2024 Dicamba Update
On February 6, federal Engenia, Tavium, and XtendiMax registrations were vacated by the Arizonia District Court due to their off-site drift and injury to non-target plants. This court action would prevent the use of these products in 2024. However, the EPA issued an order allowing use of product already in grower possession and limited sale and distribution of these dicamba products that are in the channels of trade. Continue to check MDA's website for possible updates or changes before using Engenia, Tavium, and XtendiMax in 2024. However, the Environmental Protection Agency (EPA) issued an order allowing use of product already in grower possession and limited sale and distribution of these dicamba products that are in the channels of trade.
According to the EPA's Existing Stocks Order for Dicamba Products the sale and distribution of XtendiMax, Engenia, and Tavium will end May 13, 2024 for purchasers south of I-94 and will end May 31, 2024 for purchasers north of I-94.
Additionally, XtendiMax, Engenia, and Tavium must not be applied after June 12, 2024 for users south of I-94 and June 30, 2024 for users north of I-94.
State specific restrictions still apply, see the "Cutoff Date and Cutoff Temperature" section on the Dicamba Herbicide page.
Continue to check the Dicamba Herbicide page for possible updates or changes before using Engenia, Tavium, and XtendiMax in 2024.
Dicamba is a selective systemic herbicide for post-emergence control of broadleaf weeds. It was first registered by the US Environmental Protection Agency (EPA) in 1967 and is available in several formulations (see table below). Dicamba is registered for use on a variety of food and feed crops, including corn, barley, wheat, and dicamba tolerant (DT) soybeans. It is also used to control weeds in turf including lawns, golf courses, sports fields, and parks.
Prior to 2016, dicamba in soybeans was restricted to only preplant and preharvest applications. However, since then the US EPA approved post-emergence, or over-the-top (OTT) use for specific dicamba products (Engenia, XtendiMax, Tavium) on dicamba-tolerant (DT) soybeans and cotton.
| Pesticide Type | Herbicide (Group 4) |
|---|---|
| Chemical Class | Benzoic Acid |
| Common Trade Names* | XtendiMax, Engenia, and Tavium |
| Registration Status | EPA: Registered since 1967, new Over-The-Top products are conditionally registered until December 2025 MN: Registered |
| Structure |
 |
*No endorsement is implied in the referencing of trade names.
Dicamba is a highly volatile chemical that can damage non-target plant species through spray drift (particle drift) and/or volatilization (vapor drift). New formulations were designed to reduce volatility. However, since OTT dicamba was registered for use on DT soybeans, the MDA has received complaints each year for off-site movement onto neighboring property.
Annual Total Reports for Alleged Dicamba Drift
| Year | Number of Reports |
|---|---|
| 2023 | 15 |
| 2022 | 32 |
| 2021 | 304 |
| 2020 | 128 |
| 2019 | 20 |
| 2018 | 51 |
| 2017 | 249 |
Forms of Dicamba Registered for Use (list is not all-inclusive)
| Dicamba Form | CAS # / PC code |
Trade Names* | Soybean OTT Products |
|---|---|---|---|
| Acid | 1918-00-9 029801 |
Celius; Vision; Saddle-Up |
none |
| Dimethylamine (DMA) salt | 2300-66-5 029802 |
Banvel; EndRun; Cimarron Max |
none |
| Sodium (Na) salt | 1982-69-0 029806 |
Status; Rave; Overdrive |
none |
| Potassium (K) salt | 10007-85-9 129043 |
Lawn 3iP Herbicide |
none |
| Diglycolamine (DGA) salt | 104040-79-1 128931 |
Clarity; DiFlexx; Clarifier |
XtendiMax Tavium |
| Bis aminopropyl methylamine (BAPMA) salt | 100094 | Engenia | Engenia |
*No endorsement is implied in the referencing of trade names.
How it Works
Dicamba is a systemic herbicide that functions as a plant growth regulator. Following application, dicamba is absorbed through leaves and roots of target weeds and is translocated throughout the plant. In the plant, dicamba mimics auxin, a type of plant hormone, and causes abnormal cell division and growth.
Dicamba belongs to the benzoic acid chemical class and is a Site-of-Action 4 herbicide. Other herbicides belonging to Group 4 (synthetic auxins) with a similar mode-of-action include 2,4-D, MCPA, clopyralid, halauxifen-methyl, and aminopyralid.
Use in Minnesota
In Minnesota agriculture, dicamba is used to control weeds in crops including corn, small grain, soybeans, and hay, as well as on fallow cropland, pastures, and land enrolled in conservation reserve programs. In 2016, Minnesota registered three new dicamba products (XtendiMax, Engenia, and FeXapan) for OTT application to DT soybeans to control broadleaf weeds such as pigweeds (Amaranthus spp.), ragweeds (Ambrosia spp.), horseweed (Conyza spp.), and Kochia spp. Prior to 2016, dicamba was registered for pre-plant and pre-emergence applications in conventional soybeans, Roundup Ready soybeans, and Liberty Link soybeans. New DT soybeans are tolerant to dicamba and glyphosate herbicides.
In 2017, the MDA received 249 complaints of off-site dicamba damage. To curb off-site movement, the MDA set June 20 as the annual application cutoff date for registered dicamba products from 2018 to 2020. This date was based on research and pesticide misuse complaints. In October 2020, EPA set June 30 as the application cutoff date on federal labels for OTT dicamba applications to DT soybeans. In 2022, the MDA worked with the U.S. Environmental Protection Agency (EPA) and the registrants of the three dicamba products to include the date and temperature cutoff restrictions on the product labels. Currently, three dicamba products, XtendiMax with VaporGrip Technology (EPA Reg. No. 264-1210, Bayer), Engenia (EPA Reg. No. 7969-472, BASF) and Tavium Plus VaporGrip Technology (EPA Reg. No. 100-1623, Syngenta) are registered for use in Minnesota. These products are approved for use on DT soybeans and DT cotton only.
Non-agricultural applications of dicamba include uses on residential lawns and on golf course turf throughout the state. Engenia, Tavium, and XtendiMax are not approved for these uses.
The MDA tracks the sale of pesticide active ingredients in the state. The graph below shows annual dicamba sales in Minnesota between 1996 and 2019. Dicamba sales data are pooled for all forms of dicamba and reported as the pounds of dicamba acid equivalents (a.e.) sold. Sales data are available through the Pesticide Sales database.
Toxicity
The various salts of dicamba are considered to have a similar toxicity to dicamba acid. Furthermore, Dicamba salts are rapidly transformed into the acid form in the environment. Therefore, toxicity information is listed for dicamba acid.
Human Health
Dicamba has a low acute toxicity via oral, dermal, and inhalation routes. It is an eye and dermal irritant, but it is not a skin sensitizer.
Human Health Values for Dicamba Acid. Data from US EPA1 and the Minnesota Department of Health (MDH).
| Population Adjusted Dose (PAD) | Acute=0.29 mg/kg/day Chronic=0.04 mg/kg/day |
|---|---|
| Cancer Effect | Not likely to be carcinogenic to humans |
| MDH Health Risk Limit (HRL) (chronic, 1993) |
200 µg ae/L |
Non-target Organisms
Dicamba toxicity is low for aquatic organisms, mammals, and honeybees, and it is moderately toxic to birds. Non-target plants exposed to dicamba may be damaged by this herbicide.
Dicamba acid toxicity values for aquatic and terrestrial organisms. Data from US EPA2
| Aquatic Organism | Toxicity Values | Toxicity Level |
|---|---|---|
| Freshwater fish | Acute LC50 = 28 mg ae/L Chronic NOAEC = N/A |
Slightly toxic |
| Freshwater invertebrates | Acute EC50 > 50 mg ae/L Chronic NOAEC = No data |
Practically non-toxic |
| Aquatic plants | Vascular EC50 = N/A Nonvascular EC50 = 0.493 mg ae/L |
|
| Most Sensitive Aquatic Life Benchmark (ALB)* |
61 µg/L (nonvascular plants) |
| Terrestrial Organism | Toxicity Values | Toxicity Level |
|---|---|---|
| Mammals | Acute oral LD50 = 2,740 mg ae/L Chronic NOAEC = N/A |
Practically non-toxic |
| Birds | Acute oral LC50 = 188 mg ae/L | Moderately toxic |
| Honey bee | Acute contact LD50 > 90.65 µg ae/bee | Practically non-toxic |
*ALB value based on toxicity data from US EPA3.
Dicamba in the Environment
Dicamba is quickly biodegraded in soil under aerobic conditions (with oxygen) but is more persistent under anaerobic conditions (without oxygen). It is not likely to leach to groundwater due to its fast degradation; however, dicamba may reach surface water via run-off, spray drift during application, or vapor drift. Vapor drift from the volatilization of dicamba can result in injury of nearby non-target plants.
Dicamba salts are rapidly transformed into the acid form in the environment; therefore, properties are listed for dicamba acid.
Chemical Properties
| Water Solubility | 6100 mg/L |
|---|---|
| Dissociation Constant | pKa = 1.9 |
Soil
| Adsorption | Koc = 3.45 - 21.1 mL/goc (mean = 13.4) |
|---|---|
| Soil Metabolism | Aerobic half-life = 18 days Anaerobic half-life = no data |
| Photolysis | no data |
Water
| Aquatic Metabolism | Aerobic half-life = 72.9 days Anaerobic half-life = 423 days |
|---|---|
| Photolysis | Half-life = 105 days |
| Hydrolysis | Stable |
Air
| Volatilization | Vapor pressure (25°C) = 3.41 x 10-5 torr Henry's Law constant = 1.79 x 10-8 atm m3/mol |
|---|
Degradates
3,6-dichlorosalicylic acid (DCSA) is the major degradate, or breakdown product, of dicamba. Because DCSA is primarily formed in plants, the EPA does not expect DCSA to reach groundwater at levels that would be of concern. However, DCSA is more toxic than the parent compound to certain species of birds and mammals; thus, there could be potential for adverse effects to certain species of birds and mammals. Mitigations are imposed on registration to alleviate these risks. Other minor degradates of dicamba include 3, 6-dichlorogentisic acid (DCGA) and 5-OH-dicamba.
Environmental Hazards
Dicamba product labels include the following statements; however, the language may vary among products. See individual product labels for full list of environmental hazards and spray drift management restrictions or recommendations. Always read the label before applying a pesticide.
|
Do not apply directly to water, or to areas where surface water is present or to intertidal areas below the mean high water mark. Do not contaminate water when disposing of equipment washwaters or rinsate. Apply this product only as directed This chemical is known to leach through soil into ground water under certain conditions as a result of agricultural use. Use of this chemical in areas where soils are permeable, particularly where the water table is shallow, may result in ground water contamination. Ground and Surface Water Protection
Endangered Species Concerns Use of this product in a manner inconsistent with its labeling may pose a hazard to endangered of threatened species. |
References
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US EPA Dicamba and Dicamba BAPMA Salt: Human-Health Risk Assessment for Proposed Section 3 New Uses on Dicamba-tolerant Cotton and Soybean (2016). [Docket ID: EPA-HQ-OPP-2016-0223-0002]
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US EPA Problem Formulation for the Environmental Fate, Ecological Risk, and Drinking Water Assessments in Support of the Registration Review of Dicamba (2016). [Docket ID: EPA-HQ-OPP-2016-0223-0004]
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US EPA Ecological Risk Assessment for Dicamba DGA Salt and its degradate, 3,6-dichlorosalicylic acid (DSCA), for the Proposed Post-Emergence New Use on Dicamba-Tolerant Cotton (2016). [Docket ID: EPA-HQ-OPP-2016-0187-0005]
