As soybean and cotton farmers across the Midwest and South continue to see their crops ravaged from the weed killer dicamba, new complaints have pointed to the herbicide as a factor in widespread damage to oak trees.

Monsanto and BASF, two of agriculture’s largest seed and pesticide providers, released versions of the dicamba this growing season. The new versions came several months after Monsanto released its latest cotton and soybean seeds genetically engineered to resist dicamba in 2016.

Since then, farmers across the Midwest and South have blamed drift from dicamba for ruining millions of acres of soybeans and cotton produced by older versions of seeds.

Now, complaints have emerged that the misuse of dicamba may be responsible for damage to oak trees in Iowa, Illinois and Tennessee.

  • In Iowa, the Department of Natural Resources has received more than 1,000 complaints about oak tree damage from unknown pesticides, some of which cited dicamba as a cause.
  • In Illinois, retired biologist Lou Nelms who operated a prairie seed nursey and was a researcher at the University of Illinois, has documented damage to oak trees across the state from dicamba and filed numerous complaints with Illinois Department of Agriculture and Department of Natural Resources.
  • In Tennessee, the Department of Agriculture investigated and confirmed complaints that dicamba had damaged oak trees at the state’s largest natural lake.

“I’ve seen (pre-planting damage) year after year after year,” Nelms said of dicamba’s effect. “I’ve been seeing these signs for 40 years. To me, it’s just obvious.”

When reached for comment, Monsanto spokeswoman Charla Lord requested more time to respond.

But Monsanto officials have said publicly that crop damage is caused by misapplication of dicamba or the sale of the herbicide under other labels.

BASF spokeswoman Odessa Hines said the company is aware of issues with oak trees and encourages growers to contact the company with any concerns.

“We don’t believe volatility is a driving factor based on past research and experience. For Engenia herbicide to receive registration from federal and state authorities, including authorities in Illinois, we conducted and submitted results from a wide range of studies needed to fulfill regulatory requirements,” Hines said.

Lobbyist corresponds with state officials

But, in the cases of oak tree damage, internal Monsanto emails indicate that the company has tried to shift blame away from dicamba to other pesticides.

The emails were written by company lobbyists who shared them with the Illinois agriculture department. The emails were obtained through a Freedom of Information Act request.

Nelms filed more complaints in August about damage at the Sandra Miller Bellrose Nature Preserve, an area officially recognized by the Illinois Natural Preserve Commission, and at the 412.7 acre Revis Hill Prairie, an official state natural area.

The Monsanto correspondence followed Nelms filing complaints with the department.

Nelms filed one of his complaints, on the morning of August 16, with the Department of Natural Resources about dicamba damage to oak trees at the state nature preserve Funk’s Grove.

Funk’s Grove, about 10 miles south of Bloomington, Illinois, is one of just 654 undisturbed natural areas in the state of Illinois. The 25-acre forest is famed for its sugar maples and the syrup they produce. The nature preserve, a popular destination along the famed Route 66, is also home to oak trees hundreds of years old.

But this year, the leaves on the historic oak trees “cupped” and died, exhibiting clear signs of harm from either 2,4-D or dicamba, which is the most widely used weed killer of this type, Nelms said.

Oak trees with cupped leaves, a sign of damage from drifting pesticides like dicamba.

Just one hour later after Nelms’ August 16 complaint, Jeff Williams, a Monsanto lobbyist based in Springfield, Illinois, sent an email to Dave Tierney, the regional director governmental affairs in Des Moines, Iowa.

In the email, Williams wrote he had talked with Warren Goetsch, deputy director of the Illinois Department of Agriculture, and Wayne Rosenthal, the director of the Illinois Department of Natural Resources the night before.

Williams wrote that they told him that Illinois was starting to receive complaints about oak trees being damaged by herbicides.

Iowa concerns

Later in the day, Tierney sent an article written by Iowa State professor Robert Hartzler, writing,“Here is a good piece that really quieted the situation here in Iowa. Ironically I just talked to the head of Iowa DNR about it again today.”

Hartzler’s published his article in June as a response to media reports of about 1,000 complaints in Iowa about oak tatters, another condition where oak leaf tissue disappears along the veins. The condition, present in oak trees since the 1980s, has been linked to another Monsanto weed killer called acetochlor getting absorbed in the atmosphere and falling as rain on oak trees, according to University of Illinois research.

Hartzler wrote that the oak tatters damage was so much more severe than in past years, even though less acetochlor was being used. He said it was likely something else was causing the damage but did not mention dicamba.

Williams quickly forwarded the message to Goetsch and Rosenthal, writing, “Here you go gents … hope this helps.”

In an interview with the Midwest Center, Hartzler, a weed scientist, said his article was about oak tatters and not dicamba damage.

Hartzler also said the damage cited in Nelms’ complaints was likely caused by dicamba, or another herbicide, 2,4-D.

“That’s definitely dicamba or a related herbicide,” Hartzler said.

Hartzler said after his piece, Monsanto approached Iowa State forestry officials about potentially researching the cause, but Monsanto’s interested waned as dicamba damage spread.

Three months later, Hartzler said he still isn’t sure why the oak tatters were so widespread. He does not believe it is dicamba or acetochlor but he has no idea why it’s so bad.

“I don’t think we have any idea what the cause is and maybe it’s acetochlor, but it just doesn’t make sense to me,” Hartzler said.

A previous version of this article incorrectly stated that Lou Nelms filed numerous complaints with the Illinois Department of Agriculture. The article has been updated to reflect the fact that Nelms filed one formal complaint with the Illinois Department of Agriculture and three informal complaints with the Illinois Department of Natural Resources. The Midwest Center for Investigative Reporting regrets the error.

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Join the Conversation


  1. If these chemicals are harmful to oak trees, then they are also harmful to humans and all other organic life.

  2. This is so pitiful. Big chem cares only abut one thing: making money, not the damage they do to people or our environment, including the air we breathe and the water we drink. When will the EPA do something? Certainly not as long as Scott Pruitt is there. And what about Chlorpyrifos? The DOW ag chem that causes ADD and ADHD and was set to be banned by the EPA until Donald Trump signed an Executive Order keeping it from being banned until 2024? That, after he received a $1 mil donation to his inaugural campaign from Alex Liveros the CEO of DOW. All $ in the Inaugural funds cannot be audited, and can be spent anyway they like without any reporting to anyone. It can even go into his private checking account, without any disclosure ever! And, he turned and gave the pen he used to sign the Executive order to who else? Alex Liveros. Watch the video of the signing online.

  3. Well, the lack of comments here indicate that people don’t care and that the losses are considered acceptable.

  4. We need to continue to speak out about these chemicals and put
    more pressure on the EPA to do something. The chemical companies are
    going to poison us all by spreading the chemicals on all of our food and

  5. We lost 2 walnut trees this year. Have no idea why. Well, we have some idea. They are along the side of the field that got sprayed. Not sure what was in the spray but at this point, I can only guess what it is. Hope it doesn’t affect our oak trees, also.

  6. there shouod be some bio assay technique available to pin down the culprit causing the damage to oak trees. the leaves of the effected trees could be tested for the weedkiller ingestion in the leaves resulting in the damage. forensic science has advanced very fast with latest techniques like gas chromotography etc to find our the poisoning agents in human victims. the same could be adopted to find out the cusative agent- it provies irrevocable proof to charge the weedkiller company and user with the damaged trees.

  7. The reason is known. The chemicals are known. Your voice is being silenced. You know where that is happening. You are a threat. Will you be silenced? You have to speak out to find out. I am sorry but you are right. I am so sorry that you have to to stand up to these powerful companies. It is not right but it is what it is.

  8. Not necessarily true. Douse an oak tree with vinegar and the leaves will die. I’m pretty sure you would not say that acetic acid is universally harmful to all organic life. However, that said, they may be harmful and it is certainly a topic that is worthy of discussion and research.

  9. At last, someone with the presence to be noticed has spoken. I have tried for many years to alert Ohio, and specifically, Huron County, that my trees were dying from spray. All it has accomplished is complete denial and unpleasant letter from The state agent responsible for this problem. I have pictures and letters written for the past several years to document this spray damage. It has damaged or killed Chestnuts, Flowering pear, dogwood, snow-on-the-mountain, grapes, honeysuckle, English walnut, pecan tree, beauty bush, boxwood, pear tree, two apple trees and others. The inspector of our county came out and could not find any cause for the dying trees, but he was absolutely certain it wasn’t spray. One flowering pear across the road from sprayed field was fine in morning. I came home a few hours later and every leaf looked as if it had been dipped in chocolate syrup. Spray is not new to me, I was here before spray and before “Silent Spring”. I was here probably before most of the pesticide scouts and doing ‘ hands-on’ farming before they were born. I have given up my efforts for justice, but when I look at woods and trees whose canopy get more sparse every year, my heart is sad.

  10. You can determine if dicamba was sprayed and volatizing into the air into trees into the air with pesticide testing kits sold online, there are also super sniffers available to purchase to test the air quality around your homes. The Illinois department of Ag, the Illinois EPA district 5 has the ability to come out and do these test was asked to do, so but did not. If I purchase these testing kits and super sniffers to prove that I am right in my suspicions of off site movement of dicamba I was told that my information would be biased and not accepted. As long as no one comes out to test, there will continue to be no problem. I developed what is known as a Dicamba Cough from July to August 2017 two interviews from CDC doctors i have not heard a word from anyone. You can also fill out an adverse effect form ‘google a 6a2 form for health related issues and property damage including trees. Illinois Department Ag came to my house and he said ” the worst dicamba damage he has seen in 17 years”

  11. My brother has a tree nursery in NE Nebraska and he has had $300K in damage to his trees this year. He’s been waiting 5 months for the state to get back to him. He can’t dig and sell the trees this fall because more damage won’t be evident until next spring. We took a drive around our little farming community town and he pointed out the damage from dicamba drift to the crowns of trees in the entire town. He has a lawyer but its like David fighting Goliath. There will be no stopping big Ag and big chemical lobbyist.

  12. We’ve been noticing damage to the crowns of trees all over Jefferson County, Iowa. Some of it is ash trees dying from emerald ash borer, but most of the damage is not. We lost 5 150 year old bur oaks in the past 3 years. This is a sad situation, folks.

  13. As soybean and cotton farmers across the Midwest and South continue to see their crops ravaged from the weed killer dicamba, new complaints have pointed to the herbicide as a factor in widespread damage to oak trees.

  14. A lawn weed killer containing the chemical Dicamba used last year killed 3 7 year old apple trees in our yard. Followed all directions on container. Stayed away from the drip line of all trees. Made sure the wind was blowing away from the trees, even though the wind was non existent at time of putting the weed killer down

  15. I have lost many oak trees on my 40 acre property surrounded by farmers planting either corn or beans every year. Last year I had 5 die. This year appears to be a repeat so far. Usually the crown shows the stress first but sometimes one side will be more affected. I’ve had the county ag agent out the last 2 years with him only saying it could be drift. But nobody seems to care or do anything. I’m sure the big chem companies have plenty of money to spend on lawyers to fight. They will probably say products weren’t applied per the instructions and they could be right. But that doesn’t help me on what use to be a beautiful property. Northern Kentucky.

  16. Our yard was hit by dicamba and atrazine. The path was very evident at how it traveled from the neighbors field. I am losing most of my yard., 4 1/2 acres filled with trees, shrubs, plants. The farmer doesn’t care, the chemical company who sprayed has already said they won’t do anything. Blaming the weather.

    Soil, plant tissue tests show the chemicals but they say I can’t prove anything.

    I’m fighting back. These chemical are very harmful to humans and pets. Atrazine is well known to have a long residual life.

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