Managing for the Future, Preserving Today's Technology

New brochure gives farmers the edge on giant ragweed

WEST LAFAYETTE, Ind. (September 24, 2007)-With the development of herbicide resistant giant ragweed on the horizon, Midwest corn and soybean farmers have a new education resource thanks to the efforts of a group of university weed scientists led by Bill Johnson with Purdue University. The result of this collaboration is Biology and Management of Giant Ragweed, a brochure created to help farmers minimize yield losses from giant ragweed and manage the development of herbicide resistance.

In addition to Johnson, the group of weed scientists included Mark Loux and Jeff Stachler with Ohio State University, Glenn Nice and Andy Westhoven with Purdue University, Dawn Nordby with University of Illinois and Christy Sprague with Michigan State University.

The brochure provides a detailed description of giant ragweed anatomy from seedlings to pollination patterns and offers recommendations for identification and management strategies. By being able to identify giant ragweed and understand how a population can become resistant, the researchers hope to see farmers modify their herbicide application practices and better manage current technology.

"Glyphosate and Roundup Ready® products are a once-in-a-lifetime resource but if we're not careful about how we use this technology we will greatly reduce its effectiveness and simplicity," Bill Johnson said. "We hope this information will help farmers recognize the worst weed problems in their fields and change their treatment methods by increasing the diversity in their herbicide rotations."

Farmers are facing staggering yield losses from giant ragweed. "We believe giant ragweed is the most competitive broadleaf weed in soybeans in the eastern cornbelt and can cause significant yield loss as soybeans compete for light, water and nutrients," Johnson said. "Soybean crops stand to suffer yield losses of up to 80 percent and corn up to 70 percent. By increasing herbicide diversity we can control giant ragweed and other weeds more effectively and also slow the inevitable development of glyphosate-resistant weed populations."

The brochure offers detailed management guidelines for both corn and soybean crops and reinforces the importance of combining a pre and post herbicide treatment with multiple modes of action as the most effective herbicide program.

Biology and Management of Giant Ragweed 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 which 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 and Understanding Glyphosate to Increase Performance.

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.