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Effect of Residual Herbicide and Postemergence Application Timing on Weed Control and Yield in Glyphosate-Resistant Corn

  • Mark M. Loux (a1), Anthony F. Dobbels (a1), William G. Johnson (a2) and Bryan G. Young (a3)


Field studies were conducted in 2007 and 2008 at seven sites in Ohio, Indiana, and Illinois to determine the effect of PRE herbicide and POST application timing on weed control and yield of glyphosate-resistant corn. Levels of PRE herbicide included none; low—atrazine; medium—atrazine and metolachlor; and high—atrazine, mesotrione, and metolachlor. Glyphosate was applied POST when corn was 30 cm tall, or 1 or 2 wk later. Common lambsquarters, giant foxtail, and giant ragweed infested at least six of the seven sites, and other weed species occurred at two to three sites. Control of weeds at the time of POST application ranged from 48 to 91%, 58 to 99%, and 87 to 100% for the low, medium, and high levels of PRE herbicide, respectively, averaged over POST application timing. Control of giant foxtail and redroot pigweed decreased by about 20% between the second and third POST timing, averaged over PRE herbicide, but control of other weeds was similar among timings. Late-season control of common ragweed, velvetleaf, common lambsquarters, and Pennsylvania smartweed exceeded 90%, regardless of PRE herbicide or POST timing. Control of redroot pigweed, ivyleaf morningglory, and giant ragweed was as low as 74, 67, and 83%, respectively, but the high level of PRE herbicide resulted in 90 to 97% control of these weeds. An interaction between PRE herbicide and POST timing for late-season control of giant foxtail, tall waterhemp, and yellow nutsedge reflected the more effective control among POST timings from the higher levels of PRE herbicide. The overall trend in this study was for more effective weed control in PRE/POST herbicide programs with more comprehensive PRE herbicides that have substantial activity on both grass and broadleaf weeds. Highest yield occurred where the PRE treatment consisted of a two- or three-way combination of herbicides applied at 50% of the recommended rate or higher. Yield was reduced at all POST timings with atrazine alone or in the absence of PRE herbicide.

Se llevaron al cabo estudios de campo en 2007 y 2008 en un total de 7 sitios en Ohio, Indiana e Illinois para determinar el efecto de herbicidas PRE y del tiempo de aplicación de herbicidas POST en el control de maleza y rendimiento de maíz (Zea mays) resistente a glifosato. Los niveles de herbicidas PRE incluyeron: ninguno, dosis baja de atrazina, media de atrazina y metolaclor y alta de atrazina, mesotrione, y metolaclor. Glifosato fue aplicado POST cuando el maíz alcanzó una altura de 30 cm, o una o dos semanas después. Chenopodium album, Setaria faberi, y Ambrosia trifida infestaron al menos seis de los siete sitios, mientras que otras especies de maleza ocurrieron de 2 a 3 sitios. El control de maleza al tiempo de la aplicación POST varió de 48 a 91%, 58 a 99%, y 87 a 100% para la dosis baja, media y alta de herbicidas PRE, respectivamente, promediado a través de tiempos de aplicación de los POST. El control de Setaria faberi y Amaranthus retroflexus disminuyó cerca del 20% entre el segundo y tercer tiempo de aplicación POST, promediado entre todas las aplicaciones de herbicida PRE, sin embargo, el control de otra maleza fue similar entre tiempos de aplicación. El control ya tarde en la estación de Ambrosia artemisiifolia, Abutilon theophrasti, Chenopodium album y Polygonum pensylvanicum excedió 90% indistintamente del tiempo de aplicación de herbicidas PRE o POST. El control de Amaranthus retroflexus, Ipomoea hederacea, y Ambrosia trifida fue tan bajo como 74, 67, y 83% respectivamente, pero la dosis alta de herbicida PRE resultó de 90 a 97% de control de estas últimas malezas. Una interacción entre herbicidas PRE y tiempos de POST para un control tarde en la estación de Setaria faberi, Amaranthus rudis y Cyperus esculentus, reflejó el control más efectivo entre tiempos de aplicación POST con los niveles más altos de herbicidas PRE. En este estudio, se observó una tendencia general para un control más efectivo con un programa de herbicidas PRE/POST que incluya herbicidas PRE que tengan una mayor actividad substancial sobre maleza de gramíneas y especies de hoja ancha. El más alto rendimiento ocurrió cuando el tratamiento PRE consistió de combinaciones de dos o tres herbicidas aplicados al 50% o más de la dosis recomendada. El rendimiento se redujo en todos los tiempos POST con solo atrazina o en la ausencia de herbicidas PRE.


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Effect of Residual Herbicide and Postemergence Application Timing on Weed Control and Yield in Glyphosate-Resistant Corn

  • Mark M. Loux (a1), Anthony F. Dobbels (a1), William G. Johnson (a2) and Bryan G. Young (a3)


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