Hey Martha,

There is a small chance that this could be dogwood anthracnose, which is a fungal disease. It could also simply be symptoms of stress from the tree.

To get a proper diagnosis, I would recommend you bring a sample consisting of a small branch and leaves to your local extension office. We will be able to look at it under a microscope there. We can also send it to the diagnostic laboratory at the University of Kentucky if we cannot determine what is happening within our office. A list of all of the county offices and location can be found at https://extension.ca.uky.edu/county 

Let me know if you have any further questions,

Robby