Foliar herbicide applications to waterhemp can result in inadequate control, leading to subsequent regrowth that often necessitates a second herbicide application to prevent crop interference and seed production. The most effective herbicides and application timings are unknown in situations where waterhemp has regrown from previous injury, such as failed applications of glufosinate or fomesafen. The objective of this research was to determine the optimum combination of herbicide and time from the first failed herbicide application to a sequential herbicide application for control of waterhemp regrowth. Reduced rates of either glufosinate or fomesafen were applied to 30-cm waterhemp plants to mimic failure of the initial herbicide application in separate bare-ground experiments. Respray treatments of glufosinate, fomesafen, lactofen, 2,4-D, or dicamba were applied 3, 7, or 11 d after the initial application. Glufosinate and fomesafen as respray treatments resulted in 90% to 100% control of waterhemp regardless of application timing following a failed glufosinate application. After a failed application of fomesafen, applying glufosinate or 2,4-D resulted in 87% to 99% control of waterhemp. Waterhemp control with fomesafen and lactofen was 13% to 21% greater, respectively, when those treatments followed glufosinate compared with fomesafen as the initial herbicides. On the basis of these results, glufosinate and fomesafen should be used for respray situations after inadequate control from glufosinate; and 2,4-D or glufosinate should be used for respray situations following inadequate control from fomesafen where crop tolerance and herbicide product labels allow. Although glufosinate followed by glufosinate was very effective for controlling waterhemp regrowth, caution should be exercised to avoid sequential application of herbicide with the same site of action.

中文翻译：

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在草铵膦或氟虫胺施用失败后控制水麻（Amaranthus tuberculatus）的再生

叶面除草剂对水麻的应用可能导致控制不足，导致随后的再生，这通常需要第二次除草剂应用以防止作物干扰和种子生产。最有效的除草剂和施用时机在水麻从先前的伤害中重新生长的情况下是未知的，例如草铵膦或氟磺胺草醚的施用失败。本研究的目的是确定除草剂的最佳组合和从第一次失败的除草剂施用到连续施用除草剂以控制水麻再生的时间。在单独的裸地实验中，将草铵膦或氟虫草醚的用量降低到 30 厘米的水麻植物上，以模拟初始除草剂应用的失败。草铵膦、氟磺胺草醚、乳多芬、2,4-D、或麦草畏在初次施用后 3、7 或 11 天施用。草铵膦和氟磺胺草胺作为再喷雾处理导致 90% 至 100% 的水麻控制率，无论在草铵膦应用失败后的应用时间如何。在氟虫草醚施用失败后，施用草铵膦或 2,4-D 可控制 87% 至 99% 的水麻。与氟磺胺草胺作为初始除草剂相比，当这些处理采用草铵膦时，氟磺草胺和乳多芬对水麻的控制分别高出 13% 至 21%。基于这些结果，草铵膦控制不力后，应使用草铵膦和氟磺胺草醚进行再喷雾；在农作物耐受性和除草剂产品标签允许的情况下，氟磺草胺控制不充分后，应使用 2,4-D 或草铵膦进行再喷洒。