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Late Glyphosate Applications Alter Yield and Yield Components in Glyphosate-Resistant Canola (Brassica napus)

  • Eric Tozzi (a1), K. Neil Harker (a2), Robert E. Blackshaw (a3), John T. O'Donovan (a2), Stephen E. Strelkov (a2) and Christian J. Willenborg (a1)...


The development of glyphosate-resistant canola has provided improved weed-management options for growers, but crop tolerance to glyphosate may be inadequate at later growth stages. In this study, glyphosate-resistant canola 45H28 (RR) was used to determine the effects of glyphosate application timing on yield and yield components at several sites in western Canada. Canola received a single glyphosate applications at the two-leaf, six-leaf, bolting, and early bloom stages and sequential applications at the two-leaf + six-leaf, two-leaf + bolting, and two-leaf + early bloom stages. Contrasts were made between early vs. late, single vs. sequential, and on-label (two to six-leaf stage) vs. off-label (above six-leaf stage). In general, differences between application timings were observed for yield and yield components in 3 of 8 site-yr. Off-label applications of glyphosate (later than six-leaf) significantly decreased yield, seeds per pod, and increased thousand-seed weight and aborted pods in canola at the Lethbridge and St. Albert locations. Increased glyphosate translocation because of adequate, but not excessive, moisture to new growth may have suppressed new seed formation and encouraged pod abortion at the time of application in the 2010 and 2011 seasons. Results from this experiment demonstrate the importance of proper application timing of glyphosate on canola and can help better predict the effects of late applications.

El desarrollo de colza resistente a glyphosate ha brindado más opciones de manejo de malezas para los productores. En este estudio, se usó colza resistente a glyphosate 45H28 (RR) para determinar los efectos del momento de aplicación de glyphosate sobre el rendimiento y los componentes del rendimiento, en varios sitios en el oeste de Canada. La colza recibió una aplicación sencilla en los estadios de dos hojas, seis hojas, producción de tallo floral, y floración temprana y aplicaciones secuenciales en los estadios de dos hojas + seis hojas, dos hojas + producción de tallo floral, y dos hojas + floración temprana. Se realizaron contrastes entre las aplicaciones temprana vs. tardía, sencilla vs. secuencial, y dentro de las recomendaciones de la etiqueta (estadios de dos a seis hojas) vs. fuera de las recomendaciones de la etiqueta (después del estadio de seis hojas). En general, se vieron diferencias entre momentos de aplicación en el rendimiento y los componentes del rendimiento en 3 de los 8 sitios-años. Aplicaciones de glyphosate fuera de la etiqueta disminuyeron significativamente los rendimientos, el número de semillas por vaina, e incrementaron el peso de mil semillas y las vainas abortadas en colza en las localidades de Lethbridge y St. Albert. La precipitación excesiva podría haber causado una reducción en el rendimiento en la temporada 2012. Una translocación aumentada de glyphosate hacia tejidos de crecimiento nuevo, debido a una humedad adecuada, más no excesiva, podría haber prevenido la formación de semilla nueva y promovido el aborto de vainas al momento de aplicación en las temporadas 2010 y 2011. Los resultados de este experimento muestran la importancia de la aplicación de glyphosate en el momento adecuado en la colza y ayudan a predecir mejor los efectos de aplicaciones tardías.


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Associate Editor for this paper: Darren Robinson, University of Guelph.



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Late Glyphosate Applications Alter Yield and Yield Components in Glyphosate-Resistant Canola (Brassica napus)

  • Eric Tozzi (a1), K. Neil Harker (a2), Robert E. Blackshaw (a3), John T. O'Donovan (a2), Stephen E. Strelkov (a2) and Christian J. Willenborg (a1)...


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