fungus, powdery mildew is stopped with fungicides and prevented by proper planting and care. According to the University of Kentucky, actions that invite powdery mildew include heavy pruning, overwatering and application of nitrogen fertilizer. Early signs of powdery mildew include a white, powdery coating on the leaves of the tree. As it progresses, leaves will yellow and then develop dark brownish-red spots. The leaves may also begin to look wilted or sunburned. Eventually, the entire tree will begin to take on a brown, wilted appearance.