NASHVILLE, Ill. — Agricultural weedkillers are slowly killing trees across Missouri and Illinois, scientists, state workers and landowners say.
Landowners say 200-year-old oaks have gotten sickly. State conservation workers are documenting trees with curling leaves and forests with thinning canopies. Scientists have studied hundreds of trees and found widespread evidence of chemicals in their leaves.Â
The signs are spreading across the region, from farms to conservation areas to some of Illinois’ largest forests.
Many affected trees have already died or been logged, and experts and property owners fear that others will be pushed past their limits in the next few years, if the chemical exposure persists.
“It’s pretty scary,†said Robbie Doerhoff, a forest entomologist for the Missouri Department of Conservation who leads the agency’s forest health program. She said she sees a “slow and cumulative†ecosystem-wide impact. “We’re gonna be in a world of hurt in the next few years here, I think.â€
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The same is happening in Illinois, said Kim Erndt-Pitcher, the director of ecological health for Prairie Rivers Network, a nonprofit that has tested trees across the state for years.
“This is one of our biggest threats to forest health that we have in Illinois and even in the Midwest,†she said.
The concerns have emerged with the voluminous increase in the use of industrial herbicides on genetically modified herbicide-resistant crops. With that rise has come a corresponding spike in complaints from neighboring farms that the herbicides have “drifted†onto their fields and damaged crops that aren’t engineered to withstand the chemicals.
Major agribusiness companies behind the weedkillers defend their products.
German giant Bayer, with its crop science headquarters in ºüÀêÊÓƵ, said it “stands fully behind†XtendiMax, an herbicide based on the chemical dicamba, which was found in tree samples, and has sparked years of controversy. In a statement, it called the product a “vitally important weed-control tool for many growers.â€
Bayer said XtendiMax, when used correctly, stays “on-target,†and doesn’t drift onto other fields. “Based on our data and conversations with growers this season, we believe the vast majority of XtendiMax applicators had success with on-target applications and weed control,†the statement said.
And Indianapolis-based Corteva, a major producer of the weedkiller 2,4-D, said its “unique formulation†has been rigorously reviewed by researchers, including the Environmental Protection Agency, and the reviews show the product “doesn’t impact surrounding wildlife.â€
Neither company made a representative available for an interview.
Experts in the region said they have not directly tied the weedkillers to the deaths. But they have linked exposure to elevated rates of tree mortality. Prairie Rivers, the Illinois nonprofit, has logged more than 700 visits to inspect area forests, and collected dozens of samples from area trees, and almost all of those samples show evidence of agricultural herbicides, including dicamba and 2,4-D.
And even if the chemicals themselves don’t kill any given tree, they likely weaken them, experts say, which makes them more susceptible to disease and other threats.
“These are chronic stressors,†said Martin Kemper, a retired biologist from the Illinois Department of Natural Resources who helps spearhead Prairie Rivers’ testing efforts.
‘It’s worse each year’
Dicamba, pioneered decades ago, has roared to newfound prominence in the past decade.Â
As weeds developed resistance to long-used mainstays, like Bayer’s Roundup, agribusiness companies were left searching for a successor.
Dicamba has stepped into that role in the last 10 years, ever since Creve Coeur-based Monsanto, which was purchased by Bayer in 2018, released cotton and soybean seed varieties genetically engineered to be sprayed directly with the herbicide.
Many farmers swear by the technology, hailing it as a needed tool in the fight against increasingly hard-to-control weeds. But, after the introduction of dicamba-tolerant seeds, fierce debate about the chemical quickly exploded.
Dicamba has long been notorious for its “volatilityâ€Â — or tendency to turn into a vapor and drift, especially in hot conditions.Â
And farmers across the country who didn’t immediately adopt the dicamba-resistant seeds began to blame the weedkiller for damaging their crops.
Complaints and lawsuits about suspected dicamba damage have since stretched from soybean fields to the forage for honeybees and from peach orchards to grape vineyards, resulting in hundreds of millions of dollars of legal settlements.
More recently, however, formal dicamba complaints have nearly vanished — dropping to just 12 reported to the Missouri Department of Agriculture this year, compared to a high of 315 in 2017. On one hand, experts say, farms have increasingly planted dicamba-resistant seeds. And some, including the seed and chemical companies, say that application techniques have improved. Farmers and researchers also agree that plenty of dicamba remains in the air, and that farmers have simply stopped reporting damage.
Landowners said they first started to notice signs of injury to their trees nearly a decade ago, too. And complaints of damage quickly escalated in the years to follow, as the chemical saw a roughly five-fold national increase in usage from 2015 to 2019, according to data from the U.S. Geological Survey.
Usage of 2,4-D also rose then, but more modestly.
The emerging wave of complaints prompted Prairie Rivers, the Illinois nonprofit, to launch a campaign six years ago aimed at monitoring “herbicide trespass†by sampling leaves from trees across Illinois.
The initiative aims to visit each of 260 locations around the state at least once a year, from forests to cemeteries, school grounds to residential yards. In over 700 site visits to date, more than 99% of them have revealed symptoms consistent with herbicide exposure, according to data from the group.
The most widely detected herbicide was 2,4-D, which was present in 86 out of 109 samples, or nearly 80% of affected trees. Dicamba, meanwhile, was found in 44 samples — or about 40%. But dicamba likely has a greater presence than the tests are able to confirm, because it is more quickly metabolized by plants, compared to other weedkillers — meaning traces of it won’t be detectable for as long.
Concerns span many different tree and plant species, but they are especially high for trees such as redbuds and oaks, experts said.
And signs of the damage can be found throughout the region, experts say. Like in Washington County, Illinois, about an hour’s drive east of ºüÀêÊÓƵ.
Here, around the farming community of Nashville, lots of trees exhibit signs of distress that experts attribute to herbicide exposure. That includes a grove of majestic oaks in a pasture owned by Shelley Harper. One massive tree on the property is Illinois’ biggest known post oak, and although it has likely lived for more than 200 years, it’s unclear if it and other trees around it will survive much longer, after years of struggles and symptoms of herbicide exposure.
Some trees on the property have even sprouted twigs and leaves from almost everywhere along their branches — something called epicormic branching, generally done as a last-ditch, desperate effort to get the energy needed to survive.
“I have to say, it’s worse each year,†said Harper. “You just feel sad about it and kind of helpless, too, because what can you do? What can you do in the short-term, before a lot of them die?â€
Near the small town of Venedy, signs of damage reach deep into the woods along the Kaskaskia River. In recent years, growing pockets of the forest have been transformed, with the canopy opening up as foliage withers and trees die, giving rise to thick undergrowth on the forest floor.
Local residents Glen Schuetz and Gerry Scanlan each own hundreds of forested acres in the area, and Schuetz worries that their lifetimes of stewardship of the woods are “being taken away by a force we have no control over.â€
“It’s really frustrating,†he said. “We’ve dedicated our lives to purchasing and conserving this old-growth forest in the area.â€
“It’s heartbreaking to see,†said Scanlan. “All the timberland around here is affected by this issue.â€
Calling for fixes to ‘a huge problem’
Recent years have seen tweaks to the labels and rules for using dicamba, but they have not erased questions about the chemical’s ability to safely coexist with other crops and plants. And it’s unclear what further changes, if any, might be in store.
In Missouri, for instance, no changes governing dicamba use are expected for the 2024 growing season, according to a spokesperson for the state Department of Agriculture.
Researchers and landowners said they don’t blame farmers. “They’re using what’s available to them,†said Scanlan.
Instead, he and others want to hold chemical manufacturers and regulators accountable.
The EPA says that it continues to assess whether herbicides such as dicamba pose “unreasonable risks to non-target crops and other plants,†and pointed to its recent approval of “amendments that further restrict the use†of the chemical, including some that took effect this year in Illinois and other states.
But property owners and experts who track tree damage say the status quo is untenable. They expect tree deaths will increase further if nothing changes.
“If we could stop this exposure, I think many of these trees could recover,†said Kemper, the retired Illinois state biologist.
But he fears the costs of inaction or ineffective oversight, warning that the situation might reach an extreme where “the problem is solved, because the damage is done.â€
Others agree that something has to change.
“What (the EPA) is doing isn’t working,†said Erndt-Pitcher, the Prairie Rivers researcher. “They need to address these herbicides that are not staying put. Until we address that, it’s going to be a finger-pointing time.â€
“There are a lot of us who would say this is unreasonable harm,†she added.