Control Herbicide-Resistant Waterhemp and Palmer Amaranth

Brought to You by Corteva Agriscience

ADVERTORIAL

In Brad Burkhart's 16 years with Corteva Agriscience, he's seen numerous weed shifts in corn fields, resulting in tougher weed control for farmers. That's largely due to the development of herbicide-resistant weeds, caused by the over-reliance on certain chemistries.

"Right or wrong, we kind of abused the system we had because it was easy," points out the market development specialist for Corteva. "We abandoned some of the multiple modes of action principles my grandpa or uncle would've done in the eighties and nineties. What we've learned is we must go back to the basics."

As a result, farmers face a more challenging weed spectrum. "In the last three years, especially in my area of Indiana and eastern Illinois, waterhemp is the most prevalent, tough-to-control weed we're facing now," says Burkhart. "Further south in Illinois into Kentucky, Missouri and the Delta region, it's Palmer amaranth."

CHANGING WEED SPECTRUM

Five years ago, Burkhart says they were fighting marestail, giant ragweed and cocklebur in some places. But lately, especially this year, with all the rain in the eastern Corn Belt, waterhemp has been surging.

Another weed shift pattern that has occurred is earlier waterhemp germination. Traditionally, it was mid-May before waterhemp began emerging. This season, Burkhart saw initial flushes by April 22 in southeast Indiana during an early spring.

From a farmer's perspective, if a burndown herbicide combined with good residual control isn't used, the potential for a waterhemp disaster always exists.

"At our August plot days across Indiana, we showcased Corteva and competitor technology to help farmers understand various weed control plans to combat herbicide-resistant waterhemp," Burkhart says. "When you've got waterhemp populations that are five-way resistant to PPO, glyphosate, atrazine and more, farmers tell you they've got to find a better plan."

That plan includes a layered residual approach using a burndown or preplant application with residual control followed by an in-crop application with residual. Burkhart says that message is really starting to resonate this year.

NEW FORMULATION PROVIDES FLEXIBILITY

Flexibility in a weed control program is critical when seeking a better plan to prevent patches of herbicide-resistant waterhemp or Palmer amaranth from taking over fields.

Thanks to a new Corteva formulation of popular Resicore herbicide, called Resicore(R) REV herbicide, growers will have dramatically increased application flexibility timing from burndown to preplant to in-crop application on corn up to 24 inches tall. With three proven modes of action (clopyralid, mesotrione and acetochlor), farmers can achieve contact and residual control of more than 75 tough broadleaf and grass weeds in conventional, reduced and no-till cropping systems.

"This new corn herbicide we developed gives farmers an excellent option to control difficult waterhemp and Palmer amaranth using the same three modes of action in regular Resicore herbicide," says Burkhart. "We've improved Resicore REV herbicide by encapsulating acetochlor with a safener for less crop response to deliver healthier corn and higher yield potential."

Also improved is tank-mix compatibility with micronutrients, including UAN and ammonium thiosulfate (ATS). "This improvement gives growers the added tank-mix tools they seek for a burndown application, providing flexibility and compatibility that is second to none," Burkhart says.

SPLIT APPLICATION ADVANTAGES

In field trials over the last three corn seasons, Burkhart says they've seen the best control of difficult weeds by using split applications. Start with a burndown or preplant application of multiple modes of action with up to eight weeks of residual control. Follow that with an in-crop spray on four- to six-inch weeds and provide another layered residual.

Burkhart recommends adding a calendar note to track when your initial residual weed control application will diminish, usually six to eight weeks after application. He advises doing this instead of simply watching and waiting for another weed flush before spraying. That's because, eventually, a weather event happens, and applications are delayed.

"I've said for years that the best waterhemp control you can achieve is controlling the waterhemp you never see," Burkhart adds. "Once it starts emerging and you get behind the eight ball with rain delays followed by heat and humidity that causes it to grow one to two inches per day, the challenges are magnified."

Fortunately, Resicore REV herbicide is a better tool for helping farmers reduce this waterhemp and Palmer amaranth weed shift, keeping other tough weeds like marestail, giant ragweed and morningglory from joining the shift.

"Unfortunately, we're going to be battling this waterhemp and Palmer weed shift for the next three to five years," Burkhart says. "We're always trying to innovate and deliver better tools that fit growers' weed management practices. Growers and retailers who used Resicore REV herbicide this year are happy with the fit and flexibility, so look for more product availability in 2025."

For more details about Resicore REV herbicide, talk to your local retailer or Corteva representative.

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-- For immediate product information, technical bulletin, product label and a mixing and handling guide, visit the Resicore REV website at https://www.corteva.us/…

-- Be sure to read and follow label directions.

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