The pagoda dogwood (Cornus alternifolia) is a beautiful tree with nice horizontal branching and small tree stature. It does not seem to have as many disease problems as we see with flowering dogwood (Cornus florida) and seems to have better resistance to the potentially lethal Discula anthracnose.
Pagoda dogwoods are very susceptible to a canker disease called Cryptodiaporthe. Some of my southern colleagues have reported to me that Pagoda dogwoods die after about 20 years of growth, due to infection by Cryptodiaporthe canker. Most of us know that canker fungi often infect a plant following stress. That is most likely the case with this disease as well.
Pagoda dogwoods grow best in cool, shady areas and prefer moist, acidic, well-drained soil. They are known to be very drought sensitive and decline when grown in hot, dry sites. If you have a Pagoda dogwood in a protected, shady spot, be sure to water it in periods of drought. If left to fend for itself, Cryptodiaporthe canker likely will infect and kill the tree.
Cryptodiaporthe canker is also known as golden canker because of the color of affected branches. Look for stem dieback, with cankers at the base of affected branches. Prune to remove cankered wood, cutting 4 to 6 inches below affected areas. Water the tree in periods of drought and try mulching over the root system to provide it a more even temperature. This will also help retain moisture. For more information about this disease specifically, refer to the Web site http://www.uwex.edu/ces/wihort/gardenfacts/X1125.pdf. Cankers in general are discussed in Report on Plant Disease, no. 636, “Canker and Dieback Diseases of Woody Plants.”