Preplant (PP) herbicide applications are an important tool within an integrated weed management system, specifically in no-till production. An understanding of crop tolerance regarding PP applications is important for effectively integrating a new herbicide into no-till cropping systems. Twelve field trials (six in corn and six in soybean) were conducted over a 2-yr period (2018 and 2019) near Exeter and Ridgetown, ON. The purpose of these studies was to evaluate the tolerance of soybean and corn to halauxifen-methyl applied PP, PRE, or POST at the registered rate (5 g a.i. ha−1) and twice the registered rate (10 g a.i. ha−1), hereafter referred to as the 1× and 2× rate, respectively. All trials were kept weed-free throughout the growing season to remove the confounding effect of weed interference. Halauxifen-methyl applied 14 d preplant (DPP), 7 DPP, 1 DPP, and 5 d after seeding (DAS) at the 1× and 2× rates caused ≤10% visible soybean injury. In contrast, halauxifen-methyl applied POST (cotyledon–unifoliate stage, VE-VC) caused 67% to 87% visible soybean injury, a 50% to 53% reduction in height, 65% to 81% decrease in population, 56% to 67% lower biomass, and 53% to 63% decline in yield. Halauxifen-methyl applied 10 DPP, 5 DPP, 1 DPP, 5 DAS, and POST (spike–one leaf stage, VE-V1) at the 1× and 2× rate caused ≤3% visible corn injury and caused no effect on corn height or biomass. Halauxifen-methyl applied at VE-V1 at the 2× rate reduced corn yield 10%. Based on these studies, the current application restriction of 7 DPP in soybean and 5 DPP in corn is conservative and could be expanded. Expanding the application window of halauxifen-methyl would increase the utility of this herbicide for producers.

中文翻译：

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大豆和玉米对甲基卤代芬的响应

种植前 (PP) 除草剂应用是综合杂草管理系统中的重要工具，特别是在免耕生产中。了解有关 PP 应用的作物耐受性对于有效地将新除草剂整合到免耕种植系统中非常重要。在安大略省埃克塞特和里奇敦附近进行了 2 年（2018 年和 2019 年）的 12 次田间试验（6 次玉米和 6 次大豆）。这些研究的目的是评估大豆和玉米对以注册比率（5 g a i ha-1) 和两倍的注册费率 (10 g ai ha-1)，以下分别称为 1 倍率和 2 倍率。所有试验在整个生长季节都保持无杂草，以消除杂草干扰的混杂影响。Halauxifen-methyl 以 1 倍和 2 倍的施用量在播种前 14 天（DPP）、7 DPP、1 DPP 和播种后 5 天（DAS）施用导致≤10% 的可见大豆损伤。相比之下，施用 POST（子叶-单叶期，VE-VC）的卤草芬-甲基造成 67% 至 87% 的可见大豆损伤，高度减少 50% 至 53%，种群减少 65% 至 81%，56% 至生物量降低 67%，产量降低 53% 至 63%。Halauxifen-methyl 以 1× 和 2× 施用 10 DPP、5 DPP、1 DPP、5 DAS 和 POST（穗一叶期，VE-V1）导致≤3% 可见玉米损伤，对玉米无影响高度或生物量。以 2 倍的速率在 VE-V1 上施用甲基哈洛昔芬可使玉米产量降低 10%。基于这些研究，目前大豆中7 DPP和玉米中5 DPP的应用限制是保守的，可以扩大。扩大halauxifen-methyl的应用窗口将增加这种除草剂对生产者的效用。