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Weed resistance is tough to predictWeed resistance is tough to predict

Weed resistance will come but which weeds will be resistant first is tough to predict.

Tom Bechman 1

July 21, 2015

2 Min Read

Bill Johnson talked about managing current resistant weeds and protecting further weeds from developing recently. He spoke to farmers and dealers at an event hosted by Bayer at their plots in Wayne County.

Related: Glufosinate requires different application techniques than glyphosate

Weed resistance has developed after years of use of various herbicides. There are more than a dozen weeds resistant to glyphosate, and it has garnered attention because they are key weeds, and because it is forcing growers to switch away from the glyphosate-alone or glyphosate as the primary herbicide system that worked for well over a decade.


Actually, there are more weeds resistant to the ALS herbicides, Johnson says. Some 45 weeds are known to be resistant to ALS herbicides.

So far Liberty herbicide for Liberty Link crops has a good track record, Only one weed has shown resistance to glufosinate, the active ingredient in Liberty. It's an Italian ryegrass in California, found in irrigation ditches in a nut grove, likely resulting from years of continuous use.

That doesn't mean other weeds won't develop resistance to glufosinate if it is not handled with good stewardship.

"We know that resistance genes exist to all herbicides, even those not yet invented, out there in the weed population already," Johnson says. 'The key is using management strategies so that resistance does not become an issue down the road."

Someone asked which would be the most likely weeds to develop resistance to glufosinate, or any other chemistry, in the future. "That's a hard one to predict," he says.

Just how hard? Johnson explains that he and other Extension weed specialists from the Corn Belt states talked about future resistance that might develop to glyphosate in a session about 20 years ago, when the technology was new.

Related: Managing Herbicide Resistant Weeds

"Our guesses were that the first resistant weeds to glyphosate would be velvetleaf and morning glory," he notes. "So you can see how good we are at predicting what weeds might become resistant. It's just not possible to do. "

In the coffee shop, it is known as Palmer pigweed. In university circles, it is referred to as Palmer amaranth. Whatever you want to call it, this weed is the No. 1 weed to watch. Stay on top of your control plan with our new free report, Palmer Amaranth: Understanding the Profit Siphon in your Field.

About the Author(s)

Tom Bechman 1

Editor, Indiana Prairie Farm

Tom Bechman is an important cog in the Farm Progress machinery. In addition to serving as editor of Indiana Prairie Farmer, Tom is nationally known for his coverage of Midwest agronomy, conservation, no-till farming, farm management, farm safety, high-tech farming and personal property tax relief. His byline appears monthly in many of the 18 state and regional farm magazines published by Farm Progress.

"I consider it my responsibility and opportunity as a farm magazine editor to supply useful information that will help today's farm families survive and thrive," the veteran editor says.

Tom graduated from Whiteland (Ind.) High School, earned his B.S. in animal science and agricultural education from Purdue University in 1975 and an M.S. in dairy nutrition two years later. He first joined the magazine as a field editor in 1981 after four years as a vocational agriculture teacher.

Tom enjoys interacting with farm families, university specialists and industry leaders, gathering and sifting through loads of information available in agriculture today. "Whenever I find a new idea or a new thought that could either improve someone's life or their income, I consider it a personal challenge to discover how to present it in the most useful form, " he says.

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