Tolerance of Glyphosate-Resistant Maize to Glyphosate Plus MCPA Amine Is Influenced by Dose and Timing

Nader Soltani,Chris L Gillard,Peter H Sikkema,Robert E Nurse,Kris Mcnaughton

doi:10.1155/2015/968050

Nader Soltani, Chris L Gillard + Show 3 more

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https://doi.org/10.1155/2015/968050

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Abstract

There is little information on tolerance of glyphosate-resistant maize to glyphosate plus MCPA amine as influenced by dose and timing under Ontario environmental conditions. A total of seven field trials were conducted at various locations in Ontario, Canada, in 2011–2013 to evaluate tolerance of field maize to tank mixes of glyphosate (900 g a.e./ha) plus MCPA amine (79, 158, 315, 630, 1260, 2520, or 5040 g a.e./ha) at either the 4- or 8-leaf stage. The predicted dose of MCPA amine that caused 5, 10, and 20% injury was 339, 751, and 1914 g a.e./ha when applied to 4-leaf maize but only 64, 140, and 344 g a.e./ha when applied to 8-leaf maize, respectively. The predicted dose of MCPA amine that caused 5, 10, and 20% reduction in shoot dry weight of maize was 488, 844, and 1971 g a.e./ha when applied to 4-leaf maize and only 14, 136, and 616 g a.e./ha when applied to 8-leaf maize, respectively. The predicted dose of MCPA amine that caused 5, 10, and 20% yield reduction was 2557, 4247, and >5040 g a.e./ha when applied to 4-leaf maize and 184, 441, and 1245 g a.e./ha when applied to 8-leaf maize, respectively. Based on these results, glyphosate plus MCPA amine applied at the manufacturer’s recommended dose of 630 g a.e./ha applied to 4-leaf maize has potential to cause injury but the injury is transient with no significant reduction in yield. However, when glyphosate plus MCPA amine is applied to 8-leaf maize it has the potential to cause significant injury and yield loss in maize.

Highlights

Canada produces nearly 11,000,000 metric tonnes of maize annually making it the 11th largest maize producer in the world [1]
At 8 weeks after the corresponding treatment application (WAT), the predicted dose of MCPA amine that caused 5, 10, and 20% injury was 820, 2414, and >5040 g a.e./ha when applied to 4-leaf maize and 64, 140, and 344 g a.e./ha when applied to 8-leaf maize, respectively
The predicted dose of MCPA amine that caused 5, 10, and 20% reduction in shoot dry weight of maize compared to the control was 488, 844, and 1971 g a.e./ha when applied to 4-leaf maize and 14, 136, and 616 g a.e./ha when applied to 8-leaf maize, respectively (Table 2)

Summary

Introduction

Canada produces nearly 11,000,000 metric tonnes of maize annually making it the 11th largest maize producer in the world [1]. Maize (Zea mays L.) is the third most valuable crop produced in Canada [1]. Effective weed management is critical for maize producers to be competitive in the global market. Growers need weed management options that provide grass and broadleaved weed control with a wide margin of crop safety thereby resulting in minimal yield loss due to weed interference and higher net returns for producers. Field horsetail is a competitive weed that has adapted to current agronomic practices and has moved into fertile grain fields [3]. It is increasing in prevalence in areas where growers rely on glyphosate for weed management since glyphosate is not very effective for the control of field horsetail. Significant yield losses have been reported in maize with heavy field horsetail stands that can reach densities of 400 shoots m−1 [3]

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