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Waterhemp shows resistance to Group 15 herbicides

Waterhemp shows resistance to Group 15 herbicides

Allowing this weed to thrive can result in significant yield loss, a weed scientist said

By Diego Flammini
Staff Writer

Cash croppers could have one less herbicide option when trying to manage an invasive weed.

Waterhemp, which is already resistant to Group 2, 4, 5, 9, 14 and 27 chemistry, is showing resistance to labelled rates of Group 15 herbicides (which include Dual, Surpass and Outlook) a recent University of Illinois (U of I) study found.

The weed can increase its self-protection against herbicides, said Adam Davis, a U of I weed scientist and co-author of the study.

“We’re seeing metabolic resistance in waterhemp,” he told “The plants are beefing up their general protections against toxic compounds. I believe we could see Group 15 resistance evolve in other areas because we’re seeing waterhemp resistance to multiple modes of action in corn and soybean cropping systems in different parts of the U.S.”

The weed, and ones like it, can have significant implications for corn and soybean yields if allowed to heavily populate a field.

“With full infestations of common waterhemp, yield losses of up to 40 percent are pretty common,” Davis said. “This (weed) is definitely something growers need to pay attention to.”

And farmers are paying attention.

Don Guinnip, a cash crop producer from Marshall, Ill., has run into herbicide-resistant waterhemp.

Growers may have to change their herbicide programs to keep this weed under control, he said.

“I’m right now drilling a field of soybeans that had waterhemp,” he told “Some of the waterhemp that was burned down just rejuvenated itself. I think, if we went back (and applied) 2,4-D earlier when the weed was small, it would’ve been a good option for us. I’m thinking other farmers will revisit their herbicide programs too to find out what works.”

Bayer Crop Science photo

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