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Dicamba 2020 Registration Decision — Frequently Asked Questions

  1. How is EPA making over-the-top dicamba product labels simpler to understand?
  2. Why is EPA requiring that over-the-top dicamba products be tank mixed with an approved pH-buffering agent prior to all applications, and how will this be implemented?
  3. How will EPA enforce the use of a pH buffering agent?
  4. Why is EPA expanding downwind infield buffer distances and how will this change be implemented?
  5. Why is EPA implementing calendar cut-off dates for these dicamba products and how will this change be implemented?
  6. Will EPA’s 2020 Registration Decision harm endangered species?
  7. Are there human health risk concerns associated with dicamba registration decision? Can dicamba cause cancer?
  8. Are there alternatives to dicamba?
  9. Are weeds developing resistance to dicamba?

1. How is EPA making over-the-top dicamba product labels simpler to understand? 

To clarify use directions, the labels for over-the-top dicamba products will only include uses for DT cotton and DT soybeans. The 2018 labels also included use directions for certain non-DT crop uses, which added length and a source of potential confusion to the labels. Going forward, dicamba applications to other (non-DT) registered use sites will need to be made with other appropriately registered products.

EPA has also eliminated use restrictions based on the target crop growth stage, and replaced it with specific calendar date cutoffs, after which applications of the products is prohibited. The calendar date cutoffs are clear and definite, while crop growth stage is less predictable and harder to determine as it can vary among plants in the same field. 

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2. Why is EPA requiring that over-the-top dicamba products be tank mixed with an approved pH-buffering agent prior to all applications, and how will this be implemented? 

EPA is requiring that an approved pH-buffering agent (also called a volatility reduction agent or VRA) be tank mixed with over-the-top dicamba products prior to all applications. Dicamba is diluted for use and other agricultural chemicals are typically added into the tank mix, however, that can change the pH, and dicamba becomes more volatile at low pH. 

Based upon data reviewed by agency scientists, the label requirement to include a pH-buffering agent reduces the potential for volatilization that could otherwise affect vegetation located beyond the fields treated with over-the-top dicamba products. EPA has worked with registrants to develop and implement a certification process for a variety of pH buffering agents to be available to growers. This will provide growers with the opportunity to choose which approved pH buffering agent they want to tank mix with their dicamba product. 

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3. How will EPA enforce the use of a pH buffering agent? 

The label requires the use of the pH buffering agent. EPA will enforce the use of a pH buffering agent through recordkeeping practices.

Applicators will have to document that they have mixed the pH buffering agent and that they have purchased sufficient quantities of the pH buffering agent given the amount of the dicamba product they will be applying. These pH buffering agents are not premixed and must be mixed by the applicator.

These applicators are highly trained professionals who, in addition to meet the stringent requirements of being certified, have undertaken dicamba-specific training to ensure applications occur properly.

Failure to include a pH buffering agent when mixing XtendiMax with VaporGrip Technology,  Engenia Herbicide, or Tavium plus VaporGrip Technology is a misuse and is a violation of federal law. Also, registrants are required as a term of their registrations to ensure that a sufficient supply of pH buffering agent products are available to users of dicamba products registered for use on DT cotton and soybeans.

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4. Why is EPA expanding downwind infield buffer distances and how will this change be implemented? 

Pesticide movement off of the target site can occur with all pesticide products. Pesticide exposure can affect people’s health and the environment, and damage nearby crops as well as non-crop vegetation. EPA is actively engaged in several initiatives to help minimize, including addressing off-site movement for dicamba products. 

Through this action of increasing the required buffer sizes, to help minimize drift, users of dicamba over-the-top use products must establish a single-direction in-field downwind buffer, and in specific counties with endangered species concerns, an additional omnidirectional in-field buffer.   

This registration decision will put in place a 240-foot downwind buffer in counties without endangered species concerns. In counties with endangered species concerns, this action puts in place a 310-foot downwind buffer and a 57-foot omnidirectional infield buffer.

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5. Why is EPA implementing calendar cut-off dates for these dicamba products and how will this change be implemented?

Previous dicamba registrations for DT crop use included target crop growth stage-based cutoffs after which over-the-top spraying of dicamba on cotton and soybeans was prohibited. To simplify labeling and improve label compliance, new calendar date restrictions are replacing the former growth stage requirements, whereby applications to DT soybeans may not occur after June 30, and applications to DT cotton may not occur after July 30.     

On average, the later in the season dicamba is applied over-the-top, the more possible it is that nearby vegetation, including but not limited to crops other than DT cotton and DT soybeans, will have emerged and be susceptible to damage from off-target movement of dicamba.

In addition, dicamba applications to large weeds provide incomplete control and speed the development of dicamba-resistant weeds. Repeated sub-lethal doses of herbicides are known to promote the development of resistance. For these reasons, EPA will require that dicamba applied to DT crops be used only for early season applications rather than late season rescue treatments. Alternative herbicides are available to assist with late season weed control.  

One of the dicamba products subject to this decision, Tavium plus VaporGrip Technology, contains a second active ingredient in addition to dicamba: S-metolachlor. Due to concerns specific to this other active ingredient, Tavium plus VaporGrip Technology will continue to have growth stage cutoffs in addition to having new calendar cut-off dates.

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6. Will EPA’s 2020 Registration Decision harm endangered species?   

After completing its Endangered Species Act (ESA) effects determination for dicamba uses on DT cotton and soybeans, EPA concluded that with the control measures now required on labels, EPA determined that these actions do not affect listed species. EPA included an analysis of the potential for effects to listed species as part of its 2020 ecological risk assessment for dicamba products used on DT cotton and soybeans.

The goal of an ESA effects determination is to evaluate whether the federal action poses any reasonable expectation of discernible effects to federally threatened and endangered species and designated critical habitats within the action area. The ESA effects determination makes use of the best available scientific information and considers both direct effects (e.g., toxic effects occurring from exposure to a pesticide) and indirect effects (effects occurring from impacts to plants or animals that are important to a species’ prey, pollination, habitat, or dispersal). 

In the 34 states where over-the-top dicamba products can be used, EPA identified 23 listed species as being within the action area. Information regarding these endangered species and the 287 counties in which they are located, where enhanced control measures, including both downwind 310-foot wind-directional spray drift and 57-foot omnidirectional buffer distances are in place, can be found in the effects determination.

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7. Are there human health risk concerns associated with dicamba registration decision? Can dicamba cause cancer?

EPA has not identified any risks of concern regarding human health, including all population subgroups, or for occupational handlers. EPA has not identified cancer as a human health risk of dicamba. 

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8. Are there alternatives to dicamba? 

There are alternative programs available for controlling problematic broadleaf weeds in cotton or soybean. However, not all postemergence herbicide options for the control of some problematic broadleaf weeds may be appropriate for all users, meaning that some cotton and soybean growers may benefit from the registration of dicamba for use on DT crops. This is especially true for growers facing weed populations with resistance to glyphosate, ALS (acetolactate synthase) inhibitor herbicides, and PPO (protoporphyrinogen oxidase) inhibitor herbicides. 

The registration of dicamba for use on DT cotton or soybean would give growers additional flexibility in choosing varieties for managing herbicide-resistant weed populations, thereby prolonging the effectiveness of currently available control options for herbicide-resistant weed species.

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9. Are weeds developing resistance to dicamba?  

Yes, increased use of dicamba products for use on DT crops on millions of acres of cotton and soybean has created more selection pressure and has led to the selection of dicamba-resistant Palmer amaranth biotypes in Kansas and Tennessee.

This rapid selection of an herbicide-resistant biotype was expected based on early research conducted at the University of Arkansas, which selected for dicamba-resistant biotypes in greenhouse studies and found it to develop within three generations.

While there have been no new populations of dicamba-resistant waterhemp reported since 2016, there are populations in three states that exhibit reduced sensitivity to dicamba. 

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