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Weeds evolving faster than pesticides can keep up

Photo by Ben Nuelle


Weeds are smart. They evolve to resist herbicides, and farmer’s use of only one mode of action for many years has allowed several weed species to find a way around it.

There is also a fairly bleak future for new products, according to a noted Iowa State University weed scientist. Due to a slow and rigorous process of discovery and registration of new herbicides, the strategy requires genetically modifying crops so they tolerate herbicides that once killed them while exposing resistant weeds to a pesticide that may control their growth.

Dr. Mike Owen is a senior weed scientist at Iowa State University. He is always a straight shooter in his views on weed control strategies suggested by chemical companies or tried by farmers. He is sometimes critical of both.

“I think many of us ‘drank the Kool-Aid,’ and believed that weeds would never evolve resistance to glyphosate, so we basically went whole hog, all in, with that technology,” Owen said. “For a number of reasons, that unprecedented adoption of those technologies changed how the herbicide companies were investing in research and development. It changed the seed companies, the agricultural economics and the demographics of the farming population. This ability to manage weeds effectively, efficiently, quickly and cheaply allowed farmers to get a lot bigger quicker.”

Dr. Owen believes future herbicides won’t be as effective as those we have seen in the past 40 years and weeds will continue to use Darwin’s Principles of Evolution to stay ahead of whatever defenses we develop.

“It’s been over 30 years since the last brand new mechanism, by which herbicides kills weeds, has been introduced,” Owen said. “The last one was the HPPD inhibitor herbicide. I don’t see anything in the pipeline that will come forward in the next ten to fifteen years.”