There's a liquid (Can't remember the name) available at Lowe's or Home Depot that you can get. Best way to do it is if you have enough of a trunk to drill a hole in, and pour in the liquid; this gets it into the system and kills it from inside. Or if you're close to a nursery like Paulino's in Aurora or that big one over off I-25 near 58th near the DOW, go talk to them and they can give you recommendations.