You are correct -- this is powdery mildew, one of the fungal diseases that is very prevalent on Cornus florida trees in Maryland. The best way to manage it is to choose a disease-resistant cultivar. There are several options listed on our web page about growing dogwoods, https://extension.umd.edu/resource/how-grow-dogwood. 

It is important to note that disease-resistant does not mean immune to disease. Even disease-resistant dogwoods may develop problems if they are planted in an unsuitable environment (full sun, drought, flooding).

It looks like yours is a young plant in a pot. I would recommend looking for one of the disease-resistant cultivars if you want to try and manage disease symptoms in the long run. Powdery mildew disease does not kill dogwoods but it can weaken them over time, so it is best to start out with a disease-resistant type.

Once powdery mildew symptoms are present, there is not much you can do. A fungicide labeled for powdery mildew can prevent symptoms on new foliage, but it will not cure systems that are already present.

Here is more information about the common diseases of dogwoods and how you can manage them. https://extension.umd.edu/resource/description-and-management-dogwood-diseases

Christa

You're welcome.