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 had received complaints each year for off-site movement onto neighboring property.
Annual Total Reports for Alleged Dicamba Drift
| Year | Number of Reports |
|---|---|
| 2024 | 5 |
| 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* |
|---|---|---|
| Acid | 1918-00-9029801 | Celius; Vision; Saddle-Up |
| Dimethylamine (DMA) salt | 2300-66-5029802 | Banvel; EndRun; Cimarron Max |
| Sodium (Na) salt | 1982-69-0029806 | Status; Rave; Overdrive |
| Potassium (K) salt | 10007-85-9129043 | Lawn 3iP Herbicide |
| Diglycolamine (DGA) salt | 104040-79-1128931 | Clarity; DiFlexx; Clarifier |
| Bis aminopropyl methylamine (BAPMA) salt | 100094 | Engenia |
*No endorsement is implied in the referencing of trade names.
Forms of Dicamba Registered for Use (list is not all-inclusive)
| Dicamba Form | CAS # / PC code | Trade Names* |
|---|---|---|
| Acid | 1918-00-9029801 | Celius; Vision; Saddle-Up |
| Dimethylamine (DMA) salt | 2300-66-5029802 | Banvel; EndRun; Cimarron Max |
| Sodium (Na) salt | 1982-69-0029806 | Status; Rave; Overdrive |
| Potassium (K) salt | 10007-85-9129043 | Lawn 3iP Herbicide |
| Diglycolamine (DGA) salt | 104040-79-1128931 | Clarity; DiFlexx; Clarifier |
| Bis aminopropyl methylamine (BAPMA) salt | 100094 | Engenia |
*No endorsement is implied in the referencing of trade names.
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.
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.
In Minnesota agriculture, dicamba is used to control weeds in various crops including corn, small grain, soybeans, and hay, as well as on fallow cropland, pastures, and land enrolled in conservation reserve programs. Prior to 2016, dicamba was registered for pre-plant and pre-emergence applications in conventional soybeans, Roundup Ready soybeans, and Liberty Link soybeans. From 2016 to 2024, Minnesota registered dicamba products for over-the-top (OTT) application to dicamba-tolerant (DT) soybeans to control broadleaf weeds such as pigweeds (Amaranthus spp.), ragweeds (Ambrosia spp.), horseweed (Conyza spp.), and Kochia spp. The MDA has worked with the EPA and the registrants of the three dicamba products to include the following restrictions on the product labels during 2022. Cutoff date: Do not apply south of interstate 94 after June 12. Do not apply north of interstate 94 after June 30. Cutoff temperature for the entire state: Do not apply if the air temperature of the field at the time of application is over 85 degrees Fahrenheit or National Weather Service’s forecasted high temperature for the nearest available location for the day exceeds 85 degrees Fahrenheit. Forecasted temperature must be recorded at the start of the application.
Non-agricultural applications of dicamba include uses on residential lawns and on golf course turf throughout the state.
The MDA tracks the sale of pesticide active ingredients in the state. The graph below shows annual dicamba sales in Minnesota between 1996 and 2022 (Figure 1). Dicamba sales data are pooled for all forms of dicamba and reported as the pounds of dicamba acid equivalents (a.e.) sold. Notably, dicamba sales increased significantly in 2017, rising from 428,000 pounds in 2016 to 910,000 pounds in 2017, coinciding with the release of new OTT dicamba products. Sales data are available through the Pesticide Sales database.
In Minnesota agriculture, dicamba is used to control weeds in various crops including corn, small grain, soybeans, and hay, as well as on fallow cropland, pastures, and land enrolled in conservation reserve programs. Prior to 2016, dicamba was registered for pre-plant and pre-emergence applications in conventional soybeans, Roundup Ready soybeans, and Liberty Link soybeans. From 2016 to 2024, Minnesota registered dicamba products for over-the-top (OTT) application to dicamba-tolerant (DT) soybeans to control broadleaf weeds such as pigweeds (Amaranthus spp.), ragweeds (Ambrosia spp.), horseweed (Conyza spp.), and Kochia spp. The MDA has worked with the EPA and the registrants of the three dicamba products to include the following restrictions on the product labels during 2022. Cutoff date: Do not apply south of interstate 94 after June 12. Do not apply north of interstate 94 after June 30. Cutoff temperature for the entire state: Do not apply if the air temperature of the field at the time of application is over 85 degrees Fahrenheit or National Weather Service’s forecasted high temperature for the nearest available location for the day exceeds 85 degrees Fahrenheit. Forecasted temperature must be recorded at the start of the application.
Non-agricultural applications of dicamba include uses on residential lawns and on golf course turf throughout the state.
The MDA tracks the sale of pesticide active ingredients in the state. The graph below shows annual dicamba sales in Minnesota between 1996 and 2022 (Figure 1). Dicamba sales data are pooled for all forms of dicamba and reported as the pounds of dicamba acid equivalents (a.e.) sold. Notably, dicamba sales increased significantly in 2017, rising from 428,000 pounds in 2016 to 910,000 pounds in 2017, coinciding with the release of new OTT dicamba products. Sales data are available through the Pesticide Sales database.
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.
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 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.
