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24 September 2019 Do adjuvants reduce the antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na?
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Abstract

Acetyl co-enzyme A carboxylase (ACCase)-resistant rice allows quizlaofop-p-ethyl to be applied as a POST control of troublesome grass weeds. A field study was conducted in 2017 and 2018 at the H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate the influence of a crop oil concentrate (COC), a silicon-based surfactant plus a nitrogen source (SNS), or a high-concentrate COC (HCOC) in overcoming the grass weed control antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na. Quizalofop-p-ethyl was applied at 120 g ai ha–1, bispyribac-Na was applied at 34 g ai ha–1, and all adjuvants were applied at 1% vol/vol. Antagonistic interactions were observed at 14 d after treatment (DAT) when quizalofop-p-ethyl was mixed with bispyribac-Na with no adjuvant for control of barnyardgrass, the non–ACCase-tolerant rice cultivars ‘CL-111’ and ‘CLXL-745’, and red rice. At 14 DAT, antagonism of quizalofop-p-ethyl for control of barnyardgrass was observed when mixed with bispyribac-Na plus COC, SNS, or HCOC, with an observed control of 43%, 63%, and 86%, respectively, compared with an expected control of 95% for quizalofop-p-ethyl alone. However, the antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na plus HCOC for barnyardgrass control at 14 DAT was overcome by 28 DAT, with an observed control of 91%, compared with an expected control of 97%. Synergistic or neutral interactions were observed at 14 and 28 DAT when COC, SNS, or HCOC was added to a mixture of quizalofop-p-ethyl plus bispyribac-Na for CL-111, CLXL-745, and red rice control. According to the results of this study, HCOC is the most effective adjuvant for quizalofop-p-ethyl and bispyribac-Na mixtures for control of weedy rice and barnyardgrass.

Nomenclature: Bispyribac-Na; quizalofop-p-ethyl; barnyardgrass, Echinochloa crus-galli (L.) P. Beauv.; red rice, Oryza sativa L.; rice, Oryza sativa L.

© Weed Science Society of America, 2019.
L. Connor Webster, Eric P. Webster, David C. Blouin, and Benjamin M. McKnight "Do adjuvants reduce the antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na?," Weed Technology 34(2), 180-187, (24 September 2019). https://doi.org/10.1017/wet.2019.91
Received: 17 June 2019; Accepted: 12 September 2019; Published: 24 September 2019
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