On February 6, 2024, a federal court in Arizona issued a ruling directing the Environmental Protection Agency (“EPA”) to vacate the 2020 registrations allowing over-the-top use of three dicamba-based pesticides, XtendiMax, Engenia, and Tavium. This marks the second time a court has ordered EPA to vacate a dicamba registration, following a ruling from the Ninth Circuit Court of Appeals which overturned the then-current over-the-top dicamba registration in June 2020. While the decision from the Arizona court relies on different legal arguments than the Ninth Circuit’s 2020 decision, the outcome is the same. Following the ruling, EPA has issued an order that will enable farmers to use existing stocks of dicamba directly onto crops during the 2024 growing season, but only if the pesticides were “labeled, packaged, and released for shipment” prior to February 6. After 2024, it is unclear whether dicamba will be available for over-the-top use going forward.


The herbicide known as dicamba has been used since the 1960s to target broadleaf plants. In recent years, dicamba has been used to combat weeds that have grown resistant to glyphosate including palmer amaranth, commonly known as pigweed. Prior to 2016, dicamba was primarily used as a pre-emergent, applied to the ground in late winter or early spring before any crops were planted. Dicamba is known for being highly volatile, meaning that it will evaporate into the air and travel off-target. This volatility is the reason why dicamba was historically used as a pre-emergent. However, in late 2016, EPA issued its first ever registration allowing dicamba to be used directly onto crops for the 2017 and 2018 growing seasons. The registration was granted to new, low-volatility forms of dicamba that were intended to be used on soybean and cotton seeds that were genetically modified to be resistant to dicamba.

The decision to approve over-the-top use of dicamba was highly controversial and quickly subject to legal challenge. Environmental plaintiffs filed a lawsuit against EPA claiming that the registration decision violated both the Federal Insecticide, Fungicide, and Rodenticide Act (“FIFRA”) and the Endangered Species Act (“ESA”). While the lawsuit challenging the 2016 registration was ultimately dismissed by the court after the registration expired, the plaintiffs quickly refiled to challenge the 2018 dicamba registration which EPA had issued to reapprove over-the-top use for another two years. In their challenge to the 2018 registration, the plaintiffs once again claimed that EPA had violated FIFRA and the ESA by failing to ensure that the registration decision met the standards of either statute. Ultimately, the plaintiffs were successful in their challenge and the Ninth Circuit issued a decision directing EPA to vacate the over-the-top dicamba registration for three dicamba-based products, XtendiMax, Engenia, and FeXapan. The decision was issued in June 2020, leaving many farmers with questions and uncertainty in the middle of the growing season. To learn more about the Ninth Circuit’s decision, click here.

Following the Ninth Circuit’s 2020 decision, EPA issued a Notice of Cancellation to formally cancel the 2018 dicamba registration. However, months later, EPA issued a new registration re-approving over-the-top use of dicamba for the 2021-2025 growing seasons. The new registration included additional use restrictions that EPA believed would resolve the issues the Ninth Circuit found with the 2018 registration. Once again, the same environmental plaintiffs that challenged the 2016 and 2018 registrations filed suit to challenge the 2020 registration. While the plaintiffs raised the same claims in their latest lawsuit as they had in the previous two challenges, it was the novel arguments made against the 2020 registration decision that ultimately swayed the court.

The Court’s Decision

The plaintiffs in Ctr. for Biological Diversity v. U.S. Envtl. Agency, No. 4:20-cv-00555 (D. Ariz. Feb. 6, 2024) raised various legal challenges against the 2020 over-the-top dicamba registration, claiming that the decision violated FIFRA and the ESA. The plaintiffs also raised procedural challenges, alleging that EPA had failed to follow mandatory notice-and-comment procedure when issuing the registration. Ultimately, the court agreed with the plaintiffs on the procedural arguments and vacated the registration without ever reaching the FIFRA and ESA claims. For an in-depth look at all the arguments raised by the plaintiffs in Ctr. for Biological Diversity v. U.S. Envtl. Agency, click here.

In their complaint, the plaintiffs argued that the 2020 over-the-top registration of XtendiMax, Engenia, and Tavium violated mandatory FIFRA notice-and-comment requirements. Specifically, the plaintiffs claimed that by issuing the 2020 registration decision without a period of public comment, EPA had violated FIFRA procedures for issuing a new use of a pesticide, and FIFRA procedures for “uncancelling” a pesticide use that had been formally cancelled.

Under FIFRA, EPA is directed to “publish in the Federal Register, […] a notice of each application for registration of any pesticide if it contains any new active ingredient or if it would entail a changed use pattern. The notice shall provide 30 days in which any Federal agency or any other interested person may comment.” 7 U.S.C. § 136a(c)(4), (emphasis added). In other words, FIFRA allows EPA to register a changed or new use of an already-registered pesticide after a 30-day period of public comment. In this context, a “new use” is defined as “any additional use pattern that would result in a significant increase in the level of exposure, or a change in the route of exposure, to the active ingredient of man or other organisms.” 40 C.F.R. § 152.3. The plaintiffs in Ctr. for Biological Diversity v. U.S. Envtl. Agency argued that the 2020 over-the-top dicamba registration was a “new use” registration because at the time it was issued, over-the-top use was not approved for dicamba due to EPA’s formal cancellation order. Because the 2020 registration was issued without a period of public comment, the plaintiffs claim that the decision violates FIFRA’s process for registering a new use.

In response, EPA claimed that the 2020 registrations were not new use registrations approved under section 136a(c)(4) of FIFRA, but were instead approved under a different FIFRA provision colloquially referred to as the “me-too” provision. Under this “me-too” provision, EPA may register or amend registration of a pesticide which is “identical or substantially similar in composition and labeling to a currently-registered pesticide […] or that would differ in composition and labeling from such currently-registered pesticide only in ways that would not significantly increase the risk of unreasonable adverse effects on the environment[.]” 7 U.S.C. § 136a(c)(3)(B). Under FIFRA, “unreasonable adverse effects on the environment” is defined as “any unreasonable risk to man or the environment, taking into account the economic, social, and environmental costs and benefits of the use of any pesticide.” 7 U.S.C. § 136(bb). Before a pesticide may be registered for use under FIFRA, EPA must determine that when used as intended, the pesticide will not cause any unreasonable adverse effects on the environment. FIFRA’s “me-too” registration allows EPA to register a pesticide product, or amend an already registered pesticide label, so long as the new product or amended label is “substantially similar” to a currently registered pesticide and the new product or amended label would not “significantly increase” the risk of unreasonable adverse effects to the environment. EPA argued that the 2020 over-the-top registrations were “me-too” registrations because the Ninth Circuit’s decision directed EPA to cancel over-the-top use of XtendiMax, Engenia, and FeXapan. Tavium, though registered for over-the-top use in 2019 for the 2020 growing season, was not included in the Ninth Circuit’s decision. EPA claims that the 2020 re-registration of XtendiMax and Engenia were “me-too” registrations because the products were substantially similar to Tavium. Unlike “new use” registrations, “me-too” registrations do not have a notice-and-comment requirement.

Ultimately, the court agreed with the plaintiffs that the 2020 registrations of over-the-top use for XtendiMax and Engenia were “new use” registrations that were subject to notice-and-comment requirements. Crucial to the court’s decision was the fact that Tavium itself had been approved for over-the-top use as a “me-too” registration. The 2019 Tavium registration was made pursuant to FIFRA’s “me-too” provisions based on the already-registered over-the-top dicamba products XtendiMax and Engenia. According to the court, “EPA erred when it relied on the Tavium 2019 registration, which was premised on these vacated and cancelled XtendiMax and Engenia registrations.” The court determined that the 2020 registrations met the definition of “new use” and that EPA should have followed the notice-and-comment requirements for a “new use” registration.

Along with concluding that EPA failed to provide the required notice-and-comment period for registering a new use of a pesticide, the court also concluded that EPA violated FIFRA’s requirement to provide a period of notice-and-comment when re-approving a cancelled pesticide use. According to FIFRA’s implementing regulations, if EPA would like to re-approve a pesticide registration that “has been finally cancelled or suspended,” then the agency must allow “notice and hearing opportunities.” 40 C.F.R. § 160.130. The plaintiffs argued that because EPA’s 2020 registration decision re-approved a use that had been formally cancelled without a period of public notice and comment, the registration decision violated FIFRA. The court agreed with the plaintiffs, finding that EPA had twice violated FIFRA’s procedural mandates by failing to provide the notice-and-comment period required to registering a new use of a pesticide and to re-approve a cancelled use. For those reasons, the court overturned the 2020 over-the-top registrations of XtendiMax, Engenia, and Tavium. Following that decision, there are no dicamba products with an approved over-the-top use for the 2024 growing season.

Going Forward

On February 14, EPA issued an order to allow existing stocks of XtendiMax, Engenia, and Tavium directly onto crops so long as the pesticides were “labeled, packaged, and released for shipment” prior to the February 6 court decision. The existing stocks order was welcomed by members of the agricultural industry who were concerned that farmers who had already purchased dicamba products for the 2024 growing season would be unable to use what they had already purchased. The order also provides instructions for how to dispose of unwanted or unused dicamba products.

While the existing stocks order helps to clarify requirements for the upcoming growing season, it is unclear what the fate of over-the-top use of dicamba will be going forward. Currently, it is unknown whether EPA will appeal the court’s decision, or how successful such an appeal would be. The district of Arizona is part of the Ninth Circuit, so any appeal would bring the question of over-the-top dicamba registration back before a court that has previously vacated a similar registration. It is also unknown whether EPA will look to re-register over-the-top use of dicamba, or what steps the agency would need to take to produce a registration capable of withstanding judicial scrutiny.

At the moment, farmers and pesticide applicators who had intended to make over-the-top applications of dicamba during the 2024 growing season have more questions than answers.


To read the court’s decision in Ctr. for Biological Diversity v. U.S. Envtl. Agency, click here.

To read the text of FIFRA, click here.

To read more articles in The Deal With Dicamba series, click here.

For more NALC resources on pesticides, click here.