Erysiphe tortilis is a powdery mildew affecting leaves and other parts of our native Dogwood Cornus sanguinea.  It also affects the two non-native white-berried species, Cornus alba and Cornus sericea, which are commonly planted in parks and landscaped areas. 

Other Cornus species may be affected by Erysiphe pulchra

host

Photograph on host plant, and add host species to the comments for your record

On Dogwoods

Summer to early autumn.