Herbicide-resistant weeds heading north

N. Dakota, Minnesota brace for glyphosate resistance

Expect an explosion of glyphosate-resistant weeds in North Dakota this year, says a leading weed specialist.

Herbicide-resistant weeds are becoming more common in the northern United States and are also spreading northwest toward southern Manitoba.

But this year’s seeding problems in North Dakota and Minnesota mean that farmers in those states may not do what they know they should do to control the problem.

Manitoba farmers should take on the challenge and show American farmers how to avoid the nightmare presently engulfing millions of acres south of the line.

“You guys have the chance to show the rest of the world how to do this correctly,” said Jeff Stachler, a herbicide-tolerant weed expert, during a May 31 interview in Fargo, N.D.

“If you guys want to show the U.S. how to do it right, you have the chance to do it right.”

Doing it right means killing herbicide resistant weeds before crops emerge.

After that, growers should watch like a hawk for signs of possible resistance in glyphosate-tolerant crops. 

If any weeds survive glyphosate application, there’s a problem. 

Those weeds must be pulled by hand or the problem will explode. 

“You have to get rid of the survivors,” said Stachler, who worked in weed control in Ohio, where problems are widespread, before moving to North Dakota for a weed control position with North Dakota State University. He is now a consultant who advises farmers and agronomists in a number of U.S. states.


“The survivor has to be destroyed.”

The 2014 crop season will be bad, Stachler predicts, because even the North Dakota and Minnesota farmers who intended to apply pre-emergent, soil-applied herbicides for crops like Roundup-Ready sugar beets have been stymied by the weather. 

As was the case in parts of Manitoba, a late and cool spring has brought frequent rain and prevented farmers in many areas from seeding until right on the cusp of crop insurance and maturity deadlines.

Seeding now has to take priority over pre-seed burnoff and other fieldwork.

That means the early-crippling and killing of possibly resistant weeds won’t happen in most crops and those weeds will be left for post-emergent spraying.

But that brings great risks, Stachler said. If the soil conditions are bad for seeding because of saturation, then post-seeding rains can prevent post-emergent spraying until the weeds have grown large and hard to control. 

Stachler is one of the weed experts insisting on “zero tolerance” for glyphosate-resistant and multiple-herbicide-resistant weeds if they are found in fields.

Zero-tolerance is the only way to prevent an ever-increasing seed bank of resistance from developing. 

Glyphosate-resistant weeds like waterhemp, common ragweed, giant ragweed and kochia have been steadily advancing northward toward Manitoba in recent years, with floods helping spread them down the valleys.

One of the surprising sites of resistant weeds is Mahnomen County in Minnesota, near the Canadian border. That area has become mostly corn-soybean in recent years, abandoning crops like wheat, sunflowers and edible beans that employ different in-crop herbicides. 


Now, the glyphosate resistant weeds common in southern Minnesota are up there too.

The problem doesn’t just exist south of the border, or on western areas of the Canadian Prairies. Glyphosate-resistant weeds have appeared in Manitoba, with two fields of glyphosate-resistant kochia found in 2013 after almost 300 fields were examined. 

Stachler urged Manitoba farmers against complacency. Glyphosate-resistant and multi-herbicide-resistant weeds will probably appear, but if farmers act aggressively and hand-pull small weed patches that appear to survive spraying, they can prevent the problem becoming widespread.

Key to spotting an incipient problem is seeing a patch of weeds showing different responses to a herbicide treatment. 

If some of the same variety of weeds die, some seem hurt and damaged, but some seem OK, then a resistance problem is developing, Stachler said.

“It’s that continuum of response you’re looking for,” said Stachler, who has just returned from a trip to Michigan where resistance is a growing and grave problem.

He urged farmers to forget dreams of the chemical industry coming up with a new, easy herbicide solution to glyphosate and multiple resistance. 

He said no new miracle chemicals are coming, which means farmers must pay more attention to proper application and usage methods, and to other weed control techniques to prolong the effectiveness of the chemicals they have.

“It’s fine until you have a plant that’s resistant to everything,” said Stachler.