Farmers across the country were relieved last March when the Trump administration reversed a decision to take a widely used agricultural insecticide off the market.

Without it, said Sleepy Eye farmer Cole Trebesch, he probably wouldn't even try growing soybeans.

But Bonnie Wirtz, who ended up in the emergency room six years ago after a crop duster sprayed the chemical over her Melrose, Minn., home, finds it heartbreaking that the government will still allow the sale of an insecticide that dozens of scientific studies have found toxic to children.

"If I almost died, then what is the long-term impact for my child?" she said. Her son, who was an infant at the time, now has a neurodevelopmental disorder, one of the health risks that inspired the U.S. Environmental Protection Agency (EPA) to propose a ban in the first place.

Nowhere in the country will the government's reversal be felt more profoundly than in Minnesota. The chemical, chlorpyrifos, is already the largest selling insecticide in the state — farmers spread almost a million pounds of it last year across Minnesota lands — and is likely to remain the primary weapon in their battle against insects. That's especially true for soybeans, Minnesota's second-leading commodity, which is increasingly vulnerable to an invasive aphid that is becoming resistant to other chemicals.

"They can take a third of your yield away," said Trebesch. "That's your profitability."

Even though farmers must follow strict rules in applying chlorpyrifos, it is nonetheless polluting the state's waters. About 10 of Minnesota's lakes and streams are or soon will be listed by state regulators as impaired by chlorpyrifos, a number that could grow. The Minnesota Department of Agriculture has named it one of three "pesticides of concern" because of its powerful toxicity to wildlife.

And on windy days, in the tiny farming towns in the central part of the state, some mothers call their children in from the backyard when they see a crop duster coming.

After hearing concerns from those communities, the Minnesota Department of Health is planning a study to measure how much chlorpyrifos rural kids carry in their bodies, part of a larger survey of contaminants in children.

"Chlorpyrifos is … causing harm to the most vulnerable in our population — unborn children, infants and young children," said Bob Shimek, a community activist for the White Earth Band of Ojibwe, who was among those who asked the Health Department to conduct the study. "This EPA will soon have the reputation of protecting the polluter, not the environment."

On the brink of a ban

After a decade of pressure from environmental groups, court fights, and regulatory and scientific reviews, the Obama administration was ready to take chlorpyrifos off the market last year, citing risks to wildlife, drinking water and, most important, children.

In a 2000 agreement with the chemical industry, the EPA banned its use in household insecticides and has restricted its use on certain vegetables since then. In 2016, the agency compiled a summary of health effects in humans drawn from a dozen or so studies, including research on children. Kids with more exposure to the chemical were more likely to have developmental and physical delays and attention deficit disorders. Other studies have found that fetuses exposed to the chemical through their mother's blood — especially those that live near farms — are more likely to grow up with autism and reduced intelligence, perceptual reasoning and memory.

The agency found that some 1- to 2-year-olds who ate a lot of food grown with chlorpyrifos could get 140 times more of the chemical than is considered safe from their diet alone. It's widely used on fruit, vegetables, wheat and other food crops.

The EPA concluded that while uncertainties remain, there is "sufficient evidence" that children experience neurodevelopment effects even at low levels of exposure.

But early this year, in the weeks before the ban was to take effect, Scott Pruitt, Trump's new EPA administrator, met with representatives from the Washington State Farm Bureau, who said they desperately needed chlorpyrifos to protect their crops. Pruitt promised a new day for the agency's relationship with agriculture, according to documents and e-mails compiled by the New York Times through a public records request.

And in March, Pruitt overruled his staff scientists, rescinding the ban while the scientific analysis continues until 2022.

In an interview with the Star Tribune earlier this year, Pruitt said he based his decision on an assertion by the U.S. Department of Agriculture that the EPA's analysis inflated the risks.

Dow Chemical, the maker of chlorpyrifos, has also disputed the science and the EPA's conclusions. The company says that restrictions and guidelines on how to use it safely have improved over time, and that if used as directed on the label, health risks are minimal.

Infestation of aphids

While all that was taking place in Washington, D.C., Trebesch was getting ready to plant his family's 1,200 acres of corn and soybeans outside Sleepy Eye. When his crops came up in July, he went out in his fields, as always, to look for bugs — and, pretty much as always in that part of the state, he found aphids on his beans.

Trebesch follows the state's recommendations to minimize insecticide use, and he waited until there were 250 bugs per plant. Then he called in a friend who does his aerial spraying.

Aphids, an invasive import from Asia, showed up in Minnesota in 2003 or 2004. Other Midwestern states don't have as much of a problem with them, but infestations have bloomed first in the northwest part of the state and more recently in the southwest.

Robert Koch, a University of Minnesota agricultural entomologist, said it may be that Minnesota has more buckthorn, another invasive plant that aphids need for overwintering. Or it could be the weather.

"Every year, somewhere in the state [there is] an outbreak that needs insecticides to protect yield," he said.

Farmers usually use pyrethroids, another class of insecticides, to control aphids — in part because it doesn't require a hazmat suit. Recently, however, Trebesch and other farmers found that it wasn't killing the bugs.

Koch figured out why in his laboratory: They had become resistant. It's a frequent problem in agriculture. Pests evolve to survive the most common chemicals, so new weapons become necessary.

Koch said he and other researchers are studying other ways to deal with aphids — with predator insects, for example, or removing nearby stands of buckthorn.

Farmers in hazmat suits

But for now chlorpyrifos, which does require a hazmat suit and a respirator, is the answer. Trebesch does his best not to apply it too early in the season so he doesn't kill off the lady beetles and parasitic wasps that are the aphid's natural predators. And he's careful not to go into the field for at least 24 hours after it's sprayed. He knows the risks.

"We live where we are farming," he said. "My kids are 9 and 6, and I don't want to do anything that would hurt them."

Spray planes are supposed to stay up to 100 feet from homes, but the one that flew near her farm in 2012 got too close, said Wirtz. The air conditioner sucked the spray right into her house.

"It looked like a white mist," she said. "It was straight out of a horror movie."

Her husband rushed her to the hospital, where her heart almost stopped. After that she got active with the Pesticide Action Network of North America, an advocacy group. The following year, she and others from the nonprofit set up pesticide monitoring equipment around fields to measure how much was drifting onto nearby homes.

"We found the levels were four times the EPA's safe limit for a 1-year-old child," she said.

The drift data they collected helped persuade the Minnesota Department of Health to include pesticides in a study next year that will measure a number of contaminants in 200 children, half from the intensely agricultural areas in the center of the state.

Wirtz and her family live in the Twin Cities now so her son can get treatment for his developmental disorder. She can't prove it came from chlorpyrifos, but she says kids are exposed to it in many ways — food, water, and in some rural areas, in the air they breathe.

Now she helps lobby Congress, hoping for legislation to remove it from the market.

"We have a generation in jeopardy," she said.