Farmers protecting crops from herbicide-resistant superweeds, IL

HARVARD, Ill. — Illinois is one of 22 states in the United States that have documented herbicide-resistant weeds. The state is home to 18 varieties that are resistant to one or more kinds of herbicide. Waterhemp is the most common herbicide-resistant weed in Illinois and the focus of much of the crop science researchd.

Sizing up the effect of these weeds on agriculture is not easy. Locally, no cases of herbicide-resistant weeds have been reported.

"We just haven't had anything come up here," McHenry County Farm Bureau manager Dan Volkers said.

Resistance has been documented in areas south of the county, said Jeff Kimmel, the Marengo service center manager of Conserv FS Inc., an agricultural cooperative that serves northern Illinois and southern Wisconsin.

The spread of such weeds is always a concern, Kimmel said. He estimated that re-treating crops with a different herbicide after discovering resistance could cost $20 to $30 an acre. By rotating chemicals, Kimmel believes the problem can be largely avoided.


Roundup or glyphosate resistance stems in large part from overuse of the chemical. Glyphosate is such an attractive herbicide because it is toxic to a wide range of weeds, safe for mammals, and degrades rapidly. Most of the soybeans, corn and cotton planted today are Roundup Ready crops, which are grown from seeds genetically modified to tolerate Roundup, according to a recent article in the New York Times.

Although major resistance issues haven't popped up in McHenry County yet, Hager said, the first year that resistance becomes a problem is usually the worst.

"That first year is the most costly," he said. "Once you know you have a problem, you can address it proactively."

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