Bittersweet is native to Eastern Asia. It was brought to the United States around 1860 as an ornamental plant. This is invasive because people will cut it down for a wreath and stuff like that but when people throw the Bittersweet in the woods the Bittersweet will grow on two trees and aggressively choke the other woody plants. Nothing can really be done to stop bittersweet but if you have a small section you can pull it out of the ground and dispose of it.