I'm going to start by saying that I've tried to look this up online, but I'm not knowledgeable about trees and so I came up empty handed.
This limb just fell off of this tree in the front yard. It's a very old tree, and sustained damage last winter from an ice storm. Can anyone identify the white cottony stuff on the inside of the branch? It's it something we need to worry about infecting the entire tree, or is it more likely to be something that "got in" after a crack from the ice storm.