Early Postemergence Control of Yellow Woodsorrel (Oxalis stricta) with Residual Herbicides

Three experiments were conducted to evaluate early POST control of yellow woodsorrel using PRE-applied herbicides. In experiment 1, yellow woodsorrel was seeded at two dates in a commercial pine-bark substrate and grown until reaching either the cotyledon–one-leaf (C-1L) or two- to four-leaf (2-4L) growth stage. The herbicides isoxaben, indaziflam, and dimethenamid-p were applied at these growth stages. Two rates of isoxaben and indaziflam provided yellow woodsorrel control (≥ 80% reduction in fresh weight [FW]) when applied at the C-1L stage; however, once yellow woodsorrel reached the 2-4L stage, indaziflam was the only herbicide that provided effective control at both rates tested. Experiments 2 and 3 were similar to experiment 1, except two labeled rates of dithiopyr were also evaluated. In experiment 2, all herbicides evaluated provided ≥ 90% reduction in FW of yellow woodsorrel at the C-1L stage. Although no differences in FW were observed among any of the herbicide treatments when yellow woodsorrel were treated at the 2-4L stage, control ratings indicated that indaziflam provided the most effective yellow woodsorrel control. Experiment 3 results also indicated that isoxaben, indaziflam, and dithiopyr controlled yellow woodsorrel (≥ 95% reduction in FW) when treatments were applied at the C-1L stage, whereas dimethenamid-p reduced shoot FW 70%. When yellow woodsorrel was treated after reaching the 2-4L stage, indaziflam provided the greatest control of any herbicide evaluated. Nomenclature: Dithiopyr; isoxaben; indaziflam, N-[(1R,2S)-2,3-dihydro-2,6-dimethyl-1H-inden-1-yl]-6-[(1RS)-1-fluoroethyl]-1,3,5-triazine-2,4-diamine); yellow woodsorrel, Oxalis stricta L. Se realizaron tres experimentos para evaluar el control POST temprano de Oxalis stricta usando herbicidas aplicados PRE. En el experimento 1, O. stricta se sembró en dos fechas en un sustrato comercial de corteza de pino y se dejó crecer hasta alcanzar los estados de desarrollo de cotiledón-una hoja (C-1L) o dos a cuatro hojas (2-4L). Los herbicidas isoxaben, indaziflam, y dimethenamid-p fueron aplicados en estos estados de desarrollo. Ambas dosis de isoxaben e indaziflam proveyeron control de O. stricta (≥80% reducción del peso fresco [FW] cuando se aplicó en el estado C-1L); sin embargo, una vez que O. stricta alcanzó el estado 2-4L, indaziflam fue el único herbicida que brindó control efectivo con ambas de las dosis evaluadas. Los experimentos 2 y 3 fueron similares al experimento 1, except