Coral Bark Maple - Maybe a bark splitting issue?
I recently noticed one of my coral bark maples had what looked like a long split up the trunk and at a branch juncture. It was noticeable because of what looked like a dark liquid seepage, that when I dabbed it with my finger, appeared to have a rust color. The trees are about 10 years old and at least 20-25' tall. See attached photos, it is the tree in the rear, closest to the house. I am wondering if this might be a bark splitting issue that has gotten some sort of fungus or other bug.
We cannot say for sure why the bark split. It could be due to frost cracks. This is usually not a cause for concern. Sometimes they heal on their own and no control is necessary. http://extension.umd.edu/hgic/topics/frost-cracks-sunscald-growth-cracks
The sap that you notice looks like slime flux. There are no treatments and it will not harm the tree. http://extension.umd.edu/hgic/topics/slime-flux-and-wetwood