Tom Barber says the grower would get his or her money’s worth out of the herbicide treatment for a corn field Barber was kneeling in during a presentation from the University of Arkansas System Division of Agriculture’s virtual Corn and Cotton Field Day.

There was only one Palmer amaranth plant and a couple of morning glory vines in sight in the field near Tillar, Ark., where the presentation was recorded just before harvest. But that was one pigweed plant too many, according to Barber.

“This is one of our standard herbicide treatments we compare others to in corn,” said Barber, Extension weed scientist with the University of Arkansas. “This was Dual at a pint and one-third applied at planting followed by Halex GT and Atrazine at V-4. With the (18 inches of) rain we received at Tillar in 24 to 48 hours in June, I’m impressed that it did this good.

“But we still have a pigweed escape here; there’s a morning glory escape. Overall, we’ve got a good plot. If I’m in a big field and this is all we have, I’m probably not worried about a harvest aid, but I do need to be focused on this pigweed plant.”

Rotation

Barber said corn is an excellent rotation crop for cotton and soybeans because growers can use different herbicides in their corn crop than they can in the other two. “But we really need to stay focused on our seed bank management for pigweed at the end of the season. Once we harvest this corn crop, this guy right here could cause us a problem.”

After the corn is harvested, the pigweed plant, which was two-and-a-half feet tall at the time of the recording, will continue to grow and produce large seed heads. It will have almost no competition and keep growing until the first killing frost.

“We need to focus on fields where we have these escapes,” he said. “It's not uncommon – every field may have one or two here or there, but if we only have one pigweed per acre, that's still too many.”

Weed scientists talk about the timeliness of Palmer amaranth management in season with growers needing to focus on controlling pigweed before they reach four or five inches in height.

“So using a herbicide to control this escape is not a viable option,” he noted. “The best option after harvest is to come in here with some tillage or a shredder followed by tillage sometime before this pigweed plant or other pigweeds in the field can produce a viable seed head.

“They'll have plenty of time to do that before killing frost. So moving in here, following harvest, with the shredder, and then in two weeks with tillage or coming back with tillage and rebuilding our beds for next year will be the best way to control this pigweed and manage that Palmer seed bank.”