Home / Crops / Pesticides / Herbicides / How to deal with glyphosate weed shifts

How to deal with glyphosate weed shifts

Agriculture.com Staff 12/13/2007 @ 8:46am

A simple definition of a weed is a plant out of place. Overreliance on glyphosate in corn and soybeans is creating a new spin on that definition -- weeds turning up out of place.

"We're seeing some pretty weird stuff come in," says Mike Owen, Iowa State University Extension weeds specialist.

Ever heard of wild parsnip? This jewel is typically found in waste areas. Yet, it's turning up in cornfields. Ditto for nontypical row-crop weeds like pokeweed, evening primrose, and horsetail.

The culprit? Selection pressure resulting from overreliance on glyphosate-resistant systems is shifting the makeup of weed communities.

Each herbicide has weeds that are inherently tolerant to them. In glyphosate's case, tolerant weeds include common lambsquarters, giant ragweed, velvetleaf, and Asiatic dayflower. However, the less-common weeds named previously are also surfacing in row crops where glyphosate-tolerant crops have been grown.

"Its (glyphosate's) increased adoption in corn will make for greater selection pressure resulting in 'new' weed management issues," says Owen. "We are pushing the system hard enough; now it's beginning to push back."

The good news there is new technology coming on board to complement and to offer alternatives to glyphosate. This technology features new herbicide-resistant crops like:

  • Liberty Link soybeans from Bayer CropScience. After limited marketing this year, Bayer plans a full launch in 2009.
  • Dicamba-resistant soybeans, which Monsanto plans to offer to farmers in 2012 or 2013.
  • Optimum GAT, an alternative glyphosate technology that DuPont and Pioneer Hi-Bred International plan to introduce in soybeans in 2009 and corn in 2010.
  • SmartStax, an eight-way corn hybrid stack that contains multiple methods of insect and herbicide resistance. Monsanto and Dow AgroSciences plan to launch SmartStax in 2010.
  • Dow AgroSciences officials say Dow AgroSciences Herbicide Tolerance (DHT) will boost control of hard-to-kill broadleaves and reduce selection pressure for glyphosate resistance. It's slated for corn by 2012, and slated for soybeans by 2013 or 2014.


A simple definition of a weed is a plant out of place. Overreliance on glyphosate in corn and soybeans is creating a new spin on that definition -- weeds turning up out of place.

CancelPost Comment
MORE FROM AGRICULTURE.COM STAFF more +

Farm and ranch risk management resources By: 07/07/2010 @ 9:10am Government resources USDA Risk Management Agency Download free insurance program and…

Major types of crop insurance policies By: 07/07/2010 @ 9:10am Crop insurance for major field crops comes in two types: yield-based coverage that pays an…

Marketing 101 - Are options the right tool… By: 07/07/2010 @ 9:10am "If you are looking for a low risk way to protect yourself against prices moving either higher or…

MEDIA CENTERmore +
This container should display a .swf file. If not, you may need to upgrade your Flash player.
The Future of Livestock Production
Agriculture.com

FREE MEMBERSHIP!

CLOSE [X]