Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
Glyphosate plus Liberty has been a pretty good treatment to burndown weeds prior to planting double-cropped soybeans in the past few years. With some of the newly released soybean traits, tankmixing glyphosate with Liberty is also an option for postemergence applications. We have found this combination to work very well in many situations but just a few things to keep in mind.
- Neither of these herbicides will provide residual control, so if weeds with long germination periods are present (i.e. Palmer amaranth) consider including a residual herbicide such as Dual, Zidua, Anthem, or Warrant when spraying postemergence.
- Liberty needs good spray coverage to maximize effectiveness, including when its tankmixed with glyphosate. A minimum of 20 gallons per acre should be used with medium to coarse spray droplets.
- I will occasionally see poor control of fall panicum with this combination. I am assuming the Liberty is interfering with glyphosate providing complete control. This is more likely to occur when spraying for burndown with large fall panicum plants, but I have seen it when spraying postemergence to fall panicum that is 3 to 4 inches tall. I have not seen this reduction of control with other annual weed species, but giant foxtail and large crabgrass are the only other grasses in most of my trials. I suspect an increase in glyphosate rate would help reduce the likelihood of this happening, but I have not tested this.