why does my plum tree stink
Do aphids cause my plum tree to stink?
Diseased trees can ooze a sour smelling sap.
It is important to correctly identify the exact cause of the problem and identify a possible treatment.
I would suspect a Bacterial Canker which can be treated with Copper Fungicides.
I'm listing several articles for you that may help you properly identify the cause of the odor.
Your local County Extension office may be able to help with proper identification or refer you to a local Arborist.