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Summit: Resistant weeds growing

By Staff | Mar 15, 2016

“A SUSTAINABLE RESPONSE to Glyphosate Weeds” was one of the workshop sessions offered March 4 at the Global Ag Summit in Sioux Center. Here, one of the break-out sessions asked groups to discuss several issues, such as whether or not a Christian approach to weed management should look different than methods practiced today, whether or not it’s responsible to rely on aggressive tilling for weed management.

SIOUX CENTER – A college professor offered new approaches for producers to get a handle on glyphosate-resistant weeds, a problem in both the U.S. and Canada.

Dr. Peter H. Sikkema, professor of field crops and weed management at the University of Guelph in Ridgetown, Ontario, Canada, spoke last week at the Global Ag Summit in Sioux Center.

The most troublesome glyphosate-resistant weeds in Ontario, Sikkema said, are giant ragweed, marestail and waterhemp. Resistance problems began showing up in 2008.

He said in Ontario, the numbers of species of these weeds is increasing, along with the number of acres affected globally. Yield losses have shown up greater than 60 percent in corn and soybeans where farmers didn’t do anything to address the problem.

Sikkema said the first herbicide-resistant weeds globally showed up in 1957 on a highway near Milton, Ontario, Canada.

Since then there have been more than 450 weed bio types that have resistance to herbicides.

He said the first glyphosate-resistant weed was found in 1996 in Australia, and now there are 32 types of these weeds found in the world. Five of those weeds are found in Canada (four in Ontario) while 14 are in the United States.

Sikkema said the glyphosate-resistant weed problem moved 500 miles from the U.S. border to Quebec in a four-year period – 2010 to 2014.

The whole issue came about, he said, because producers became over-reliant on glyphosate for weed control.

Sikkema said there are practices producers can employ to try to control the glyphosate-resistant weed problem. They include:

  • Adding non-Roundup Ready crops to rotations, or adding an additional non-Roundup Ready crop to diversified crop rotations.
  • Applying multiple herbicide modes-of-action on every acre, every year.
  • Strategically incorporating some of the alternate/new technologies when they become available.
  • Including tillage at strategic points in diversified crop rotations.
  • Seeding a cover crop after winter wheat harvest to reduce weed emergence.
  • Inter-seeding a cover crop in corn to reduce weed emergence.
  • Making near-perfect weed control an objective in order to reduce weed seed return to the soil.

Due to the event’s Christian theme, those attending were asked if it was responsible to rely on aggressive tillage for weed management, knowing that in many areas of the world the topsoil is less than 6 inches deep.

Sikkema warned producers to take extra care of top soils to keep ground productive enough to sustain life.

One question asked whether synthetic chemical herbicides should be preserved/protected for the benefit of future farmers and food production.

One attendee argued the products should be protected, saying chemicals always have a place in agriculture, but producers have to be responsible on how to apply them.

Sikkema’s personal opinion is that there are times when overuse of tillage creates more harm for the environment than the “judicious use of herbicides.”

Finally, they were asked if, as Christians, weed management practices should look different in comparison with global norms for agriculture.

Greg De Haan, of Hollandale, Minnesota, said over-application of Roundup has changed his operation, as waterhemp has taken over.

“I got my cultivator out again because I had to,” he said, adding that, even though he was applying according to label directions, others around him were not, and he’s also paying the price.

“Christians and non-Christians alike were not being as careful as they should have been and everyone is paying the price,” De Haan said. “Yes, there should be a difference, but it’s not as easy as you would think.”

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