Abstract
A total of seven field studies were conducted in southwestern Ontario from 2018 to 2020 to evaluate S-metolachlor/mesotrione/bicyclopyrone (Acuron Flexi®) and S-metolachlor/atrazine/mesotrione/bicyclopyrone (Acuron®) for the control of glyphosate-resistant (GR) Canada fleabane in corn. Acuron Flexi® and Acuron® applied preplant (PP) controlled GR Canada fleabane 90-97% and 99-100%, respectively. Commonly used PP herbicides in Ontario, dicamba/atrazine + glyphosate and tolpyralate + atrazine + glyphosate controlled GR Canada fleabane 97-99%. Acuron Flexi® and Acuron® applied postemergence (POST) provided 75-92% and 92-99% control of GR Canada fleabane, respectively. Dicamba/atrazine + glyphosate and tolpyralate + atrazine + glyphosate applied POST provided 84-97% and 94-98% control of GR Canada fleabane, respectively. Glyphosate applied POST at 900 ae ha-1 provided only 35-38% control of Canada fleabane in corn. Orthogonal contrasts indicated that herbicides applied PP provided up to 10% greater control of GR Canada fleabane than POST. There was no significant difference between the low and high rates of Acuron® or Acuron Flexi® in controlling GR Canada fleabane. Acuron® controlled GR Canada fleabane 14, 9 and 7% greater than Acuron Flexi® at 4, 8, and 12 WAA, respectively. GR Canada fleabane interference with corn reduced yield up to 42%. However, there was no difference in corn yield between herbicides treatments evaluated. Orthogonal contrasts indicated that reduced GR Canada fleabane interference with PP herbicides evaluated provided 0.9 t ha-1 greater corn yield than the POST herbicides evaluated. There was no significant difference in corn yield with Acuron® or Acuron Flexi® at the lower rate or higher rates. Additionally, Acuron Flexi® applied PP provided a similar corn yield as when applied POST. Based on these results, the use of Acuron® results in improved GR Canada fleabane control than Acuron Flexi® but this did not result in an increase in corn yield. The study concludes that there is potential for Acuron Flexi® for GR Canada fleabane control in corn especially in areas where atrazine use is restricted, however additional weed control tactics may be required for acceptable control.
Highlights
Corn is one of the most important crops grown in the world (Statista, 2021)
A study conducted by the Weed Science Society of America (WSSA) has found an average corn yield loss of 50% if weeds were not controlled (Soltani et al, 2016)
The results from this study show that Acuron® and Acuron Flexi®, applied PP and POST, can provide good to excellent residual control of GR Canada fleabane in corn
Summary
Corn is one of the most important crops grown in the world (Statista, 2021). Canada produced nearly 14 million metric tons of corn in 2020 (Statista, 2021). Most of the corn grown in Canada is produced in Ontario. In 2020, Ontario corn growers seeded nearly 900,000 ha and produced nearly 9 million tonnes of corn with a farm gate value of approximately $1.8 billion (OMAFRA, 2021). One of the main production concerns of corn growers is weed control. A study conducted by the Weed Science Society of America (WSSA) has found an average corn yield loss of 50% if weeds were not controlled (Soltani et al, 2016)
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