The XtendFlex and Enlist technologies offer great control of glyphosate-resistant Palmer amaranth in cotton if used properly, but Alan York encourages farmers not to rely on the new technology alone and to continue to use multiple modes of action in weed management programs.

Speaking at winter cotton meetings this year, York, weed specialist and William Neal Reynolds distinguished professor of crop science at North Carolina State University, urged farmers to be very timely with their applications in XtendFlex and Enlist cotton. He also said cotton farmers need to continue to use tank mixes in their post-emergence applications. He is also promoting the use of residual herbicides up front.

“I want to encourage you to not relegate this technology to salvage control. You get a whole lot better control with small weeds. Also, if we make timely applications, we’re going to reduce early season weed competition,” York said at the cotton meeting in Clinton.

“We made progress with Palmer amaranth in the last 10 years. I don’t see the absolute disaster fields like we did initially. One of the things that allowed us to get here was the use of residual herbicides. I don’t want to see us back sliding.”

York said North Carolina could potentially see resistance to auxin herbicides which shows the importance of not relying on one technology alone for weed control. Farmers still need to use multiple mechanisms of action.

“You need as much diversity in your weed control program as you can get for resistance management. If you can’t rotate crops, then rotate your chemistry. In the case of these auxin herbicides, if I’m going to rotate crops, for example cotton and corn, and I want to use one of these auxins in my cotton crop then I want to minimize my use of auxins on that corn crop. I’m reducing selection pressure,” he said.

Non-chemical control is important as well.

“We are seeing more interest in very heavy cover crops such as rye,” York said. “You put fertilizer on it and get it to be seven feet tall and thick then roll it down where you have a layer of solid residue on the surface, three to four inches deep. Small weeds can’t push through that. Some weeds like Palmer amaranth need light to germinate; the weeds can’t get the light. This will do a good job helping with weed control if you have the equipment to plant into it.”

York noted that crop tolerance to auxin herbicides with XtendFlex and Enlist cotton is good, but cotton plants may see some injury. “We think it is cosmetic injury, but you need to be aware that it can happen so it won’t scare you to death,” he said.

Farmers are still awaiting approval from the Environmental Protection Agency for tank mixes with Enlist Duo, Engenia, and XtendiMax, and York remains optimistic that approval will come in time for use season this year. When approval comes, York advises farmers to use a residual with these auxin herbicides in their post-emergence program.

“I want to encourage you to be very timely with POST application of these new products. Small weeds are going to be controlled better,” he said.