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Corn+Soybean Digest

Researchers Tackle Waterhemp With Practical Solutions

Midwest farmers struggling with waterhemp issues have a new resource for information thanks to the efforts of university weed scientists Kevin Bradley with University of Missouri, Bob Hartzler with Iowa State University and Dawn Nordby with University of Illinois. The result of this collaboration is Biology and Management of Waterhemp, a brochure created to help farmers minimize yield losses from waterhemp and manage the development of herbicide resistance.

“Waterhemp is probably the number one concern in the Midwest because everyone has it,” Nordby says. “With this publication, we wanted to give a history of how waterhemp went from obscurity just 20 years ago to the leading offender in resistant weeds today.”

Waterhemp density and its potential impacts on yield present the biggest concern for farmers.

“The other issue is that waterhemp control does significantly increase management costs in terms of additional traditional applications,” Hartzler said. “The adaptability of waterhemp to our management practices is the primary reason it has become the number one weed problem for many farmers in the western Corn Belt.”

One of the primary goals of the publication is to address the current waterhemp situation and to encourage farmers to take action now.

“We wanted to paint a pretty clear picture of what will happen when we develop resistance to glyphosate. We will basically lose all our mode of actions for controlling waterhemp,” Nordby says. “But, there are options out there to prevent this and if farmers want to do something about this problem, they need to do it now.”

Bradley supports a preventative approach to managing herbicide-resistant waterhemp.

“The number one treatment method is to avoid applying the same herbicide year after year – that is where prevention meets management,” Bradley says. “The key is mode of action rotation. By using an effective preemergence herbicide like Sonic, Authority First, Valor, Dual II Magnum or any of the other options listed in this publication, you can control populations that have exhibited resistance.”

Biology and Management of Waterhemp is one of many publications in The Glyphosate, Weeds and Crops Series. The series will be comprised of 10 publications, each focusing on a particular aspect of glyphosate stewardship, including individual weeds that have become more problematic to control in Roundup Ready cropping systems. The goal of the series is to create an easy-to-use tool for farmers, retailers and crop advisors that will help them manage weeds and preserve the benefits of the Roundup Ready cropping system technology. Other publications in print in the series include Biology and Management of Horseweed, Biology and Management of Wild Buckwheat, Facts about Glyphosate-Resistant Weeds, Understanding Glyphosate to Increase Performance, Biology and Management of Common Lambsquarters and Biology and Management of Giant Ragweed.

Farmers can attain a copy of these publications through the Glyphosate Stewardship Working Group’s Web site at, or by contacting their state extension weed scientist.

Valent U.S.A. Corporation, BASF Corporation, Bayer CropScience, Dow AgroScience LLC, Dupont, Monsanto Company, Syngenta Crop Protection, Inc., the Indiana Soybean Alliance, the Illinois Soybean Program Operating Board and USDA North Central IPM Competitive Grants Program have all provided the financial support to make communicating this message possible.

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