A study was conducted in Stoneville and Verona, MS, to evaluate control of failed stands of corn and soybean with different herbicide treatments and application timings, as well as control of failed stand of corn with soybean planted 1 and 7 DAT (days after treatment). Clethodim plus glyphosate proved most effective across all growth stages of corn with > 90% control 7, 14, and 21 DAT. Paraquat plus metribuzin provided the greatest control of a simulated failed corn stand 3 DAT compared with all other treatments. Pooled across all herbicide treatments, 49% control was achieved when replant occurred 7 DAT compared with 46% following replant 1 DAT. These studies demonstrated clethodim plus glyphosate was most effective in control of failed stands of corn as well as the benefits of not replanting immediately after herbicide treatment. Paraquat and paraquat plus metribuzin both provided > 90% control 3, 7, and 14 DAT.

Field studies were conducted to test three application methods for applying antagonistic herbicide combinations: 1) tank mix (TMX), 2) mix-in-line (MIL), and 3) separate boom (SPB). Sethoxydim applied with bentazon, glyphosate applied with dicamba or 2,4-D, and clethodim applied with dicamba or 2,4-D had higher efficacy when applied using the SPB method. Antagonism of all the herbicide combinations above was observed when applied using the TMX and MIL methods. In some cases, antagonism was avoided when using the SPB method. Three application methods tested in greenhouse studies were 1) TMX, 2) synthetic auxin applied first (AAF), and 3) synthetic auxin applied second (AAS). The AAS application method resulted in higher weed control than the TMX and AAF methods. Analysis done through liquid chromatography mass spectrometry supported the greenhouse results with higher rates of glyphosate detected with the AAS method.