Soil-applied residual herbicide options for soybeans
The Kixor-containing products Sharpen and OpTill can be used any time before soybean emergence (cracking), but are most effective if applied before plants get too big. To optimize marestail control with Sharpen and OpTill, use an adequate spray volume to insure good spray coverage and apply in combination with a methylated seed oil. Ignite herbicide may be the best option as a rescue treatment to burndown bolted marestail prior to planting. No waiting interval required between an Ignite application and planting soybeans, but it will not provide any residual marestail control. Other residual preplant herbicides that can help with burndown and residual marestail control include FirstRate-based herbicides, such as Authority First, Sonic, or Gangster.
- Morningglory. Glyphosate sometimes has trouble controlling morningglory. To help get better control, you can use either Authority-based or Valor-based herbicides preplant or preemergence.
- Crabgrass and other small seed grasses. Glyphosate usually gives good control of most grasses, but producers may want to apply a foundation herbicide to control grasses early, then make just one postemergence glyphosate application later. Prefix, Intrro, Dual II Magnum, Outlook, and Prowl H2O can all provide good early season grass and pigweed control ahead of Roundup Ready soybeans. Of these, Prefix generally provides the best pigweed control, and Prowl H20 the least. Warrant is a new herbicide from Monsanto that can be applied as a postemergence tank-mix partner with glyphosate for residual grass and pigweed control. However, Warrant will not control emerged weeds, so it would not be effective for postemergence control of glyphosate-resistant waterhemp or Palmer amaranth.