Stewardship to weed management; evolution of herbicide resistance

Agriculture and Natural Resources Extension
Iowa State University

Extension Lead(s)
(name, position, counties served, contact information)

Micheal D.K. Owen, Associate Chair and Professor of Agronomy, State-wide, 3218 Agronomy Hall,, 515-294-5936

Your Position


POW # and Team

 ­­­­­___x__100 Corn and Soybean Production and Protection
­­­­­_____ 110 Dairy
­­­­­_____ 120 Farm and Business Management
­­­­­_____ 130 Horticulture: Commercial and Consumer
­­­­­_____ 140 Iowa Beef Center
­­­­­_____ 150 Iowa Pork Industry Center
­­­­­_____ 160 Natural Resources and Stewardship

ANR Priority (select all that apply)

­­­­­___x__Global Food Security and Hunger
­­­­­_____Regional Food Systems
­­­­­___x__Natural Resources & Environmental Stewardship
­­­­­_____Food Safety
­­­­­_____Sustainable Energy – Biofuels & Biobased Products
­­­­­_____Climate Change

Title of Success Story

Stewardship to weed management; evolution of herbicide resistance

Continuing Story

__x___ No                _____  Yes (If continuing, what story?)

Knowledge Areas: (USDA categories)

Weed science

Desired Changes

Learning and actions

(Why is it important to address this issue with education?  What are the desired changes?)

Weeds are the most important economic pest problem that continues to cause more profit losses in Iowa agriculture than any other pest complex.  Currently, genetically modified corn and soybean, specifically cultivars that are resistant to glyphosate, dominate Iowa production systems and glyphosate has been misused in the perspective that this herbicide is typically the only tactic used when controlling weeds.  This has resulted in weed population shifts including the evolution of glyphosate resistant weed biotypes.  Furthermore, other herbicide resistances have evolved thus making weed management difficult.  These weed shifts have been documented by ISU field research conducted on grower fields.  ISU Extension has an obligation to provide clientele with information about risks related to various agricultural technologies and the adoption of these technologies.  ISU Extension is the sole source of objective information for Iowa agricultural endeavors and thus has an obligation to develop and deliver information that is important to the well being of Iowa Agriculture.

(Outputs: activities, numbers reached, publications, products)

Develop and deliver science-based objective information describing the implications of various crop production and weed management technologies on the evolution of herbicide resistant weed populations and potential crop yield.  Specifically, the implications of genetically modified crops and the use of glyphosate will be the focus of these efforts.  The dissemination of information will be via traditional strategies (grower meetings, AgChem dealer meetings, short courses, conferences, publications, and popular press/radio offerings) and via web-based education tactics.  A number of in-field demonstrations have also been established.  ISU Extension Weed Science continues to provide valuable science-based objective information about herbicide stewardship for Iowa growers.

RESULTS (Outcomes:  specific changes that occurred in Learning, Actions, Conditions; how outcomes were measured)

Short-term results measure awareness and knowledge.  Growers will demonstrate a high knowledge level about the implications of the evolution of glyphosate resistant weed populations and weed population shifts.  Furthermore, growers will understand the implications of weed management tactics on crop yield and profitability.  Medium-term results measure behavior change.  Growers will begin to understand weed populations dynamics and the implications of weeds on crop yields.  They will adopt more effective and sustainable weed management practices.  Specifically, they will use and integrated approach to weed management rather than just spraying glyphosate. The AgChem industry will promote more effective weed management programs and incorporate stewardship practices in their marketing of proprietary products.
Long-term results measure condition (i.e., new standard). Stewardship of herbicides and weed management will result in more consistent and profitable crop production and deter the future evolution of herbicide resistant weeds and weed population shifts.  Better IPM practices will be incorporated into crop production.  Higher crop yields and lower input costs for weed management will result from the stewardship programs. 

Public Value (now or future)
(Impact:  Who benefits beyond participants and how?  What conditions changed?)

While the primary audience is growers and agchem dealers, the Iowa citizenry will benefit from the stewardship.  The benefits include but are not limited to protected natural resources, reduced potential for herbicide exposure and improved food quality.

Major Partners or Collaborators

Field Agronomimsts, Iowa Soybean Association, growers and agchem dealers

Where story took place
(Region, campus, multi-regional)

Campus and state

Fiscal Year


Multi-state or Integrated (Ext + Research)


Funding Source



Herbicide, resistance, stewardship, management


Page last updated: July 1, 2011
Page maintained by Julie Honeick,