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1 June 2013 Palmer Amaranth ( Amaranthus palmeri) Control by Glufosinate plus Fluometuron Applied Postemergence to WideStrike® Cotton
Kelly A. Barnett, A. Stanley Culpepper, Alan C. York, Lawrence E. Steckel
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Glyphosate-resistant (GR) weeds, especially GR Palmer amaranth, are very problematic for cotton growers in the Southeast and Midsouth regions of the United States. Glufosinate can control GR Palmer amaranth, and growers are transitioning to glufosinate-based systems. Palmer amaranth must be small for consistently effective control by glufosinate. Because this weed grows rapidly, growers are not always timely with applications. With widespread resistance to acetolactate synthase-inhibiting herbicides, growers have few herbicide options to mix with glufosinate to improve control of larger weeds. In a field study using a WideStrike® cotton cultivar, we evaluated fluometuron at 140 to 1,120 g ai ha−1 mixed with the ammonium salt of glufosinate at 485 g ae ha−1 for control of GR Palmer amaranth 13 and 26 cm tall. Standard PRE- and POST-directed herbicides were included in the systems. Glufosinate alone injured the WideStrike® cotton less than 10%. Fluometuron increased injury up to 25% but did not adversely affect yield. Glufosinate controlled 13-cm Palmer amaranth at least 90%, and there was no improvement in weed control nor a cotton yield response to fluometuron mixed with glufosinate. Palmer amaranth 26 cm tall was controlled only 59% by glufosinate. Fluometuron mixed with glufosinate increased control of the larger weeds up to 28% and there was a trend for greater yields. However, delaying applications until weeds were 26 cm reduced yield 22% relative to timely application. Our results suggest fluometuron mixed with glufosinate may be of some benefit when attempting to control large Palmer amaranth. However, mixing fluometuron with glufosinate is not a substitute for a timely glufosinate application.

Nomenclature: Fluometuron; glufosinate; glyphosate; Palmer amaranth, Amaranthus palmeri S. Wats.; cotton, Gossypium hirsutum L.

Las malezas resistentes a glyphosate (GR), especialmente Amaranthus palmeri GR, son muy problemáticas para los productores de algodón en las regiones Sureste y Sur-medio de los Estados Unidos. Glufosinate puede controlar A. palmeri GR, y los productores están cambiando a los sistemas basados en glufosinate. A. palmeri debe estar pequeño para el control consistentemente efectivo con glufosinate. Debido a que esta maleza crece rápidamente, los productores no siempre realizan las aplicaciones a tiempo. Con la resistencia a herbicidas inhibidores de acetolactate synthase ampliamente distribuida, los productores tienen pocas opciones de herbicidas para mezclar con glufosinate para así mejorar el control de malezas más grandes. En un estudio de campo usando un cultivar de algodón WideStrike®, evaluamos fluometuron a 140 a 1,120 g ai ha−1 en mezcla con sal amónica de glufosinate a 485 g ae ha−1 para el control de A. palmeri GR con alturas de 13 y 26 cm. Herbicidas estándar en PRE y POST-dirigido se incluyeron en los sistemas. Glufosinate solo dañó el algodón WideStrike® menos de 10%. Fluometuron incrementó el daño hasta 25%, pero no afectó el rendimiento en forma adversa. Glufosinate controló A. palmeri de 13 cm al menos 90%, y no hubo mejora en el control de malezas ni respuesta en el rendimiento del algodón al fluometuron en mezcla con glufosinate. A. palmeri de 26 cm de altura fue controlado solamente en 59% con glufosinate. Fluometuron mezclado con glufosinate incrementó el control de las malezas más grandes hasta un 28% y hubo una tendencia a obtener mayores rendimientos. Sin embargo, al retrasar las aplicaciones hasta que las malezas tuvieron 26 cm redu

Kelly A. Barnett, A. Stanley Culpepper, Alan C. York, and Lawrence E. Steckel "Palmer Amaranth ( Amaranthus palmeri) Control by Glufosinate plus Fluometuron Applied Postemergence to WideStrike® Cotton," Weed Technology 27(2), 291-297, (1 June 2013).
Received: 25 October 2012; Accepted: 1 January 2013; Published: 1 June 2013

Application timing
Cotton cultivar ‘PHY 375 WRF'
herbicide mixtures
Herbicide-resistant weeds
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