Abstract
Limited information exists on the efficacy of pethoxamid for annual grass and broadleaf control in corn and soybean in Ontario. A total of 10 field experiments (5 with corn and 5 with soybean) were conducted during 2015 to 2017 in Ontario, Canada, to compare the weed control efficacy of dimethenamid-P at 544 g·ai·ha−1, pethoxamid at 840 g·ai·ha−1, pyroxasulfone at 100 g·ai·ha−1, and S-metolachlor at 1050 g·ai·ha−1 applied preemergence (PRE). Reduced weed interference with pyroxasulfone and dimethenamid-P resulted in corn yield that was similar to the weed-free control; however, weed interference with pethoxamid and S-metolachlor reduced corn yield 28 and 33%, respectively. Reduced weed interference with pyroxasulfone resulted in soybean yield that was similar to the weed-free control; however, weed interference with pethoxamid, dimethenamid-P, and S-metolachlor reduced soybean yield 27, 27, and 30%, respectively. At 4 and 8 weeks after application (WAA), all VLCFA inhibitor herbicides (Group 15) provided excellent redroot pigweed control (90 to 99%) in corn. There were no differences in common ragweed control, density, and dry weight among the VLCFA inhibitor herbicide evaluated; pyroxasulfone provided highest numeric common ragweed control and lowest numeric density and dry weight. At 4 and 8 WAA, pyroxasulfone provided the best common lambsquarters and wild mustard control and lowest numeric density and dry weight in corn and soybean. At 8 WAA, the VLCFA inhibitor herbicides controlled green foxtail 91 to 96% in corn; dimethenamid-P provided better control of green foxtail than pethoxamid in soybean. There were no differences in barnyard grass control among the VLCFA inhibitor herbicides evaluated.
Highlights
Soybean and corn are two major agricultural crops produced in Canada [1, 2]
Reduced weed interference with pyroxasulfone and dimethenamid-P resulted in corn yield that was similar to the weed-free control (Table 1)
Corn grain yield was similar to weed-free control with pyroxasulfone and dimethenamid-P. ere was excellent redroot pigweed control with all very long chain fatty acid (VLCFA) inhibitor herbicides in corn. ere were no differences in common ragweed control, but pyroxasulfone provided the highest numeric control with the lowest density and aboveground dry weight among the VLCFA inhibitor herbicides evaluated in corn
Summary
Soybean and corn are two major agricultural crops produced in Canada [1, 2]. Nearly 50% of soybean and >60% of corn produced in Canada is grown in Ontario [2]. Soybean and corn are ranked as the 1st and 2nd most important field crops grown in Ontario, respectively [1]. In 2016, Ontario soybean and corn growers harvested 1.09 and 0.81 million ha and produced 3.38 and 8.05 million tonnes with a total farm gate value of $1.59 and $1.54 billion, respectively [1]. Effective weed management is critical for profitable soybean and corn production. Growers need new weed management options to control problematic weeds in corn and soybean
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