By Aaron Hager

The continual evolution of weed biotypes and populations resistant to various herbicides/herbicide families presents new and significant challenges to weed practitioners in many cropping environments.

Understanding how herbicides work and knowing the factors that influence the selection for herbicide-resistant biotypes are critical for designing and implementing weed management strategies that reduce the selection for resistant populations.

The Weed Science Society of America (WSSA) has developed new resources to explain the phenomenon of herbicide-resistant weeds. The training is divided into five modules: the current status of herbicide resistance; how herbicides work; what herbicide resistance is; scouting after a herbicide application and confirming herbicide resistance; and principles of managing herbicide resistance.

The modules, which can be viewed in several formats, are available free on the Internet.

Development of the program was supported by the National Corn Growers Association, the National Cotton Council, and the American Soybean Association. It was funded by WSSA and the Herbicide Resistance Action Committee, an industry coalition focused on herbicide stewardship.

The Weed Science Society of America, a nonprofit scientific society, was founded in 1956 to encourage and promote the development of knowledge on weeds and their impact on the environment.

For more information, visit