Epyrifenacil Herbicide

Review date: August 2026

Overview

Epyrifenacil (Rapidicil®) is a new herbicide active ingredient registered by the U.S. Environmental Protection Agency (EPA) in June 2026. 

The Minnesota Department of Agriculture (MDA) routinely conducts reviews of new pesticide active ingredients (a.i.) prior to registration in Minnesota. The MDA completed its review of epyrifenacil in August 2026 and did not identify any risks of concern specific to Minnesota. To evaluate the potential impacts of epyrifenacil on groundwater and surface water, the MDA may add this a.i. to its water-quality monitoring program. Epyrifenacil is a per-/polyfluoroalkyl substance (PFAS) based on Minnesota’s PFAS definition (MINN. STAT. §18B.01.15c); therefore, products containing epyrifenacil are subject to additional regulations under the Pesticide Control Law.

The following is a summary of the MDA’s review of the EPA’s epyrifenacil risk assessments and product labels (EPA Docket EPA-HQ-OPP-2022-0354). 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: 353292-31-6
• EPA Pesticide Chemical Code: 116100
• Chemical class: Pyrimidinedione
• Mode of Action (Herbicide Resistance Action Committee): Group 14 – Protoporphyrinogen Oxidase (PPO) inhibitor
• Basic Manufacturer: Valent USA, LLC

Use Profile

Use Sites

Epyrifenacil is registered as a pre-plant burndown herbicide for agricultural and non-agricultural uses. It is labelled for use on canola, field corn, soybean, wheat, fallow land (corn, soybean, and wheat), and non-crop areas, including along guard rails, railroads, parking and storage areas, airports, industrial sites, fence rows, and windbreaks.

Target Pests

Epyrifenacil products are labeled to control a variety of broadleaf and grass weed species, including Palmer amaranth, Italian ryegrass, barnyard grass, marestail, pigweed species, and certain biotypes resistant to other PPO inhibiting herbicides.

Application Rates and Methods

Maximum application rates vary by product and use site. Epyrifenacil products can be applied by aerial, ground boom, and handheld equipment; chemigation is prohibited. Aerial applications are not allowed for non-agricultural uses. 

Table 1. Maximum application rates for select use sites (S-3100 0.46 EC Herbicide)

Products

The EPA registered one technical product and two end-use products containing epyrifenacil. Empera Herbicide (S-3100 0.46 EC Herbicide; EPA Reg. No. 59639-262) is an emulsifiable concentrate containing only epyrifenacil. Empera Viragess Herbicide (V-10488 0.94 SE Herbicide; EPA Reg. No. 59639-263) is a suspoemulsion that combines epyrifenacil with flumioxazin and pyroxasulfone. To view details for epyrifenacil products registered for use in Minnesota, visit the Kelly Solutions registered pesticide product database.

Projected Use in Minnesota

Epyrifenacil is labeled for use on several major Minnesota crops, including corn and soybean, and may be a useful burndown herbicide for no-till acres in the state. It may offer growers greater flexibility with its minimal preplant restrictions and compatibility with glyphosate based burndown programs. Additionally, its systemic action can contribute to improved grass weed control compared with other PPO inhibitors.

Human Health

Toxicity Profile

• Signal Word: Caution (technical product)
• Toxicity Category (based on acute exposure): Category III (low toxicity) for oral and dermal exposure; Category IV (very low toxicity) for inhalation exposure and eye and skin irritation
• Population-Adjusted Dose (PAD) for Dietary Exposure: Acute PAD = 0.6 mg/kg/day; Chronic PAD = 0.001 mg/kg/day
• Cancer Classification: "Not likely to be carcinogenic to humans"

Drinking Water

The EPA identified the parent compound, epyrifenacil, and seven major degradates (S-3100-CA, S-3100-CA-RD, S-3100-CA-UR, S-3100-DA, S-3100-DA-RD, 4”-OH-S-3100-CA, and S-3100-DA-UR) as residues of concern for drinking water. The estimated drinking water concentrations (EDWCs) in surface water were 2.6 µg/L and 1.2 µg/L for acute and chronic exposure, respectively. EDWCs in groundwater were 8.1 µg/L and 6.3 µg/L for acute and chronic exposure, respectively. The EPA did not identify any dietary (food + drinking water) risks for epyrifenacil.

Occupational and Residential Exposure

The EPA did not identify any occupational or residential risks of concern from the use of epyrifenacil. Occupational handlers may experience short term (1-30 days) or intermediate term (1-6 months) dermal and inhalation exposure, but when label required personal protective equipment is used (i.e., baseline attire and chemical-resistant gloves), no risks of concern are expected. There are no anticipated residential risks because epyrifenacil is not registered for residential use.

Environmental Fate

The movement and breakdown of epyrifenacil in the environment can vary depending on numerous factors including application site and methods. Epyrifenacil enters the environment through direct application and has potential to move offsite via spray drift, runoff, and erosion. It is not persistent in soil or aquatic systems and is unlikely to bioaccumulate. Epyrifenacil is moderately mobile in soil and is not expected to volatilize from soil or water.

Table 2. Epyrifenacil properties

Table 3: Epyrifenacil dissipation rates

Degradates

Epyrifenacil has 17 major degradates, including S-3100-CA (epyrifenacil acid), S-3100-CA-RD, S-3100-CA-UR, trifluoroacetone (TP1), and trifluoroacetic acid (TFA). These degradates are relatively more mobile and persistent than the parent compound.  TFA was a major degradate in aquatic metabolism studies (up to 28% of applied after 365 days) and may be a terminal degradate (i.e., final stable product). TFA tends to volatilize in air or dry soil; however, it persists in waterbodies and wet soil, which raises a possible exposure concern.

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.

The EPA identified epyrifenacil alone as the residue of concern (ROC) for all taxa except aquatic plants, which also included seven major degradates as ROC. The degradates exhibited similar or lower toxicity than the parent compound for most non-target organisms. 

Aquatic Ecotoxicology and Risk

Table 4. Epyrifenacil aquatic toxicity. LC50 = Lethal Concentration 50%; NOAEC=No Observable Adverse Effect Concentration; IC50 = Inhibition Concentration 50%; EC50 = 50% Effect Concentration.

According to EPA’s ecological risk assessment, risk from epyrifenacil to freshwater fish and invertebrates, is expected to be low. The calculated RQ exceeded the LOC for aquatic plants, which indicates potential risks of concern that may also extend to species that depend on aquatic plants for food or habitat. Mitigation measures taken by the EPA to address potential risks to aquatic plants are described in the following section.

Terrestrial Ecotoxicology and Risk

Table 5. Epyrifenacil terrestrial toxicity. LD50 = Lethal Concentration 50%; NOAEL=No Observable Adverse Effect Level; NOAEC=No Observable Adverse Effect Concentration; TEP = Typical end-use product.

The EPA did not identify any risks of concern for birds, mammals, or terrestrial invertebrates from epyrifenacil use; however, RQ exceedances were observed for terrestrial and wetland plants. Species that rely on these plants for food or habitat also may be affected. Potential chronic risks to mammals dependent on these plants also were noted with the co-formulated product containing flumioxazin and pyroxasulfone. 

To address the potential risks, EPA added label mitigation measures, including spray-drift buffers for aerial and ground agricultural applications, use of coarse droplets for aerial agricultural applications, and only allowing small-area applications (< 0.1 acre) with coarse droplets for non-agricultural uses.

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 epyrifenacil 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 six vulnerable terrestrial plant species. In Minnesota, PULAs for epyrifenacil were established for Leedy’s roseroot (Rhodiola integrifolia ssp. Leedyi) in Fillmore, Olmsted, and Wabasha counties to address potential future jeopardy or adverse modifications. A Biological Opinion by the U.S. Fish and Wildlife Service and/or National Marine Fisheries Service has not yet been published for epyrifenacil.

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

The product may impact surface water quality due to runoff of rainwater. This is especially true for poorly draining soils and soils with shallow ground water. This product is classified as having a high potential for reaching both surface water and aquatic sediment via runoff for several months or more after application. Runoff of this product will be reduced by avoiding applications when rainfall is forecasted to occur within 48 hours.  

Groundwater Advisory

This chemical has properties and characteristics associated with chemicals detected in groundwater. This chemical may leach into groundwater if used in areas where soils are permeable, particularly where the water table is shallow.

Non-target Organism Advisory

This product is toxic to plants and aquatic invertebrates. 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 wash waters or rinsate. Drift and runoff may be hazardous to aquatic organisms in water and to plants adjacent to the treated areas. Do not apply when weather conditions favor drift from treated areas.

Mandatory Spray Drift Management Mitigations

Applicators must comply with spray-drift requirements listed on the label. Users must follow requirements for wind speed, nozzle and pressure, wind speed and direction documentation, temperature inversion guidance, and boom height and location. Users are required to maintain a mandatory ecological spray drift buffer downwind from the edge of the treated area. Buffer reduction options are provided on the EPA’s Mitigation Menu website. Additional drift mitigation requirements may exist outside of this section for which reduction options may not apply. Follow label instructions for implementing other label listed buffers.

Mandatory Runoff/Erosion Mitigations

Do not apply when soils are saturated or above field capacity. Do not apply during rain. Applicators must comply with other mandatory runoff/erosion mitigation requirements listed on the label. The number of required mitigation points may vary by product. Users are required to use the EPA’s Mitigation Menu website to determine if mitigations are required and to select and implement measures to meet the point requirement.

Endangered and Threatened Species Protection Requirements

Applicators must access EPA's Bulletins Live! Two (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: October 13, 2026