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1 August 2015 Influence of Carrier Water pH, Hardness, Foliar Fertilizer, and Ammonium Sulfate on Mesotrione Efficacy
Pratap Devkota, Douglas J. Spaunhorst, William G. Johnson
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Abstract

Carrier water pH, hardness, coapplied foliar fertilizer, water conditioning agents, and plant height are critical considerations for optimum herbicide performance. Field studies were conducted to evaluate the effect of carrier water pH (4, 6.5, and 9) and zinc (Zn) or manganese (Mn) foliar fertilizer on mesotrione for horseweed and Palmer amaranth control. Additionally, effect of carrier water pH and foliar fertilizer was evaluated on 7.5-, 12.5-, and 17.5-cm tall horseweed. Greenhouse treatments consisted of carrier water pH and foliar fertilizer (Zn, Mn, or without fertilizer); or water hardness (0 to 1,000 mg L−1) in the presence or absence of ammonium sulfate (AMS) for mesotrione control of giant ragweed, horseweed, and Palmer amaranth. Mesotrione activity was greater on horseweed with carrier water pH 6.5 compared to pH 4 or 9. Coapplied Zn fertilizer reduced mesotrione activity on Palmer amaranth in the field study in 2014 and horseweed in the greenhouse study. Mesotrione efficacy was greatly influenced by horseweed height. Percent control ranged from 96 to 99%, 75 to 89%, or 61 to 64% with mesotrione applied on 7.5-, 12.5-, or 17.5-cm tall horseweed, respectively, and results were similar for plant height and dry weight reduction. Increasing carrier water hardness from 0 to 1,000 mg L−1 reduced mesotrione efficacy 28, 18, and 18% (or greater) on giant ragweed, horseweed, and Palmer amaranth, respectively. The addition of AMS enhanced mesotrione efficacy 9, 6, or 9% (or greater) for giant ragweed, horseweed, and Palmer amaranth control, respectively. Mesotrione should be applied at near neutral carrier water pH, hardness < 200 mg L−1, and with AMS for achieving optimum weed control.

Nomenclature: Mesotrione; giant ragweed, Ambrosia trifida L AMBTR; horseweed, Conyza canadensis (L.) Cronq. ERICA; Palmer anaranth, Amaranthus palmeri S. Wats. AMAPA.

El pH y la dureza del agua, fertilizantes foliares co-aplicados, agentes acondicionadores del agua, y la altura de planta son consideraciones críticas para el desempeño óptimo de los herbicidas. Se realizaron estudios de campo para evaluar el efecto del pH del agua (4, 6.5, y 9), y fertilizantes foliares de zinc (Zn) o manganese (Mn) sobre la actividad de mesotrione para el control de Conyza canadensis y Amaranthus palmeri. Adicionalmente, el efecto del pH del agua y del fertilizante foliar fue evaluado en plantas de C. canadensis de 7.5, 12.5, y 17.5 cm de altura. Los tratamientos de invernadero consistieron de pH del agua y fertilizantes foliar (Zn, Mn, o sin fertilizante); o dureza del agua (0 a 1,000 mg L−1) en presencia o ausencia de ammonium sulfate (AMS) para el control con mesotrione de Ambrosia trifida, C. canadensis, y A. palmeri. La actividad de mesotrione fue mayor sobre C. canadensis con agua pH 6.5 al compararse con pH 4 ó 9. Fertilizante de Zn co-aplicado redujo la actividad de mesotrione sobre A. palmeri en el estudio de campo en 2014 y sobre C. canadensis en el estudio de invernadero. La eficacia de mesotrione fue altamente influenciada por la altura de C. canadensis. El porcentaje de control varió de 96 a 99%, 75 a 89%, o 61 a 64% con mesotrione aplicado sobre plantas de C. canadensis de 7.5, 12.5, ó 17.5 cm de altura, respectivamente, y los resultados fueron similares para la reducción de altura de planta y peso seco. El incrementar la dureza del agua de 0 a 1,000 mg L

Pratap Devkota, Douglas J. Spaunhorst, and William G. Johnson "Influence of Carrier Water pH, Hardness, Foliar Fertilizer, and Ammonium Sulfate on Mesotrione Efficacy," Weed Technology 30(3), 617-628, (1 August 2015). https://doi.org/10.1614/WT-D-16-00019.1
Received: 3 February 2016; Accepted: 1 March 2016; Published: 1 August 2015
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