Hello,

Thank you for sending a clear picture. The ooze or liquid you are seeing is called bacterial wetwood/slime flux. It is caused by several types of bacteria that enter pruning wounds, trunk cracks, V-shaped branch crotches, and injection holes. The bacteria live off the nutrients in the tree sap. The sap eventually is forced out of the wound by pressure from gases produced by the microorganisms living in the sap and the liquid flows down the bark. As the slime flux dries, a light gray to white encrustation remain on the trunk. Many trees develop slime flux including elm, oak, and mulberry, and to a lesser extent maple, birch, butternut, redbud, sycamore, and walnut. It is not uncommon for this in older trees. There is no cure for this disease and it will not necessarily kill the tree but if the tree is under stress from other factors, wetwood bacteria can move into the sapwood and cause leaf yellowing, wilting, and branch dieback.

It is best to monitor this tree this summer for these and any other issues. You eventually may want to have an arborist out to make an onsite assessment. If so, you can find a certified arborist at the following website by using your zip code. Make sure they are certified since they are the ones with the education in all things woody.

https://www.treesaregood.org/

I have included several links on wetwood/slime flux that you may find beneficial.

https://extension.umd.edu/hgic/topics/slime-flux-and-wetwood

http://extension.colostate.edu/topic-areas/yard-garden/bacterial-wetwood-2-910/

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=21997

http://extension.msstate.edu/publications/information-sheets/the-plant-doctor-bacterial-wetwood-and-alcoholic-flux

https://www.mortonarb.org/trees-plants/tree-and-plant-advice/help-diseases/wetwood

I hope all this helps you out and good luck