One method that can be used is a cut stem treatment with a glyphosate or triclopyr based systemic herbicide. Dabbing a tiny amount of the herbicide on a freshly cut stem/stump will kill the plant down to the roots, and not affect nearby plants. Only a very small amount of herbicide is needed. The label will provide exact directions.

Here is a link that might be useful: WSU

Thannks, that is just the info I needed on killing sumac!