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Response of Direct-Seeded Dry Bulb Onion to Simulated Glyphosate Drift with Variable Rates and Application Timings

Joel Felix, Rick Boydston and Ian C. Burke
Weed Technology
Vol. 26, No. 4 (OCTOBER-DECEMBER 2012), pp. 747-756
Stable URL: http://www.jstor.org/stable/23358280
Page Count: 10
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Response of Direct-Seeded Dry Bulb Onion to Simulated Glyphosate Drift with Variable Rates and Application Timings
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Abstract

Field studies were conducted in 2011 at the Malheur Experiment Station, Ontario, OR and Prosser, WA to evaluate the effect of simulated glyphosate drift on direct-seeded dry bulb onion. Glyphosate was applied at 8.6, 25.8, 86, 290, 434, and 860 g ae ha −1 when onion plants were at the flag-, two-, four-, and six-leaf stages. Onion foliar injury was directly related to the glyphosate dose and varied with application timing. Foliar injury at 7 d after treatment (DAT) ranged from 0 to 12% for glyphosate ≤ 25.8 g ha −1 . Foliar injury increased at 21 DAT when glyphosate was applied ≥ 25.8 g ha −1 to plants at the flag- and four-leaf stage, and ranged from 24 to 99%. The 50%-injury glyphosate dose at 21 DAT was lowest when onion was treated at the four-leaf and flag stages and was estimated to be 76.8 and 81 g ha −1 , respectively. Onion injury severity increased when glyphosate was applied at ≥ 86 g ha −1 and eventually resulted in plant death at 860 g ha −1 . Foliar injury was inversely correlated to U.S. no. 1 onion yield. Onions displayed sensitivity to very low glyphosate doses especially at the four-leaf stage. Shikimic acid accumulation increased with the increase in glyphosate dose and was positively correlated with foliar injury and negatively correlated with plant height and onion yield. Se realizaron estudios de campo en 2011 en la Estación Experimental Malheur, Ontario, OR y Prosser, WA para evaluar el efecto de la deriva simulada de glyphosate sobre el bulbo de cebolla seca de siembra directa. Se aplicó glyphosate a 8.6, 25.8, 86, 290, 434 y 860 g ae ha −1 cuando las plantas de cebolla estaban en los estadios de hoja bandera, dos, cuatro y seis hojas. El daño foliar de la cebolla estuvo directamente relacionado a la dosis de glyphosate y varió con el momento de aplicación. El daño foliar a 7 días después del tratamiento (DAT) varió de 0 a 12% para glyphosate a ≤25.8 g ha −1 . El daño foliar incrementó a 21 DAT cuando glyphosate se aplicó a ≥25.8 g ha −1 a plantas en los estados de bandera y cuatro hojas y varió de 24 a 99%. La dosis más baja de 50% de daño de glyphosate a 21 DAT se observó cuando la cebolla fue tratada en los estados de cuatro hojas y hoja bandera y se estimó que fue 76.8 y 81 g ha −1 , respectivamente. La severidad del daño de la cebolla aumentó cuando glyphosate se aplicó a ≥86 g ha −1 y eventualmente resultó en la muerte de la planta a 860 g ha −1 . El daño foliar estuvo inversamente correlacionado con el rendimiento de cebolla U.S. no. 1. La cebolla mostró sensibilidad a dosis muy bajas de glyphosate especialmente en el estado de cuatro hojas. La acumulación de shikimic acid aumentó con el incremento en la dosis de glyphosate y estuvo positivamente correlacionada con el daño foliar y negativamente correlacionada con la altura de la planta y el rendimiento de la cebolla.

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