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About 50 miles southeast of St. Louis, in the small town of Tilden, Illinois, the leaves on the burr oak trees looked odd earlier this spring.
Some were curled and cupped around the edges, while others were misshapen.
These are classic symptoms of drift from potent herbicides like dicamba or 2,4-D, said Kim Erndt-Pitcher, director of ecological health at Prairie Rivers Network.
“Once you see it, you can’t unsee it,” Erndt-Pitcher said.
The nonprofit has been documenting pesticide drift in Illinois for nine years.
In 2024, the group published their findings, reporting 99.6% of the 280 sites surveyed statewide had symptoms of drift damage, and 90% of the tree tissue samples collected had herbicide in them.
“Year after year, we're seeing decline in numerous species,” Erndt-Pitcher said. “Some of the most concerning are our oak species because they are keystone species in our hardwood forests and really important to our communities as well.”
The Environmental Protection Agency’s decision to issue a new set of regulations for the herbicide dicamba in February brought forth a plethora of concerns from fruit and vegetable producers and environmentalists who worry the rules won’t stop the chemical from drifting.
The EPA has dubbed the rules for how dicamba is applied to genetically modified soybeans and cotton the “strongest protections in agency history," but weed scientists say the reality is mixed, as some regulations have gotten more restrictive and others have been loosened.
Regardless, Erndt-Pitcher doesn’t think the new federal labels for dicamba will break the cycle of legal challenges. Federal courts struck down previous iterations of the EPA’s rules issued in 2020 and 2024.
“Over and over, the courts have dealt with this issue, and we've had extremely technical, long labels to follow, and it's still causing injury,” she said. “It's really frustrating to see it come back.”
Two weeks after the EPA issued the most recent labels, a coalition of nonprofits and advocacy organizations filed a lawsuit against the federal agency.
Still, some cotton and soybean growers say dicamba is one of the few tools available for controlling noxious agricultural weeds — and assert it can be used responsibly.
Dicamba can drift onto neighbors' plants
Many farmers have come to rely on dicamba, which is sold by agrichemical companies under a variety of brand names, including Stryax, Engenia and Tavium. The herbicide is particularly effective at killing broadleaf weeds like waterhemp and palmer amaranth, which can rapidly take over farm fields and reduce crop yields.
Dicamba’s use in row crop farming dates back to the 1960s when it was first manufactured for crops like corn, which is naturally resistant to the herbicide. However, other plants — grapes, tomatoes, pears and oak trees, for example — are highly sensitive to dicamba.
Even small concentrations of the chemical can damage certain plants, particularly soybeans that aren't genetically modified to resist the herbicide, said Tommy Butts, a weed science professor at Purdue University.
“We're seeing that through all of these different methods, even when we have the smallest amount move off target, you're going to see [drift damage] with something like dicamba,” he said.
While the federal government doesn’t document it annually, dicamba drift allegedly damaged more than 1 million acres of non-resistant soybeans in 2021, according to an EPA report. The agency said this estimate probably "significantly understates the actual number of incidents" given prior research and stakeholder meetings.
Dicamba can drift onto other fields and plants in two ways: as droplets in the wind or as vaporized gas.
With any herbicide, farmers need to be aware of wind conditions before spraying to prevent drift, but dicamba can vaporize — turning from a liquid to a gas — even days after being applied in warmer weather. That gas can be carried for miles in the wind.
An eastern Missouri jury in 2020 found Monsanto, which is now owned by Bayer, and German chemical company BASF liable for negligent design and failure to warn about their dicamba products. The decision came after the owners of the state’s largest peach farm sued the two companies, alleging dicamba-based herbicide drift destroyed their crops. Jurors awarded the peach farmers $15 million in damages.
The herbicide has been a topic of heated disagreement among growers in years past and can still be controversial, said Aaron Hager, a professor of weed science at the University of Illinois Urbana-Champaign.
The divide between farmers who use dicamba and those who don’t “was like the 2016 presidential election,” Hager said. “You were in one camp or the other. And if you weren't in my camp, you were wrong — if for no other reason than you're not in my camp.”
The reality that drift may occur leaves neighbors of those using dicamba in awkward or sometimes contentious situations, said Randall Vos, a horticulture specialist with Iowa State University Extension.
“You don’t want to be the squeaky wheel in the community,” said Vos, who advises Iowa fruit producers.
Herbicide drift can be a big deal for a grower's bottom line, he added. If a producer loses 5% of their crop and profit margins are around 5%, it’s hard to make money.
For the fruit producers Vos works with, reporting drift can also create a conundrum.
It may take the Iowa Department of Agriculture and Land Stewardship one week to investigate a plant that’s suspected of being damaged by drift. By that point, the herbicide levels may be undetectable, so the state agency may not be able to come to a conclusion — and that’s especially problematic for organic farmers, Vos said.
What’s in the new dicamba regulations?
In a statement, the EPA attributed its revised dicamba regulations to the “strong advocacy of America’s cotton and soybean farmers.”
These farmers, the federal agency went on to say, “have been clear and consistent about the critical challenges they face without access to this tool for controlling resistant weeds in their growing crops.”
In some ways, the federal rules are more restrictive than previous iterations, said Hager and Butts, the weed scientists. For example, there are stricter temperature requirements that don’t allow dicamba to be sprayed if it’s hotter than 95 degrees to prevent the herbicide from vaporizing.
The rules also stipulate a mandatory, unsprayed 240-foot buffer zone around areas where dicamba is applied. Previously, farmers could use an adjacent field as part of the buffer zone, but regulations will now require them to leave an unsprayed barrier around the outside of the field, Butts said.
In other ways, the rules have gotten more relaxed, weed scientists say. The EPA dropped regulations that prevented dicamba from being applied after June when temperatures are generally hotter and could lead to more vapor drift.
These federal rules provide baseline protections, but a handful of states have implemented more stringent regulations. For example, Illinois doesn’t allow dicamba to be sprayed after June 20 or when it’s hotter than 85 degrees. In Indiana, the cut off date is June 12.
Regardless, the revised rules may not substantially affect farmers’ growing practices this year.
The federal agency’s February announcement came after many farmers in the Midwest and Great Plains had already decided what to plant, meaning they may not have chosen a dicamba-resistant seed, Hager and Butts said. Therefore, both said they didn’t expect to see much more dicamba use than in previous years.
Farmers further south generally plant more dicamba-resistant soybeans and cotton, Butts said.
“I would expect that they'll be quite a bit sprayed because even when they didn't have the herbicide label, they still stayed, for the most part, with those genetics,” he said.
How farmers use and talk about dicamba
Communication is key to using dicamba responsibly, said Illinois farmer Kevin Johnson.
Johnson, his dad and two brothers raise corn and soybeans on the eastern side of Illinois near the Indiana border. They rotate herbicide-resistant soybeans in conjunction with their neighbors, so that one person’s fields aren’t susceptible to damage from dicamba drift.
“If we can work together, that is the best way to do this in the end,” said Johnson, who also serves as the director of governmental affairs for the Illinois Soybean Association. “I think we’re getting better at that. But up until that point, I don’t think everybody was having a conversation. Nobody loves those conversations, but you got to have those conversations.”
If farmers have fields near specialty crop growers, whose produce may be highly sensitive to dicamba, they may want to rethink herbicide use or take extra precautions to avoid drift, Johnson said.
“I don’t want to kill their livelihood,” he said. “I wouldn’t want somebody to kill my livelihood.”
While he hopes the controversy over dicamba has subsided, Johnson said he wants to avoid situations that arose about a decade ago, like a drift dispute that ended when an Arkansas farmhand killed another farmer in 2016.
Bad actors who improperly apply dicamba threaten its use for farmers who use it responsibly, Johnson said. That’s why he tells everyone that the “label is the law.”
At their farm, the Johnsons are careful to check the forecasted temperature, look for temperature inversions and monitor wind speeds because farmers can’t spray dicamba if there are gusts of more than 15 miles per hour in Illinois, Johnson said.
While Johnson knows there are many out there who don’t support the use of dicamba, he believes it can be a valuable tool when used properly, especially for farmers like him who practice no-till farming to preserve the health of the soil.
At the end of the day, growers need options for controlling aggressive weeds that threaten their crops, Johnson said, and manufacturing new tools isn’t a quick process.
“I want new stuff to come to market, but that takes a lot of money and a lot of [research and development] to get it to where it needs to go,” he said.
In an ideal world, Johnson said, they’d have other tools to control weeds. But for now, he added, they’ll have to work with what they have.
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest and Great Plains. It reports on food systems, agriculture and rural issues.
