Dicamba is a selective systemic herbicide used to control annual, biennial and perennial broadleaf weeds in a variety of food and feed crops and in non-agricultural settings.
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Dicamba has been used as a pesticide since 1967 in both agricultural and non-agricultural areas:
- The largest agricultural markets for dicamba in terms of total pounds of active ingredient include corn, cotton, fallow, pasture, sorghum, soybeans, sugarcane and wheat crops.
- It is also used on asparagus, barley, conservation reserve program land, uncultivated land, hay, grass grown for seed, oats, pastures/rangelands, proso millet and triticale.
- Some dicamba products can be sprayed over-the-top (OTT) of genetically engineered soybeans and cotton after the crops have emerged from the ground.
- Non-agricultural uses include agricultural premises, commercial and residential turf, cut stump treatment, forestry, golf courses, gardens/ornamentals, outdoor industrial areas, rights of ways, recreational and residential lawns, and residential areas.
Dicamba products are sold as liquids, liquid concentrates, granules, water dispersible granules, ready-to-use sprays, and wettable powders. Products may be applied by ground and aerial equipment, banded wiper, soil incorporation, basal bark/cut stem and spot treatment methods.
Dicamba is currently undergoing registration review, a program that re-evaluates all pesticides on a 15-year cycle.
In July 2022, EPA released a second addendum to the 2016 draft human health risk assessment and a draft ecological risk assessment and a draft ecological risk assessment for dicamba. The draft risk assessments (DRAs) are part of a multi-step re-evaluation process for the full dicamba case and considers all registered products and all registered uses, including OTT applications to growing plants. The human health risk assessment identified potential occupational handler risks of concern for mixing and loading dry flowable formulations for application to sod and field crops. The Agency did not identify dietary, residential, aggregate, or post-application risks of concern.
In addition, the draft ecological risk assessment identified potential adverse effects to birds, mammals, bees (larvae), aquatic plants and non-target terrestrial plants for all dicamba uses but did not include an Endangered Species Act (ESA) assessment of risk to listed species. The primary ecological risk of concern is for non-target terrestrial plants from exposure through spray drift and volatilization. Numerous non-target plant incidents associated with the use of dicamba have been reported. Since the initial registration of OTT uses in 2016, there has been a substantial increase in the overall number of reported non-target plant incidents which appear to be linked to the OTT uses. EPA continues to monitor the incidents information for dicamba.
After reviewing and considering the public comments received on the DRAs, EPA will issue a proposed interim decision (PID), which will identify potential risk mitigation and control measures for herbicide as needed to address any of concern identified in the DRAs. This PID is the next step in the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) registration review process.
Over the Top Dicamba Uses
Over-the-top (OTT) uses on dicamba-tolerant soybean and cotton were first registered in 2016 on a two-year time limited registration. In 2017 and again in 2018, EPA amended the registrations of all OTT dicamba products following reports that growers had experienced crop damage and economic losses resulting from the off-site movement of dicamba. The U.S. Court of Appeals for the Ninth Circuit vacated the 2018 registrations in June 2020 on the basis that “EPA substantially understated risks that it acknowledged and failed entirely to acknowledge other risks.” EPA’s Office of the Inspector General concluded that EPA deviated from typical procedures in its 2018 decision despite the best efforts of EPA’s career scientists and managers to recommend a different approach that was scientifically, procedurally, and legally sound.
In October 2020, EPA issued new registrations for two dicamba products and extended the registration of an additional dicamba product. These registration decisions were expected to address the risk concerns noted by the Ninth Circuit. All three registrations included cutoff dates for applications in late summer and expanded infield buffers for counties with listed species that the Agency expected would prevent off-target movement and damage to non-target crops and other plants.
In December 2021, EPA released a summary of dicamba-related incident reports from the 2021 growing season obtained from pesticide registrants, States, the general public, and non-governmental organizations. Despite the control measures implemented in EPA’s October 2020 dicamba registration decision, the 2021 incident reports show little change in the number, severity, and/or geographic extent of dicamba-related incidents when compared to the reports the Agency received before the 2020 control measures were required.
In March 2022, EPA approved additional labeling to further restrict use of OTT dicamba in Minnesota and Iowa and in February 2023, EPA approved additional labeling for Iowa, Illinois, Indiana, and South Dakota. The restrictions are intended to reduce the likelihood of volatility and offsite movement of OTT dicamba by avoiding application on days with high temperatures. For Iowa, the February 2023 amendment supersedes the March 2022 amendment.
EPA is currently working with states and other stakeholders to collect incident information for the 2022 growing season. The Agency is reviewing whether OTT dicamba can be used in a manner that does not pose unreasonable risks to non-target crops and other plants, or to listed species and their designated critical habitats. EPA is also evaluating its options for addressing future dicamba-related incidents. The Agency is committed to helping states address issues related to incidents in their jurisdictions. If a state wishes to further restrict or narrow the OTT uses of dicamba, the Agency will work with each state to support its goals.
In response to a lawsuit against EPA concerning these registrations, on February 6, 2024, a ruling by the U.S. District Court of Arizona vacated the 2020 registrations for OTT dicamba products - XtendiMax, Engenia, and Tavium. As of February 6, 2024, these products are unregistered, and sale or distribution of these products is unlawful except as provided in EPA’s February 2024 existing stocks order.
On February 14, 2024, EPA issued an Existing Stocks Order for Dicamba Products Previously Registered for Over-the-Top Use on Dicamba-Tolerant Cotton and Soybean. This Order addresses use of the formerly- registered dicamba products and authorizes limited sale and distribution of dicamba products that are already in the possession of growers or in the channels of trade and outside the control of the pesticide companies. Read the existing stocks order (pdf)