1

OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 129112

Chemical: Trifloxystrobin

DP Barcode: D413110

August 18, 2014

MEMORANDUM

SUBJECT: Ecological Risk Assessment for New Uses of Trifloxystrobin on Chickpeas, Dry

Peas, and Lentils

TO: Tony Kish, Product Manager

Fungicide Branch

Registration Division (7505P)

FROM: Nicholas Mastrota, Wildlife Biologist

Melanie Biscoe, Physical Scientist

Environmental Risk Branch 3

Environmental Fate and Effects Division (7507P)

REVIEWED Melissa Panger, Ph.D., Senior Biologist

BY: Environmental Risk Branch

Environmental Fate and Effects Division (7507P)

THROUGH: Dana Spatz, Branch Chief

Environmental Risk Branch 3

Environmental Fate and Effects Division (7507P)

This memorandum summarizes the potential ecological risks associated with the proposed new 

uses of the fungicide trifloxystrobin (PC code: 129112) on chickpeas, dry peas, and lentils. The 

proposed single application rate for use on chickpeas, dry peas, and lentils is 0.119 lb a.i./acre. 

Up to two applications may be made. The maximum annual rate is 0.24 lb a.i./A. The rate for 

the proposed uses is within the range of existing registered uses on food crops and less than the 

existing rate for use on turf. The ecological risks associated with these new uses are no greater 

than those of existing uses.
2

Risk	Summary

EFED’s Tier I risk assessment indicates that potential ecological risks from trifloxystrobin parent 

and its isomers resulting from the proposed new uses do not exceed the EPA’s level of concern 

(LOC) for non-endangered species. However, all proposed uses exceed the endangered species 

level of concern for acute risk to saltwater invertebrates and terrestrial plants, and uses with 

aerial application exceed the endangered species LOC for acute risk to freshwater fish. These 

risks are similar to those identified in previous risk assessments for other uses of trifloxystrobin.

Previous	Risk	Conclusions

Trifloxystrobin has been previously evaluated by EFED for use on numerous commodities 

including pome fruits, grapes, cucurbits, peanuts, and turf (New Chemical Review, D244219, 

D245281, D254206, D254285, D254286); almonds, fruiting vegetables, hops, potatoes, sugar 

beets, and wheat (D254215, D254220, D254222); root vegetable subgroup 1B (except beet and 

radish) and leaf petiole subgroup 4B (D286427); barley, oats, sweet corn, and soybeans 

(D315580, D314187, D318621, D318623, D363130); grass grown for seed (D332979, 

D332982); asparagus, tropical crops, radish, root vegetables, strawberries (D331915, D339548, 

D348876), and artichoke (D378918). Detailed summaries of these assessments can be found in 

the following previous risk assessments: D309489, D331915, D378918. 

Based on previous reviews, EFED concluded that some uses are expected to present risk on an 

acute basis to freshwater and/or estuarine/marine aquatic organisms (fish and invertebrates); 

including Federally-listed endangered and threatened species. Those uses include turf, cucurbits, 

grasses grown for seed, tropical crops, root vegetables, leaf petiole, almonds, fruiting vegetables, 

hops, and potatoes. Ecological risks are not expected for any of the other registered uses based 

on previous assessments.

Overview	of	Pesticide Usage

The active ingredient in USF 0728 325 SC Fungicide is the E,E isomer of trifloxystrobin, which 

referred to generally as trifloxystrobin for the purposes of this risk assessment. New use sites that 

are proposed for the registration of trifloxystrobin are chickpea, dry pea, and lentil. For all of 

these proposed new uses, the maximum single-application rate is 0.12 lb a.i./A1, and no more 

than 0.24 lb a.i./A of trifloxystrobin may be applied per year. Up to two applications may be 

made per year, with a 10- to 14 day interval between applications. The product is sprayed onto 

the foliage of plants. Spray applications may be made with ground or aerial spray equipment, or 

through irrigation systems (chemigation).

 

1 The label direction actually states the maximum single application rate as 12.0 fl oz/acre, which is equivalent to 

0.119 lb a.i./acre. For simplicity, this rate has been rounded up to 0.12 lb a.i./A in this assessment.
3

Environmental	Fate	and	Transport

Trifloxystrobin isomers E,E (parent); E,Z; Z,E; and Z,Z, are expected to be in equilibrium in the 

environment. For the purposes of this assessment, all four isomers are considered in the exposure 

estimates using a Total Toxic Residues (TTR) approach. This approach was used to determine 

the environmental fate data parameters for modeling in conjunction with the Guidance for 

Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides, 

Version 2.1, October 22, 2009 and the draft Guidance for Modeling Pesticides Total Toxic 

Residues (TTR) May 20, 2009.

Although trifloxystrobin’s major degradation product (CGA-321113) comprises >50% of applied 

trifloxystrobin in some dissipation studies, the available data suggest that CGA-321113 is 

considerably less toxic to aquatic organisms on an acute and chronic basis than trifloxystrobin 

(see Appendix 1). Therefore, it is 'anticipated that risk quotients based on chronic studies using 

trifloxystrobin and its isomers would be protective of aquatic organisms exposed to CGA321113 on a chronic basis. Since the mode of action of trifloxystrobin (inhibition of cellular 

respiration) is the same in terrestrial and in aquatic organisms, CGA-321113 is assumed to be 

also less toxic to terrestrial organisms than the parent. Therefore, the risk assessment will be 

based on exposure to the parent compound and the three aforementioned isomers and not CGA321113.

The chemical names and structures for the trifloxystrobin isomers considered in this assessment 

are summarized in Table 1.

Table 1. Chemical identification information for trifloxystrobin isomers

Chemical Structure

CGA279202, Trifloxystrobin, (Parent) (EEisomer) 

(E,E)-Methoxyimino-{2-[1-(3-trifluoro 

methyl-phenyl)-ethylideneaminooxymethyl]-

phenyl}-acetic acid methyl ester 

Chemical Abstracts #: 141517-21-7

CGA357262 (ZZ-isomer) 

(Z,Z)-Methoxyimino-{2-[1-(3-trifluoro 

methyl-phenyl)-ethylideneamino-oxymethyl]-

phenyl}-acetic acid methyl ester
4

CGA357261 (ZE-isomer) 

(Z,E)-Methoxyimino-{2-[1-(3-trifluoro 

methyl-phenyl)-ethylideneaminooxymethyl]-

phenyl}-acetic acid methyl ester

CGA331409 (EZ-isomer) 

(E,Z)-Methoxyimino-{2-[1-(3-trifluoro 

methyl-phenyl)-ethylideneamino-oxymethyl]-

phenyl}-acetic acid methyl ester

Parent: Trifloxystrobin E,E Isomer

Available data suggest that trifloxystrobin is not persistent and has low mobility in the 

environment. The major routes of degradation and dissipation for trifloxystrobin are associated 

with alkaline-catalyzed hydrolysis, microbial-mediated metabolism, photodegradation, and soil 

binding. Hydrolysis of trifloxystrobin is most important under alkaline conditions. Dispersion of 

trifloxystrobin will also occur in the environment by spray drift, in runoff water and eroded soil.

The major degradate in hydrolysis, metabolism and photodegradation on soil is CGA-321113, 

the free acid degradation product of trifloxystrobin; however, as previously mentioned, CGA321113 is not considered to be a degradate of concern in this risk assessment. 

Trifloxystrobin has a low solubility (0.61 mg/L @ pH 7) in water. The vapor pressure is 2.55 x 

10-8torr at 25 °C, and the calculated Henry’s Law Constant is 2.25 x 10-8atm-m

3 mol-1

. These 

values suggest that trifloxystrobin is non-volatile under field conditions from water and moist 

soil surfaces. Volatilization is not a likely route of dissipation. 

Trifloxystrobin is non-persistent in soil. Laboratory studies indicate that biotransformation is an 

important route of trifloxystrobin transformation in aerobic soil. Trifloxystrobin degraded rapidly 

in aerobic soils with half-lives ranging between 0.41 and 0.91 days. The photo-induced 

isomerization half-life (t1/2) was 2.1 days on soils. Based upon the soil organic carbon 

coefficient, KFOC (median KFOC =2709 mL/goc), trifloxystrobin would fall into the slightly mobile 

class2. There is no correlation between soil organic matter and KF (r2=0.04, p-value=0.72) and 

the coefficient of variation for the KF’s is lower than that for the KFOC’s. This indicates that 

sorption is controlled by factors other than soil organic carbon content.

Laboratory studies indicate that trifloxystrobin is also not persistent in water. The aerobic and 

anaerobic metabolism half-lives for trifloxystrobin are each less than one day. Hydrolysis of 

 

2 USEPA Office of Pesticide Programs, Environmental Fate and Effects Division. Standardized Soil Mobility 

Classification Guidance. April 21, 2006.
5

trifloxystrobin is dependent on pH; while trifloxystrobin is stable to hydrolysis under acidic 

conditions (pH 4), it readily hydrolyzes in alkaline conditions (t1/2 = 55.2 days at pH 7 and 0.83 

days at pH 9). In the aquatic environment, the photo-induced isomerization half-life (t1/2) was 

14.8 days. 

Trifloxystrobin demonstrated a biphasic degradation pattern in field dissipation studies 

conducted in California, New York, and Georgia. For the first degradation phase, trifloxystrobin 

half-life values ranged from 1.9 to 24 days. In the second degradation phase, half-life values 

ranged from 6.5 days to 4 months. 

The log Kow of 4.5 suggests that trifloxystrobin may bioaccumulate. Trifloxystrobin has 

bioconcentration factors in bluegill sunfish edible tissues of 130-166X, 1172-1144X for 

nonedible tissues, and 542-547X in whole fish. The bioaccumulation plateau was rapid (3 days 

post exposure). However, depuration was rapid, with 96.7-98.1% of the total [14C]residues 

accumulated by exposure day 28 eliminated from all tissues by 7 days in the 0.16 μg/L system, 

and 98.3-98.5% eliminated from all tissues by 14 days in the 1.6 μg/L system. Due to the 

relatively low fish bioconcentration factors in fish tissue, rapid aquatic biotransformation to 

CGA-321113 (acid) and the rapid depuration of trifloxystrobin observed in the fish study, 

bioaccumulation is unlikely.

Trifloxystrobin Total Toxic Residues (TTR): Parent and Isomers of Concern in Aquatic 

Environments

The trifloxystrobin isomers considered in the TTR approach are expected to have the same 

physical and chemical properties as the parent isomer.

The proposed degradation pathways of trifloxystrobin in aquatic systems indicate that the E,Z;

Z,E; and Z,Z isomers are in equilibrium with the parent (E,E) isomer in aquatic environments

(DP405629). 

The Z,E isomer is the major transformation product resulting from photo-induced isomerization 

of the parent in aqueous environments. The Z,E isomer formed up to 63.8% and 1% of the 

applied radioactivity in the aqueous photolysis and aerobic soil metabolism studies, respectively.

The Z,E isomer was not detected in the other fate laboratory studies, and was not detected below 

18 inches in the terrestrial field dissipation studies.

The Z,E isomer is expected to be more mobile than the parent, with KFOC’s ranging from 389 to 

567 mL/goc. Sorption is highly dependent on soil organic carbon content, as the KF’s are highly

correlated with percent organic carbon (r2=0.99, p-value=7e-4) and the coefficient of variation for 

the KFOC’s is lower than that for the KF’s. Because the Z,E isomer is more mobile than the parent 

isomer, the KFOC for the Z,E isomer is used in modeling estimated exposure concentrations.

The Z,Z isomer is a minor transformation product in the aqueous photolysis, soil photolysis, and 

aerobic soil metabolism studies, forming up to 9.1%, 4.1%, and 0.5% of applied radioactivity, 

respectively. The Z,Z isomer was not detected in the other fate laboratory studies. In the 
6

terrestrial field dissipation studies, it was detected once in the 12-18 inch segments, and not 

detected below 18 inches. An adsorption/desorption study is not available for this isomer.

The E,Z isomer is a minor transformation product in the aerobic soil metabolism, soil photolysis, 

and aerobic aquatic metabolism studies, forming up to 4.2%, 4.1%, and 0.4% of applied 

radioactivity, respectively. The E,Z isomer was not detected in the other fate laboratory studies 

or in the terrestrial field dissipation studies. An adsorption/desorption study is not available for 

this isomer.

The aqueous photolysis half-life for trifloxystrobin TTR is 54.7 days and the aerobic aquatic 

metabolism half-life for trifloxystrobin TTR is 0.492 days. Aerobic soil metabolism half-lives 

could not be calculated for trifloxystrobin TTR because the submitted studies did not measure 

the non-parent isomers of concern until mid-way through each study. Although an uncertainty, 

this is not expected to substantially change the estimated exposure concentrations, as the nonparent isomers were observed at < 5% applied radioactivity in these studies. The soil photolysis 

half-life for trifloxystrobin TTR was not calculated, as it is not currently used in aquatic exposure 

modeling. The half-lives for trifloxystrobin TTR in the other laboratory studies are the same as 

those for the parent.

Environmental fate data for trifloxystrobin and trifloxystrobin TTR are summarized in Table 2.

Table 2. Physical/Chemical Properties and Environmental Fate Data for Trifloxystrobin and Trifloxystrobin 

TTR

Parameter Trifloxystrobin1 Trifloxystrobin TTR2Source

Molecular Weight 408.4 MRID 44052801

Solubility (20 ◦C) 0.61 mg/L at pH7 MRID 44052801

Vapor Pressure (20 

◦C)

2.55e-08 mm Hg DP Barcode D254920

Henry’s Law 

Constant 2.2e-08atm m3 mol

-1 DP Barcode 405629

Hydrolysis Half-life

Stable at pH 4

55.2 days at pH 7

0.83 days at pH 9

MRID 44496727

Aquatic Photolysis 

Half-life 14.8 days at pH 5 54.7 days at pH 5

MRID 44496727

TTR half-life calculated using NAFTA 

Degradation Kinetics Guidance (2012) 

and includes isomers identified in the 

study and expected to be in equilibrium 

with the parent in aquatic environments: 

CGA-357261 and CGA-357262

Photolysis on soil 

Half-life 2.1 days Not calculated3 MRID 44496729
7

Parameter Trifloxystrobin1 Trifloxystrobin TTR2Source

Aerobic Soil 

Metabolism Halflife

0.74, 0.41, and 0.91 

days

Mean = 0.69 d, Std = 

0.25 d

Not calculated4

MRID 44496732

MRID 44496730

MRID 44496731

Anaerobic Aquatic 

Metabolism Halflife0.72 days

MRID 44496733

No isomers identified in this study are 

expected to be in equilibrium with the 

parent in aquatic environments.

Aerobic Aquatic 

Metabolism Halflife0.60 days 0.492 days

(tR IORE)

MRID 44496734

TTR half-life calculated using NAFTA 

Degradation Kinetics Guidance (2012) 

and includes an isomer identified in the 

study that is expected to be in 

equilibrium with the parent in aquatic 

environments: CGA-331409.

Organic Carbon 

Partition Coefficient 

(KFOC) (mL/g-oc)

Data for the parent 

(E,E) isomer:

2354, 951, 3064, 

3927, 9871, 951 

KF vs. organic matter 

coefficient of 

determination (r2) = 

0.03

p-value = 0.72

Data for the Z, E 

isomer:

476, 526, 479, 389, 

567

KF vs. organic matter 

coefficient of 

determination (r2) = 

0.99, p-value = 0.001 MRID 44496802 (Parent)

MRID 44496805 (Z,E isomer)

For trifloxystrobin parent and the three 

isomers expected to be present in aquatic 

environments, only two adsorption 

desorption studies are available and 

considered – one for the parent and one 

for CGA-357261. CGA-357261 is more 

mobile and is therefore used as the 

Soil Partition model input.

Coefficient (KF)

(mL/g)

Data for the parent 

(E,E) isomer:

6.8 Loamy Sand

7.7 Sandy Loam

16.0 Low Organic 

Matter Sand

59.4 High Organic 

Matter Sand

91.8 Clay Loam

33.2 Silt Loam

Mean = 35.8; Std = 

33.8

Data for the Z, E 

isomer:

14.9 Loam

12.8 Clay Loam

2.8 Hanford Sandy 

Loam

3.2 Saw-Wake Sandy 

Loam

4.6 Sand

Mean = 7.7 Std = 5.7

1 Trifloxystrobin Parent is the E,E isomer

2 Trifloxystrobin TTR includes the parent E,E, isomer and the E,Z; Z,E; and Z,Z, isomers.

3 Value currently not used in modeling, and was therefore not calculated for trifloxystrobin TTR.
8

4 Although the Z,E; Z,Z; and E,Z isomers were detected in the aerobic soil metabolism studies at levels below 5% of 

applied radioactivity, the studies did not report data for these isomers during the initial stages of each study. As a 

result, reliable half-lives for trifloxystrobin TTR could not be calculated.

Estimation	of	Exposure

Aquatic	Exposure

The aquatic estimated environmental concentrations (EECs) in surface water were estimated 

with the Surface Water Concentration Calculator (SWCC version 1.106). The SWCC generates 

daily exposures and 1-in-10-year EECs of trifloxystrobin that may occur in surface water bodies 

adjacent to application sites receiving trifloxystrobin through runoff and spray drift. A detailed 

description, documentation, and direct links for running the SWCC can be found at 

http://www.epa.gov/oppefed1/models/water/index.htm.

EECs for trifloxystrobin TTR were estimated for the Michigan Beans, Washington Beans, and 

California Row Crop scenarios, using the maximum application rates on the proposed label and 

assuming an annual application for thirty years. Details on the pesticide application assumptions 

used for the modeling are summarized in Table 3, and the environmental fate properties used for 

modeling are summarized in Table 4. The maximum peak, 21-day, 60-day means for the 

trifloxystrobin new uses are summarized in Table 5. A sample SWCC output file from the 

Michigan Beans (aerial) modeling is in Appendix 3.

 

Table 3. Summary of application input parameters used in aquatic modeling for total toxic residues.

Model Input Parameter Input Value and Unit Source/

Comment

SWCC Scenarios

MI Beans

WA Beans (NMC)1

CA Row Crop (RLF v2)2

Proposed End-Use Label (EPA Reg. # 264-

Maximum Single 1055)

Application Rate 0.1344 kg ai/ha

Maximum Number of 

Applications per Year 2

Method of Application Ground Aerial

Proposed End-Use Label (EPA Reg. # 264-

1055) allows chemigation as well as ground and 

aerial applications; ground application is 

assessed instead of chemigation and is assumed 

to be protective of potential exposures from 

chemigation.

Application Efficiency 0.99 0.95 December 2013 EFED Spray Drift Guidance
9

Model Input Parameter Input Value and Unit Source/

Comment

Spray Drift Fraction 0.062 0.125

Type of Application Foliar Proposed End-Use Label (EPA Reg. # 264-

1055).

Initial Date of Application 

(month/day)

MI Beans: June 1 

WA Beans (NMC): June 16 

CA Row Crop (RLF v2): January 

1 

Initial application dates are assumed to occur on 

the crop emergence dates listed in scenario 

metadata.

Minimum Interval 

between Applications 10 days

Proposed End-Use Label (EPA Reg. # 264-

1055)

1

Scenario developed for the N-Methyl Carbamate Cumulative Risk Assessment

2

Scenario developed for the Red-Legged Frog Endangered Species Risk Assessment

Table 4. Summary of environmental fate input parameters used in aquatic modeling for total toxic residues.

Model Input Parameter Input Value and Unit Source/Comments

Foliar Half-life Stable Assumption based on Input Parameter Guidance

Molecular Weight 408.37 g/mol Calculated molecular weight of trifloxystrobin (C20H19F3N2O4)

Vapor pressure (25°C) 2.55 x 10-8torr USEPA Fact Sheet reports 3.4 x 10-6

torr (@25 °C), PMRA Reg2004-

03 and Trifloxystrobin (213) report 3.4 x 10-6Pa @ 25 °C

Solubility in water

(20C, pH 7)

0.61 mg/L MRID 44502801

Hydrolysis half-life 

(25±1C, pH 4)

Stable MRID 44496727

Aqueous photolysis halflife (25±1C, pH 5)

54.7 days MRID 44496727

Aerobic soil metabolism 

half-life (25±1°C) 0.96 days

MRIDs 44496732, 44496730, 44496731

The 90th percentile upper bound of mean (0.74, 0.41, and 0.91 

days).

Anaerobic soil metabolism 

half-life Stable No Data Submitted

Aerobic aquatic 

metabolism half-life

(25°C)

1.48 days

MRID 44496734

3 x the aerobic aquatic metabolism half-life for a single test 

system (0.492 days), per input parameter guidance.

Anaerobic aquatic 

metabolism half-life (20-

29C)

2.16 days (assume 25 

deg C)

MRID 44496733

3 x the anaerobic aquatic metabolism half-life for a single test 

system (0.72 days).

Freundlich soil-water 

partition coefficient for 

isomer CGA-357261 (Koc) 

(25±1°C)

487.4 mL/g-oc

MRID 44496802

Mean Koc for isomer CGA-357261. 
10

Table 5. SWCC Trifloxystrobin TTR Estimated Environmental Concentrations (EECs) for the Proposed New 

Uses

Crop Application 

Method

Maximum 

Application 

Rate

(lb a.i./

acre)

# of 

Applications

Minimum 

Application

Interval

(days)

Scenario

(State 

crop)

1

st 

Appl.

date

(daymo)

EECs* (μg/L)

Peak 21 

day 60 day

Chickpea, 

Dry Peas, 

Lentil

Aerial 

Spray 0.12 2 10

MI Beans 1-Jun 1.08 0.341 0.123

WA 

Beans 

(NMC)

16-

Jun 0.902 0.289 0.103

CA Row 

Crops 

(RLF)

1-Jan 1.04 0.479 0.190

Ground 

Spray 0.12 2 10

MI Beans 1-Jun 0.667 0.205 0.0736

WA 

Beans 

(NMC)

16-

Jun 0.448 0.143 0.0511

CA Row 

Crops 

(RLF)

1-Jan 0.540 0.258 0.101

*Values in bold are the most conservative values.

Terrestrial	Exposures

The T-REX Model (version 1.5.2) was used to calculate EECs for wildlife food items. To 

calculate maximum EECs, the model assumed two applications at the maximum application rate 

of 0.12 lb a.i./A, separated by a 10-day interval. EECs represent predicted peak residue levels 

which are expected to occur immediately after the second application. The model’s default foliar 

half-life of 35-day is used, which is expected to account for persistence of trifloxystrobin and its 

isomers. 

Table 6 provides predicted dietary-based EECs for the proposed new use on chickpeas, dry peas, 

and lentils.

Table 6. Terrestrial Dietary-Base EECs for Proposed New Uses of Trifloxystrobin

Crop Food Item EEC (ppm)

Chickpea, Dry Peas, Lentil

Short Grass 52.4

Tall Grass 24.0

Broadleaf Plants 29.5

Fruits/Pods/Seeds 3.28

Arthropods 20.5

The EECs were converted to an oral dose and compared with the oral toxicity data. These “dosebased” EECs were calculated for small, medium, and large birds and mammals. Body weights of 

20 g, 100 g, and 1000 g were assumed for small, medium, and large birds, respectively, and body 

weights of 15 g, 35 g, and 1000 g were assumed for small, medium, and large mammals, 

respectively. Predicted dose-based EECs are presented in
11

Table 7.

Table 7. Terrestrial Dose-Based EECs Proposed New Uses of Trifloxystrobin

Crop Food Item

EEC (mg/kg-bw)

Small Medium Large

Avian EECs

Chickpea, Dry 

Peas, Lentil

Short Grass 59.7 34.1 15.2

Tall Grass 27.4 15.6 6.99

Broadleaf Plants 33.6 19.2 8.57

Fruits/Pods/Seeds 3.73 2.13 0.95

Arthropods 23.4 13.3 5.97

Seeds 0.83 0.47 0.21

Mammalian EECs

Chickpea, Dry 

Peas, Lentil

Short Grass 50.0 34.6 8.01

Tall Grass 22.9 15.8 3.67

Broadleaf Plants 28.1 19.4 4.51

Fruits/Pods/Seeds 3.12 2.16 0.50

Arthropods 19.6 13.5 3.14

Seeds 0.69 0.48 0.11

TerrPlant (Version 1.1.2) was used to calculate EECs for non-target plant species inhabiting dry

and semi-aquatic (wetland) areas. Parameter values for application rate, drift assumption and 

incorporation depth are based upon the use and related application method. A runoff value of 

0.01 is utilized based on trifloxystrobin’s solubility, which is classified by TerrPlant as <10 

mg/L. Predicted terrestrial plant EECs are provided in Table 8.

Table 8. Terrestrial Plant EECs for the New Uses of Trifloxystrobin

Exposure Scenario

EEC

Ground Applications Aerial Applications

Runoff to dry areas 0.0012 0.0012

Runoff to semi-aquatic areas 0.012 0.012

Spray Drift 0.0012 0.006

Total for dry areas 0.0024 0.0072

Total for semi-aquatic areas 0.0132 0.018

Ecological	Effects	Characterization

Effects	to	Aquatic	Organisms
12

Table 9 provides aquatic toxicity data that was used to assess the risk of trifloxystrobin to aquatic 

plants and animals. The toxicity data indicate that trifloxystrobin is very highly toxic to fish and 

aquatic invertebrates on an acute exposure basis. Data for green algae (Pseudokirchneriella

subcapitata) indicate toxicity to algae occurs at relatively low exposure levels, with toxicity

endpoints comparable to the acute toxicity endpoints for fish and aquatic invertebrates. On a 

chronic basis, the most sensitive test species was the waterflea (Daphnia magna), in which

significant growth and reproduction was observed at 5.98 μg ai/L. The waterflea NOAEC was 

established at 2.76 μg ai/L. 

Table 9. Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for Trifloxystrobin 

Taxonomic 

Group

Study 

Type Surrogate Species

Toxicity Value

(all units in terms of 

measured active 

ingredient)

Acute 

Toxicity 

Classification Source

Freshwater fish1

Acute

Rainbow Trout

(Oncorhynchus 

mykiss)

96-hr LC50 = 14.3 

μg/L

Very highly 

toxic

MRID 

44502803

Chronic 

(Early 

LifeStage)

Rainbow Trout

NOAEC = 4.3 μg/L

LOAEC = 7.7 μg/L

Endpoint: Post-hatch 

survival

--

MRID 

44502804

Freshwater 

invertebrates

Acute Water Flea 

(Daphnia magna)

48-hr EC50 = 25.3

μg/L

Very highly 

toxic

MRID 

44496611

Chronic Water Flea 

NOAEC = 2.76 μg/L

LOAEC = 5.98 μg/L

Endpoint: Dry weight 

and fecundity

-- 44496615

Estuarine/marine 

fish Acute

Sheepshead Minnow 

(Cyprinodon 

variegatus)

96-hr LC50 = 78.0

μg/L

Very highly 

toxic

MRID 

44496612

Estuarine/marine 

invertebrates Acute

Mysid

(Americamysis 

bahia)

96-hr EC50 = 8.62

μg/L 

Very highly 

toxic 44496614

Aquatic plants 

and algae

Vascular Duckweed 

(Lemna gibba)

NOAEC = 410 μg/L2

14-d EC50 >1930

μg/L2

--

MRID 

44496725

Nonvascular

Green Algae 

(Pseudokirchneriella 

subcapitata)

NOAEC = 10.5 μg/L

5-d EC50 = 37.1 μg/L --

MRID 

44496724

1 Freshwater fish may be surrogates for aquatic-phase amphibians.

2 These results are uncertain because the test material was unstable and renewals were not done, resulting in dramatic declines of 

the test material during the duration of the exposure period. The study was classified as Supplemental.

Available toxicity data for CGA-321113, the major degradation product of trifloxystrobin, are 

given in Table 10. The data indicate that this compound is much less toxic to fish, aquatic 

invertebrates, and algae than the parent compound. CGA-321113 is classified as practically 

nontoxic to fish and aquatic invertebrates on an acute basis. A supplemental life-cycle study with 

CGA-321113 established an NOAEC for chronic effects at 3.2 mg/L. The chronic toxicity

endpoints derived from this study were greater than 3 orders of magnitude higher than that 
13

obtained for this species when tested with the parent compound. Although the lack of evaluation 

of growth endpoints (dry weight or length) may make this study less sensitive than a study that 

adhered to the test guideline, the study provides sufficient evidence to conclude that this 

degradation product has much less chronic toxicity than the parent compound.

Table 10. Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for CGA-321113

Taxonomic 

Group

Study 

Type Surrogate Species

Toxicity Value

(all units in terms 

of measured active 

ingredient)

Acute

Toxicity 

Classification

Source

(MRID No.)

Freshwater fish1 Acute Rainbow trout 96-hr EC50 > 106 

mg/L

Practically 

nontoxic 44527502

Freshwater 

invertebrates

Acute Water Flea

(Daphnia magna)

48-hr EC50 > 95.3

mg/L

Practically 

nontoxic 44527503

Chronic Water Flea

NOAEC= 3.2 

mg/L2

LOAEC= 10.0 

mg/L2

Endpoint: Survival

-- 44869701

Aquatic plants 

and algae

Nonvascular

Green Algae 

(Pseudokirchneriella 

subcapitata)

NOAEC = 15.7

mg/L

5-d EC50 = 77.1

mg/L

-- 44496724

1 Freshwater fish may be surrogates for aquatic-phase amphibians.

2 This study was classified as Supplemental because it did not follow the experimental design prescribed by the test guideline.

The study did not evaluate growth parameters (dry weight or length) and thus the results may not be as sensitive as a fully 

acceptable study.
14

Effects	to	Terrestrial	Organisms

Table 11 provides toxicity data that was used to assess the risk of trifloxystrobin to terrestrial 

plants and animals. All available acute oral and subacute dietary studies indicate that 

trifloxystrobin is practically nontoxic to birds, mammals, and bees on an acute basis. Acute 

testing with the rat (Rattus norvegicus) show that acute toxicity to mammals from the dermal and 

inhalation routes of exposure is also low. With chronic exposure, trifloxystrobin did not cause 

any observable toxic effect to birds at dietary concentrations up to 320 mg a.i./kg-diet. Chronic 

toxicity to birds at exposures greater than 320 mg ai/kg-diet is not known; however, maximum 

residues on terrestrial food items from the proposed uses are not expected to reach this 

concentration. Chronic toxicity studies with the laboratory rat showed bodyweight effects to 

adult and young with chronic exposures of 750 mg a.i./kg-diet and above, with an NOAEL 

established at 500 mg a.i./kg-diet. No reproductive impairment was noted in rats exposed to up to 

1500 mg a.i./kg-diet. Testing with the honey bee found that trifloxystrobin is practically nontoxic 

to bees. Tier I phytotoxicity studies found that exposure of trifloxystrobin to terrestrial plants at 

approximately 0.25 lb a.i./A caused some inhibition of growth (no more than 13% inhibition). 

These studies are adequate for demonstrating that the proposed uses of trifloxystrobin would 

have little toxicity to target plants that are sprayed directly at the maximum label application rate.

Table 11. Summary of the Most Sensitive Endpoints from Terrestrial Toxicity Studies for Trifloxystrobin 

Taxonomic 

Group Study Type Surrogate Species

Toxicity Value

(all units in terms of 

active ingredient)

Acute Toxicity 

Classification

Source

(MRID No.)

Birds1

Acute

Bobwhite 

(Colinus 

virginianus)

LD50 > 2000 mg/kg-bw

(No mortality)

Practically 

nontoxic 44496606

Sub-acute 

dietary

Bobwhite and 

Mallard (Anas 

platyrhynchos)

LC50 > 5050 mg/kg-diet

(No treatment-related 

mortality)

Practically 

nontoxic

444966-07

444966-08

Chronic Bobwhite quail

NOAEC = 320 mg/kgdiet

LOAEC > 320 mg/kg-diet

-- 44496609

Mammals

Acute Oral

Laboratory rat 

(Rattus 

norvegicus)

LD50 > 5000 mg/kg-bw

(No mortality, minor 

sublethal effects2)

Practically 

nontoxic 44496622

Acute

Dermal Laboratory rat LD50 > 2000 mg/kg-bw Toxicity Category III-IV 44496627

Acute 

Inhalation Laboratory rat LC50 > 4.65 mg/L Toxicity Category IV

44496630
15

Taxonomic 

Group Study Type Surrogate Species

Toxicity Value

(all units in terms of 

active ingredient)

Acute Toxicity 

Classification

Source

(MRID No.)

Chronic

(2-Gen. 

Repro.)

Laboratory rat 

(Rattus 

norvegicus)

Parental:

NOAEL: 50 ppm

LOAEL: 750 ppm

Endpoint: Reduced body 

weight, body weight gain, 

and food consumption

Offspring:

NOAEL: 50 ppm

LOAEL: 750 ppm

Endpoint: Reduced body 

weight

Reproduction:

NOAEL: 1500 ppm

LOAEL: >1500 ppm

-- 44496710

Insects Acute 

contact

Honey bee 

(Apis mellifera 

L.)

LD50 > 200 μg/bee Practically 

nontoxic 44496726

Terrestrial 

plants

Seedling 

Emergence

Dicot – cabbage 13% inhibition in dry 

weight at 0.249 lb a.i./A

-- 44496723

Monocot –

ryegrass

7% inhibition in dry 

weight at 0.249 lb a.i./A

Vegetative 

vigor

Dicot – tomato 10% inhibition in dry 

weight at 0.249 lb a.i./A

44496723

Monocot –

ryegrass

9% inhibition in dry 

weight at 0.249 lb a.i./A

1 Birds represent surrogates for terrestrial-phase amphibians and reptiles.

2 Observed sublethal effects included hypersensitivity to touch, red stained face, excessive salivation, soft or watery stool, and 

dark stained or wet urogenital area, and decreased body weight (3-4%) in three of five females during the 7 to 14 day interval.

No in vivo studies are available on the toxicity of CGA-321113 to terrestrial organisms.

However, an in vitro study of this compound using rat hepatocyte cultures has been submitted to 

the EPA (MRID 44496720). This study found that CGA-321113 does not express the toxic 

mechanism of action of the parent compound, i.e., inhibition of mitochondrial respiration, and is 

much less toxic to hepatocyte cells than is the parent. The NOAEL was 600 μM for CGA321113 compared to <30 μM for trifloxystrobin. These results agree with the findings of aquatic 

toxicity studies which also showed that CGA-321113 is much less toxic to animals and plants 

than trifloxystrobin.
16

Ecological	Risk	Estimation	

Risk characterization compares EECs to toxicity endpoints to determine whether the proposed 

uses pose ecological risks that exceed EPA’s levels of concern (LOC). In a deterministic 

approach, a single point estimate of toxicity is divided by an exposure estimate to calculate a risk 

quotient (RQ). The RQ is then compared to Agency LOCs, which serve as criteria for 

categorizing potential risk to non-target organisms (see Appendix 2). In this assessment, RQs 

were calculated with EECs that represent total concentrations of all racemic isomers of 

trifloxystrobin.

Risk	to	Aquatic	Organisms

Acute aquatic RQs range from <0.01 to 0.13 (Table 12). Because acute RQs are less than the 

acute LOC for non-listed species (0.5), the proposed uses are not expected to pose high acute risk 

to fish and aquatic invertebrates. However, RQs for saltwater invertebrates are above the 

endangered species LOC. The RQ for freshwater fish also exceeded the listed species LOC for 

aerial applications.

Chronic RQs ranged from <0.01 to 0.06 (Table 13). Because all of the chronic RQs were less 

than the chronic LOC (1), the proposed uses are expected to pose minimal chronic risk to fish 

and aquatic invertebrates.

Table 12. Acute RQs for Fish and Aquatic Invertebrates

Use Scenario Habitat Type Peak EEC

( μg/L)

EC50 (μg a.i./L) RQ2(EEC/EC50)

Fish Inverts. Fish Inverts.

Aerial Applications

2 applications at 0.119

lb a.i./A, separated by 

10-day interval

Freshwater 1.08 14.3 25.3 0.076* 0.043

Saltwater 1.08 78.0 8.62 0.014 0.13*

Ground Applications

2 applications at 0.119

lb a.i./A, separated by 

10-day interval

Freshwater 0.667 14.3 25.3 0.047 0.026

Saltwater 0.667 78.0 8.62 <0.01 0.077*

*Exceeds the LOC for Acute endangered species (RQ ≥ 0.05)

Table 13. Chronic RQs for Fish and Aquatic Invertebrates

Use Scenario Habitat Type

Average 

EEC

(μg/L)1

NOAEC (μg a.i./L) RQ1(EEC/NOAEC)

Fish Inverts. Fish Inverts.

Aerial Applications

2 applications at 0.119 

lb a.i./A, separated by 

10-day interval

Freshwater 21-d: 0.479

60-d: 0.190 4.3 2.76 0.044 0.17

Saltwater2 21-d: 0.479

60-d: 0.190 23.5 0.94 <0.01 0.51

Ground Applications

2 applications at 0.119 

lb a.i./A, separated by 

10-day interval

Freshwater 21-d: 0.258

60-d: 0.101 4.3 2.76 0.023 0.060

Saltwater2 21-d: 0.258

60-d: 0.101 23.5 0.94 <0.01 0.27
17

1 The 60-d average EEC is used for fish RQs, whereas the 21-d EEC is used for invertebrate RQs.

2 Chronic endpoints for saltwater species were estimated from acute toxicity endpoints on acute-to-chronic ratios (ACRs) derived from freshwater 

species. The ACR was 3.33 for fish and 9.17 for crustaceans.

For aquatic vascular and non-vascular plants, RQs range from <0.01 to 0.029 for non-listed 

species, and <0.01 to 0.10 for listed species (Table 14). Because all of the RQs are less than the 

LOC for aquatic vascular and non-vascular plants (1), the proposed new uses are expected to 

pose minimal risk to listed and non-listed species of aquatic vascular and non-vascular plants.

Table 14. RQs for Vascular and Non-vascular Aquatic Plants 

Use Scenario Peak EEC

(μg/L)

Vascular Plant RQ1 Non-Vascular Plant RQ2

Non-listed

Species

(EEC/EC50)

Listed Species

(EEC/NOEC)

Non-listed

Species

(EEC/EC50)

Listed Species

(EEC/NOEC)

Aerial Applications

2 applications at 0.119 lb a.i./A, 

separated by 10-day interval

1.08 <0.01 <0.01 0.029 0.10

Ground Applications

2 applications at 0.119 lb a.i./A, 

separated by 10-day interval

0.667 <0.01 <0.01 0.018 0.063

1 Based on the green algae EC50 of 0.024 ppm

2 Based on the duckweed EC50 of >1.93 ppm 

In conclusion, the risk assessment for aquatic organisms indicates that the new use of 

trifloxystrobin on chickpeas, dry peas, and lentils will not pose a risk to any aquatic organism 

that exceeds the EPA LOC for non-listed species, but the LOC for listed saltwater invertebrates 

is exceeded, as is the LOC for listed freshwater fish when trifloxystrobin is applied by air.

Risk	to	Terrestrial	Organisms

The T-REX model was used to calculate acute and chronic risk quotients (RQs) for the proposed 

new uses on chickpea, dry peas, and lentils. For acute risk, the non-definitive “greater than” 

value generated by the acute toxicity values were entered into the model as if they were 

definitive values. Thus, while the actual acute RQs are unknown, we know that they are less than 

the RQs generated by this approach. This approach is, therefore, appropriate for conducting a 

conservative screen of acute risk. Endpoints from chronic studies were definitive, and thus the 

chronic RQs are the actual values.

For birds, acute dose-based RQs ranged from <0.01 to 0.06 (Table 15), and acute dietary-based 

RQs were all less than or equal to 0.01 (Table 17). All acute RQs were less than the LOC for risk 

to non-endangered species (0.5), as well as the LOC for risk to threatened and endangered 

species (0.1). As mentioned above, these RQs are conservative since they were calculated using 

the limit dose of 2000 mg a.i/kg and no mortality was observed at this limit dose. For chronic 

risk, RQs ranged from 0.01 to 0.16 (Table 17). All chronic RQs were less than the EPA’s LOC 

for chronic risk (1.0). In conclusion, the risk assessment indicates that the proposed new uses 

will pose minimal risk to birds, and are not expected to directly harm any threatened or 
18

endangered (listed) species of birds. These conclusions also apply to reptiles and terrestrialphased amphibians, for which birds serve as a surrogate.

For mammals, acute dose-based acute RQs were all less than 0.01 (Table 15). All acute RQs 

were therefore less than the LOC for risk to listed species (0.1) as well as the LOC for non-listed

species (0.5). Chronic dose-based RQs ranged from <0.01 to 0.30 (Table 16) and chronic dietarybased RQs ranged from <0.01 to 0.03 (Table 17). All chronic RQs were less than the EPA’s 

LOC for chronic risk (1.0). In conclusion, the risk assessment indicates that the proposed new 

uses will pose minimal risk to mammals, and are not expected to directly harm any listed species 

of mammals.
19

Table 15. Acute Terrestrial Dose-Based RQs for Proposed New Uses of Trifloxystrobin

Crop Food Item

Risk Quotient

Small Medium Large

Birds1

Chickpea, Dry 

Peas, Lentil

Short Grass 0.06 0.03 0.01

Tall Grass 0.03 0.01 <0.01

Broadleaf Plants 0.03 0.01 <0.01

Fruits/Pods/Seeds <0.01 <0.01 <0.01

Arthropods 0.02 0.01 <0.01

Seeds <0.01 <0.01 <0.01

Mammals2

Chickpea, Dry 

Peas, Lentil

Short Grass <0.01 <0.01 <0.01

Tall Grass <0.01 <0.01 <0.01

Broadleaf Plants <0.01 <0.01 <0.01

Fruits/Pods/Seeds <0.01 <0.01 <0.01

Arthropods <0.01 <0.01 <0.01

Seeds <0.01 <0.01 <0.01

1 Assumed bodyweights for small, medium, and large birds are 20 g, 100 g, and 1000 g, respectively. Avian 

toxicity is based on the LD50 for the bobwhite (>2000 mg a.i./kg-bw, MRID 44496606). The weight-adjusted 

LD50 estimates are 1038, 1322, and 1867 mg a.i./kg-bw for small, medium, and large birds, respectively.

2 Assumed bodyweights for small, medium, and large mammals are 15 g, 35 g, and 1000 g, respectively.

Mammalian toxicity is based on the LD50 for the laboratory rat (>5000 mg a.i./kg-bw, MRID 44496622). The 

weight-adjusted LD50 estimates are 10,890, and 8891, and 3846 mg a.i./kg-bw for small, medium, and large 

birds, respectively.

Table 16. Chronic Mammalian Dose-Based RQs for Proposed New Uses of Trifloxystrobin

Crop Food Item

Risk Quotient

Small Medium Large

Chickpea, Dry 

Peas, Lentil

Short Grass 0.30 0.26 0.14

Tall Grass 0.14 0.12 0.06

Broadleaf Plants 0.17 0.15 0.08

Fruits/Pods/Seeds 0.02 0.02 0.01

Arthropods 0.12 0.10 0.05

Seeds <0.01 <0.01 <0.01

1 Assumed bodyweights for small, medium, and large birds are 20 g, 100 g, and 1000 g, respectively. Avian 

toxicity is based on the LD50 for the bobwhite (>2000 mg a.i./kg-bw, MRID 44496606). The weight-adjusted 

LD50 estimates are 1038, 1322, and 1867 mg a.i./kg-bw for small, medium, and large birds, respectively.

2 Assumed bodyweights for small, medium, and large mammals are 15 g, 35 g, and 1000 g, respectively.

Mammalian toxicity is based on the LD50 for the laboratory rat (>5000 mg a.i./kg-bw, MRID 44496622). The 

weight-adjusted LD50 estimates are 10,890, and 8891, and 3846 mg a.i./kg-bw for small, medium, and large 

birds, respectively.
20

Table 17. Terrestrial Dietary-Base Acute and Chronic RQs for Proposed New Uses of Trifloxystrobin

Crop Food Item

RQs

Acute Chronic

Birds1

Chickpea, Dry Peas, 

Lentil

Short Grass 0.01 0.16

Tall Grass <0.01 0.08

Broadleaf Plants 0.01 0.09

Fruits/Pods/Seeds <0.01 0.01

Arthropods <0.01 0.06

Mammals2

Chickpea, Dry Peas, 

Lentil

Short Grass N/A30.03

Tall Grass N/A 0.02

Broadleaf Plants N/A 0.02

Fruits/Pods/Seeds N/A <0.01

Arthropods N/A 0.01

1 Avian acute RQs are based on the dietary LC50 for the bobwhite and mallard (>5050 mg a.i./kg-diet, MRID 

44496607 and 44496608). Avian chronic RQs are based on the avian reproductive NOAEC for the bobwhite 

(320 mg/kg-diet, MRID 44496609).

2 Mammalian acute RQs are were not calculated because no acute dietary LC50 was available. Mammalian 

chronic RQs are based on the two-generation reproduction NOAEC for the laboratory rat (50 mg a.i./kg-diet, 

MRID 44496710).

3 RQ could not be calculated because acute dietary toxicity data are not available for mammals. 

The acute contact toxicity value for honeybees is >200 ug/bee, which is practically non-toxic.

Risk estimations for terrestrial invertebrates are not routinely conducted. Based on the low acute 

contact toxicity study to honeybees, acute risk to adult terrestrial insects is expected to be low. 

However, additional data are needed for the EPA to conduct a complete risk assessment for 

potential adverse effects to honey bees and other insect pollinators. Because bees are attracted to 

the blooms of legume crops, bees may be exposed to nectar and pollen of the crops of this new 

use. Therefore, a honeybee acute oral toxicity study is needed to assess risk from oral exposure. 

Also, chronic toxicity studies with adult and larval bees are needed to assess the risk of lethal and 

sublethal effects from chronic exposure to trifloxystrobin. 

Table 18 provides RQs for non-target plants for the proposed new uses on chickpeas, dry peas, 

and lentils. For both aerial and ground applications, all RQs calculated for non-listed terrestrial 

plants were less than 0.1. These RQs were less than one-tenth the LOC for listed terrestrial 

plants, and thus indicate minimal risk to all non-target plants. RQs for listed species of terrestrial 

plants could not be calculated because phytotoxicity tests failed to obtain either a NOAEL or an 

EC05 for terrestrial plants. In the Tier I phytotoxicity test with trifloxystrobin, exposure to plants 

at 0.25 lb a.i./A did not have any more than a 13% inhibitory effect on any plant tested. The 

maximum seasonal application rate for the proposed new uses is approximately equal to the 

exposure rate used in this limit test. Therefore, while the risk to terrestrial plants appears to be 

low, possible adverse effects to listed species of terrestrial plants cannot be discounted.
21

Table 18. RQs for Plants in Dry and Semi-aquatic Areas Exposed to Trifloxystrobin TTR through Runoff 

and/or Spray Drift.

Use Scenario Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Aerial 

Application on 

Chickpea, Dry 

Peas, or Lentil

Monocot

Non-listed <0.1 <0.1 <0.1

Listed N/A1 N/A N/A

Dicot

Non-listed <0.1 <0.1 <0.1

Listed N/A N/A N/A

Ground 

Application on 

Chickpea, Dry 

Peas, or Lentil

Monocot

Non-listed <0.1 <0.1 <0.1

Listed N/A N/A N/A

Dicot

Non-listed <0.1 <0.1 <0.1

Listed N/A N/A N/A

1 RQs are not available for listed species because phytotoxicity studies with trifloxystrobin failed to establish an 

NOAEC.

Incident Reports

On 4 August 2014, the Ecological Incident Information System (EIIS, v. 2.1), Incident Data 

System (IDS), and Avian Incident Monitoring System (AIMS) were queried for ecological 

incidents involving exposure to trifloxystrobin. The EIIS database contains 28 incidents that 

were associated with trifloxystrobin (Table 19). All of these incidents involved damage to plants 

that were directly treated with trifloxystrobin. All of the incidents had a certainty index of either 

“possible” or “probable.” None of the incidents were associated with known misuse of 

trifloxystrobin. Except for incidents on ornamental plants, most of the incidents involved 

exposure to one or more pesticide other than trifloxystrobin, and thus the causal agent is 

uncertain. For ornamental plants, however, all but one of these involved exposure to only

trifloxystrobin, providing stronger evidence that trifloxystrobin caused the plant damage. All of 

the ornamental plant incidents occurred in nurseries in Florida.

Table 19. Ecological Incidents Associated with the Use of Trifloxystrobin.

Crop Number of Incidents Involving

Trifloxystrobin and other Pesticides

Number of Incidents Involving

Trifloxystrobin

Cereal 1 0

Corn 4 0

Grape 1 1

Ornamental Plants 1 10

Soybean 2 1

Wheat, spring 5 0

Wheat, winter 1 0

Tomato 0 1

Total 15 13

The Incident Data System (IDS) was also queried for aggregated incident reports that listed 

ecological incidents for products containing trifloxystrobin. Ten aggregated incident report were 

reported for minor plant damage incidents associated with products containing trifloxystrobin. 

The products involved in these incident reports included Stratego YLD (5), Stratego (3), and 
22

Gem 25WG (2). No aggregated incidents were reported for adverse effects to animals. Also, no 

avian incidents have been reported for trifloxystrobin in the AIMS database of the American 

Bird Conservancy.

Altogether, ecological incidents suggest that trifloxystrobin may cause adverse effects to plants 

that are sprayed directly. They do not provide evidence of risk to plants exposed by spray drift or 

runoff, or risk to non-target organisms other than plants.

Risk Description

Non-target Aquatic Animals and Plants

Aquatic Animals

Although trifloxystrobin is highly toxic to aquatic animals, the low application rate, low 

persistence, and low mobility in soils together work to limit aquatic exposure. Based on water 

modeling conducted with three different scenarios (Michigan beans, Washington beans, and 

California row crops), the combined aquatic residues of trifloxystrobin and its racemic isomers 

are not expected to reach levels where the risk would exceed the EPA’s level of concern (LOC) 

for non-listed species. However, peak EECs for ground and aerial applications were high enough 

to result in RQs that exceed the listed species LOC for saltwater invertebrates, and peak EECs 

for aerial applications also exceeded the listed species LOC for freshwater fish. These acute 

aquatic risks are similar to those previously predicted for other registered uses of trifloxystrobin. 

Concentrations of trifloxystrobin and its racemic isomers did not reach toxic levels on a chronic 

basis.

Trifloxystrobin was found to be less toxic to aquatic plants than to aquatic animals. None of the 

RQs for aquatic plants exceeded the LOC for either non-listed or listed species. Therefore, risk to 

aquatic plants is not a concern.

Non-target Terrestrial Animals and Plants

Toxicity studies indicate that trifloxystrobin has low acute toxicity to all terrestrial animals 

tested. Because of this low toxicity, combined with the relatively low application rate, the acute 

risk to terrestrial animals are predicted to be below the LOC for both listed and non-listed

species. Because peak EECs did not exceed the NOAEC for chronic effects to birds or mammals, 

chronic RQs are less than one, indicating that chronic risk to terrestrial animals is not a concern.

The proposed new use of trifloxystrobin are expected to result in both contact and oral exposure 

to bees and other insect pollinators. Because the acute contact toxicity of trifloxystrobin to the 

honeybee is very low (LD50 > 200 μg a.i./bee) and the application rates of trifloxystrobin are 

low, acute risk to bees and other insect pollinators from contact exposure is assumed to be low.

However, additional tier-1 honey bee toxicity studies are needed for EFED to conduct a 
23

complete tier-1 risk assessment for insect pollinators. The additional honey bee studies that are 

needed are listed below in the section on uncertainties.

Both the Tier I phytotoxicity tests and the incident data indicate that trifloxystrobin can cause 

some phytotoxicity to plants that receive full direct spray at the application rate. Tier I seedling 

emergence and vegetative vigor studies found that exposure of some plants at or near the 

maximal seasonal rate of 0.25 lb a.i./A resulted in inhibition of growth ranging from 7% to 13%. 

Incidents have also been reported that allege that crops have been damaged by direct application 

of trifloxystrobin. However, the risk assessment indicates that off-site exposure from spray drift 

and runoff is not expected to reach levels that are toxic to plants. RQs calculated for non-listed

terrestrial plants were all below 0.1, well below the LOC of 1. Therefore, risk to non-listed

terrestrial plants is not a concern. However, because some growth effects were observed in the 

Tier I phytotoxicity studies, and some incidents of plant damage have been reported, the 

possibility of adverse effects to listed plants cannot be excluded at this time.

Uncertainties

The Registration Review Preliminary Problem Formulation completed for trifloxystrobin in 2013 

requests the following ecotoxicity studies (DP405629):

 Guideline 850.4500, Aquatic Algae Growth and Reproduction, Tier II (The guideline is 

satisfied for freshwater green algae, but additional testing is needed with a freshwater 

diatom and a saltwater diatom.)

 Guideline 850.4450, Cyanobacteria Toxicity with Anabaena flos-aquae (bluegreen algae)

 Guideline 850.4100, Terrestrial Plant Toxicity, Seedling Emergence Test

 Guideline 850.4150, Terrestrial Plant Toxicity, Vegetative Vigor Test

Tier 1 honey bee toxicity studies are now also requested for assessing all new pesticide uses with 

potential exposure to insect pollinators. In addition to the honey bee acute contact toxicity study,

which has already been submitted, the following studies are now needed to complete the tier-1 

bee risk assessment:

 A honey bee acute oral study (OECD 213)

 A honey bee chronic oral toxicity study with adult bees

 A honey bee chronic oral toxicity study with bee larvae.

Depending on the results of these studies, additional higher-tiered honey bee testing may be 

required.

For terrestrial plants, the EC25 is > 0.25 lb a.i./A. Using that value, the LOC for non-listed

terrestrial plants would not be exceeded; however, neither a NOAEC nor an EC05 has been 
24

established for terrestrial plants. Therefore, there is uncertainty in whether there is or is not a 

hazard to threatened and endangered terrestrial plants. Since the data from the Tier I study are 

not sufficient for calculation of an EC05 nor determining a NOAEC, risk to endangered plant 

species cannot be assessed. Tier 2 phytotoxicity studies have been recommended in the recent 

Registration Review problem formulation for trifloxystrobin (D405269) to reduce this 

uncertainty and to support uses with application rates above 0.25 lb a.i./A. However, considering 

that the single application rate of the current new use is half of the application rate used in the 

terrestrial plant study mentioned above (MRID 44496723), significant adverse effects to listed 

terrestrial plants appear to be unlikely. 
25

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Carsel et al. 1997. PRZM (Pesticide Root Zone Model) Version 3.12.2 Environmental 

Research Laboratory. U. S. Environmental Protection Agency. Athens, GA.

FAO 2000. Appendix 2. Parameters of pesticides that influence processes in the soil. In FAO 

Information Division Editorial Group (Ed.), Pesticide Disposal Series 8. Assessing Soil 

Contamination. A Reference Manual. Rome: Food & Agriculture Organization of the United 

Nations (FAO). http://www.fao.org/docrep/003/x2570e/x2570e00.htm

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the 

EPA food-chain (Kenaga) nomogram, an instrument for estimating pesticide residues on plants. 

Environ. Tox. Chem. 13:1383-1391.

Hoerger, F. and E. E. Kenaga. 1972. Pesticide Residues on Plants: Correlation of 

Representative Data as a Basis for Estimation of their Magnitude in the Environment. In F. 

Coulston and F. Korte, eds., Environmental Quality and Safety: Chemistry, Toxicology, and 

Technology, Georg Thieme Publ., Stuttgart, West Germany, pp. 9-28.

USEPA. 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum, Office of

Research and Development, Washington, D.C. EPA/630/R-95/002F. April 1998. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=30759

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic 

Substances, Office of Pesticide Programs, Washington DC. January 23, 2004.

USEPA. 2006. User’s Guide TerrPlant version 1.2.2. December 2006. United States 

Environmental Protection Agency. Environmental Fate and Effects Division. Office of Pesticide 

Programs.

USEPA 2009a. Guidance for Selecting Input Parameters in Modeling the Environmental Fate 

and Transport of Pesticides. Version 2.1 October 22, 2009. 

http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm. U.S. Environmental 

Protection Agency, Office of Pesticide Programs, Environmental Fate and Effects Division. 

Arlington, VA.

USEPA 2009b. DRAFT Guidance for Modeling Pesticides Total Toxic Residues (TTR) May

20, 2009. U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental 

Fate and Effects Division. Arlington, VA.
26

USEPA 2012a. Guidance for Residues of Concern in Ecological Risk Assessment. December 

20, 2012. U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental 

Fate and Effects Division. Arlington, VA.

USEPA 2012b. NAFTA Guidance for Evaluating and Calculating Degradation Kinetics in 

Environmental Media. December 17, 2012. U.S. Environmental Protection Agency, Office of 

Pesticide Programs, Environmental Fate and Effects Division. Arlington, VA.

USEPA 2012c. Standard Operating Procedure for Using the NAFTA Guidance to Calculate 

Representative Half-life Values and Characterizing Pesticide Degradation. November 30, 2012.

U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. Arlington, VA.

APPENDIX 1. SWCC Output File: Michigan Beans, Aerial Application

Variable Volume Water Model, SWCC Compatible Version

*******************************************

Performed on: 7/22/2014 at 11: 2

Peak 1-in-10 = 1.08 ppb

Chronic 1-in-10 = 0.202E-01 ppb

Simulation Avg = 0.184E-01 ppb

4-day avg 1-in-10 = 0.668 ppb

21-day avg 1-in-10 = 0.341 ppb

60-day avg 1-in-10 = 0.123 ppb

90-day avg 1-in-10 = 0.820E-01 ppb

Benthic Pore Water Peak 1-in-10 = 0.609E-01 ppb

Benthic Pore Water 21-day avg 1-in-10 = 0.433E-01 ppb

Benthic Conversion Factor = 19.9 -Pore water (ug/L) to (total mass, ug)/(dry sed mass,kg)

Benthic Mass Fraction in Pore Water = 0.186E-01

YEAR Peak 4-day 21-day 60-day 90-day Yearly Avg Benthic Pk Benthic 21-day

 1 9.27E-01 6.04E-01 3.40E-01 1.23E-01 8.20E-02 2.02E-02 5.01E-02 3.11E-02

 2 1.39E+00 7.84E-01 3.37E-01 1.21E-01 8.05E-02 1.98E-02 1.30E-01 4.73E-02

 3 9.19E-01 5.71E-01 3.16E-01 1.13E-01 7.56E-02 1.86E-02 3.55E-02 2.58E-02

 4 9.03E-01 5.55E-01 3.08E-01 1.11E-01 7.40E-02 1.83E-02 5.37E-02 2.78E-02

 5 8.99E-01 5.44E-01 2.94E-01 1.05E-01 7.03E-02 1.73E-02 3.20E-02 2.44E-02

 6 9.43E-01 5.99E-01 3.41E-01 1.22E-01 8.17E-02 2.01E-02 4.01E-02 2.93E-02

 7 9.40E-01 5.89E-01 3.31E-01 1.18E-01 7.87E-02 1.94E-02 3.82E-02 2.75E-02

 8 9.29E-01 5.77E-01 3.26E-01 1.20E-01 7.97E-02 1.96E-02 3.70E-02 2.72E-02

 9 1.00E+00 6.73E-01 3.83E-01 1.40E-01 9.36E-02 2.31E-02 5.30E-02 4.43E-02

10 9.01E-01 5.38E-01 2.88E-01 1.03E-01 6.85E-02 1.69E-02 3.09E-02 2.21E-02

11 9.19E-01 5.79E-01 3.17E-01 1.14E-01 7.60E-02 1.87E-02 3.79E-02 2.63E-02

12 8.96E-01 5.39E-01 2.89E-01 1.04E-01 6.92E-02 1.71E-02 3.50E-02 2.28E-02

13 9.37E-01 5.89E-01 3.32E-01 1.18E-01 7.89E-02 1.95E-02 3.93E-02 2.90E-02

14 9.17E-01 5.66E-01 3.11E-01 1.11E-01 7.42E-02 1.83E-02 3.39E-02 2.48E-02

15 8.93E-01 5.23E-01 2.75E-01 9.89E-02 6.60E-02 1.63E-02 2.97E-02 2.17E-02

16 9.15E-01 5.57E-01 3.03E-01 1.08E-01 7.21E-02 1.78E-02 3.32E-02 2.38E-02

17 8.85E-01 5.17E-01 2.69E-01 9.68E-02 6.45E-02 1.59E-02 2.80E-02 1.99E-02
27

18 8.92E-01 5.30E-01 2.79E-01 9.94E-02 6.63E-02 1.64E-02 3.09E-02 2.11E-02

19 9.05E-01 5.59E-01 3.00E-01 1.09E-01 7.23E-02 1.78E-02 3.32E-02 2.36E-02

20 9.12E-01 5.73E-01 3.10E-01 1.13E-01 7.55E-02 1.86E-02 3.49E-02 2.51E-02

21 9.20E-01 5.75E-01 3.17E-01 1.13E-01 7.55E-02 1.86E-02 4.65E-02 2.73E-02

22 1.09E+00 6.22E-01 2.97E-01 1.06E-01 7.08E-02 1.75E-02 6.17E-02 3.39E-02

23 9.35E-01 6.04E-01 3.36E-01 1.22E-01 8.12E-02 2.00E-02 3.98E-02 2.86E-02

24 9.31E-01 5.77E-01 3.23E-01 1.15E-01 7.68E-02 1.89E-02 3.68E-02 2.64E-02

25 9.10E-01 5.63E-01 2.97E-01 1.07E-01 7.14E-02 1.76E-02 3.37E-02 2.36E-02

26 1.43E+00 8.72E-01 3.80E-01 1.37E-01 9.12E-02 2.25E-02 9.93E-02 4.69E-02

27 8.75E-01 4.88E-01 2.44E-01 8.64E-02 5.76E-02 1.42E-02 2.43E-02 1.62E-02

28 8.90E-01 5.26E-01 2.73E-01 9.75E-02 6.50E-02 1.60E-02 2.90E-02 1.99E-02

29 9.05E-01 5.40E-01 2.92E-01 1.05E-01 6.97E-02 1.72E-02 3.11E-02 2.28E-02

30 9.22E-01 5.84E-01 3.21E-01 1.15E-01 7.65E-02 1.89E-02 4.04E-02 2.72E-02

*********************************************************************************************

*******

Effective compartment halflives averaged over simulation duration:

zero washout 0

water col metab halflife (days) = 3.74860934970674 

zero hydrolysis 0

photolysis halflife (days) = 7704.75777615493 

volatile halflife (days) = 13967.9605636501 

total water col halflife (days) = 3.74578164510793 

zero burial 0

benthic metab halflife (days) = 5.47094337524768 

zero benthic hydrolysis 0

total benthic halflife (days) = 5.47094337524768 

***********************************************************************

Fractional Contribution of Transport Processes to Waterbody & Total Mass (kg):

Due to Runoff = 0.0370 0.3917E-01

Due to Erosion = 0.0112 0.1187E-01

Due to Drift = 0.9518 1.008 

***********************************************************************

Flow in/out Characteristics of Waterbody:

Average Daily Runoff Into Waterbody (m3/s) = 4.882614124166565E-004

Baseflow Into Waterbody (m3/s) = 0.000000000000000E+000

Average Daily Flow Out of Waterbody (m3/s) = 4.882614124166484E-004

***********************************************************************

Inputs:

 487.4 = oc partitioning coefficient

 1.480 = water column half Life

 25.00 = reference temp for water column degradation

 2.160 = benthic Half Life

 25.00 = Reference temp for benthic degradation

 2.000 = Q ten value

 54.70 = photolysis half life

 40.00 = reference latitude for photolysis study

 0.000 = hydrolysis half life

 408.4 = molecular wt

 0.2550E-07 = vapor pressure

 0.6100 = solubility

 0.1000E+06 = field area

 0.1000E+05 = water body area
28

 2.000 = initial depth

 2.000 = maximum depth

 2 1=vvwm, 2=usepa pond, 3 = usepa reservoir, 4 = const vol no flow, 5 = const vol w/flow 

F T = burial, else no burial

 0.1000E-07 = mass transfer coefficient 

 0.5000 = PRBEN

 0.5000E-01 = benthic compartment depth

 0.5000 = benthic porosity

 1.350 = benthic bulk density

 0.4000E-01 = OC frcation in benthic sediment

 5.000 = DOC in benthic compartment

 0.6000E-02 = benthic biomass

 1.190 = DFAC

 30.00 = SS

 0.5000E-02 = chlorophyll

 0.4000E-01 = OC frcation in water column SS

 5.000 = DOC in water column

 0.4000 = biomass in water column

FRACTION AREA CROPPED = 1.00000000000000 
29

APPENDIX 2. Output from T-REX Model for Trifloxystrobin

Upper Bound Kenaga Residues For RQ Calculation

Chemical Name: Trifloxystrobin

 Use

Dry Peas, chickpeas, and 

lentils

 Formulation All products

Application Rate 0.12 lbs a.i./acre

Half-life 35 days 

Application Interval 10 days

Maximum # Apps./Year 2

Length of Simulation 1 year

Variable application rates? no

Endpoints

Avian

Mallard duck LD50 (mg/kg-bw) 2000.00

Bobwhite quail LC50 (mg/kg-diet) 5050.00

Bobwhite quail NOAEL(mg/kg-bw) 0.00

Bobwhite quail NOAEC (mg/kg-diet) 320.00

Mammals

LD50 (mg/kg-bw) 5000.00

LC50 (mg/kg-diet) 0.00

NOAEL (mg/kg-bw) 75.00

NOAEC (mg/kg-diet) 1500.00

Dietary-based EECs 

(ppm)

Kenaga

Values

Short Grass 52.43

Tall Grass 24.03

Broadleaf plants 29.49

Fruits/pods/seeds 3.28

Arthropods 20.53
30

Avian Results

Avian Body 

Ingestion 

(Fdry)

Ingestion 

(Fwet) % body wgt FI

Class Weight (g) (g bw/day) (g/day) consumed (kg-diet/day)

Small 20 5 23 114 2.28E-02

Mid 100 13 65 65 6.49E-02

Large 1000 58 291 29 2.91E-01

20 5 5 25 5.06E-03

Granivores 100 13 14 14 1.44E-02

1000 58 65 6 6.46E-02

Avian Body Adjusted LD50

Weight (g) (mg/kg-bw)

20 1038.45

100 1322.00

1000 1867.37

Dose-based EECs 

(mg/kg-bw)

Avian Classes and Body Weights (grams)

small mid large

20 100 1000

Short Grass 59.71 34.05 15.24

Tall Grass 27.37 15.61 6.99

Broadleaf plants 33.59 19.15 8.57

Fruits/pods 3.73 2.13 0.95

Arthropods 23.39 13.34 5.97

Seeds 0.83 0.47 0.21

Dose-based RQs 

(Dose-based EEC/adjusted LD50)

Avian Acute RQs

Size Class (grams)

20 100 1000

Short Grass 0.06 0.03 0.01

Tall Grass 0.03 0.01 0.00

Broadleaf plants 0.03 0.01 0.00

Fruits/pods 0.00 0.00 0.00

Arthropods 0.02 0.01 0.00

Seeds 0.00 0.00 0.00
31

Dietary-based RQs 

(Dietary-based EEC/LC50 or NOAEC) RQs

Acute Chronic

Short Grass 0.01 0.16

Tall Grass 0.00 0.08

Broadleaf plants 0.01 0.09

Fruits/pods/seeds 0.00 0.01

Arthropods 0.00 0.06

Note: To provide risk management with the maximum possible information,

it is recommended that both the dose-based and concentration-based 

RQs be calculated when data are available

Mammalian Results

Mammalian Body 

Ingestion 

(Fdry)

Ingestion 

(Fwet) % body wgt FI

Class Weight (g bwt/day) (g/day) consumed (kg-diet/day)

15 3 14 95 1.43E-02

Herbivores/ 35 5 23 66 2.31E-02

insectivores 1000 31 153 15 1.53E-01

15 3 3 21 3.18E-03

Grainvores 35 5 5 15 5.13E-03

1000 31 34 3 3.40E-02

Mammalian Body Adjusted Adjusted

Class Weight LD50 NOAEL

15 10989.15 164.84

Herbivores/ 35 8891.40 133.37

insectivores 1000 3845.80 57.69

15 10989.15 164.84

Granivores 35 8891.40 133.37

1000 3845.80 57.69
32

Dose-Based EECs 

(mg/kg-bw)

Mammalian Classes and Body weight

(grams)

15 35 1000

Short Grass 49.98 34.55 8.01

Tall Grass 22.91 15.83 3.67

Broadleaf plants 28.12 19.43 4.51

Fruits/pods 3.12 2.16 0.50

Arthropods 19.58 13.53 3.14

Seeds 0.69 0.48 0.11

Dose-based 

RQs

(Dose-based 

EEC/LD50 or NOAEL)

Small mammal Medium mammal Large mammal

15 grams 35 grams 1000 grams

Acute Chronic Acute Chronic Acute Chronic

Short Grass 0.00 0.30 0.00 0.26 0.00 0.14

Tall Grass 0.00 0.14 0.00 0.12 0.00 0.06

Broadleaf plants 0.00 0.17 0.00 0.15 0.00 0.08

Fruits/pods 0.00 0.02 0.00 0.02 0.00 0.01

Arthropods 0.00 0.12 0.00 0.10 0.00 0.05

Seeds 0.00 0.00 0.00 0.00 0.00 0.00

Dietary-based RQs 

(Dietary-based EEC/LC50 or NOAEC)

Mammal RQs

Acute Chronic

Short Grass #DIV/0! 0.03

Tall Grass #DIV/0! 0.02

Broadleaf plants #DIV/0! 0.02

Fruits/pods/seeds #DIV/0! 0.00

Arthropods #DIV/0! 0.01

Note: To provide risk management with the maximum possible information,

it is recommended that both the dose-based and concentration-based 

RQs be calculated when data are available
33

APPENDIX 3. Output from TERRPLANT Model for Trifloxystrobin

TerrPlant v. 1.2.2

Table 1. Chemical Identity.

Chemical Name Trifloxystrobin

PC code 129112

Use Chickpeas, lentils, and dry peas

Application Method Aerial

Application Form Spray 

Solubility in Water 

(ppm) 0.61

Table 2. Input parameters used to derive EECs.

Input Parameter Symbol Value Units

Application Rate A 0.12 lb ai/A

Incorporation I 1 none

Runoff Fraction R 0.01 none

Drift Fraction D 0.05 none

Table 3. EECs for Trifloxystrobin. Units in lb ai/A.

Description Equation EEC

Runoff to dry areas (A/I)*R 0.0012

Runoff to semi-aquatic areas (A/I)*R*10 0.012

Spray drift A*D 0.006

Total for dry areas ((A/I)*R)+(A*D) 0.0072

Total for semi-aquatic areas ((A/I)*R*10)+(A*D) 0.018

Table 4. Plant survival and growth data used for RQ derivation. Units are in lb ai/A.

Seedling Emergence Vegetative Vigor

Plant type EC25 NOAEC EC25 NOAEC 

Monocot 0.25 x 0.25 x

Dicot 0.25 x 0.25 x

Table 5. RQ values for plants in dry and semi-aquatic areas exposed to Trifloxystrobin through runoff 

and/or spray drift.*

Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Monocot non-listed <0.1 <0.1 <0.1

Monocot listed #VALUE! #VALUE! #DIV/0!

Dicot non-listed <0.1 <0.1 <0.1

Dicot listed #VALUE! #VALUE! #DIV/0!

*If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group.