What is in this article?:
- Several good corn weed control options available for Georgia growers
- Plant damage?
- Tropical spiderwort
• Everyone probably should not be using the same program.
When you look at the yield data, there’s not a statistical difference in yield between the recommend postemergence treatments.
POST-HARVEST CONTROL is an important component of controlling troublesome corn weeds such as glyphosate-resistant Palmer amaranth pigweed and tropical spiderwort.
“But this past year, I probably got as many questions on tropical spiderwort as I did on Palmer amaranth. We need to make sure tropical spiderwort doesn’t come back and cause us more problems.
“Most tropical spiderwort doesn’t come up until later in the season, especially if you planted early. If you planted in February or March, your herbicides will probably be effective until June.
“Aim or 2,4-D postemergence work very well on tropical spiderwort, and Sequence plus atrazine or Expert works well in Roundup Ready corn. Aim, Gramoxone or Evik plus Dual is effective at layby.”
What growers do after harvest for tropical spiderwort might be even more important than what they do in-season, says Prostko.
“We can use tillage or two applications of 2,4-D, Gramoxone or Aim. When most of the spiderwort comes up, it’s past the point to where it will influence your yields.”
The other bane to corn growers’ existence is morningglory, he says.
“I wish I could tell you we had the answer, but because of where we farm, we’ll always be battling morningglory. Our crop comes up so early, and the sunlight gets through the canopy early, so nothing really lasts for the full length of our growing season.
“That’s why you should use as much atrazine as possible, some at planting and some at early postemergence.”
Other herbicides that work on morningglory include 2,4-D, Clarity, Status, Aim and ET, he says.
“We could tank-mix those with glyphosate if we needed to. Liberty is a lot more effective on morningglory than glyphosate. It’s even possible to consider getting the corn out of the field early, before morningglory becomes too much of a problem.”
Prostko advises corn producers to be vigilant in rotating chemistries with different modes of action.
“Most farmers in Georgia grow multiple crops, and in the last two years we’ve seen a significant increase in the use of Dual and Warrant, and now there’s Zidua.
“These are great products, but they all have the same mode of action. Watch how you use these products. If you don’t, you could create resistance problems with this mode of action.
“We don’t have it yet, and we want to keep it that way. If you’re rotating these products, it doesn’t mean you’re rotating modes of action.”