Palmer amaranth is the most common and troublesome broadleaf weed species of rice in Mississippi because of the effects of early-season interference and infestations on rice levees, and herbicides for residual or POST control of Palmer amaranth in rice are limited. Three studies were conducted in 2012 and 2013 to evaluate application rates and timings of saflufenacil in rice and to determine the influence of adjuvants when mixed with saflufenacil applied POST. In a PRE study, no injury occurred after saflufenacil PRE, and no control was observed from carfentrazone. Hemp sesbania and Palmer amaranth control increased with increasing saflufenacil rate when applied PRE. Hemp sesbania control with saflufenacil at any rate PRE was ≤ 25% at 35 d after treatment (DAT). Palmer amaranth and ivyleaf morningglory control with saflufenacil at 75 g ai ha⁻¹ PRE was ≥ 94% 35 DAT. In a POST study, rice injury was influenced by application timing and rate of saflufenacil; however, efficacy was not. Rice injury with saflufenacil at 25 g ha⁻¹ and carfentrazone early POST (EPOST) and late POST was similar 7 DAT. Saflufenacil at 50 and 75 g ha⁻¹ EPOST were the most injurious 7 DAT. Control of hemp sesbania and ivyleaf morningglory was similar for all rates of saflufenacil and carfentrazone; however, Palmer amaranth control with saflufenacil at any rate was greater than that of carfentrazone 14 and 28 DAT. In an adjuvant study, rice injury was influenced by adjuvant and saflufenacil rate. Saflufenacil applied alone or in mixture with crop oil concentrate (COC) was least injurious, and saflufenacil at 50 g ha⁻¹ was more injurious than saflufenacil at 25 g ha⁻¹. Saflufenacil applied in combination with any adjuvant provided better control of hemp sesbania and Palmer amaranth than saflufenacil alone. On the basis of this research, saflufenacil should be applied PRE at 50 or 75 g ha⁻¹, depending on weed spectrum, and POST applications should be made at 25 g ha⁻¹ in combination with COC after the two-leaf rice growth stage.

Nomenclature: Carfentrazone; saflufenacil; hemp sesbania, Sesbania herbacea (P. Mill.) McVaugh SEBEX; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. IPOHE; Palmer amaranth, Amaranthus palmeri S. Wats AMAPA; rice, Oryza sativa L.

Amaranthus palmeri es la especie de malezas de hoja ancha más común y problemática en arroz en Mississippi debido a sus efectos en la interferencia temprano durante la temporada de crecimiento y sus infestaciones en los diques en los campos de arroz, además hay pocos herbicidas para el control residual y POST de esta maleza en arroz. En 2012 y 2013, se realizaron tres estudios para evaluar la dosis y momentos de aplicación de saflufenacil en arroz y así determinar la influencia de adyuvantes cuando estos se mezclaron con saflufenacil y fueron aplicados POST. En un estudio PRE, no hubo daño después de aplicaciones PRE de saflufenacil, y no se observó control alguno con aplicaciones de carfentrazone. El control de Sesbania herbacea y A. palmeri aumentó con el incremento en las dosis de saflufenacil cuando se aplicó PRE. A cualquier dosis, el control de S. herbacea con saflufenacil PRE fue ≤25% a 35 d después del tratamiento (DAT). El control de A. palmeri e Ipomoea hederacea con saflufenacil a 75 g ai ha⁻¹ PRE fue ≥94% 35 DAT. En un estudio POST, el daño en el arroz fue influenciado por el momento y dosis de aplicación de saflufen