Farm Progress is part of the Informa Markets Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Serving: Central

Arkansas rice: History lesson: glyphosate-resistant pigweed

I recently spent a morning with Bob Scott, University of Arkansas weed scientist, looking at his Palmer pigweed control research plots in the Newport, Ark., area.

I have a long history working with pigweeds in that area as a weed scientist in the same job Bob now has. It began when I was a young Ph.D. who thought he had an answer for about any problem a farmer could come up with.

I thought I had done a particularly good job speaking to a farmer group in that area in the late 1970s and during the question and answer session several farmers asked why they were not controlling pigweeds with Treflan anymore. I answered by telling them that they were obviously either not using a high enough rate or they were not incorporating it properly or both.

The same farmers came back to the meeting the next year and reported that they had followed my suggestions and failed again. I made some more suggestions in subsequent years, and after a couple more failures, one of the farmers suggested that since I knew so much, why didn't I just come up the next spring and show them how to do it.

I just knew it had to be them since farmers in other areas of the state were not having any problem controlling pigweeds with Treflan. Anxious to strut my stuff, I accepted the challenge and promptly went up there and failed miserably.

Those failures, and subsequent knowledge about pigweed resistance to the DNA herbicides like Treflan, were the beginning of a lot of Palmer pigweed research in the northeast Arkansas area.

It was not long before Scepter was introduced as a soybean herbicide. It provided excellent pigweed control for a couple of years but resistance occurred quickly and we were back to square one.

On the sandy soils in the Newport area we conducted several research trials each year with every combination of herbicides we could think of or that the companies could come up with for us to try. Treatments such as Dual or Treflan plus Scepter or Canopy followed by one or two applications of Reflex would provide around 80 percent control, but the plots would still be so overgrown they could not be harvested. In contrast, even single treatments out of these combinations would give complete control at our Little Rock location

The clock rolled forward a few short years and we were able to include Roundup Ready soybeans into the research trials at Newport. All of a sudden, Palmer pigweed control was easy and to some farmers it was fun. A lot of farmers vented a lot of frustration from years of pigweed control failures with Roundup Ready technology.

I remember one farmer bragging on how well he had done with Roundup the first year the technology was available to farmers. I asked him if it took two applications like I said instead of the one application he was planning on. His response was it actually took three but he was having so much fun killing them that he didn't care.

We have now rolled the clock ahead another 10 or so years and we have this thing called glyphosate-resistant Palmer pigweed. The more pigweed populations the university guys test from fields where glyphosate failures are occurring, the more resistant populations they are confirming. The Palmer pigweed population is extremely diverse.

I actually predicted it would be the pigweeds where glyphosate resistance first occurred. I was wrong on that count but will maintain my prediction that pigweed resistance will spread rapidly and quickly become the worst glyphosate resistance problem we have.

The weed science group at the University of Arkansas is to be commended for taking on the weed resistance issue. They are moving forward quickly with both research and an education program.

The obvious question is where do we go from glyphosate? That is what Bob Scott is trying to answer at Newport.

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.