01
Aug
Herbicide Dicamba Linked to Crop and Plant Damage and Cancer Subject of Deregulation Despite Court Ruling
(Beyond Pesticides, August 1, 2025) On June 30, Kyle Kunkler started work as deputy assistant administrator for pesticides in U.S. Environmental Protection Agency’s (EPA) Office of Chemical Safety and Pollution Prevention. Mr. Kunkler is an experienced agribusiness lobbyist, having come directly from the American Soybean Association, where he was director of government affairs. He joins Nancy Beck, PhD, herself a migrant from the American Chemistry Council. Not coincidentally, a mere three weeks after Mr. Kunkler’s appointment, EPA opened the floodgates to allow use of the controversial herbicide dicamba to flow unrestricted once again through the nation’s ecosystems. Dicamba has been associated with phytotoxic crop/plant damage (leaf damage, stunted growth, or death) and cancer. Three formulations of the herbicide whose registrations had been vacated via litigation will be reinstated by EPA after a public comment period that expires on August 22 at 11:59 PM EDT.
Dicamba is manifestly one of the worst ideas the pesticide industry has ever devised, according to many farmers and pesticide safety advocates. Because of resistance to other herbicides, pesticide scientists developed the “[insert pesticide]-ready†concept in which a crop plant is genetically engineered to resist exposure to a herbicide, “Roundup-Ready†seeds being the most obvious example, so that the herbicide can be sprayed liberally on fields to kill all other susceptible plants. Dicamba plus dicamba-ready seeds follow this pattern. The application technique is called “over-the-top†(OTT) because it is sprayed directly above resistant plants to kill target plants around them.
Introduced in 1967, dicamba rapidly showed itself to be associated with extensive crop damage. A 1969 study in Weed Science compared damage to soybeans from 2,4-D, picloram and dicamba. The authors wrote, “[E]xperience with dicamba and picloram indicates that these compounds may have far greater potential for damage to nearby soybean fields. Spray or vapor drift into nearby soybean fields might seriously damage soybeans.†In fact, dicamba is extremely volatile compared to other herbicides like glyphosate and 2,4-D. Because of its propensity to volatilize and drift, EPA registered it initially only for use in late winter or early spring.
In 2016, EPA registered three “less volatile†forms of dicamba when Monsanto marketed genetically engineered soybean and cotton seeds, largely because weeds were by then resistant to glyphosate. But within a year, the damage was staggering. State agriculture departments reported 2,708 official crop injury investigations to EPA. Between 2021 and 2023, that number approached 3,500. In 2017, at least 5 million acres of non-dicamba-resistant soybeans in 24 states were damaged; the next year, 15 million acres were struck. Downwind specialty crops and, actually, anything that was not dicamba-ready soybean or cotton, faltered or failed.
The pesticide industry claimed to have solved the spray drift problem by adding ammonia compounds called amines to their formulations. Amines were supposed to increase solubility and tamp down dicamba’s extreme volatility. Beyond Pesticides reported on a study in 2022 in Environmental Science & Technology that tracked the environmental behavior of the amines used in dicamba, 2,4-D, and glyphosate. As the pesticide application dried, more amines than pesticides entered the atmosphere. Amines in the air oxidize to form the potent carcinogens nitrosamines and nitroamines. Because at least half of glyphosate and 2,4-D and almost 90% of dicamba formulations contain amines, the “solution†to the spray drift problem is yet another example of the endless chain of pesticide-created threats to ecosystem and human health.
And dicamba itself is no Good Witch Glinda. As Beyond Pesticides noted last year, “[T]here is a strong association between dicamba use and increased risk of developing various cancers, including liver and intrahepatic bile duct cancer, chronic lymphocytic leukemia, and acute myeloid leukemia. In the Gateway on Pesticide Hazards and Safe Pest Management entry for Dicamba, there is a slew of medical studies detailing adverse health and environmental effects, including neurotoxicity, kidney/liver damage, sensitization/irritation, birth/developmental defects, reproductive damage, and respiratory illnesses.†And because dicamba kills nontarget plants, including trees and critical pollinator species, entire ecosystems are at risk.
The initial registrations for the claimed “low-volatility†OTT dicamba products were set to expire in 2018, but EPA granted extensions with some rather complicated and difficult-to-enforce restrictions on application conditions. A group of environmental stakeholders petitioned the Ninth Circuit to review EPA’s action. In June 2020, the court found that EPA violated the Federal Fungicide, Insecticide, and Rodenticide Act (FIFRA) in six ways. The next week EPA canceled all OTT uses of dicamba—for a mere four months. In October, EPA abruptly, and without notice to any adversarial stakeholder, reregistered all three products unconditionally for five years. The Center for Biological Diversity and others sued EPA and Bayer CropScience. In February 2024, the U.S. District Court for the District of Arizona re-vacated the 2020 registrations for the three “low-volatility†dicamba products. This once again made the sale and use of these products illegal.
Just as with the tobacco industry and innumerable other chemical industry strategies, the companies that had developed dicamba and its resistant seeds—BASF and Monsanto—covered up dicamba’s dirty little secret in their pitches to growers. An Investigate MidWest report in 2020 revealed that Monsanto (now owned by Bayer) knew there would be massive crop kills. Monsanto’s own pre-market tests revealed so much spray drift that Monsanto simply suspended the tests. The company subsequently gave Midwest farmers an offer they could not refuse: either buy Monsanto’s dicamba-ready soybean and cotton seeds, or expect their own crops to die, according to Investigate MidWest.
Dicamba use will inevitably surge if EPA is not stopped from this policy change. But for those hoping to resist its damage, it is getting even easier to detect dicamba spray drift. Researchers at the University of Illinois Urbana-Champaign have developed a method to detect and measure dicamba’s damage to soybeans at one ten-thousandth of the amount prescribed for application as long as eight days after application. The team used drones fitted with cameras, but are now working on adapting the spectroscopic signature of dicamba to satellite imagery. It will also be applicable to dicamba spray drift injury to any plant cover, from trees to ornamental shrubs and other plants.
Many plants are exquisitely sensitive to dicamba at very low concentrations. There is evidence that even residues left over in spray applicator reservoirs can be enough to harm plants being sprayed with some other pesticide. A 2019 study by scientists at the University of Missouri examined the effects of 2,4-D and dicamba with or without glyphosate on a large set of ornamental, fruit, and nut species. They tested three levels of exposure, or driftable rates, as fractions of the manufacturer’s labeled rates for each of the four chemical formulations. Visual injuries were seen at up to 1/200th of the manufacturer’s labeled rate for both dicamba and 2,4-D. These did not change the plants’ survival, but likely made them unmarketable. At higher concentrations, there were changes in shoot length and trunk diameter as well as malformed leaves. The most sensitive species to all the herbicides was grapevine—bad news for viniculture everywhere—but apple, peach, elderberry, dogwood, maple, oak, and viburnum were also extremely sensitive to dicamba.
The EPA’s July 23 announcement claims it “has conducted a robust human health risk assessment for these proposed products and has not identified any human health or dietary risks of concern,†nor any “risks of concern for aquatic invertebrates, fish or aquatic plants,†and only “low risk for honeybees and other non-listed bees from the proposed uses of dicamba.†It also includes proposed “mitigation measures,†including a requirement not to apply dicamba at temperatures above 95 degrees Fahrenheit and to maintain a 240-foot downwind buffer. Several comments on EPA’s regulations page note that the temperature requirement will be impossible to conform to because of the unpredictable nature of weather conditions and the importance of applying pesticides at the right time in the crop cycle. Nor will climate change be reducing the number of 95-degree days any time soon. A 240-foot buffer does not appear to be nearly large enough to contain spray drift that can travel up to at least two to three miles.
The saga of dicamba also reflects the current administration’s efforts to deregulate chemicals. It seems unlikely that the agency’s forthcoming registration rationale will be more restrictive than the ones that have already failed it twice, in the district and appeals courts. It appears EPA is going to claim that further instructions to users—such as wearing long-sleeved shirts, long pants, and socks and shoes—will suffice to solve any downsides to dicamba. The agency clearly is choosing winners and losers here: pesticide companies and large soybean and cotton operations are the winners, while farmers of the vast number of vital food crops and ornamental and specialty plants will be left holding their shrinking investments, leaf by wilting leaf. And since the agency has already decided there are no health or environmental risks associated with dicamba, those risks will likely be completely ignored as well.
The Make America Healthy Again (MAHA) movement, which shares some values and goals with the organic and regenerative agriculture community, is coming into conflict with corporate power both directly and through its influence on lawmakers. President Trump appointed Robert F. Kennedy Jr., who has attacked the pesticide industry for years, as Secretary of Health and Human Services and created a Make America Healthy Again Commission. To encourage the administration to adopt more restrictive pesticide regulations, the Center for Biological Diversity submitted a petition to the President, Secretary Kennedy and the commission last April to significantly alter EPA, FDA and USDA rules concerning pesticide residues on foods and to require USDA to subsidize crop insurance for farmers pledging to eliminate use of many pesticides, including glyphosate, atrazine, paraquat and several neonicotinoids, according to a Civil Eats analysis. This prompted pushback in a letter to the commission from 79 U.S. senators from both parties worried that “safe, well-regulated agricultural inputs†—namely, pesticides—would be banned under a MAHA administration. Beyond Pesticides issued the action: Tell HHS Secretary Robert F. Kennedy, Jr. to revise the memorandum of agreement with EPA on pesticide residues in food and set protective levels.
Mr. Kunkler’s appointment and EPA’s reversal on dicamba indicate that the Trump administration is siding with industry interests. In May, Mr. Kennedy assured the Senate Appropriations Committee that he was not going to “jeopardize†the “business model†represented by corn and glyphosate. Clearly Kennedy’s promises to reform pesticide policy are likely to die on the vine—killed by the spray drift from the pesticide industry.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources:
EPA Announces Proposed Decision to Approve Registration for New Uses of Dicamba, Outlines New Measures to Protect Human Health, Environment
Environmental Protection Agency July 23, 2025
https://www.epa.gov/pesticides/epa-announces-proposed-decision-approve-registration-new-uses-dicamba-outlines-new
EPA Hires Farm and Pesticide Lobbyist to Oversee Pesticide Regulation
Lisa Held
Civil Eats June 30, 2025
https://civileats.com/2025/06/30/epa-hires-farm-and-pesticide-lobbyist-to-oversee-pesticide-regulation/
Court Strikes Down EPA’s Allowance of Weedkiller Dicamba after Scathing Inspector General Report
Beyond Pesticides, February 13, 2024
https://beyondpesticides.org/dailynewsblog/2024/02/court-strikes-down-epas-allowance-of-weedkiller-dicamba-after-scathing-inspector-general-report/
Chemicals Added to Herbicides to Reduce Drift Actually Drift Themselves, Are Significant Air Pollutants
Beyond Pesticides, November 2, 2022
https://beyondpesticides.org/dailynewsblog/2022/11/chemicals-added-to-herbicides-to- reduce-drift-actually-drift-themselves-and-represent-significant-source-of-air-pollution/
‘Buy it or else’: Inside Monsanto and BASF’s moves to force dicamba on farmers
Johnathan Hettinger
Investigate Midwest December 4, 2020
https://investigatemidwest.org/2020/12/04/buy-it-or-else-inside-monsanto-and-basfs-moves-to-force-dicamba-on-farmers/
Dicamba: concerns about health risks and crop damage
Carey Gillam
U.S. Right to Know July 23, 2025
https://usrtk.org/pesticides/dicamba/
Scientists warned this weed killer would destroy crops. EPA approved it anyway
Liza Gross
Reveal News November 13, 2018
https://revealnews.org/article/scientists-warned-this-weed-killer-would-destroy-crops-epa-approved-it-anyway/
New research detects dicamba damage from sky
AgriNews July 24, 2025
https://www.agrinews-pubs.com/news/science/2025/07/24/new-research-detects-dicamba-damage-from-sky/
