The Continuing Problem with Weed Resistance and the Need for Herbicide Stewardship

Micheal D. K. Owen, Associate Chair and Professor of Agronomy


Weeds continue to remain the principle economic pest problem in Iowa agriculture.  Currently, transgenic corn and soybean, specifically cultivars that are resistant to glyphosate, dominate Iowa production.  Thus, glyphosate is most often the only tactic used when controlling weeds.  This has resulted in weed population shifts including the evolution of glyphosate resistant weed biotypes.  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.


Develop and deliver 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 transgenic 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.

Outcome Statement:   

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 weed management practices.  Specifically, they will use 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 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. 


100  Corn and Soybean Production and Protection

Page last updated: July 21, 2009
Page maintained by Linda Schultz,