Understanding the Current State of the Pesticide Dicamba

By: Food law attorney Richard M. Blau, Chair, Nationwide Food Law Team

Dicamba is a selective herbicide in the chlorophenoxy family of chemicals. It comes in several salt formulations and an acid formulation. It is a common herbicide used in getting rid of weeds and woody plants. Dicamba is sold under the names XtendiMax (Monsanto), Engenia (BASF), and FeXapan (DuPont).

On October 13, 2017, the Environmental Protection Agency announced that farmers may continue spraying the weed-killing chemical dicamba on dicamba-tolerant soybeans and cotton. According to EPA, the agency reached an agreement with the manufacturers “on measures to further minimize the potential for drift to damage neighboring crops from the use of dicamba formulations used to control weeds in genetically modified cotton and soybeans.

New requirements for the use of dicamba "over the top" (above-ground spraying application to growing plants) will allow farmers to make informed choices for seed purchases for the 2018 growing season. The decision represented a victory for the biotech giants Monsanto, BASF and DuPont, as well as the farmers who want to use dicamba-based postemergents XtendiMax, Engenia or FeXapan.

Under the agreement with EPA, BASF, DuPont and Monsanto are making significant label changes for over-the-top dicamba product use. Key changes include:

  • Products will be reclassified for “restricted use.” Only certified applicators with dicamba-specific training can apply them. That may limit use.
  • Farmers are required to maintain specific product use records.
  • Maximum wind speeds must be below 10 mph (down from 15 mph) to reduce potential drifort
  • Applications may be made only between dawn and dusk.
  • Tank clean-out rules must be followed to avoid cross-contamination.
  • Nearby sensitive crop registries must be notified.

With EPA’s approval, farmers are expected to plant even more dicamba-tolerant soybeans as part of next summer’s 2018 crop. Farmers planted approximately 20 million acres of dicamba-tolerant soybeans during the summer of 2017. Industry observers expect that number to double next year; so long as the demand for these agricultural commodities remains strong, the need to control difficult-to-manage weeds also will remain strong. 


In the eyes of many farmers and farming experts, however, the new guidance and usage requirements on dicamba announced by the EPA do not address the problem of "volatilization," i.e., when dicamba evaporates from soil or plants where it was sprayed and drifts in unpredictable directions.  Farmers across the Midwest and South, and now even in Northern states such as Minnesota and the Dakotas, are nervous about the continued use of dicamba because the pesticide has an established record of drifting into thousands of fields where it did not belong and damaging those crops.

Moreover, many independent scientists say that this vapor drift was a major cause of damage to neighboring fields this summer. For example, scientists with the Integrated Pest Management Department at the University of Missouri issued “"A Final Report on Dicamba-injured Soybean Acres" to provide a quantitative analysis of the extent of dicamba-injured 2017 crop soybeans throughout the United States, either in the form of official dicamba-related cases that currently are under investigation by the Missouri Departments of Agriculture, or as estimates of injured acreage from university extension weed scientists across America. The final report, issued on October 30, 2017, indicates that there are 2,708 dicamba-related injury cases currently under investigation by various state departments of agriculture around the United States.  

The report also concludes that there were approximately 3.6 million acres of soybean that were injured by off-site movement of dicamba at some point during 2017. These numbers reflect an increase from previously-compiled data, primarily due to changes that occurred in some of the northern states like Minnesota, North Dakota, and South Dakota.

While farmers have used dicamba for decades, it was only this past summer that they received permission to use it in a new way, spraying it over the top of soybean and cotton crops that Monsanto has genetically modified to tolerate the chemical. This meant that more dicamba was sprayed, and it was being applied in the heat of summer, which makes chemicals more likely to turn into a vapor and drifort


Professor Robert Scott is a scientist in the Crop, Soil and Environmental Science Department at the University of Arkansas. Prof. Scott and several colleagues recently performed a series of experiments testing the volatility of dicamba’s transmission capacities. The scientists sprayed trays of soil with dicamba, then placed those trays in a field of soybeans far from any dicamba spraying. The soybean plants next to the dicamba-treated soil showed clear signs of exposure to the chemical. The results help explain why Arkansas farmers lodged more than a thousand complaints with state agriculture officials during the past year.

Dicamba drift or volatilization is problematic for many reasons. The obvious concern is contamination to fields that are cultivated under organic or sustainable conditions, without the use of chemical pesticides. Yet, an equally important concern is the impact of dicamba’s volatile transmission tendencies on a farmer’s decision regarding seed selection. Farmers who previously planted seeds that are pesticide free, but who are situated in proximity to neighbors that farm with dicamba, may be compelled to buy Monsanto's dicamba-tolerant seeds next year because those crops will not be vulnerable to windblown dicamba. 

Monsanto continues to insist that vapor drift was not responsible for any of the damage that farmers saw this past summer. The company also rejects the concern that farmers are buying dicamba-tolerant seeds to defend themselves from neighbors who use dicamba. Rather, Monsanto contends that its dicamba-tolerant Xtendimax seeds are popular because they are high-yielding seeds.


In 2016, Missouri imposed most of the restrictions that the EPA is now requiring, and farmers in the state still saw widespread damage from drifting dicamba. Many state departments of agriculture are deciding whether they will impose any additional state requirements for the use of dicamba-related products.

The issue is about to reach a boil in Arkansas. 

The Arkansas State Plant Board (ASPB) investigates complaints or allegations filed by citizens relating to alleged chemical misuse. Since 2015, the ASPB has worked to investigate and in some cases prosecute for a higher than normal volume of dicamba-related complaints.

As a result of those complaints, Arkansas banned dicamba use in July of this year for 120 days. The ASPB subsequently voted to approve regulatory changes for the application of products labeled for agricultural use that contains dicamba in Arkansas during its regularly scheduled quarterly meeting on September 21, 2017. The approved changes, if implemented, will prohibit the use of dicamba in Arkansas between April 16 and October 31 of 2018. The regulations provide exemptions for the use of dicamba in pastures, rangeland, turf, ornamental, direct injection for forestry, and home use. 

As a matter of administrative procedure, the ASPB’s regulatory changes concerning the use of dicamba were subject to a 30 day public comment period, which ended on October 30, 2017. Over 25,000 comments were received by email and mail.

As a result of the extraordinary public interest, the ASPB will hold a special hearing on November 8, 2017, to sift through public comments, receive additional input from stakeholders, and attempt to achieve a consensus regarding next steps for addressing volatilization concerns regarding dicamba. Following a growing season where nearly 1,000 off-target drift complaints were filed, expectations are for an abundance of speakers at the meeting offering vigorously-voiced and widely-diverging points of view.


The decision made by Arkansas authorities could have national repercussions. Even in states where agriculture regulators decline to take action, negatively-impacted farmers are pursuing alternative legal remedies. 

As agri-science continues to explore the impact of volatilization, injured farmers are filing lawsuits for losses caused by the herbicide’s over-the-top spraying that was not approved for on-crop use until late last year. Plaintiffs are contending that dicamba works for farmers who use it properly, but if their neighbors also do not use proprietary dicamba-resistant seeds, then the pesticide spreads to their fields ruining their crops. 

Several law firms across the country have begun focusing on representing farmers injured by dicamba volatilization. Complaints typically claim that Monsanto and the other defendants deceptively marketed their latest dicamba formulations as “low-volatility” herbicides that would not be as prone to off-target movement. As a result, these lawsuits say that significant damage was done to millions of acres of American crops. 

Not surprisingly, some plaintiff’s lawyers perceive the current dicamba situation as one that is best addressed through class action litigation. One example is the advertisement used by ClassAction.com attorney Rene Rocha, who filed a lawsuit against Monsanto, BASF, and DuPont in the Southern District of Illinois on behalf of Brian Warren, owner and operator of Warren Farms in Broughton, Illinois.  

The Warren complaint alleges that in June and July of 2017, Mr. Warren observed cupping, curling, strapping, discoloration, leaf elongation, wrinkling, stunting, and twisting on his soybean and pumpkin crops. As a result, he sustained a loss of crop yield and will also sustain future losses.

The complaint goes on to state: “Numerous farmers within the vicinity of plaintiff purchased and planted Xtend variety soybean and cotton, and applied Xtendimax, Engenia, and Fexapan to their Xtend variety crops.” It also alleges that the neighboring farmers used the herbicides in the manner intended and expected by Monsanto, BASF, and DuPont, yet the resulting damage still occurred.

The lawsuit notes that there have been thousands of allegations of dicamba damage in dozens of states, and that “millions of acres of American crops have been damaged.” due to dicamba’s volatilization.


Dicamba is just the latest in a long line of quandaries facing modern agriculture. At the heart of the dilemma is the correct balance between the demands for greater efficiency and yield versus the concerns over environmental integrity and safety. 

As with the debate over GMOs, however, this dispute entails more than just the safety and purity of the crop itself.  While many farmers choose to reap the benefits of insecticide-resistant seeds, others are determined to shun such genetically-engineered options. The issue posed by the current dicamba crisis is whether these two diametrically-opposed methods of farming can co-exist?