Deb, unfortunately we do not have good ways to diagnose plant pathogens over Ask Extension. I would recommend that you reach out to the MSU Plant & Pest Diagnostic lab. You can email our plant pathologist, Dr. Jan Byrne, directly at <personal data hidden>. A sample may be requested for a more thorough diagnosis so that the best recommendations can be made. 

The lab's website, with information on submitting a sample can be found here: https://www.canr.msu.edu/pestid/submit-samples/