No Easy Solutions for Cotton Weed Control

During an episode of the Cotton Grower® magazine’s Cotton Companion podcast, Extension Weed Scientists Dr. Larry Steckel (Tennessee) and Dr. Tom Barber (Arkansas) discussed the current status of cotton weed control, including ongoing legal and regulatory challenges.  

Q: What’s the impact of metabolic resistance? 

Steckel: We understand specific site resistance that’s been going on for years. But metabolic resistance has been building up in the background. We’re now seeing things like Dual [Magnum] (Syngenta) not lasting as long as it did several years ago. That’s metabolic. Dicamba resistance is probably metabolic. I think a lot of those things are linked, and they have huge ramifications on where we go forward for control.  

Barber: We’ve been using the same herbicides for decades, so it’s understandable that we’re just not going to have the response we used to. We don’t have a lot of herbicide options to use on some pigweed populations in Northeast Arkansas. Growers really have to know what kind of pigweed population they’re dealing with in order to develop a weed control program. It’s why we push the multiple residual/multiple mode of action approach to help counteract some of the metabolic resistance.  

Lose a few key herbicides, and cotton growers could be facing this — or worse — in their fields. (Photo: Jim Steadman) 

 

Q: Regulatory challenges continue on established herbicides. What happens if the auxins or other important products are lost?  

Steckel: We’ll be living with a lot of pigweed. Diuron (Alligare) is important in our residual program and now it could be gone. It’s really restricting the tools to the point where we’re living with a lot of weeds. I’m not sure how we’re going to raise a crop without some of those herbicides.  

Barber: Some growers in Northeast Arkansas already have hand-weeding crews on the payroll to help take care of escapes. That just adds another expense to the cost of production, and I don’t think we could effectively manage like that on every acre. If we lose Diuron and Cotoran (Corteva AgriScience), I just really don’t have an answer right now.  

Q: What’s the latest on glufosinate resistance? 

Barber: So far, areas that we’ve identified with glufosinate resistance are still sensitive to the auxin products, and growers have shifted to an Enlist (Corteva AgriScience) or Xtend (Bayer Crop Science) system to manage it with dicamba or 2,4-D. We do have some populations that are resistant to those or at least have increased tolerance. I don’t think the glufosinate problem is metabolic.  

Q: What about new products and new uses for older products?  

Steckel: We need every little bit of help we can get. We looked at Staple (Corteva) pre-emerge and picked up a little bit of pigweed control. We took 3.2 ounces of Zidua (BASF), made it into a slurry, and put it out with a grower’s fertilizer blend. This is the closest we can get to a layby, and heavy dew will activate it. I’m really high on this use. We’re also looking at a similar option with Brake (SePRO).  

Barber: Something new from a technology standpoint in cotton is the BASF’s Axant Flex trait and Alite 27 herbicide [pending registration]. It’s a system that we can build a good pigweed program around, especially if we lose Diuron and Cotoran.  

Steckel: It seems like we can lose any of these herbicides at the drop of a hat. It’s evolution, and it’s supposed to be slow. But it’s fast. It seems like 5 to 7 years is about all we can get anymore.