Pigweed plants are already germinating. With soil temps at 68 and 64 at the 2 inch and 4 inch level, this isn’t surprising.
Remember: whether you’re spraying or harrowing to control pigweed, the size of the weed is critical. You can’t kill a large pigweed with one pass of a disk, and bedding pigweed doesn’t kill them either. Unless a person is willing to be in a field and disk multiple times (weekly, or every few weeks) from Feb. or March until planting day, the field will not be clean at planting.
With no residual herbicide, seeds germinate quickly after disking. Using paraquat is an option, but needs to be applied correctly, and possibly more than once before planting. Timeliness is important with paraquat sprays.
Here is a pigweed with regrowth 2 weeks after being bedded and then sprayed with paraquat. Don’t bed live pigweed and don’t wait until the weeds are too large to spray.
What’s the solution? Use a pre emergent herbicide. Whether it’s cotton or peanut being planted, you can disk the field (or use burn down herbicide) and then put a pre emergent herbicide out. Products like valor give nearly 30 days of residual control.
For peanut land Valor can be applied prior to planting and there’s no waiting period. There are also other pre-emergent herbicides available depending on the crop grown.
For cotton, on strip till land Valor can be applied 10 days ahead of planting as long as strip till operation (including a ripper shank) occurs between applying Valor and planting
Options In Both No-Till And Conventional Cotton
For no till or when the strip is run prior to spraying you’ll need 21 to 28 days (28 days following a disk because no residue) between application and planting and add 7 more days if using reflex.
If you are planting cotton conventionally, consider the split reflex system. The split reflex system works real well, especially in dryland fields. Incorporate 12 oz Reflex + yellow herbicide in moist soil then put another 8 to 10 oz of Reflex with Warrant or Direx behind planting and you are off to a great start. Stay timely with POST applications.
The key is you have to start clean at planting, and the only way to do that is to not let pigweed get too large to control before planting.