Sap on Plum Tree?

Have just found this on one of my plum trees which looks like sap from some form of injury.



Is this the case or is it potentially something else? In addition, is this going to be a problem when it comes to silver leaf?

 

It is probably insect damage, boring through the bark to reach the sap. Silver leaf is more usually from branch/bark damage due to pruning at the wrong time of year. You may find ants come to collect the sap.

 

Prunus trees are prone to this, its not good but they seem to go on a long time after it first appears.
Its called gummosis.
As for silver leaf, I'm not sure but I dont think it should be a problem.

 

Thanks for the replies, I may have to get my tree surgeon to check how much of an issue it is.