Please refer to Question:214683 submitted on 9/29/14. I am enclosing a...
As promised, we wanted to contact you again. Our plant pathologist was able to look at your photo and he thinks that this is not hypoxylon canker after all.
He thinks this looks more like like a fungus which grows on dead wood. We can't tell from your photo, but is this whole branch already dead? If so it should be removed. The fungus would not have caused the death of the branch.
This looks like hypoxylon canker, which is a wood rot disease common to nut trees.
Here is a page detailing it from Clemson University Extension: http://www.clemson.edu/extension/hgic/tyk/2011/pdf/tyk0111.pdf
Our plant pathologist is not in the office this week to confirm this. We will contact you if we find out any further (or contrary) information.