Diquat-based Razorooter II root-control herbicide from Duke’s Root Control is registered by the U.S. Environmental Protection Agency for controlling nuisance tree roots in sanitary sewer collections systems, and received a classification of “evidence of noncarcinogenicity for humans.” In 2014, the EPA further approved an amendment of labels to lower the signal word from “warning” to “caution.” Crews insert a hose from manhole to manhole, preparing to fill the affected sewer pipe with herbicide. The foam is released, compressing against pipe surfaces and penetrating cracks, joints and connecting sewers. Roots are killed on contact, decay naturally and slough away. Application is designed to prevent root-related stoppages for two to three years. 800/447-6687; www.dukes.com.