National Summit on
Strategies to Manage
Herbicide-Resistant Weeds
PROCEEDINGS OF A WORKSHOP
Organized by the
Planning Committee for a National Summit on
Strategies to Manage Herbicide-Resistant Weeds
Board on Agriculture and Natural Resources
Division on Earth and Life Studies
NATIONAL RESEARCH COUNCIL
OF THE NATIONAL ACADEMIES
THE NATIONAL ACADEMIES PRESS
Washington, D.C.
www.nap.edu
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NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.
This study was funded by the Herbicide Resistance Action Committee, the Iowa Soybean Association, the National Cotton Council of America, the United Soybean Board, the U.S. Department of Agriculture, Economic Research Service; the U.S. Department of Agriculture, National Institute of Food and Agriculture; and the Weed Science Society of America. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.
International Standard Book Number-13: 978-0-309-26556-0
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Cover: Photos credits from top of the page: waterhemp, U.S. Department of Agriculture, Agricultural Research Service; wheat, U.S. Department of Agriculture; johnsongrass, U.S. Department of Agriculture, Agricultural Research Service (Barry Fitzgerald); sugarbeets, U.S. Department of Agriculture; farmer and corn, ©iStockphoto.com/Chris Fertnig; marestail, Ohio State University Extension; alfalfa, U.S. Department of Agriculture, Agricultural Research Service.
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PLANNING COMMITTEE FOR A NATIONAL SUMMIT ON STRATEGIES TO MANAGE HERBICIDE-RESISTANT WEEDS
CHARLES J. ARNTZEN (Chair), Arizona State University, Tempe
HAROLD D. COBLE, U.S. Department of Agriculture, Agricultural Research Service
DAVID E. ERVIN, Portland State University, Oregon
JODIE S. HOLT, University of California, Riverside
TERRANCE M. HURLEY, University of Minnesota, St. Paul
RAYMOND A. JUSSAUME, JR., Michigan State University, East Lansing
MICHEAL D. K. OWEN, Iowa State University, Ames
JILL SCHROEDER, New Mexico State University, Las Cruces
DAVID R. SHAW, Mississippi State University, Mississippi State
Staff
KARA N. LANEY, Program Officer
RUTHIE S. ARIETI, Research Associate
BOARD ON AGRICULTURE AND NATURAL RESOURCES
NORMAN R. SCOTT (Chair), Cornell University (Emeritus), Ithaca, New York
PEGGY F. BARLETT, Emory University, Atlanta, Georgia
HAROLD L. BERGMAN, University of Wyoming, Laramie
RICHARD A. DIXON, Samuel Roberts Noble Foundation, Ardmore, Oklahoma
DANIEL M. DOOLEY, University of California, Oakland
JOAN H. EISEMANN, North Carolina State University, Raleigh
GARY F. HARTNELL, Monsanto Company, St. Louis, Missouri
GENE HUGOSON, Global Initiatives for Food Systems Leadership, St. Paul, Minnesota
MOLLY M. JAHN, University of Wisconsin, Madison
ROBBIN S. JOHNSON, Cargill Foundation, Wayzata, Minnesota
A.G. KAWAMURA, Solutions from the Land, Washington, DC
KIRK C. KLASING, University of California, Davis
JULIA L. KORNEGAY, North Carolina State University, Raleigh
VICTOR L. LECHTENBERG, Purdue University, West Lafayette, Indiana
PHILIP E. NELSON, Purdue University (Emeritus), West Lafayette, Indiana
KEITH PITTS, Marrone Bio Innovations, Davis, California
CHARLES W. RICE, Kansas State University, Manhattan
HAL SALWASSER, Oregon State University, Corvallis
ROGER A. SEDJO, Resources for the Future, Washington, DC
KATHLEEN SEGERSON, University of Connecticut, Storrs
MERCEDES VÁZQUEZ-AÑÓN, Novus International, Inc., St. Charles, Missouri
Staff
ROBIN A. SCHOEN, Board Director
EVONNE P. Y. TANG, Senior Program Officer
CAMILLA YANDOC ABLES, Program Officer
KARA N. LANEY, Program Officer
PEGGY TSAI, Program Officer
KAREN L. IMHOF, Administrative Coordinator
JANET M. MULLIGAN, Senior Program Associate for Research
RUTHIE S. ARIETI, Research Associate
KATHLEEN REIMER, Senior Program Assistant
Acknowledgments
This proceedings has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise in accordance with procedures approved by the National Research Council’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making the published proceedings as sound as possible and to ensure that the proceedings meets institutional standards of objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following for their review of this proceedings:
Stephen O. Duke, U.S. Department of Agriculture, Agricultural Research Service, University, Mississippi
David E. Ervin, Portland State University, Oregon
Jerry Green, DuPont Ag Biotechnology/Pioneer Hi-Bred International, Newark, Delaware
Raymond A. Jussaume, Jr., Michigan State University, East Lansing
Nancy Ragsdale, U.S. Department of Agriculture, Agricultural Research Service (retired), Beltsville, Maryland
Siyuan Tan, BASF Corporation, Research Triangle Park, North Carolina
Alan Tasker, U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Riverdale, Maryland
Although the reviewers listed above have provided many constructive comments and suggestions, they did not see the final draft of this proceedings before its release. The review of this proceedings was carried out in accordance with institutional procedures and all review comments were carefully considered.
The National Research Council would like to thank the generous sponsors of this project.
Herbicide Resistance Action Committee
Iowa Soybean Association
National Cotton Council of America
United Soybean Board
U.S. Department of Agriculture, Economic Research Service
U.S. Department of Agriculture, National Institute of Food and Agriculture
Weed Science Society of America
Preface
Preserving the efficacy of herbicides and of herbicide-resistance technology depends on awareness of the increasing resistance of weeds to herbicides used in agriculture and coordinated action to address the problem by individuals at the farm level and beyond. This summit served as a venue to bring the attention of important stakeholders to the issue and as an opportunity for experts from diverse disciplines to strategize in a coordinated way to address herbicide-resistant weeds. In convening stakeholders for this event, participants took a step toward a recommendation from the 2010 National Research Council report, The Impact of Genetically Engineered Crops on Farm Sustainability in the United States, that federal and state government agencies, private-sector technology developers, universities, farmer organizations, and other relevant stakeholders collaborate to document emerging weed-resistance problems and to develop cost-effective resistance-management programs and practices that preserve effective weed control. The summit provided the opportunity for stakeholders to explore the scientific basis of the emergence of herbicide resistance and to consider different perspectives on both opportunities and barriers to overcoming the problem of herbicide-resistant weeds. Summaries, presentation materials, and a video recording of the summit can be found at http://nas-sites.org/hr-weeds-summit/. This document contains a brief synopsis of key points made by each speaker at the summit. The National Research Council does not endorse the statements made by summit presenters.

Horseweed (Marestail. Conyza canadensis; mature plant), courtesy of the Weed Science Society of America.
Contents
Charles J. Arntzen
HERBICIDE RESISTANCE IN WEEDS: WHAT IS THE NATURE OF THE PROBLEM?
Micheal D. K. Owen
THE EPIDEMIOLOGY OF HERBICIDE RESISTANCE
Jodie Holt
THE AUSTRALIAN EXPERIENCE OF MANAGING HERBICIDE RESISTANCE AND ITS CONTRASTS WITH THE UNITED STATES
Michael Walsh
BEST MANAGEMENT PRACTICES TO CONTROL AND COMBAT RESISTANCE
David R. Shaw
ADDRESSING THE PRESSING PROBLEM OF HERBICIDE RESISTANCE
Harold Coble
PANEL 1: THE IMPEDIMENTS TO USING BEST MANAGEMENT PRACTICES
Ben Barstow
Chuck Farr
David Miller
Steve Reeves
Dale Shaner
A SOCIAL SCIENCE PERSPECTIVE ON WEED MANAGEMENT PRACTICES
George Frisvold
PANEL 2: WHAT APPROACHES ARE MOST LIKELY TO ENCOURAGE THE ADOPTION OF BEST MANAGEMENT PRACTICES?
Tom Green
John Hamer
John Soteres
Paul B. Thompson
Michael Walsh
Steven Leath