50 year old magnolia tree
I have a beautiful, very large, magnolia tree. It was already large when we bought this house 36 years ago. One major branch has a black area about the size of a dinner plate on the bottom side of the branch. Diameter of this branch (not circumference) is about 10-12 inches. The branch has a long crack (3' or so) and it appears that the black liquid is dripping out from the crack. Big black drops on the plants below the tree. I thought it was oil. No scale in sight. What is this and what should I do? We love this tree!!
That sounds like a canker. Their are several different causes of canker. Here is more info on cankers:
With a tree that old, I would recommend that you contact your local extension service and have them recommend a tree expert in the area to help you. An onsite expert will be better at identifying the canker's source and how to address it. If you give me the county you are in, I can find the contact info for your local extension service.
I also have a 50 year old magnolia in my yard. I would not trade it for anything. :)