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1 October 2013 Influence of Dicamba and Dicamba plus Glyphosate Combinations on the Control of Glyphosate-Resistant Waterhemp ( Amaranthus rudis)
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Abstract

A total of four field experiments were conducted over a 2-yr period (2011 and 2012) near Mokane and Moberly, Missouri, to determine the control of glyphosate-resistant (GR) waterhemp with dicamba and glyphosate applied alone or as a tank-mix combination. In one experiment, dicamba was applied at 0.14, 0.28, 0.42, and 0.56 kg ae ha−1 with or without 0.86 kg ae ha−1 glyphosate to GR waterhemp plants 7.5, 15, and 30 cm in height. In a second experiment, sequential treatments of dicamba or dicamba plus glyphosate were applied 4, 7, and 14 d after the initial herbicide treatment to plants measuring either 7.5 or 23 cm in height. Control of GR waterhemp ranged from 7 to 62%, 11 to 40%, and 8 to 30% when applied to 7.5-, 15-, and 30-cm plants, respectively. Control of 7.5-cm GR waterhemp increased by 16 to 36%, and biomass reduction increased by 29 to 52% in response to 0.14, 0.28, 0.42, and 0.56 kg ha−1 dicamba plus glyphosate compared to these same rates of dicamba alone. When sequential dicamba-containing treatments were averaged across all treatments and application timings, GR waterhemp control ranged from 46 to 47%, and biomass reduction ranged from 55 to 66%. No differences in control were observed based on the timing of the sequential herbicide treatment. However, in terms of GR waterhemp biomass reduction, sequential treatments applied 4 d after the initial treatment reduced GR waterhemp biomass more than sequential treatments applied 14 d after the initial treatment. Results from these experiments indicate that, in the absence of crop competition, a single treatment of dicamba up to 0.56 kg ha−1 provides less than 62% control of GR waterhemp, and sequential dicamba plus glyphosate treatments targeting 7.5 cm plants are required to achieve at least 72% control.

Nomenclature: Dicamba; glyphosate; waterhemp; Amaranthus rudis Sauer.

Un total de cuatro experimentos de campo fueron realizados durante un período de 2 años (2011 y 2012) cerca de Mokane y Moberly, Missouri, para determinar el control de Amaranthus rudis resistente a glyphosate (GR) con dicamba y glyphosate aplicados solos o combinados en mezcla en tanque. En un experimento, se aplicó dicamba a 0.14, 0.28, 0.42, y 0.56 kg ae ha−1 con o sin 0.86 kg ae ha−1 de glyphosate a plantas de A. rudis GR de 7.5, 15, y 30 cm de altura. En un segundo experimento, se realizaron tratamientos de aplicaciones secuenciales de dicamba o dicamba más glyphosate 4, 7, y 14 d después del tratamiento inicial a plantas que midieron 7.5 ó 23 cm de altura. El control de A. rudis GR varió de 7 a 62%, 11 a 40%, y 8 a 31% cuando se aplicó plantas de 7.5, 15, y 30 cm de altura, respectivamente. El control de A. rudis GR de 7.5 cm de altura incrementó de 16 a 36%, y la reducción de la biomasa aumentó de 29 a 52% en respuesta a 0.14, 0.28, 0.42, y 0.56 kg ha−1 de dicamba más glyphosate al compararse con las mismas dosis de dicamba solo. Cuando se promedió los tratamientos secuenciales y los momentos de aplicaciones que contenían dicamba, el control de A. rudis GR varió entre 46 y 47%, y la reducción en la biomasa varió entre 55 y 66%. No se observaron diferencias según el momento del tratamiento secuencial con el herbicida. Sin embargo, en términos de la reducción de la biomasa de A. rudis GR, los tratamientos secuenciales aplicados 4 d después del tratamiento inicial redujeron la biomasa de A. rudis GR más que los tratamientos secuenciales aplicados 14 d después del tratamiento inicial. Los resultados de estos experimentos

Douglas J. Spaunhorst and Kevin W. Bradley "Influence of Dicamba and Dicamba plus Glyphosate Combinations on the Control of Glyphosate-Resistant Waterhemp ( Amaranthus rudis)," Weed Technology 27(4), 675-681, (1 October 2013). https://doi.org/10.1614/WT-D-13-00081.1
Received: 2 May 2013; Accepted: 1 July 2013; Published: 1 October 2013
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