Male Mulberry tree has brownish thick liquid where some limbs diverge. What could it be?

Question

Runs down the trunks leaving a black trail. Seems to be severing the affected branch from the main trunk.

Answer 1

This condition is not necessarily fatal to your tree, but indicates that there's been an injury, or a branch has grown out in an odd way, creating a naturally occurring "injury." The only remedy I've found in my research is spraying the area with a diluted mixture of bleach and water to kill the bacteria that gravitates toward the "wound." Here are two article that should help:
https://www.extension.iastate.edu/news/2007/jun/070801.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/wetwood-bleeding-trees.htm