A single female Palmer pigweed dug up by Mississippi consultant Phillip McKibben.

The term “Superweed” is bandied about in a lot of headlines — over used and often incorrectly applied. The continued confusion prompted the Weed Science Society of America (WSSA), in league with 6 other scientific organizations, to recommend a new definition for the term.

Why is this necessary? Because many normally respected sources have it wrong. For instance, The Oxford Dictionary defines superweeds as “a weed which is extremely resistant to herbicides, especially one created by the transfer of genes from genetically modified crops into wild plants.”  Wrong.

And that is just one example, according to WSSA, of why a new definition is needed.

There’s no evidence that gene transfer from genetically modified crops to weeds is  a major factor in the development of herbicide resistance issues faced by farmers ,” says Lee Van Wychen, Ph.D., and WSSA science policy director. “What’s causing herbicide resistance to develop in weed populations is the overreliance on herbicides with a single mechanism of action to control certain weeds. That leads to the selection of weeds resistant to that mechanism of action.”

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The new definition of “superweed” proposed by WSSA is:

“Superweed: slang used to describe a weed that has evolved characteristics that make it more difficult to manage, due to the repeated use of the same management tactics. Over-dependence on a single tactic as opposed to using diverse approaches can lead to such adaptations.”

According to the WSSA, the most common use of the slang “refers to a weed that has become resistant to one or more herbicide mechanisms of action due to their repeated use, in the absence of more diverse control measures. Dependence on a single mechanical, biological or cultural management tactic has led to similar adaptations.”

For more information about superweeds and to download the new WSSA fact sheet on superweeds, click here.