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Glufosinate Safety in WideStrike® Acala Cotton

  • Steven D. Wright (a1), Anil Shrestha (a2), Robert B. Hutmacher (a3), Gerardo Banuelos (a1), Kelly A. Hutmacher (a1), Sonia I. Rios (a1), Michelle Dennis (a2), Katherine A. Wilson (a1) and Sara J. Avila (a1)...

Abstract

WideStrike® Acala cotton is a two-gene, in-plant trait that provides broad-spectrum and season-long control of lepidopteran insect pests, and the varieties available in California also have resistance to glyphosate. There have been indications that WideStrike cotton has some glufosinate tolerance as well, so the level of tolerance to glufosinate needed to be ascertained. A 2-yr (2008 and 2009) study was conducted in California to evaluate the potential crop injury caused by three different rates (0.59, 0.88, and 1.76 kg ai ha−1) of glufosinate–ammonium at four different growth stages (cotyledon, 2-node, 5- to 6-node, and 18- to 19-node stages) of WideStrike Acala cotton. The effects of these treatments on the cotton plants and yield were closely monitored. Glyphosate at 1.54 kg ae ha−1 was applied at all cotton growth stages as a standard application, and a nontreated control was included. The greatest level of injury (58%) was observed with the highest rate of glufosinate applied at both the cotyledon and the two-node stage of cotton. However, injury was less than 10% following glufosinate at 0.59 kg ha−1 applied at the 18- to 19-node stage. The level of injury increased with the higher application rate of glufosinate at all crop growth stages. In 2008 and 2009, the glufosinate treatments had no effect on cotton lint yield. Therefore, the study showed that glufosinate can be applied safely topically at 0.59 kg ha−1 at the cotyledon- to 2-node stage or as POST-directed spray between the 5- to 19-node stages. Although injury occurred at this rate, the plants recovered within 2 to 3 wk of the treatment. Increasing glufosinate rates beyond 0.59 kg ha−1 can increase the possibility of greater crop injury.

El algodón Acala WideStrike® posee dos genes que brindan control de amplio espectro de plagas insectiles-lepidóptera a lo largo de la temporada de crecimiento, y las variedades disponibles en California también tienen resistencia a glyphosate. Han habido indicaciones de que el algodón WideStrike también tiene algo de tolerancia a glufosinate, así que es necesario definir el nivel de tolerancia a este herbicida. Se realizó un estudio de dos años de duración (2008 y 2009) en California, para evaluar el potencial de daño al cultivo causado por tres dosis diferentes (0.59, 0.88, y 1.76 kg ai ha−1) de glufosinate ammonium en cuatro estadios de crecimiento (cotiledón, 2 nudos, 5 a 6 nudos, y 18 a 19 nudos) de algodón Acala WideStrike. Se le dio seguimiento detallado a los efectos de estos tratamientos en las plantas y el rendimiento del algodón. Se aplicó glyphosate a 1.54 kg ae ha−1 en todos los estadios de crecimiento como estándar de aplicación, y se incluyó un testigo sin tratamiento. El mayor nivel de daño (58%) se observó con la dosis mayor de glufosinate aplicada en los estadios de cotiledón y 2 nudos del algodón. Sin embargo, el daño fue menos de 10% después de aplicaciones de glufosinate a 0.59 kg ha−1 en el estadio de 18 a 19 nudos. El nivel de daño incrementó con la dosis mayor de glufosinate en todos los estadios de crecimiento del cultivo. En 2008 y 2009, los tratamientos de glufosinate no tuvieron ningún efecto en el rendimiento de fibra del algodón. Así, el estudio mostró que se puede aplicar glufosinate tópicamente en forma segura a 0.59 kg ha−1 en los estadios de cotiledón y de 2 nudos, o en forma POST-dirigida en los estadios de 5 a 19 nudos. Aunque hubo daños con esta dosis, las plantas se recuperaron 2 a 3 semanas después del tratamiento. Aumentar las dosis de glufosinate más allá de 0.59 kg ha−1 puede incrementar la posibilidad de observar un mayor daño en el cultivo.

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Corresponding author

Corresponding author's E-mail: sdwright@ucdavis.edu.

References

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