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1 December 2014 Palmer Amaranth ( Amaranthus palmeri) Management in GlyTol® LibertyLink® Cotton
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Field trials were conducted in Lubbock, TX in 2010 and 2011 to evaluate tank-mix combinations of glyphosate and glufosinate in GlyTol® LibertyLink® cotton for control of Palmer amaranth. Herbicide treatments included glyphosate and glufosinate applied at various tank-mix rate combinations (1X:1X, 1X:0.75X, 1X:0.5X, 1X:0.25X and 1X:0X of glyphosate plus glufosinate), proportional tank-mix rate combinations (1X:0X, 0.75X:0.25X, 0.5X:0.5X, 0.25X:0.75X, and 0X:1X of glyphosate plus glufosinate, where X is 0.84 kg ae ha−1 of glyphosate or 0.58 kg ai ha−1 of glufosinate ammonium), and in sequential (1X followed by 1X) applications of both herbicides in an overall weed management system. Greenhouse studies were conducted to quantify antagonistic or synergistic effects. Treatments included a nontreated control; glyphosate at 0.84, 0.63, 0.42, and 0.21 kg ha−1; glufosinate at 0.58, 0.44, 0.29, and 0.15 kg ha−1; and all tank-mix combinations of each herbicide rate. Dry weights were converted to percent growth values for each rate of the two herbicides alone, and these values were used to calculate expected responses of tank-mix combinations with the use of Colby's method. Expected values were compared to observed percent growth values using an augmented mixed-model method. Results of field studies indicated that tank mixes of glyphosate and glufosinate were less effective at controlling Palmer amaranth than glyphosate applied alone. The addition of any rate of glufosinate to a 1X rate of glyphosate reduced Palmer amaranth control compared to glyphosate alone. Greenhouse studies confirmed antagonism seen in the field. These results indicate that sequential applications of these two herbicides are a better option for Palmer amaranth weed management.

Nomenclature: Glufosinate; glyphosate; Palmer amaranth, Amaranthus palmeri S. Wats.; cotton, Gossypium hirsutum L. ‘FiberMax 9250GL'.

Se realizaron experimentos de campo en Lubbock, TX en 2010 y 2011 para evaluar combinaciones de mezclas en tanque de glyphosate y glufosinate en algodón GlyTol® LibertyLink® para el control de Amaranthus palmeri. Los tratamientos de herbicidas incluyeron glyphosate y glufosinate aplicados en varias combinaciones de dosis de mezclas en tanque (1X:1X, 1X:0.75X, 1X:0.25, y 1X:0X de glyphosate más glufosinate), combinaciones de dosis de mezclas en tanque proporcionales (1X:0X, 0.75X:0.25X, 0.5X:0.5X, 0.25X:0.75X, y 0X:1X de glyphosate más glufosinate, donde X es 0.84 kg ae ha−1 de glyphosate o 0.58 kg ai ha−1 de glufosinate ammonium), y en aplicaciones secuenciales (1X seguido de 1X) de ambos herbicidas en un sistema de manejo de malezas general. Se realizaron estudios de invernadero para cuantificar los efectos sinérgicos y antagónicos. Los tratamientos incluyeron un testigo no-tratado; glyphosate a 0.84, 0.63, 0.42, y 0.21 kg ha−1; glufosinate a 0.58, 0.44, 0.29, y 0.15 kg ha−1; y todas las combinaciones de mezcla en tanque de cada herbicida. Los pesos secos fueron convertidos a porcentaje de valores de crecimiento para cada dosis de los dos herbicidas solos, y estos valores fueron usados para calcular las respuestas esperadas de combinaciones de mezclas en tanque con el uso del método Colby. Los valores esperados fueron comparados a los porcentajes de crecimiento observados usando un método de modelo mixto. Los resultados de los experimentos de campo indicaron que las mezclas en tanque de glyphosate y glufosinate fueron menos efectivas para el control de A. palmeri que glyphosate aplicado solo. La adición de cualquier dosis de glufosinate a una dosis 1X de glyphosate redujo el control de A. palmeri al

Jacob D. Reed, J. Wayne Keeling, and Peter A. Dotray "Palmer Amaranth ( Amaranthus palmeri) Management in GlyTol® LibertyLink® Cotton," Weed Technology 28(4), 592-600, (1 December 2014).
Received: 24 March 2014; Accepted: 1 August 2014; Published: 1 December 2014

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