Field research was conducted in southern New Mexico to determine the effect of halosulfuron rate, timing of application, and adjuvant on purple nutsedge suppression and chile pepper injury under cultivated conditions. POST-directed treatments of 36 or 53 g ai/ha were applied 2 or 4 wk after thinning direct-seeded chile pepper. Herbicide treatments included a nonionic surfactant or methylated seed oil plus ammonium sulfate plus polyacrylamide polymer. Herbicide rate, adjuvant, and timing of the application had little effect on overall nutsedge suppression; however, herbicide treatment proved to be an important component for managing purple nutsedge in this experiment. Yields were higher with halosulfuron treatment compared with the weedy control. Whereas halosulfuron treatment with 53 g/ha increased chile yield relative to the weedy control, injury and yield results comparing 36 and 53 g/ha rates consistently suggested that halosulfuron should be applied at rates ≤ 36 g/ha in a single application to avoid possible injury. Halosulfuron treatment combined with cultivation and effective crop rotation may reduce the impact of purple nutsedge interference in chile pepper.

Nomenclature: Halosulfuron, purple nutsedge, Cyperus rotundus L. CYPRO, chile pepper, Capsicum annuum L. ‘Sandia’