A wet and mostly cold March has us well behind the pace for burndown. As weather permits, corn planting will take priority followed by burndown for grain sorghum.
What should my burndown strategy be for those crops with planting time upon us?
In corn, a burndown at planting (in Tennessee) of Gramoxone + atrazine can be an effective choice. Another good option would be glyphosate + Verdict or Sharpen which should be both effective and allow for flexibility if the corn stand is lost and then replanted to soybean.
The bottom line in corn is that even if some marestail recovers from the burndown application herbicides like Halex GT or Capreno spiked with either atrazine or Status have been very effective controlling large marestail in our research.
In the case of grain sorghum, please be aware that dicamba and 2,4-D can be used pre-plant for burndown but not pre-emergence. The reason for this is that rain can wash those herbicides into the planting slot and harm stand establishment.
In grain sorghum, a burndown at planting of Gramoxone can be an effective choice. Another good option would be glyphosate + Verdict or Sharpen which should be both effective and allow for flexibility if the grain sorghum stand is lost and then replanted to soybean. Marestail that survives burndown can be fairly easily controlled with Huskie spiked with atrazine.
Please note that herbicides we commonly use in corn like Princep and Status are not labeled in grain sorghum due to crop injury potential. Even atrazine should be used with caution pre emergence as some stand establishment problems have been documented. Post emergence atrazine applications are fine.
In the case of corn and grain sorghum, it will be more critical to control Italian ryegrass than marestail before the crop emerges. In both crops there is no herbicide that can be applied post emergence that will control ryegrass. Sequential applications of Gramoxone separated by a week to 10 days can be an effective ryegrass option pre-crop emergence. In corn, Select Max can be applied 6 days before planting at 6 oz/A and when tankmixed with glyphosate has proven to be fairly effective. The plant back to grain sorghum from a Select Max application is 30 days.
In some cases where the plan is to plant some fields to soybean in early April, dicamba, which has been our “go to” glyphosate-resistant horseweed herbicide is no longer an option. Sharpen or Verdict would be a good new “go to” in these situations for soybean burndown.