Hello,

Please check out the following link that shows two possible diseases and photos that may match to what you're seeing. Check out the symptoms as well. I wouldn't say definitively that either one is what is affecting your tree but if they are a close match, I recommend getting a a diagnosis with a plan of action, if needed, by sending in a live sample to the U of MN Extension Plant Disease Clinic. Here is the link to their site where you'll learn about their services, prices, and how to submit a sample.

Good-luck!

Hello, thank you for the reply.  My husband dropped off a live sample at the plant disease clinic last week.  Someone there indicated I would receive an invoice to diagnose the problem, but I haven't seen one yet.  I'm very interested in learning exactly what the problem is (and a recommended solution, if there is one).  And I am happy to pay for the diagnosis.  Thank you for any further information on this process!  

Elizabeth 

The PDC team is separate from the Extension master gardeners so I'm not familiar with how they work except that testing can take time while they're growing cultures from the material sent in.

Good-luck!