Unwanted Plants Threaten Crops in North-Central US

Across the north-central United States, weeds that resist control efforts are worrying farmers. This development is the latest sign that weeds are becoming resistant to chemicals faster than major companies can make new weed-fighting products.

Scientists say that some sorts of weeds are developing resistance to chemicals used to destroy them.

Reuters news agency recently spoke with more than 20 farmers, scientists, weed specialists and company leaders. The news agency also studied eight research papers published since 2021. The studies described how weeds, including kochia, waterhemp, and giant ragweed, are affecting crops in North Dakota, Iowa, Wisconsin and Minnesota.

Over the last 20 years, chemical companies have reduced the percentage of revenue meant for research and development spending. These companies are also introducing fewer products, says AgbioInvestor, a company based in Britain that studies the agricultural chemical industry.

Farmers say their battle with weeds threatens grain and oilseed harvests at a time when growers face inflation and extreme weather.

"We're in for big problems over the next 10 years for sure," said Ian Heap of the International Survey of Herbicide Resistant Weeds. It is a group of international scientists who work with governments and industry. He added, "We are in for a real shake-up."

The research group has a database of information on the reduced effectiveness of glyphosate, one of the most common weed-killing chemicals, against 361 weed species, including 180 in the U.S.

These weeds affect corn, soy, sugar beets and other crops.

Around the world, 21 weeds globally showed resistance to dicamba, the most recent major U.S. chemical, which launched in 2017.

Environmental groups argue that farmers should embrace natural weed-control methods instead of chemicals.

One Kochia plant can spread as many as 30,000 seeds. It can result in yields reduced by up to 70 percent if nothing is done to stop it. That information comes from Take Action, a farmer resource program of the United Soybean Board.

Other issues, including the development of stronger seeds, have pushed overall crop yields higher around the world. But scientists expect weed problems to worsen. Some weeds are even showing resistance the first time they are treated with chemicals.

In Douglas, North Dakota, farmer Bob Finken used dicamba and glyphosate to kill weeds late in the growing season. Neither product completely killed kochia.

"That was really scary," said Finken, age 64. "Each year seems to get a little worse."

Finken had to clear the weeds with harvesting equipment, which risks damaging the machinery.

Other farmers are hiring workers to pull weeds by hand, said Sarah Lovas of GK Technology, an agriculture company.

North Dakota was the largest spring wheat producing state in 2023 and ninth-biggest soybean grower.

Five of North Dakota's 53 counties have confirmed populations of dicamba-resistant kochia. That is only one year after it was first reported in the state, said Joe Ikley of North Dakota State University.

"It's just a matter of time before it hits your farm," said 65-year-old Monte Peterson who grows soybeans near Valley City, North Dakota.

Chemical producers Bayer, Corteva and FMC say longer development and government approval processes have limited new products to combat weed resistance. Industry leaders also say officials have become stricter about possible environmental and health effects.

The U.S. Environmental Protection Agency (EPA) said standards for approving new herbicides have not changed greatly since 1996. However, the EPA said recent efforts to study the effects of new active ingredients on threatened plants and wildlife have delayed some decisions.

The EPA did not estimate the increased processing time. The agency said it speeds up studies of lower-risk products.

I'm John Russell.

Rod Nickel and Tom Polansek reported on this story for Reuters. John Russell adapted it for VOA Learning English.

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weed – n. a plant that grows very quickly and covers or kills more desirable plants

shake-up – n. is an important change or series of changes.

yield – n. the amount of something that is produced by a farm

standard – n. an acceptable level of quality or achievement; something that is used to judge the quality of something else