Weather Forecast


Crop expo addresses weed control

GRAND FORKS, N. D. — Upper Midwest farmers are on the road to perdition, or utter ruin, unless they change the way they control weeds, according to Phillip Glogoza, a University of Minnesota Extension agronomist.

“Herbicide resistance is gonna happen,” he says. “Our goal, if nothing else, should be to slow down on that road or to make as much effort as possible to prolong the value of the technology we have, in terms of herbicide.”

Glogoza, who’s stationed in Moorhead, Minn., spoke Feb. 19 at the annual International Crop Expo at the Alerus Center in Grand Forks, N.D.  The show, which combines activities sponsored by small grains, potato and soybean groups, was expected to draw 5,000 people and about 175 exhibits.

Resistance to herbicide, particularly glyphosate, which often is sold under the brand name Roundup, continues to grow. Waterhemp, kochia and ragweed are among the weeds developing resistance in the Upper Midwest.

Unfortunately, farmers sometimes say, ‘“Dead weeds don’t breed resistance.’ They’re right. It’s the survivors that breed resistance,” Glogoza said.

“Resistance is a numbers game,” so limiting the number of survivors is essential, he said.

Farmers’ short-term goal in fighting weeds is preserving crop yields. But their long-term goal needs to be depleting weed seed reserves and preventing additional weed seed from entering the seed bank, he said.

In tackling weeds long term, it’s important to remember that herbicides kill in different ways. Mode of action is the overall method in which an herbicide affects a plant. Site of action is the specific process in the plant that herbicide disrupts to interfere with its growth and development.

In fighting weeds and herbicide resistance, “You need to mix it up,” Glogoza said.

“One of your goals as a good weed manager is to use a diversity of site-of-action herbicides. Preferably, we’d like to see two or three different sites of action being used in a (growing) season,” he said.

His advice to farmers:

“Start planning. Sit down and make charts. (Say), ‘I’ve got these weeds in this field. These are the modes of action that I need to try to get into that field in order to get effective management and avoid that road to perdition,”’ he said.

Rotating crops on a field also is an important tool. Crop rotation, including adding small grains to a corn-soybean rotation, allows farmers to utilize more modes of action in fighting a weed, thereby reducing its ability to develop herbicide resistance, Glogoza said.

Other recommendations from Glogoza:

  • Identify main target weeds.

  • Pick the most effective sites of action available, making sure to “mix it up.”

  • Use pre-emergent herbicides whenever possible.

  • Don’t let escapes (weeds that avoided earlier herbicide treatments) produce seeds if at all possible.

  • Focus on early season weed control.