Review Date: August 2026
Overview
Diflufenican is a selective contact herbicide first registered by the U.S. Environmental Protection Agency (EPA) in June 2026.
The MDA routinely conducts reviews of new pesticide active ingredients (a.i.) prior to registration in Minnesota. The MDA completed its review of diflufenican in August 2026 and did not identify any risks of concern specific to Minnesota. To evaluate the potential impacts of diflufenican on groundwater and surface water, the MDA may add this a.i. to its water-quality monitoring program. Diflufenican is a per-/polyfluoroalkyl substance (PFAS) based on Minnesota’s PFAS definition (MINN. STAT. §18B.01.15c); therefore, products containing diflufenican are subject to additional regulations under the Pesticide Control Law.
The following is a summary of the MDA’s review of the EPA’s diflufenican risk assessments and product labels (EPA Docket EPA-HQ-OPP-2021-0435). The EPA uses high-end, conservative exposure estimates to evaluate risk based on various use scenarios; therefore, exposure estimates may not reflect future use and impacts in Minnesota.
Active Ingredient Details
- Chemical Abstracts Service (CAS) Number: 83164-33-4
- EPA Pesticide Chemical Code: 128009
- Chemical class: Pyridinecarboxamide
- Mode of Action (Herbicide Resistance Action Committee): Group 12 – inhibition of Phytoene Desaturase
- Basic Manufacturer: Bayer CropScience
Use Profile
Use Sites
Diflufenican is registered for preplant and pre-emergence control of broadleaf weeds in corn and soybean. It is the first Group 12 herbicide registered for use in these crops in the United States.
Target Pests
Diflufenican is labeled for control of waterhemp, Palmer amaranth, and other pigweed species. It also can be a valuable tool for managing weeds resistant to multiple herbicide modes of action.
Application Rates and Methods
Maximum single application rates vary by crop, with a maximum of one application per year. Only ground application (broadcast or banded) is approved for diflufenican.
Table 1. Maximum application rates for select use sites
| Use Site | Max Single Rate (LB A.I./ACRE) | Max Annual Rate (LB A.I./ACRE/YEAR) |
|---|---|---|
| Corn | 0.134 | 0.134 |
| Soybean | 0.16 | 0.16 |
Products
The EPA registered one technical product and one end-use product containing diflufenican. The end-use product is formulated as a suspension concentrate and is registered as Diflufenican SC 500 Herbicide (alternative name, Convintro). To view details for diflufenican products registered for use in Minnesota, visit the Kelly Solutions registered pesticide product database.
Projected Use in Minnesota
Diflufenican, with its novel mode of action, can be a valuable pre-emergence tool in integrated weed management and resistance management programs. There is considerable interest in this product because of its potential to diversify herbicide programs. When rotated with herbicides that have different modes of action, it may particularly be useful in managing herbicide-resistant waterhemp, Palmer amaranth, and other pigweed species. Because diflufenican has a relatively narrow weed-control spectrum, it can be tank-mixed with other residual herbicides for broad-spectrum control rather than used as a standalone product.
Human Health
Toxicity Profile
- Signal Word: Caution
- Toxicity Category (Based on acute exposure): Category III (moderate toxicity) for dermal exposure; Category IV (low toxicity) for oral and inhalation exposure and eye and skin irritation
- Population-Adjusted Dose (PAD) for Dietary Exposure: Acute PAD not calculated – no acute dietary endpoint attributable to a single dose identified; Chronic PAD = 0.37 mg/kg/day
- Cancer Classification: "Not likely to be carcinogenic to humans"
Drinking Water
The EPA identified the parent compound, diflufenican, and two of its degradates (diflufenican-acid and diflufenican-amide) as residues of concern for drinking water. The estimated drinking water concentrations (EDWCs) in surface water were 7 µg/L and 2.4 µg/L for acute and chronic exposure, respectively. Based on the EDWC, the chronic dietary risk estimate was below the EPA’s level of concern. Risk from acute exposure to diflufenican is not a concern because there were no adverse effects in the diflufenican database attributed to a single dose.
Occupational and Residential Exposure
The EPA did not identify any occupational or residential risks of concern from the use of diflufenican on corn and soybean. Workers who mix, load, or apply the pesticide have minimal inhalation risk, and the recommended 12-hour restricted-entry interval (REI) is considered protective of post-application exposure. There are no anticipated residential exposures because the product is not intended for residential use.
Environmental Fate
The movement and breakdown of diflufenican in the environment can vary depending on numerous factors including application site and methods, soil type, and weather. Diflufenican enters the environment through direct application, with potential off-site movement from spray-drift and runoff of soil-bound residues. It is slightly mobile in soil and binds to soil and sediment, which limits leaching to groundwater and lowers the concentration in the water column. Diflufenican is persistent in both soil and water, but it is not expected to bioaccumulate. Diflufenican primarily breaks down through soil metabolism.
Table 2. Diflufenican properties
| Property | Value |
|---|---|
| Solubility in Water (20°C) | 0.05 mg/L (Very low solubility) |
| Vapor Pressure (20°C) | 3.2 x 10-8 torr (Non-volatile under field conditions) |
| Henry's Law Constant (20°C) | 1.18 × 10-2 atm-m3 mol–1 |
| Binding Affinity/Sorption | Koc = 4,074 to 7,197 L/kgoc (Slightly mobile) |
| Octanol-Water Partition Coefficient | Log Kow = 4.2 |
Table 3. Diflufenican dissipation rates
| Degradation Study Type | Representative Half Life |
|---|---|
| Abiotic Hydrolysis | Stable at pH 5, 7, and 9 |
| Aqueous Phtolysis | Stable |
| Soil Photolysis | Stable |
| Aerobic Soil Metabolism | 21.2 to 273 days |
| Anaerobic Soil Metabolism | 102 to 1,100 days |
| Aerobic Aquatic Metabolism | 126 to 1,250 days |
| Anaerobic Aquatic Metabolism | 251 to 526 days |
| Terrestrial/Field Dissipation | 12 to 115 days |
Degradates
Diflufenican primarily breaks down through soil metabolism into three major degradates: diflufenican-acid (DFF-acid), diflufenican-amide (DFF-amide), and 2,4-difluoroaniline. DFF-acid, DFF-amide, and 2,4-difluoroaniline are more soluble and mobile than the parent compound (mean Koc: 8.75, 111, and 155.5 mL/goc, respectively) and may reach surface water or groundwater, but they are much less persistent with aerobic soil half-lives of 9-18 days (DFF-acid), 14-59 days (DFF-amide), and 0.5-1 hour (2,4-difluoroaniline).
Ecotoxicology
Risk Assessment and Residues of Concern
The EPA uses the Risk Quotient (RQ) Method to evaluate potential ecological risks from pesticides. The RQ is calculated by dividing the estimated environmental exposure concentration of a chemical by its toxicity endpoint. RQ values are then compared to established Levels of Concern (LOCs). RQ values above the LOC indicate a potential risk and need for further assessment or mitigation measures.
In the EPA’s ecological risk assessment, the parent diflufenican is considered the only residue of concern. Its major degradates are not considered residues of concern, based on available toxicity data.
Aquatic Ecotoxicology and Risk
Table 4. Diflufenican aquatic toxicity. LC50 = 50% Lethal Concentration; NOAEC = No Observable Adverse Effect Concentration; EC50 = 50% Effect Concentration.
| Taxa | Toxicity Information | Acute Risk Category |
|---|---|---|
| Freshwater Fish (Surrogates for Aquatic-Phase Amphibians) | Acute: 96-hr LC50 > 32.8 μg a.i./L Chronic: NOAEC = 2.99 μg a.i./L | No more than slightly toxic |
| Freshwater Invertebrates (Water-Column Exposure) | Acute: LC50 > 42.9 μg a.i./L Chronic: NOAEC = 76.5 ug a.i./L | No more than slightly toxic |
| Aquatic Non-Vascular Plants | EC50 = 0.283 μg a.i./L | - |
| Aquatic Vascular Plants | EC50 > 48.2 μg a.i./L | - |
According to the EPA’s ecological risk assessment, risk from diflufenican to freshwater fish, invertebrates, and vascular plants is expected to be low. The calculated RQ exceeded the LOC for non-vascular aquatic plants. However, the required mitigation measures, including a 24-inch maximum boom height, use of coarse or coarser spray droplets, and runoff/erosion reduction practices, adequately reduce risks to these aquatic plants.
Terrestrial Ecotoxicology and Risk
Table 5. Diflufenican terrestrial toxicity. LD50 = Lethal Concentration 50%; NOAEL=No Observable Adverse Effect Level; NOAEC=No Observable Adverse Effect Concentration; TEP = Typical end-use product.
| Taxa | Toxicity | Acute Risk |
|---|---|---|
| Mammals | Acute: LD50 > 5,000 mg a.i./kg bw (rat) Chronic: NOAEL = 11/13 mg a.i./kg bw/day (rat) | Practically non-toxic |
| Birds | Acute: LD50 > 4,080 mg a.i./kg bw Chronic: NOAEC = 1,040 mg a.i./kg diet | Practically non-toxic |
| Terrestrial Invertebrates - Bees | Acute: Oral (adult) LD50 > 107.4 µg a.i./bee Oral (larval) LD50 = 51.8 µg a.i./larva Contact (adult) LD50 > 100 µg a.i./bee Chronic: Oral (adult) NOAEL = 113 µg a.i./bee/day Oral (larval) NOAEL = 5.9 µg a.i./larva/day | Practically non-toxic |
| Terrestrial Plants | Seedling emergence: NOAEC = 0.0016 lb a.i./A (TEP) Vegetative vigor: NOAEC = 0.010 lb a.i./A (TEP) | - |
The EPA did not identify any risks of concern for birds or terrestrial invertebrates. RQ values exceeded the LOC for small- and medium-sized mammals feeding on short grass, but the EPA concluded that direct effects on mammals are extremely unlikely to occur. The EPA also found RQ exceedances for terrestrial plants. However, population-level impacts are unlikely to extend beyond treated fields given the low boom height and coarse droplet size required on the amended label.
Listed Species
The EPA conducts a Biological Evaluation to assess whether a pesticide may affect any federally listed threatened or endangered species or critical habitat. In its effects determination, the EPA concluded that diflufenican may affect or is likely to adversely affect multiple listed species and critical habitats. The EPA implemented runoff/erosion mitigations and spray-drift mitigations to address the potential likelihood of future jeopardy or adverse modification identified for most listed species. Pesticide Use Limitation Areas (PULAs) were established for one vulnerable species, the Spring Creek bladderpod; however, no PULAs for this species fall within Minnesota.
A Biological Opinion by the U.S. Fish and Wildlife Service and/or National Marine Fisheries Service is not yet published for diflufenican.
Product Labels
The following hazard warnings or use restrictions appear on at least one end-use product but may not appear on all products. Always read and follow the label for the specific product you are applying. For additional information on product labeling criteria, see the EPA’s Label Review Manual.
Environmental Hazards
Surface Water Advisory
This product may impact surface water quality due to runoff of rainwater. This is especially true for poorly draining soils and soils with shallow groundwater. This product is classified as having a medium potential for reaching both surface water and aquatic sediment via runoff for several months or more after application.
Non-target Organism Advisory
This pesticide is toxic to fish, aquatic invertebrates, oysters and shrimp. Drift and runoff may be hazardous to aquatic organisms in neighboring areas. For terrestrial uses, 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 apply when weather conditions favor drift from areas treated. Do not contaminate water when disposing of equipment wash waters or rinsate. Do not use the same spray equipment for other purposes unless thoroughly cleaned. Do not contaminate water used for irrigation or domestic purposes.
Spray Drift Management and Mitigation
Do not apply this product aerially. Applicators must comply with additional spray-drift requirements listed on the label. Users are required to access the EPA’s Mitigation Menu website to determine if buffers are required and how to implement options for buffer reduction. Additional buffer requirements may exist outside of this section for which reductions options may not apply. Follow instructions for implementing other buffers listed on the label.
Mandatory Runoff/Erosion Mitigation
Applicators must check EPA’s Bulletins Live! Two (BLT) system within six months before or on the day of application to determine whether the application area is within a PULA and follow any site-specific restrictions. If the application site is outside a PULA, applicators must implement two runoff/erosion mitigation points as required by the label for all listed field crops.
Endangered and Threatened Species Protection Requirements
Applicators must access BLT within six months of the application to determine whether the application site falls within a PULA. If the application site is within a PULA, the applicator must obtain any applicable Bulletin and implement the requirements set forth in the bulletin.
Date Posted: September 2, 2026
