I work at Sheridan Nurseries and I received this sample of a Hornbeam twig with black spots on the dead portions that did not come back to life after this winter’s harsh weather. Do you think it IS a blight of some sort, or just harmless fungi recycling the twig. I couldn’t find anything in a Google search.
The tree is one year in the ground, leaves look OK, but there was some die back this spring.
It is difficult to see the spots clearly in this picture. If the tree is continuing to leaf out and looks otherwise healthy, I wouldn’t worry. However, if this is spreading, or especially, if you are starting to see leaf distortion, it may be a fungal disease, as you suggest. Anthracnose is one that attacks hornbeams. Here is a fact sheet from Cornell University that you may find helpful. They are also subject to canker diseases, which you can read about in this write up from the University of California.
If you can bring that twig, or your client can bring others, to the Toronto Botanical Garden on a Thursday between 2pm and 7pm, there is usually a Master Gardener Advice table where the sample can be examined and, if possible, diagnosed.