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Controlling herbicide resistance takes persuading

Brad Haire brad-haire-farm-press-pigweed-smallish-cotton-GA.jpg
Charlie Cahoon urges farmers to be on the lookout for Palmer amaranth surviving 2,4-D or dicamba.
Integrated pest management is key for tackling herbicide resistance.

The answers to managing herbicide resistance are fairly simple, the hard part comes in persuading farmers to implement the practices that do the most good.

Charlie Cahoon, North Carolina State University Extension weed specialist, says integrated pest management is key. Farmers need to rotate herbicide chemistries and turn to cultural and mechanical methods to alleviate some of the pressure on over-used herbicides.

“As Extension specialists, we’ve been using fire and brimstone. We think one of the tactics that drives folks to change practices on their farm is to scare them to death,” Cahoon said in a presentation at the virtual North Carolina Crop Protection School Dec. 2.

“My daddy has trained bird dogs his whole life. He used to think the way to train a dog was to use discipline. My three-year old daughter just taught him it is quite easy to train a dog with a handful of treats. There are studies to back this up, rewarding good behavior. I think that’s what we are having to learn right now with pesticide resistance: How do we get our growers to put into practice the tactics we’ve been preaching for years,” Cahoon said.

One option, Cahoon says, is providing farmers an economic incentive to implement integrated pest management practices. But where will the incentive come from?

Companies do have inventive programs, but Cahoon believes the incentive programs must cross company lines to encourage farmers to rotate modes of action and implement cultural practices to better control weeds.

Moreover, incentives must be in place for farmers to use cover crops, better crop rotation and other tools such as harvest weed seed control. “It really needs to be a whole industry initiative where we all get on the same page and say, ‘hey let’s reward some of these good behaviors and try to get ahead of this pesticide resistance issue,” Cahoon said.

Herbicide resistance is a problem that’s not going away.

In North Carolina, Cahoon says there is widespread Palmer amaranth resistance to glyphosate and ALS inhibitors, plus expected resistance to PPO inhibitors. There is common ragweed resistance to glyphosate and ALS inhibitors, primarily in the eastern part of the state. And there is widespread Italian ryegrass resistance to ALS inhibitors, mostly in the southern Piedmont.

Looking to the future, Cahoon said he won’t be surprised if North Carolina farmers begin to see resistance to group 15 herbicides, such a Dual, Warrant, Harness and Zidua.

“We use them repeatedly in most of our crops —  corn, soybeans, cotton, peanuts, and sweet potatoes. We are putting quite a bit of pressure on the group 15s, and there is already group 15 Palmer amaranth resistance in Arkansas and also a cousin to Palmer amaranth, waterhemp, is resistant to the group 15s in Illinois,” Cahoon said.

And as the use of dicamba and 2,4-D continues to grow, resistance to these chemistries can be expected as well. “There is evidence we are abusing dicamba and 2,4-D like we did glyphosate. That is unacceptable,” Cahoon said.

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