Herbicide Regulators Differ on Whether to Ban Dicamba

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Arkansas and EPA take different approaches to regulating a controversial herbicide called dicamba.

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As the weather heats up and summer gets into full swing, so does the growing season for major crops in America, bringing with it an enduring problem: weeds.

Chemicals that kill weeds—herbicides—serve as an important tool for weed control. The state of Arkansas, however, has banned the use of one herbicide—dicamba—during the upcoming growing season after it reportedly damaged millions of acres of crops last summer. The U.S. Environmental Protection Agency (EPA) has also taken steps to prevent a repeat of the damage, but it did not go so far as to ban the herbicide.

Dicamba has been used for decades to kill certain groups of weeds, including dandelions, clover, and ground ivy. In 2016, EPA approved a version of the herbicide for use with crops specifically engineered to resist it. Instead of using dicamba to target weeds only before planting crops, farmers can spray it over an entire field of the resistant corn, soybeans, or cotton, and the weeds will die while the crops continue to grow.

Although this combination of herbicide and herbicide-resistant crops can effectively kill weeds later in the season, dicamba used in 2017 apparently damaged millions of crops in nearby fields.

In the early part of the season, the application of dicamba did not cause problems because it stayed where farmers sprayed it. Later in the summer—when farmers’ applications coincided with high temperatures, which caused more of the herbicide to remain on the leaves of resistant soybeans instead of making it to the ground—enough of the dicamba evaporated and drifted to nearby fields to hurt the crops in those fields that were not dicamba-resistant. This drift reportedly impacted 3.6 million acres of soybeans, as well as residential gardens and other crops such as tomatoes, watermelon, cantaloupe, and pumpkins.

EPA has worked with states, universities, and dicamba manufacturers to make changes in application instructions that, if followed, the agency hopes will prevent a repeat of the damage caused in 2017. After the 2018 growing season, EPA will then make a determination about whether to allow the use of dicamba in the future.

EPA lauded its approach—which emphasized working with states and manufacturers to mitigate drift while still allowing growers to use dicamba and dicamba-resistant crops—as “an example of cooperative federalism leading to workable national level solutions.”

Regulators in Arkansas, however, seem to disagree that EPA’s required changes to product labels will provide a “workable solution.” The state officials do not want to take the chance that dicamba will damage crops this year.

Of the states affected by dicamba drift in 2017, Arkansas had both the highest number of dicamba-injury cases reported, at nearly 1000 reports, and the largest reported soybean acreage affected, at an estimated 900,000 acres.

In response to this widespread damage, the Arkansas Legislative Council earlier this year approved a rule adopted by the Arkansas State Plant Board to ban the use of dicamba during summer months. The rule has exceptions for use on turf, ornamental plants, and pastures found one mile in any direction from sensitive areas or susceptible crops, but it otherwise prohibits spraying dicamba over resistant crops between April and October.

Monsanto, one of the producers of dicamba, sued the Arkansas State Plant Board to challenge the ban. The company argued that the decision was arbitrary and that it violated the Commerce Clause of the U.S. Constitution as well as Monsanto’s constitutional right to due process.

In a brief decision delivered at the end of March, an Arkansas judge dismissed Monsanto’s suit. The judge found that, based on a recent Arkansas Supreme Court ruling, a sovereign immunity provision in the Arkansas Constitution barred Monsanto’s claim. The judge dismissed the case without ever ruling on the merits of whether the dicamba ban exceeds the Arkansas State Plant Board’s authority or violates Monsanto’s rights.

Monsanto has filed notice that it will appeal the lower court’s decision. In a recent court motion, Monsanto argued that the judge’s dismissal of the company’s lawsuit was “clearly erroneous” because it misapplied precedent.

As Monsanto’s appeal moves through the courts, the Arkansas Agriculture Department has put out an official statement saying that until the court system provides more certainty, the Department will “at a minimum” enforce federal label requirements. That Department also reminded users that the state can impose civil penalties of up to $25,000 for use of dicamba that damages other crops.

It remains to be seen whether Arkansas’s more cautious approach will prove necessary to protect crops this summer. Farmers in other states remain free to use dicamba as long as they follow the new application guidelines EPA and manufacturers agreed upon. Regulators from both the state of Arkansas and EPA will likely reevaluate their regulatory approaches to dicamba based on the results from this growing season.