ADJUVANT COMBINATIONS WITH QUIZALOFOP FOR WILD OAT (AVENA-FATUA) CONTROL IN PEPPERMINT (MENTHA-PIPERITA)

Field experiments were conducted at Kalispell, MT, to determine the op timum adjuvant combination for wild oat control in peppermint with qui zalofop. Quizalofop was applied to four- and eight-leaf wild oat plant s at 20 and 50 g ai/ha with either a nonionic surfactant (NIS) or meth ylated seed oil (MSG) alone or in combination with 28% urea ammonium n itrate (UAN) liquid fertilizer. Differences among adjuvants were most apparent when quizalofop was applied at the lowest rate. MSO was more effective than NIS for enhancing quizalofop activity. Quizalofop effic acy with both adjuvants increased when applied with UAN. Greater than 90% wild oat control was obtained with the lowest, rate when applied w ith MSO plus UAN to four-leaf wild oat plants. These results demonstra te the potential to improve the consistency of weed control as well as reduce postemergence herbicide rates when applied with the proper adj uvant combination.