Dogwood Tree Bark Disease

Dogwoods require little more than full sun (at least 6 hours a day) and well draining soil. Mulch is appropriate, too, but it should never come within 3 feet of the tree trunk. Removal of dead branches and raking away of fallen leaves is also necessary. However, even when these precautions are taken, dogwoods may be attacked by some diseases, many of which appear on the bark of the tree.

The fungus Discula destructiva causes a disease known as dogwood anthracnose, according to the North Carolina State University College of Agriculture and Life Sciences. Symptoms of this disease include small leaf spots bordered in purple, larger splotches of tan, discolored twigs, and in severe cases, brown cankers on the tree bark. When the latter appears, the branches or trunk may "girdle," which prevents water and nutrients from properly circulating throughout the tree. This usually results in the tree's death.

Good maintenance can help prevent dogwoods from infection. This includes removing shoots springing from dormant or recently pruned trunks. Pruning to thin older trees, and therefore improve air circulation, may also prove helpful.

In areas where Anthracnose is a common problem, spray dogwoods with a fungicide in the spring when leaves begin appearing. Chlorothalonil, mancozeb is a good choice, according to the USDA Forest Service. In addition, high nitrogen fertilizers should be avoided.

Remove all infected leaves, twigs, and branches, place them in a plastic garbage bag, and throw them away.

In some cases, the bark of dogwood trees infected with canker become sunken. Girdling may occur as a result, and the tree may die. In other cases, the bark on branches or trunks swells and roughens. In both cases, sprouts may begin appearing at the base of the tree.

There is no known cure for Dogwood canker, according to North Carolina State University College of Agriculture and Life Sciences.

Also called "crown canker," the first sign of this disease is usually reduced leaf production, according to Cornell University. The leaves may also appear smaller than usual, and turn yellow or red prematurely. Infected trees may also produce unusually large amounts of blooms and fruit. Gradually, the twigs and branches die. A canker on the lower trunk will appear. The bark may ooze. Eventually the bark will sink, dry up, and fall off in the area of the canker.

Aside from proper dogwood care, fungicides may be used to help prevent collar rot. The University of Oregon Extension suggests using phenylamide and phosphonate fungicides.

Sometimes collar rot can be treated by removing small amounts of bark in the area of the canker. Removing all infected leaves, branches, and twigs may also save the tree.