narrow crotch is structurally weak and prone to breakage. This branch needs to be pruned off--the sooner the better.
In pruning off a narrow-angled branch of this size, I employ the 3 cut technique of limb removal (photo series below). The first step in the process is to use a chainsaw to carve a undercut on the limb. This cut is made to eliminate the possibility of the bark tearing down the trunk when the weight of the limb is cut from the tree. The second cut is made above the undercut and is used to remove most of the limb from the tree. That leaves me with a short stub that can be easily carved off the tree with my saw. Because of the narrow branch angle, I plunge cut into the side of the branch to remove the stub. The plunge cut technique allows me to achieve the proper angle for branch removal without damaging the main trunk with the saw.