Farmers in Minnesota and across the country are watching closely as a battle over a key agricultural pesticide plays out in court.

A panel of judges in the Ninth Circuit Court of Appeals in August ordered the Environmental Protection Agency to ban the pesticide chlorpyrifos because of studies that show its residue on food can cause brain damage in children.

Farm groups say the ruling would “wreak havoc” on American agriculture, arguing there are no good alternatives to the pesticide for many crops.

Chlorpyrifos (pronounced klor’-peer-ih-foss) has been registered for crop use in the United States since 1974 and is used to kill insects that damage more than 50 crops, including cotton, citrus, corn, sugar beets and wheat. In Minnesota, the pesticide is used on soybeans the most, and on corn, wheat and alfalfa.

“This is the only real viable option right now, until some other options are developed,” said Brian Thalmann, a corn and soybean farmer south of Plato, Minn., and president of the Minnesota Corn Growers Association.

The dilemma for farmers is compounded because soybean aphids have developed resistance to a class of pesticides called pyrethroids. Meanwhile, another type of pesticides that still work on soybean aphids, neonicotinoids, is a danger to bees.

“These neonicotinoid insecticides have been favored because they are safer to the humans doing the application, but that’s where the concerns about pollinators have come, so it’s hard to know where to turn,” Thalmann said. “It’s really mainly about keeping options open.”

Concerns about the chemical are not new; chlorpyrifos was banned for indoor use by the EPA in 2000.

Environmental groups have been pushing to ban chlorpyrifos for outdoor use for more than a decade. The Natural Resources Defense Council and Pesticide Action Network North America filed a petition asking the EPA to ban it in 2007, then took the case to the Ninth Circuit in 2014.

Turnaround at the EPA

In the last two years of the Obama administration, it appeared the EPA was on course to ban the chemical, but in 2017, then-EPA Administrator Scott Pruitt denied the petition. His order said that chlorpyrifos needs further study and said the agency would need “greater certainty as to whether the potential exists for adverse neurodevelopmental effects to occur from current human exposure to chlorpyrifos.”

The Ninth Circuit stepped in this past August, ruling that “there was no justification for the EPA’s decision in its 2017 order to maintain a tolerance for chlorpyrifos in the face of scientific evidence that its residue on food causes neurodevelopmental damage to children.”

The EPA is now asking the court to rehear the case, and the appellate court has not decided whether to do so.

“The Trump administration is shameless in its refusal to ban this dangerous chemical that is poisoning our children’s brains,” Erik Olson, senior director for food and health at the Natural Resources Defense Council, said in a statement.

Olson said in an interview that industry concerns about a ban are overblown, noting that many farmers are productive without using the chemical.

“It’s sort of the boy-who-cried-wolf kind of thing that every time there’s any discussion of EPA taking action on a pesticide that’s dangerous, we hear that it’s impossible to have crops without them,” Olson said. “Then it always seems to turn out that farmers are creative and smart and they can figure out ways around it.”

According to the U.S. Geological Survey, from 367,000 to 600,000 pounds of chlorpyrifos were used in Minnesota in 2016, the most recent year for which data are available. By comparison, in California, about 900,000 pounds of the chemical were sprayed in 2016.

Farmers like Thalmann argue that the pesticide is used differently in Minnesota than it is on fruits and vegetables in other states and thus should be regulated differently.

“On soybeans it’s just a one-shot application,” Thalmann said. “A fruit crop, you’re trying to protect something throughout the season.”

If the chemical must be further restricted, Thalmann said, he hopes an allowance is made to “maintain the status quo” in the Midwest.