Corn+Soybean Digest

Think Different: Weed Denial Not Good


As a farm journalist who has logged vast windshield time on Corn Belt blue highways every summer for umpteen years, something struck me different looking across bean fields in 2011. In a word: statues. Of tall, random and proud waterhemp.

The weed-free soybeans fields that used to stretch across the horizon into tomorrow are gone. And if you don't 'think different' now about management of glyphosate-resistant waterhemp, you'll pay later as each prolific weed can scatter 300,000 or more herbicide-resistant seeds at harvest. If you're not controlling 99-100% of them, you're already behind the proverbial eight-ball.

I was not alone in my prognosis. Midwest weed scientists, who have been warning growers for numerous years, proclaimed 2011 the breakout year for glyphosate-resistant waterhemp and marestail. And in many cases, these weeds resist multiple herbicide classes, adding to the management complexity of these superweeds.

I also decided to visit Arkansas to view soybean fields literally overrun by waterhemp's pigweed cousin, glyphosate-resistant Palmer amaranth. And that was scary, to say the least. Bob Scott, University of Arkansas weed scientist, showed me what happens when growers missed spraying 2-in.

Palmer – it turns into 6-ft.-tall Palmer, loaded with resistant seed.

Scott sends a warning to Midwest growers after he visited Indiana last summer, seeing waterhemp and giant ragweed rise above the soybeans. "If you think there's not a serious weed-resistance problem developing with glyphosate, then you're not paying attention. You're in denial. Arkansas looked the same way four or five years ago, when farmers were in denial here," he says.

 Today, attempted control of this superweed now involves residual herbicides, multiple modes of action, multiple postemergence sprays – all to the tune of $60-80/acre.

Arkansas growers, along with Tennessee and Georgia, were all in denial, continuing to spray glyphosate only, until it was too late. Apparently, you may be following that denial path as well, since only 30% of Midwest soybean growers use a soil-applied residual herbicide, according to industry sales figures in 2011.

Iowa State University weed specialist Mike Owen calls the glyphosate-resistant weed outbreak "a train wreck that is not slowing down at all." University of Illinois weed scientist Aaron Hager says the best way to manage multiple herbicide-resistant weeds is to never get them. "Unfortunately, that horse has left the barn, whether farmers admit it or not," he adds. (See our story on page 18 to read more about this weed revolt.)

Bryan Young, weed scientist at Southern Illinois University, estimates that glyphosate-resistant waterhemp has invaded 5-6 million acres in a wide swath across the state.

You get the picture. I wish you success. I sincerely thank you for reading and for being willing to Think Different.


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.