Promotion of Integrated Weed Management Systems

Bob Hartzler, Faculty, Agronomy Department


The need to minimize trips across field due to increasing farm size has resulted in the simplification of weed management systems in corn and soybean.  This has been accomplished with the widescale adoption of herbicide resistant crops (HRC).  HRC allow the use of broad-spectrum herbicides with greater flexibility in application timing.  While these systems provide growers the opportunity to reduce time spent on managing weeds, these systems increase the risk of weed related yield losses and the adaptation of weeds to control tactics.


Increase awareness of farmers and agribusiness personnel on the importance of integrated weed management systems in maximizing profits and reducing the likelihood of weed shifts.


A combination of research and extension activities were used to educate Iowa agribusinesses and farmers on the importance of integrated weed management systems.  Research/demonstration experiments at outlying farms showed the value of preemergence herbicides in enhancing weed control and protecting yields in HRC.  A series of extension bulletins were prepared and published online.  Monsanto, the leading provider of HRC in Iowa, also utilized these bulletins in their educational efforts.  Results were also disseminated at meetings and field days, and in 2006 demonstration trials were established on four farmer fields in cooperation with agribusiness partners.


The acres planted to HRC continues to expand in Iowa, a situation which results in heavy reliance of a few herbicides for weed control.  However, surveys have shown that farmers adopting herbicide resistant corn varieties typically use a preemergence herbicide in combination with the postemergence herbicide associated with the herbicide resistance trait.  In soybean, the percentage of acres treated with preemergence herbicides continues to increase.  The integration of multiple control tactics is improving consistency of weed control, minimizing risks of yield losses, and reducing the likelihood of weeds adapting to current control systems.

142 Integrated Pest and Crop Management

Page last updated: November 30, 2006
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