UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

Date: November 24, 2015 

PC Code: 138009 

DP Barcodes: 425591, 425593, 425596, and 425599 

MEMORANDUM 

SUBJECT: 

TO: 

FROM: 

THROUGH: 

Ecological risk assessment for t he proposed new uses of the fungicide, fluxapyroxad, 

application to citrus; grass forage, fodder, straw, and hay; grass for seed; and nongrass animal feed, including alfalfa and clover 

Driss Benmhend, Risk Manager Reviewer 

Shaja Joyner, Product Manager 

Rachel Holloman, Branch Chief 

Fungicide Herbicide Branch 

Registration Division (7505P) 

Catherine Au bee, Senior Scientist 

Chuck Peck, Environmental Fate Scientist 

Environmental Risk Branch IV 

Environmental Fate and Effects Division (7507P) 

Jean Holmes, DVM, Branch Chief 

Thomas Steeger, Ph.D., Senior Science Advisor 

James N. Carleton, Ph.D., Senior Fate Scientist 

Environmental Risk Branch IV 

Environmental Fate and Effects Division (7507P) 

Office of Pesticide Programs 

2015.11.24 08:08:58 

-05'00' 

BASF Corporation, the technical registrant for the fungicide active ingredient (a.i.), fluxapyroxad (PC Code 

138009), submitted a Section 3 New Use (S3NU) petition for uses on citrus, grass forage, fodder, straw, 

and hay, grass for seed, and non-grass animal feed, including alfalfa and clover. The uses are proposed 

for the formulated end-use products, Sercadis® (27% a.i.) and lmbrex® (6% a.i.), and for the dual a.i. 

product, Priaxor® (14.4% fluxapyroxad, 27.1% pyraclostrobin). The Environmental Fate and Effects 

Division (EFED) has completed its ecological risk assessment for the proposed new uses. 

1 
2

The risk conclusions for the new uses are similar to those for previously assessed uses. The proposed 

application rates are lower than those previously assessed for proposed uses on turf and ornamentals(DP 

Barcode 424038, 2015). The key finding is that aerial spray of Priaxor® to citrus presents acute (mortality) 

risks of concern from spray drift exposure in fish and amphibians in aquatic habitat, including species that 

are not federally listed as threatened or endangered (i.e., “non-listed”). Acute risks of concern to listed 

species are identified both for runoff and spray drift of the fluxapyroxad active ingredient (a.i.), for citrus 

only, and for spray drift of the Priaxor® product, from all proposed uses. For conclusions based on spray 

drift only, this assessment incorporates peak estimated environmental concentrations (EECs) resulting 

from applications of each formulated product in a single year of use. A single year (as opposed to a longer 

time frame) is modeled for acute exposures from spray drift because, in this case, the relative proportions 

of formulation ingredients in the environment are expected to change over time. Toxicity and therefore 

risk conclusions differ to some extent across formulated products. Spray drift buffers may reduce these 

risks below the level of concern (LOC). Regarding chronic risks, fluxapyroxad is persistent, and reduced 

growth has been seen in laboratory studies with aquatic and terrestrial organisms. Chronic risks exceed 

the LOC in freshwater fish and aquatic-phase amphibians (for use on citrus) and in mammals, birds, 

reptiles, and terrestrial-phase amphibians (all proposed uses). There is less certainty in the risk conclusion 

for birds because growth effects have been observed at relatively low exposure levels in one test species

only. For plants, the proposed uses of Priaxor® present risks of concern to listed species of terrestrial 

dicotyledonous (dicot) plants, but risks to other terrestrial and aquatic plants are below levels of concern. 

The risk conclusions are summarized in Table 1.

Table 1. Summary of risk conclusions for proposed new uses of fluxapyroxad on citrus; grass forage, fodder, 

straw, and hay; grass for seed; and nongrass animal feed, including alfalfa and clover. “Yes” indicates that risk 

exceeds the Agency’s level of concern based on risk estimates (risk quotient values) and other lines of evidence.

Animals

Status TGAI Sercadis® Imbrex® Priaxor® TGAI

Acute Risk 

(Mortality)

Acute Risk

(Mortality – Spray Drift Only) Chronic Risk

Freshwater fish and 

amphibians

Listed Yes

(Citrus only) No No Yes Yes

Reduced 

growth

(Citrus only)

Nonlisted No No No

Yes

(Citrus-aerial 

only)

Freshwater 

invertebrates

Listed No No No Yes No Nonlisted No No No No

Estuarine/marine 

fish

Listed No Noa Noa Yesa

No Nonlisted No Noa Noa Yesa

(Citrus-aerial 

only)

Estuarine/marine 

invertebrates

Listed No Noa Noa Yesa

No Nonlisted No Noa Noa Noa

Mammals

Listed No Nob Nob Nob Yes

Reduced 

growth Nonlisted No Nob Nob Nob

Birds, reptiles, and 

amphibiansc

Listed No Nob Nob Nob Yes 

Reduced 

growth Nonlisted No Nob Nob Nob

Bees Listed No No No No ND Nonlisted

Plants Status Risk

(Reduced growth) Risk (Spray Drift Only)

Aquatic vascular Listed No Nob Nob ND
3

Nonlisted No Nob Nob ND

Aquatic 

nonvascular

Listed No Nob Nob No

Nonlisted No Nob Nob No

Terrestrial 

monocots

Listed NDd No Noe No

Nonlisted NDd No Noe NDf

Terrestrial dicots Listed NDd No Noe Yes

Nonlisted NDd No Noe NDf

ND Not determined. Bold cells exceed the listed species LOC. Shaded cells also exceed the nonlisted species LOC. a Based on magnitude of exceedance for spray drift exposure to freshwater fish, amphibians, and invertebrates. Typical end-use product 

toxicity data were not submitted for estuarine/marine organisms.

b Based on risk conclusions for the TGAI.

c Exposed through the diet. d Risk estimates were calculated using toxicity data for Priaxor®.

e Based on risk conclusions for Sercadis®. f Risk estimates were not calculated for nonlisted species because no effects >25% were observed. However, the studies with Priaxor® only 

tested up to 0.087 lbs a.i./A, which is 71% of the maximum single application rate proposed for citrus.

Previous Risk Assessments

EFED first assessed the ecological risks resulting from fluxapyroxad use in 2012 (DP Barcode 376883)

following a global joint review of data for its initial registration (DP Barcode 376981, 2011) (DP Barcode 

377186, 2011). Shortly thereafter, a Section 18 emergency exemption petition was assessed for use to 

control sheath blight on rice in Louisiana (DP Barcode 398595, 2012). Subsequent risk assessments

addressed proposed new uses for field applications (foliar, banded, in furrow, sprinkler) and agricultural 

seed treatments on multiple crops and on turf (DP Barcode 403913, 2013) (DP Barcode 413485, 2014) (DP 

Barcode 419669, 2015) (DP Barcode 425707, 2015) (DP Barcode 426251, 2015) (DP Barcode 426422, 

2015). The most recent fluxapyroxad assessment addressed a proposed foliar use on ornamentals and a 

rate increase for the existing use on turf (DP Barcode 424038, 2015). 

Risks identified in the most recent S3NU assessment included

• Risk of acute mortality in aquatic organisms exposed to spray drift of fluxapyroxad co-formulated 

with pyraclostrobin; and,

• acute dietary risk to honey bees (Apis mellifera) that consume residues of fluxapyroxad coformulated with pyraclostrobin (BAS 703 Orn) when applied to ornamentals at the maximum 

proposed rate.

The environmental fate and ecotoxicity of fluxapyroxad have been thoroughly reviewed in prior 

assessments. A comprehensive discussion of these data is available in the most recent S3NU for cotton 

and sugar beet seed (DP Barcode 419669, 2015). To summarize briefly, fluxapyroxad is a persistent and 

moderately mobile compound which inhibits fungal growth by limiting activity of the succinate 

dehydrogenase enzyme needed for mitochondrial respiration (MRID 47923771). There are no additional 

stressors of concern other than the parent compound. As a newer active ingredient, monitoring data for 

fluxapyroxad are not available, but a similarly-structured fungicide (boscalid, PC Code 128008) has been 

detected in air, surface water, sediment, and beeswax (Reilly, Smalling, Orlando, & Kuivila, 2012)

(Schumer, Mothiron, Appenzeller, Rizet, & Millet, 2010) (Smalling & Orlando, 2011) (DP Barcode 418672, 

2014). Fluxapyroxad is at least moderately toxic to aquatic organisms and practically nontoxic to 

terrestrial organisms on an acute exposure basis. Chronic effects on growth and reproduction have been 

noted in both animals and plants. End-use products containing fluxapyroxad co-formulated with the 

fungicide, pyraclostrobin (PC Code 099100), are generally more toxic than fluxapyroxad alone.
4

S3NU Assessment for Proposed New Uses

The analysis plan and data used to evaluate potential ecological risks associated with the proposed new 

uses (Table 2) are generally the same asthose used in the previous S3NU assessment (DP Barcode 424038, 

2015). However, this assessment considers only one year of use when calculating acute (peak) EECs for 

spray drift exposure to formulated products, as the toxicity of the formulated product is dependent on

contributions of the relative proportions of the product’s constituents, which are expected to change in 

the environment over long periods of time. Previous assessments have determined peak spray drift EECs 

based on accumulated exposure over a 30-year timeframe and have presented a one-year refinement 

only when recommending minimum buffer distances. This assessment does not provide recommended 

buffer distances.

Table 2. Fluxapyroxad application rates and retreatment intervals for proposed foliar uses.

Use(s) App. 

Method

Max. Single 

App. Rate

(lbs a.i./A)

No. of 

Apps. Per 

seasona

Retreatment 

Interval 

(days)b

PHI 

(days)

Max. Annual App. 

Rate

(lbs a.i./

A/yr)

Citrus Foliar 0.122 4 10 0 0.488

Grass forage, 

fodder, and hay Foliar 0.089 3 14 14 0.267

Grass for seed Foliar 0.089 3 14 14 0.267

Non-grass 

animal feed, 

including alfalfa 

and clover

Foliar 0.089 3 14 14 0.267

App. - Application. Max. - Maximum. N/A - Not applicable. No. – Number. PHI – Pre-harvest interval. a Maximum number of applications specified on label.

b Label specifies no more than 2 consecutive applications before alternating to a fungicide with a different mode of action.

This assessment tests the risk hypothesis that the proposed new uses may result in exposure at 

magnitudes sufficient to cause adverse effects to plants and/or animals in terrestrial and aquatic habitats. 

The assessment determines whether the likelihood of such adverse effects exceeds the Agency’s 

established LOCs. Where available, typical end-use product (TEP) toxicity data are used to assess risks 

from acute exposure to spray drift of formulated product to aquatic habitats and for terrestrial plant risk

(Table 3).
5

Table 3. Fluxapyroxad products proposed for new uses and their TEPs used in the ecotoxicity assessment.

New Use Product (TEP) 1

Proposed Uses

Name % Fluxapyroxad % Pyraclostrobin

Sercadis SC

(BAS 700 04 F) 27.0 NA

Citrus; grass forage, fodder, and hay; grass for 

seed; non-grass animal feed, including alfalfa and 

clover

Imbrex 6.0 NA

Citrus; grass forage, fodder, and hay; grass for 

seed; non-grass animal feed, including alfalfa and 

clover

Priaxor SC

(BAS 703 02 F) 14.4 27.1 Citrus; grass for seed; alfalfa

The reported percentages of active ingredient in TEP are for ecotoxicity test material and may differ slightly from registered 

labels.

Estimated Environmental Concentrations (EECs)

Estimated environmental concentrations (EECs) are calculated for non-target organisms in aquatic and 

terrestrial habitats. The SWCC (surface water concentration calculator) modeling scenarios used to 

generate EECs in surface water are shown in Table 4. Of these, only the results from the scenario 

generating the highest EECs are shown in subsequent tables. For estimated exposures to sedimentdwelling invertebrates, the FLcitrus scenario was run, as this scenario generated the highest peak (i.e., 

daily) surface water EECs in the SWCC runs. This estimate was converted to units of μg/kg dry sediment 

by using the pore water/water column concentrations, the sediment organic carbon partition coefficient 

(Koc=931 L/kgoc), and an assumption of equilibrium partitioning (US EPA, 2008). For terrestrial exposure 

modeling, EECs are calculated using T-REX (v. 1.5.2) and TerrPlant with the application rates in Table 2

and a default foliar dissipation half-life of 35 days (T-REX only).

Table 4. Application scenarios and start dates for SWCC modeling.

Use(s) SWCC Scenario Application dates1 Application Rates (lbs a.i./A)

Citrus CACitrus

FLCitrus 0, 10, 20, 30 0.122 x 4

Grass for 

seed

CATurfRLF

FLturfSTD

PATurfSTD

0, 14, 28 0.089 x 3

Grass 

forage, 

fodder, and 

hay, nongrass 

animal feed

CAalfalfaOP

ILalfalfaNMC

MNalfalfaOP

NCalfalfaOP

PAalfalfaOP

TXalfalfaOP

0, 14, 28 0.089 x 3

1. Dates are relative to emergence date.

 
6

The highest surface water EECs from combined loading of runoff and spray drift to a water body are shown 

in Table 5. Peak EECs for acute exposure from spray drift only, which are used to assess aquatic exposure 

to formulated fluxapyroxad, are shown in Table 6.

The 1-in-10 year peak and 21-day benthic pore water concentrations for use on citrus were each 26.9

μg/L, which yielded an estimated sorbed concentration of 1,012 μg/kg dry sediment. The uses on grass 

for seed and grass for forage are expected to result in lower benthic pore water and sediment EECs than 

the use on citrus.

Table 5. Surface water EECs of fluxapyroxad from runoff plus spray drift (SWCC). 

Use(s) Scenario Application 

Method

Application Rate (lbs 

a.i./A), Number of 

apps, RTI

EECs (μg/L)

Peak 21 day 60 day

Citrus

FLcitrus Aerial

0.122 x 4, 10 days

29.5 28.9 28.3

FLcitrus Ground 25.4 24.9 24.4

Grass for seed

CATurfRLF Aerial

0.089 x 3, 14 days

12.5 12.3 12.1

CATurfRLF Ground 7.68 7.58 7.50

Grass forage, 

fodder, and 

hay, non-grass 

animal feed

ILalfalfaNMC Aerial

0.089 x 3, 14 days

22.0 21.6 21.2

TXalfalfaOP Ground 17.9 17.4 17.0

RTI – retreatment interval.

Table 6. Surface water EECs from spray drift only (SWCC) based on the proposed maximum number of 

fluxapyroxad applications in one year of use.

Use(s) Scenario Application Method EECs (μg/L)

Peak

Citrus

FLcitrus Aerial 2.66

FLcitrus Ground 1.32

Grass for seed

CATurfRLF Aerial 1.49

CATurfRLF Ground 0.74

Grass forage, fodder, and 

hay; non-grass animal feed

ILalfalfaNMC Aerial 1.48

TXalfalfaOP Ground 0.73

Table 7 shows EECs for terrestrial vertebrates exposed to fluxapyroxad residues in the diet. The highest 

EECs are for small vertebrates that primarily consume items like short grass (EECs up to 102 mg/kg bw 

and 56.7 mg/kg bw for small birds exposed following use on citrus and on grass and non-grass feed, 

respectively). For honey bees potentially exposed to fluxapyroxad through contact and through the diet, 

Table 8 provides exposure estimates using equations documented in the bee risk assessment guidance 

(US Environmental Protection Agency (EPA), 2014). Table 9 shows EECs for terrestrial plants exposed to 

runoff and spray drift of fluxapyroxad adjacent to the treated field. 
7

Table 7. Terrestrial EECs as food residues for animals exposed to fluxapyroxad as a result of the proposed foliar uses (T-REX).

Food Type

Dietary-based

(mg/kg diet)

(mammals and birds)

Dose-based

(mg/kg bw)

(birds)

Dose-based

(mg/kg bw)

(mammals)

All Size Classes Small

(20 g)

Medium

(100 g)

Large

(1000 g)

Small

(15 g)

Medium

(35 g)

Large

(1000 g)

Citrus; 0.122 lbs a.i./A; 4 applications; 10-day interval

Short grass 89.2 102 57.9 25.9 85.0 58.8 13.6

Tall grass 40.9 46.5 26.5 11.9 39.0 26.9 6.24

Broadleaf plants/small insects 50.2 57.1 32.6 14.6 47.8 33.1 7.66

Fruits/pods/seeds 5.57 6.35 3.62 1.62 5.31 3.67 0.85

Arthropods 34.9 37.8 22.7 10.2 33.3 23.0 5.34

Seeds (granivore) N/A 1.41 0.80 0.36 1.18 0.82 0.19

Grass for seed; grass forage, fodder, and hay; non-grass animal feed; 0.089 lbs a.i./A; 3 applications; 14-day interval

Short grass 49.8 56.7 32.4 14.5 47.5 32.8 7.61

Tall grass 22.8 26.0 14.8 6.64 21.8 15.1 3.49

Broadleaf plants/small insects 28.0 31.9 18.2 8.15 26.7 18.5 4.28

Fruits/pods 3.11 3.55 2.02 0.91 2.97 2.05 0.48

Arthropods 19.5 22.2 12.7 5.67 18.6 12.9 2.98

Seeds (granivore) N/A 0.79 0.45 0.20 0.66 0.46 0.11

N/A Not applicable.
8

Table 8. Contact and dietary exposure estimates for honey bees exposed to fluxapyroxad based on proposed new 

uses.

Use Measurement

Endpoint

Exposure 

Route Equation EEC

Citrus

Individual Survival (adults) Contact AREnglish*(2.7 μg a.i./bee) 0.329

Individual Survival (adults) Diet AREnglish *(110 μg a.i /g)*(0.292 g/day) 3.92

Brood size and success Diet AREnglish *(110 μg a.i /g)*(0.124 g/day) 1.66

Grass for seed; grass 

forage, fodder, and 

hay; non-grass animal 

feed

Individual Survival (adults) Contact AREnglish*(2.7 μg a.i./bee) 0.240

Individual Survival (adults) Diet AREnglish *(110 μg a.i /g)*(0.292 g/day) 2.86

Brood size and success Diet AREnglish *(110 μg a.i /g)*(0.124 g/day) 1.21

AREnglish = application rate in lbs a.i./A (citrus: 0.122 lbs a.i./A , grass and non-grass animal feed: 0.089 lbs a.i./A)

Table 9. EECs for non-target terrestrial and semi-aquatic plants based on proposed uses of fluxapyroxad 

(TerrPlant). App. - Application. Max. - Maximum. N/A - Not applicable.

Use(s) Single Max. App. Rate

(lbs a.i./A)

App 

Method

EECs (lbs a.i./A)

Dry Area SemiAquatic 

Area

Spray Drift 

Only

Citrus 0.122

Aerial 0.007 0.018 0.006

Ground 0.002 0.013 0.001

Grass for seed; grass 

forage, fodder, and hay; 

non-grass animal feed

0.089

Aerial 0.005 0.013 0.004

Ground 0.002 0.010 0.001

Risk Estimation: RQ Values

Estimates of risk are calculated as risk quotients (RQs) based on the ratio of EECs to point estimates of 

toxicity, generally derived from laboratory studies. The RQ values are then compared to an established 

LOC to evaluate risk to listed or non-listed species. In some cases (i.e., chronic risk) the LOC is the same 

for both listed and non-listed species. Risk quotients generally are not calculated in the absence of a 

definitive toxicity endpoint. For fluxapyroxad, risk quotients are calculated in this assessment for acute 

and chronic risk to fish and invertebrates, risk to aquatic plants, subacute (dietary) risk to birds, chronic 

risk to mammals, and risk to listed terrestrial plants. Other lines of evidence are integrated in the 

subsequent discussion of these risks and of other risks for which RQ values could not be calculated.

Aquatic Organisms

The proposed use on citrus results in RQ values that exceed the LOC for acute risk to listed species of 

freshwater fish and for chronic risk to listed and non-listed species of freshwater fish (Table 10). These 

risk estimates are used as surrogates for risk to amphibiansin aquatic habitat. Other RQ values for aquatic 

animals exposed to fluxapyroxad a.i. in the water column and in sediment are below LOCs. 
9

Estuarine/marine and sediment toxicity values for fish and invertebrates are provided for reference in 

footnotes2,3,4,5

.

Table 10. Acute and chronic RQ values for freshwater fish and invertebrates exposed to fluxapyroxad in surface 

water (runoff and spray drift combined, based on toxicity data for TGAI).

Use

App Rate

lbs a.i./A

(#app)

App 

Method

RQ Values

Freshwater Fish

LC50=290 μg/L

NOAEC (from ACR)=

22 μg/L

Freshwater Invertebrate 

EC50=5,100 μg/L

NOAEC=460 μg/L

Acute Chronic Acute Chronic

Citrus 0.122 (4) Aerial 0.10 1.3 0.01 0.06

Ground 0.09 1.1 0.01 0.05

Grass for seed 0.089 (3) Aerial 0.04 0.55 <0.01 0.03

Ground 0.03 0.34 <0.01 0.02

Grass forage, fodder, and 

hay; non-grass animal feed 0.089 (3) Aerial 0.08 0.96 <0.01 0.05

Ground 0.06 0.77 <0.01 0.04

Bold values are RQs that exceed the Agency’s acute risk LOC (RQ>0.05) for listed species or the chronic risk LOC (1) for 

listed/non-listed species.

Freshwater fish are up to 64 times more sensitive to fluxapyroxad co-formulated with pyraclostrobin

(LC50=4.5 μg/L) than to fluxapyroxad TGAI (LC50=290 μg/L). Freshwater invertebrates are up to 614 times 

more sensitive to fluxapyroxad co-formulated with pyraclostrobin (EC50=8.3 μg/L) than to the fluxapyroxad 

TGAI (EC50=5,100 μg/L). As a result, all proposed uses of the Priaxor formulation present acute risk

concerns for listed species of aquatic animals (Table 11 and Table 12). Aerial application to citrus presents 

RQs that exceed the acute risk level of concern for non-listed species of fish and aquatic-phase 

amphibians. RQ values are not calculated for estuarine/marine organisms exposed to fluxapyroxad enduse products because formulated product toxicity data for these organisms were not submitted. 

Nonetheless, based on the relative increase in sensitivity of freshwater organisms to formulations of 

fluxapyroxad that include pyraclostrobin, acute risk to estuarine/marine fish and invertebrates from spray 

drift exposure of these products is presumed likely to exceed the listed species LOC. Although exposure 

to the fluxapyroxad a.i. through spray drift and runoff (combined) presents risks of concern for the use on 

citrus, exposure to single a.i. formulations through spray drift (alone) does not present acute risks of 

concern for fish, or aquatic invertebrates. Spray drift-only EECs represent a single year of applications, 

as the toxicity of the formulated product is dependent on the relative contributions of the product’s 

constituents, which are not expected to be in the same proportions beyond a year.

Table 11. Acute RQ values for freshwater fish exposed to fluxapyroxad end-use products in surface water as a 

result of spray drift only, for multiple applications in a single year.

Use

App Rate

lbs a.i./A

(#app)

App Method

Spray Drift RQ Values

Fish

Sercadis

LC50=660 μg/L

Fish

Imbrex

LC50=470 μg/L

Fish

Priaxor

LC50=4.5 μg/L

 2 Sheepshead minnow (Cyprinodon variegatus): LC50=1,300 μg/L; estimated NOAEC=100 μg/L (from fathead 

minnow, Pimephales promelas, ACR=0.077) 3 Eastern oyster (Crassotrea virginica) IC50=960 μg/L 4 Freshwater amphipod (Hyalella azteca): 10-d NOAEC=67,000 μg/kg dry sediment 5 Estuarine/marine amphipod (Leptocheirus plumulosus): 10-d NOAEC=27,000 μg/kg dry sediment
10

Acute Acute Acute

Citrus 0.122 (4) Aerial <0.01 <0.01 0.59

Ground <0.01 <0.01 0.29

Grass for seed 0.089 (3) Aerial <0.01 <0.01 0.33

Ground <0.01 <0.01 0.16

Grass forage, fodder, and 

hay; non-grass animal feed 0.089 (3) Aerial <0.01 <0.01 0.33

Ground <0.01 <0.01 0.16

Bold values are RQs that exceed the Agency’s acute risk LOC (0.05) for listed aquatic species. Shaded 

values also exceed the acute risk LOC (0.5) for nonlisted species.

Table 12. Acute RQ values for freshwater invertebrates exposed to fluxapyroxad end-use products in surface 

water as a result of spray drift only, for multiple applications in a single year.

Use

App Rate

lbs a.i./A

(#app)

App 

Method

Spray Drift RQ Values

Invertebrates

Sercadis

LC50=28,000 μg/L

Invertebrates

Imbrex

LC50=680 μg/L

Invertebrates

Priaxor

LC50=8.3 μg/L

Acute Acute Acute

Citrus 0.122 (4)

Aerial <0.01 <0.01 0.32

Ground <0.01 <0.01 0.16

Grass for seed 0.089 (3) Aerial <0.01 <0.01 0.18

Ground <0.01 <0.01 0.09

Grass forage, fodder, and 

hay; non-grass animal feed 0.089 (3) Aerial <0.01 <0.01 0.18

Ground <0.01 <0.01 0.09

Bold values are RQs that exceed the Agency’s acute risk LOC (0.05) for listed aquatic species. Shaded 

values also exceed the acute risk LOC (0.5) for nonlisted species.

All RQ values calculated for aquatic plants are below LOCs for listed and non-listed species. Toxicity values 

are presented in footnotes for reference6,7,8

. Risk estimates are not calculated for formulated product 

exposure in aquatic vascular plants because formulated product toxicity data are not available for this 

taxonomic group.

Terrestrial organisms

In this assessment, RQ values are calculated for subacute, dietary-based risk to birds (not shown), for 

chronic risk to mammals (Table 13), and for acute risks to honey bees (Table 14). RQ values are not 

calculated for acute, dose-based risk to birds, chronic risk to birds, or acute risk to mammals because the 

toxicity endpoints needed for these calculations are non-definitive. Specifically, the LD50 values for birds 

and mammals were greater than the highest dose tested in each study; whereas, the NOAEC value for 

chronic toxicity to birds was estimated to be less than the lowest treatment level tested in the avian 

reproduction study with bobwhite quail (Colinus virginianus).

For the foliar uses of fluxapyroxad on citrus and on grass and non-grass animal feed, the subacute dietarybased RQ values for birds are below the Agency’s LOCs for acute risk to listed (RQ≥0.1) and non-listed 

(RQ≥0.5) species. Dose-adjusted RQ values9 exceed the level of concern for chronic risk to mammals 

 6 Aquatic vascular plants exposed to fluxapyroxad TGAI: EC50=2,400 μg a.i./L, NOAEC=440 μg a.i./L 7 Aquatic nonvascular plants exposed to fluxapyroxad TGAI: EC50=370 μg a.i./L, NOAEC=150 μg a.i./L 8 Aquatic nonvascular plants exposed to Priaxor: EC50=120 μg a.i./L, NOAEC=14 μg a.i./L 9 Two-generation reproduction in rat (Rattus norvegicus): NOAEC=112 mg ai/kg diet, NOAEL=10 mg ai/kg bw/day
11

(RQ>1) that consume certain types of dietary items within a fluxapyroxad treatment area, particularly 

short grass and broadleaf plants (Table 13). For the use on citrus, calculated residues on tall grass and 

arthropods within the treatment area also exceed the chronic risk LOC for wild mammals.

Table 13. Chronic dietary and dose-based RQ values for mammals exposed to fluxapyroxad as a result of the 

proposed foliar uses.

Food Type

Dietary-based

(mg/kg diet)

Rat NOAEC = 112 

mg ai/kg diet

Dose-based

(mg/kg bw)

Rat NOAEL = 10 mg ai/kg bw/day

All Size Classes Small

(15 g)

Medium

(35 g)

Large

(1000 g)

Citrus; 0.122 lbs a.i./A; 4 applications; 10-day interval

Short grass 0.80 3.87 3.30 1.77

Tall grass 0.36 1.77 1.51 0.81

Broadleaf plants 0.45 2.18 1.86 1.00

Fruits/pods 0.05 0.24 0.21 0.11

Arthropods 0.31 1.52 1.29 0.69

Seeds N/A 0.05 0.05 0.02

Grass for seed; grass forage, fodder, and hay; nongrass animal feed;

0.089 lbs a.i./A; 3 applications; 14-day interval

Short grass 0.44 2.16 1.85 0.99

Tall grass 0.20 0.99 0.85 0.45

Broadleaf plants 0.25 1.22 1.04 0.56

Fruits/pods/seeds 0.03 0.14 0.12 0.06

Arthropods 0.17 0.85 0.72 0.39

Seeds N/A 0.03 0.03 0.01

N/A Not applicable. Bolded values in shaded cells exceed the Agency’s Level of Concern (LOC) for chronic risk to listed and 

nonlisted wild mammals (RQ > 1). 

Fluxapyroxad is practically non-toxic to young adult honey bees on an acute oral and an acute contact 

exposure basis10,11. The LD50 values for the Priaxor product are greater than the highest dose tested12. 

Using the acute contact and oral LD50 values for Imbrex® as a conservative screen for the toxicity of 

fluxapyroxad, the acute RQ values for the proposed new uses are below acute risk LOCs (0.4) for both 

contact and dietary exposure of adult bees (Table 14). No Tier 1 chronic toxicity data with the honey bee 

are available; therefore, chronic RQ values for fluxapyroxad risk to honey bees are not calculated. A semifield study (bee brood tunnel test) conducted with another dual a.i. product, Merivon (BAS 703 01 F), 

indicated no significant effects on bee brood development or viability at the single treatment rate of 0.14 

lbs fluxapyroxad a.i./A (MRID 48812702, 2015). Although a slight and transient treatment-related effect 

on foraging of adult bees was noted, it was not identified as statistically significant and recovery occurred 

within the course of the study with no apparent adverse effect on the bee colonies.

 10 TGAI: acute contact and oral LD50 >100 μg a.i./bee 11 Imbrex® end-use product (BAS 700 01 F, 6% a.i.): contact LD50 = 15.7 μg a.i./bee; oral LD50 = 62.8 μg a.i./bee 12 Priaxor: contact LD50 > 33.3 μg fluxapyroxad a.i./bee, oral LD50 > 32.4 μg fluxapyroxad a.i./bee
12

Table 14. Contact and dietary exposure RQ values for honey bees exposed to fluxapyroxad based on proposed 

new uses.

Use Measurement Endpoint Exposure Route EEC Acute Chronic

Citrus

Individual Survival (adults) Contact 0.329 0.02 Not 

Individual Survival (adults) Diet 3.92 0.06 calculated

Brood size and success Diet 1.66 Not calculated

Grass for seed; grass 

forage, fodder, and hay; 

non-grass animal feed

Individual Survival (adults) Contact 0.240 0.02

Individual Survival (adults) Diet 2.86 0.05

Brood size and success Diet 1.21 Not calculated

AREnglish = application rate in lbs a.i./A 

Based on Imbrex® EP: contact LD50 = 15.7 ug a.i./bee; oral LD50 = 62.8 ug a.i./bee.

For terrestrial plants, RQ values for the foliar uses in this assessment (Table 15) are calculated based on 

the most sensitive toxicity endpoints from the submitted seedling emergence and vegetative vigor tests 

with Sercadis®13 and Priaxor®14. When comparing EECs to the toxicity data for Sercadis®, risk to terrestrial 

plants from exposure to solo formulations of fluxapyroxad (Sercadis® and Imbrex®) is below the LOC. 

However, the proposed uses of Priaxor® result in RQ values for dicotyledonous(dicot) plants which exceed 

the Agency’s LOC for risk to listed plants in semi-aquatic areas. The aerial (including airblast) use of 

Priaxor® on citrus yields RQ values that also exceed the LOC for listed dicot plants in dry areas and for 

listed dicot plants exposed through spray drift only. No RQ values are calculated for non-listed plant 

species exposed to fluxapyroxad because all differences from control plants are less than 25% at the 

highest application rates tested. 

Table 15. RQ values for listed species of non-target terrestrial and semi-aquatic plants based on proposed uses of 

fluxapyroxad (TerrPlant).

Use(s) Formulation App 

Method

Dry Area

RQs

Semi-Aquatic Area 

RQs

Spray Drift Only

RQs

Monocot Dicot Monocot Dicot Monocot Dicot

Citrus

Sercadis®13

Aerial <0.10 <0.10 <0.10 <0.10 <0.10 <0.10

Ground <0.10 <0.10 <0.10 <0.10 <0.10 <0.10

Priaxor®14 Aerial 0.16 1.33 0.41 3.33 0.14 1.11

Ground <0.10 0.44 0.30 2.44 <0.10 0.22

Grass for seed; 

grass forage, 

fodder, and 

hay; non-grass 

animal feed

Sercadis®13

Aerial <0.10 <0.10 <0.10 <0.10 <0.10 <0.10

Ground <0.10 <0.10 <0.10 <0.10 <0.10 <0.10

Priaxor®14 Aerial 0.12 0.97 0.30 2.43 <0.10 0.81

Ground <0.10 0.32 0.22 1.78 <0.10 0.16

 13 Based on seedling emergence and vegetative vigor (monocot and dicot NOAEL=0.226 lbs a.i./A) data for 

Sercadis. 14 Based on seedling emergence (monocot NOAEL=0.0446 lbs a.i./A, dicot NOAEL = 0.0055 lbs a.i./A) and 

vegetative vigor (monocot NOAEL=0.0681 lbs a.i./A, dicot NOAEL=0.0167 lbs a.i./A) data for Priaxor.
13

Risk Description and Conclusions

The best available data for fluxapyroxad support the risk hypotheses that the proposed new uses on citrus 

and on grass and non-grass animal feed may result in exposure and adverse effects to certain terrestrial 

plants and to animals in terrestrial and aquatic habitats. Specifically, the Agency’s LOCs are exceeded for 

• Acute risks to non-listed species of fish and aquatic-phase amphibians from spray drift of Priaxor® 

(citrus – aerial)

• Acute risks to listed species of freshwater fish and aquatic-phase amphibians from runoff and 

spray drift, combined (citrus – ground and aerial)

• Acute risks to listed species of fish, aquatic-phase amphibians, and invertebrates from spray drift 

of Priaxor® (all proposed uses)

• Chronic risks to freshwater fish and aquatic-phase amphibians (citrus – ground and aerial)

• Chronic risks to mammals and to birds, reptiles, and terrestrial-phase amphibians exposed 

through the diet (all proposed uses)

• Risks to listed species of dicot plants (all proposed uses of Priaxor®)

Acute risk to aquatic animals from exposure to fluxapyroxad co-formulated with pyraclostrobin (Priaxor®) 

may be reduced below LOCs by implementing spray drift buffers of a specified distance in combination 

with a specified droplet size distribution (e.g., medium-to-coarse).

There is uncertainty regarding the potential for chronic risk to birds (and other non-mammalian 

vertebrates exposed through the diet). Bobwhite quail exposed to fluxapyroxad in the laboratory diet 

grew less than untreated birds. The difference was slight (<10%) but statistically significant at treatment 

levels as low as 100 mg/kg diet. The highest dietary EECs for the proposed uses (citrus: 89.2 mg/kg diet, 

grass and non-grass animal feed: 49.8 mg/kg diet) are below this value, but a lower bound (NOAEC) for 

the effect has not been established. Therefore, the potential for adverse effects (impaired growth) in 

birds following chronic exposure is uncertain. However, given that similar effects were not reported in 

mallard ducks, the magnitude of potential effects is likely to vary according to species.

Overall, the risks identified for the proposed new uses of fluxapyroxad on citrus and on grass and nongrass animal feed are similar to those associated with previously assessed uses.
14

References

Reilly, T., Smalling, K., Orlando, J., & Kuivila, K. (2012). Occurrence of boscalid and other selected 

fungicides in surface water and groundwater in three targeted use areas in the United States. 

Chemosphere, 89, 228-234.

Schumer, C., Mothiron, E., Appenzeller, B., Rizet, A., & Millet, M. (2010). Temporal variations of 

concentrations of currently used pesticides in the atmosphere of Strasbourg, France. 

Environmental Pollution, 158, 576-584.

Smalling, K., & Orlando, J. (2011). Occurrence of Pesticides in Surface Water and Sediments from Three 

Central Califorina Coastal Watersheds, 2008-09. Data Series 600. United States Geological Survey 

(USGS).

Ta, C. (2010). BAS 700 F: Anaerobic Aquatic Metabolism. Project Number 2009/7006124/OCR, 

2009/7006124, 319648. Unpublished Study Report. MRID 47923714. .: BASF Agro Research and 

Agvise Laboratories, Inc.

US Environmental Protection Agency (EPA). (2008). Science Advisory Panel (SAP): Selected Issues 

Associated with the Risk Assessment Process for Pesticides with Persistent, Bioaccumulative, and 

Toxic Characteristics. Washington, DC: US EPA Office of Pesticide Programs.

US Environmental Protection Agency (EPA). (2009). Guidance for Selecting Input Parameters in Modeling 

the Environmental Fate and Transport of Pesticides. Version 2.1. Washington, DC: US EPA Office 

of Pesticide Programs.

US Environmental Protection Agency (EPA). (2011). Global Joint Review of Ecotoxicity Studies for 

Fluxapyroxad. DP Barcode 376981. Washington, DC: US EPA Office of Pesticide Programs.

US Environmental Protection Agency (EPA). (2011). NAFTA Review of Ecotoxicity Studies for Fluxapyroxad 

End-Use Products. DP Barcode 377186. Washington, DC: US EPA Office of Pesticide Programs.

US Environmental Protection Agency (EPA). (2012). Environmental Fate and Ecological Risk Assessment 

for Foliar and Seed Treatment Uses of the New Fungicide Fluxapyroxad (BAS 700 F). DP Barcode 

376883. Washington, DC: US EPA Office of Pesticide Programs.

US Environmental Protection Agency (EPA). (2012). Section 18 Request for Use of Fluxapyroxad to Control 

Sheath Blight of Rice. DP Barcode 398595. Washington, DC: US EPA Office of Pesticide Programs.

US Environmental Protection Agency (EPA). (2013). Environmental Fate and Ecological Risk Assessment 

for Proposed Foliar and Seed Treatment Uses of the Fungicide Fluxapyroxad. DP Barcode 403913.

Washington, DC: US EPA Office of Pesticide Programs.

US Environmental Protection Agency (EPA). (2014). Ecological Risk for Section 3 Label Amendment of 

Fluxapyroxad: Proposed In-Furrow and Banded Application Methods of Priaxor to Multiple Crops. 

DP Barcode 413485. Washington, DC: US EPA Office of Pesticide Programs.
15

US Environmental Protection Agency (EPA). (2014). Guidance for Assessing Pesticide Risks to Bees.

Washington,DC: US EPA Office of Pesticide Programs.

US Environmental Protection Agency (EPA). (2014). Registration Review: Draft Problem Formulation for 

Environmental Fate, Ecological Risk, Endangered Species, and Human Health Drinking Water 

Exposure Assessments for Boscalid. DP Barcode 418672. Washington, DC: US EPA Office of 

Pesticide Programs.

US Environmental Protection Agency (EPA). (2015). Buffer Zones for Section 3 Proposed New Foliar Use of 

Fluxapyroxad on Cotton. DP Barcode 426422. Washington, DC: US EPA Office of Pesticide 

Programs.

US Environmental Protection Agency (EPA). (2015). Ecological Risk Assessment for the Proposed New Uses 

of the Fungicide, Fluxapyroxad, on Turf and Ornamentals. Washington, DC: US EPA Office of 

Pesticide Programs.

US Environmental Protection Agency (EPA). (2015). Environmental Fate and Ecological Risk Assessment 

for the Proposed Foliar and Seed Treatment Uses of the Fungicide Fluxapyroxad (BAS 700 F). DP 

Barcode 419669. Washington, DC: US EPA Office of Pesticide Programs.

US Environmental Protection Agency (EPA). (2015). Review of Nonguideline Honey Bee Brood Test with 

BAS 703 01 F (21.3% Fluxapyroxad a.i. and 21.3% Pyraclostrobin a.i.). MRID 48812702. DP Barcode 

419110. Washington, DC: US EPA Office of Pesticide Programs.

US Environmental Protection Agency (EPA). (2015). Review of Proposed Label Language Submitted in 

Response to Ecological Risk Concerns. DP Barcode 425707. Washington, DC: US EPA Office of 

Pesticide Programs.

US Environmental Protection Agency (EPA). (2015). Sensitivity Analysis for Chronic Risk to Seed Predators 

(Mammals and Birds) from Consumption of Fluxapyroxad-treated Sugar Beet Seed. DP Barcode 

426251. Washington, DC: US EPA Office of Pesticide Programs.