Most of the diseases listed are seen most often on Cornus florida. However other dogwoods are susceptible to the diseases listed.
Early symptoms of crown canker are smaller and paler leaves. Leaves on infected branches are red earlier in the fall. At first the symptoms appear only on the infected side of the tree but become more general as the canker enlarges. There is no chemical control for the disease. Avoid trunk wounds during and after planting.
Flower and leaf blight caused by Botrytis cinerea attacks fading bracts, especially during wet weather. Infected flower parts fall on the leaves spreading the infection. Botrytis can be controlled with benomyl.
A large number of leaf spots attack dogwood. No chemical controls are listed. Clean up and dispose of infected leaves.
Powdery mildew coats the leaves with a fine white coating. This disease may be controlled with sprays of benomyl used according to label directions.
Leaf scorch occurs during hot, dry, windy weather. This condition looks like a disease. Scorch symptoms are drying and browning of the leaf margins, or, in more serious cases, drying and browning of the interveinal area.