Adjuvants and growth stage affect purple nutsedge (Cyperus rotundus) control with chlorimuron and imazethapyr

Chlorimuron and imazethapyr applied with nonionic surfactant, crop oil concentrate, or organosilicone-based adjuvant were evaluated for purple nutsedge control in the field. Additional experiments compared chlorimuron and imazethapyr control of purple nutsedge when applied with crop oil concentrate at two growth stages. Chlorimuron controlled purple nutsedge better than did imazethapyr in most experiments. Chlorimuron performed better when applied with crop oil concentrate than with nonionic surfactant or organosilicone-based adjuvant. Imazethapyr control with the organosilicone-based adjuvant or crop oil concentrate was similar and greater than imazethapyr with nonionic surfactant. Control was greater when herbicides were applied to 2- to 6-cm tall purple nutsedge compared with plants 8 to 10 cm tall in two of three trials. Nomenclature: Chlorimuron, 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino] carbonyl]amino] sulfonyl]benzoic acid; imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid; purple nutsedge, Cyperus rotundus L. #(3) CYPRO.