Dogwood powdery mildew, caused by the fungi Erysiphe pulchra and Phyllactinia guttata, has become more common on dogwoods in the landscape. Leaves may take on a yellowish or reddish cast in summer, or may develop reddish blotches or dead, scorched patches. In some cases, a white powdery growth is visible on the leaves, but this is not always apparent. Yearly infections may weaken trees and cause reduced flowering. Gardeners should avoid cultural practices that stimulate succulent growth, which encourages powdery mildew.

Rake up fallen leaves and remove them from the site. Fungicide applications can be used to prevent infections on dogwoods, but must be applied throughout the season. Not all dogwoods in the landscape are equally susceptible to powdery mildew. New powdery mildew-resistant dogwood cultivars are being developed. Contact your local Extension office for fungicide and resistant cultivar recommendations.

You may want to read the following University of Kentucky extension publication: Dogwood Powdery Mildew.