Preemergence and postemergence suppression of kochia on rights-of-way

Kochia poses a challenge to vegetation management in both agricultural and noncrop areas. This species has developed widespread resistance to several herbicides with differing modes of action, including acetolactate synthase inhibitors and photosynthesis inhibitors. Resistance is also beginning to appear against the synthetic auxins and glycines. Therefore, alternative PRE and POST herbicides are needed for effective kochia management, especially in roadside bare-ground zones. Both PRE and POST herbicides were screened on rights-of-way in Pennsylvania. Mixtures containing diuron, flumioxazin, sulfentrazone, pendimethalin, prodiamine, and bromacil were evaluated for PRE activity in combination with glyphosate. POST kochia control was assessed for 15 noncrop herbicides. Results from all trials varied with kochia size and vigor at time of treatment. Although diuron is the current industry standard for PRE control in tank mixes, sulfentrazone appeared to have the most POST activity against vigorously growing kochia. All PRE herbicides evaluated performed better than the standard, sulfometuron plus chlorsulfuron alone. Dicamba, dicamba plus diflufenzopyr, fluroxypyr, and glyphosate performed best against kochia when applied POST. The recently available chemistries saflufenacil and aminocyclopyrachlor require further evaluation of application timing and use rates, respectively, for POST activity on kochia. Nomenclature: Aminocyclopyrachlor, 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid; bromacil; chlorsulfuron; diflufenzopyr, 2-(1-[([3,5-difluorophenylamino] carbonyl)-hydrazono]ethyl)-3-pyridinecarboxylic acid; dicamba; diuron; flumioxazin; fluroxypyr; glyphosate; pendimethalin; prodiamine; saflufenacil, 2-chloro-5-[3,6-dihydro-3-methyl-2,6-dioxo-4-(trifluoromethyl)-1(2H) -pyrimidinyl]-4-fluoro-N-[[methyl(1-methylethyl)amino]sulfonyl]benzamide; sulfentrazone; sulfometuron; kochia, Kochia scoparia (L.) Schrad.