The poor dogwood — perennially beset with problems. Dogwood borers and leaf spots have always been regulars. But then there's dogwood anthracnose, a deadly fungus that decimated many native flowering dogwoods (Cornus florida). Powdery mildew, an unsightly fungal infection, doesn't usually kill the tree but probably weakens it until another pest comes along and delivers the final blow.
To increase your chances of enjoying a healthy dogwood, choose a cultivar with disease resistance to both anthracnose and powdery mildew; developed by Rutgers, the Stellar series, including 'Stellar Pink', 'Constellation', 'Celestial' and 'Aurora', show some resistance against anthracnose and powdery mildew and a high degree of resistance against dogwood borer. 'Appalachian Spring' is extremely resistant to anthracnose.
Cornus florida 'Barton', with its lovely white blooms, would make a nice addition to a woodland garden in zones 5b-8a. It grows up to 25 feet tall, and can spread up to 30 feet wide. Its blooms can appear in early through late spring. Like other dogwoods, 'Barton' appreciates well-drained soil.
Cornus florida 'Welchii' features variegated leaves of green, creamy white and pink. Its white blooms can appear from early to late spring. 'Welchii' is hardy in zones 5a-9a. This cultivar can grow up to 25 feet tall and spread up to 30 feet. Consider using in a woodland garden or as a specimen tree.
In the meantime, however, a better option might be the Kousa dogwood (Cornus kousa), which has better resistance to anthracnose and moderate resistance to powdery mildew. Unlike C. florida, Kousa dogwood "flowers" after the leaves appear, so you don't get that fairyland burst of white that's so welcome on an early spring day. But getting a leg up over two devastating diseases is pretty nice too.