UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 128810

DP Barcode: 427660

December 10, 2015

MEMORANDUM

Subject: Registration Review: Draft Risk Assessment of the Environmental Fate and 

Ecological Risk of Azoxystrobin

To: Veronica Dutch, Chemical Review Manager 

Jill Bloom, Team Leader

Linda Arrington, Branch Chief

Risk Management and Implementation Branch 5

Pesticide Re-Evaluation Division (7508P)

Stephen Savage, Chemical Review Manager 

Rose Kyprianou, Team Leader

Lance Wormell, Branch Chief

Regulatory Management Branch II 

Antimicrobials Division (7510P)

From: Stephen Carey, Biologist

William P. Eckel, Senior Science Advisor

Environmental Risk Branch 6

Environmental Fate and Effects Division (7507P)

Laura Parsons, Associate Branch Chief

Risk Assessment and Science Support Branch

Antimicrobial Division (7510P)

Through: Mark Corbin, Branch Chief

Monica Wait, RAPL

Amy Blankinship, Senior Biologist

Ibrahim Abdel-Saheb, Environmental Scientist 

Environmental Risk Branch 6

Environmental Fate and Effects Division (7507P)

Steven Weiss, Branch Chief

Risk Assessment and Science Support Branch

Antimicrobial Division (7510P)
The Environmental Fate and Effects Division (EFED) and Antimicrobials Division (AD) have 

completed the draft risk assessment (DRA) for the environmental fate and ecological risk, and 

endangered species, for the registration review of the fungicide, azoxystrobin (PC Code 128810). 

At this current stage of the registration review process, it is premature to make direct or indirect 

effects determinations until further refinements are conducted. An in-depth listed species 

evaluation determining the potential co-occurrence of listed species and use patterns of 

azoxystrobin is needed; however, additional information on the biology of listed species, the 

locations of these species, and the locations of use sites are needed to determine the extent to 

which screening assumptions regarding an action area apply to a particular listed organism. 

Risk Conclusions Summary

The risks of azoxystrobin to terrestrial and aquatic animals including plants are summarized 

below. As a result of the DRA review for Registration Review, EFED determined that 

azoxystrobin exposures to aquatic organisms and nonvascular plants continue to be potentially at

risk as the new aquatic EECs (estimated environmental concentrations) are similar to previous 

calculated EECs. For azoxystrobin exposures to terrestrial animals, chronic risk concerns for 

birds and mammals are anticipated depending on the azoxystrobin use site; for example, there is 

a concern for birds only when foraging on azoxystrobin-treated seeds; for mammals the concern 

is foraging on food items with azoxystrobin residues and/or azoxystrobin-treated seeds. 

Terrestrial plants, specifically dicots and those identified in incident reports as possibly

susceptible to azoxystrobin, are a concern. 

For materials preservative uses, AD determined that exposure to aquatic taxa from process water

created from manufacturing and leaching of azoxystrobin during in-service use of manufactured 

products is expected to be low; further, these uses are not expected to result in exposures to 

terrestrial taxa. In summary, risk to aquatic and terrestrial taxa exposed to process water is 

expected to be negligible. 

The risks to each taxon exposed to foliar applications or azoxystrobin-treated seeds are 

summarized below in Tables 1 and 2, respectively.

Table 1. Potential for Direct Effects for the Foliar Uses of Azoxystrobin1.

Taxa Exposure Duration 

and Endpoint Maximum RQ

Potential for 

Direct Effects? Data gaps/ 

Refinements/

Listed Lines of evidence Nonlisted

Aquatic vascular 

plants Frond Count 0.2 No No None

Aquatic nonvascular plants Measures of biomass 7.5 (listed)

3.1(non-listed) Yes Yes None

Dicot terrestrial 

plants Measures of biomass 1.1 (listed)<0.1 (non-listed) Yes No Monocots not adversely affected and only two dicot

species affected >25%; 

however,

incident data on plants

Monocot terrestrial 

plants Measures of biomass <0.1 No No

Freshwater fish Acute: mortality 0.32 Yes No None
Table 1. Potential for Direct Effects for the Foliar Uses of Azoxystrobin1.

Taxa Exposure Duration 

and Endpoint Maximum RQ

Potential for 

Direct Effects? Data gaps/ 

Refinements/

Listed Lines of evidence Nonlisted

Chronic: Reduced body 

length 1.0 Yes

Estuarine/ marine 

fish

Acute: mortality 0.22 Yes No

Chronic: NOAEC 

extrapolated using ACR 

for freshwater fish

0.72 No

Freshwater 

invertebrates

Acute: mortality 0.58 Yes Yes

None Chronic: Reduced 

number of 

young/adult/day 

3.5 Yes

Estuarine/ marine 

Invertebrates

Acute: mortality 2.7 Yes Yes

None Chronic: Reduced 

young/adult/day and 

mortality

16 Yes

Mammals

Acute oral dose:

No mortality Not calculated No No

None

Chronic: decreased 

growth in F1 and F2 pups

8 Yes

Birds

Acute oral dose:

Sub-Acute dietary:

No mortality 

Not calculated No No

Chronic: number of 

eggs laid; 3-wk 

hatchlings; 14-day 

survivors

0.2 No

Terrestrial 

invertebrates

Individual survival:

No mortality Not calculated No Tier 1 larval acute and 

chronic larval and adult 

data are not available to 

evaluate risk. 

Individual survival:

Chronic dietary No data

Brood Size and success:

Acute and chronic larval No data

ACR=Acute-to-chronic; RQ=risk quotient; LOC=level of concern; E/M=estuarine/marine; NOAEC=No observable adverse 

effect concentration; BCF=bioconcentration factor; EEC=estimated environmental concentration 1 ‘Taxa’ cells and ‘potential for direct effects’ cells are shaded as follows: 

- red indicates high confidence in a high likelihood of direct adverse effects (e.g., multiple lines of evidence, RQs 

exceed LOCs, RQs based on reliable data and exposure estimate);

- yellow indicates lower confidence in a high likelihood of direct adverse effects (e.g., low confidence in data used to 

calculate RQs, lack of data, or few lines of evidence support the conclusion); and

- green indicates a high confidence in a low likelihood of direct adverse effects (e.g., full data set, high confidence in 

exposure estimates and toxicity dataset). 

- When data were not available to evaluate risk and there are no lines of evidence suggesting a potential for direct 

effects, the cell was not shaded.
Table 2. Potential for Direct Effects for the Seed Treatment Uses of Azoxystrobin1.

Taxa Exposure Duration 

and Endpoint Maximum RQ

Potential for 

Direct Effects? Data gaps/ 

Refinements/

Listed Lines of evidence Nonlisted

Aquatic vascular 

plants Frond Count <0.1 No No None

Aquatic nonvascular plants Measures of biomass <0.1 No No None

Dicot terrestrial 

plants Measures of biomass <0.1 No No

None Monocot terrestrial 

plants Measures of biomass <0.1 No No

Freshwater fish

Acute: mortality 0.01 No No

None

Chronic: Reduced body 

length <0.1 No

Estuarine/ marine 

fish

Acute: mortality <0.01 No No

Chronic: NOAEC 

extrapolated using ACR 

for freshwater fish

<0.1 No

Freshwater 

invertebrates

Acute: mortality 0.02 No No

None Chronic: Reduced 

number of 

young/adult/day 

0.14 No

Estuarine/ marine 

Invertebrates

Acute: mortality 0.1 Yes No

Chronic: Reduced 

number of 

young/adult/day and 

mortality

0.6 No

Mammals

Acute oral dose:

No mortality Not calculated No No

Chronic: decreased 

growth in F1 and F2 pups

15 Yes

Birds

Acute oral dose:

Sub-Acute dietary:

No mortality 

Not calculated No No

Chronic: number of 

eggs laid; 3-wk 

hatchlings; 14-day 

survivors

2 Yes

Terrestrial 

invertebrates

Individual survival:

No mortality Not calculated No Tier 1 larval acute and 

chronic larval and adult 

data are not available to 

evaluate risk. 

Individual survival:

Chronic dietary No data

Brood Size and success:

Acute and chronic larval No data
Table 2. Potential for Direct Effects for the Seed Treatment Uses of Azoxystrobin1.

Taxa Exposure Duration 

and Endpoint Maximum RQ

Potential for 

Direct Effects? Data gaps/ 

Refinements/

Listed Lines of evidence Nonlisted

ACR=Acute-to-chronic; RQ=risk quotient; LOC=level of concern; E/M=estuarine/marine; NOAEC=No observable adverse 

effect concentration; BCF=bioconcentration factor; EEC=estimated environmental concentration

1 ‘Taxa’ cells and ‘potential for direct effects’ cells are shaded as follows: 

- red indicates high confidence in a high likelihood of direct adverse effects (e.g., multiple lines of evidence, RQs 

exceed LOCs, RQs based on reliable data and exposure estimate);

- yellow indicates lower confidence in a high likelihood of direct adverse effects (e.g., low confidence in data used to 

calculate RQs, lack of data, or few lines of evidence support the conclusion); and

- green indicates a high confidence in a low likelihood of direct adverse effects (e.g., full data set, high confidence in 

exposure estimates and toxicity dataset). 

- When data were not available to evaluate risk and there are no lines of evidence suggesting a potential for direct 

effects, the cell was not shaded.

Data Gaps

The ecological effects and environmental fate database is largely completed for azoxystrobin 

except for the following required studies under 40 CFR Part 158:

Environmental Fate:

• None.

Ecological Effects:

• Pollinators may be exposed to azoxystrobin when foraging from off-site plants that are 

contaminated by spray drift. A complete set of toxicity data to honey bee adults and larvae 

have not been submitted for azoxystrobin and are now needed under EPA’s recent policy on 

pollinator protection1

. Thus, the following six Tier I, II and III honey bee studies, yet to be 

submitted for azoxystrobin, are needed:

o Honey bee larval acute oral toxicity study (following OECD 237)

o Honey bee adult 10-day chronic oral (special study)

o Honey bee larval repeated dose study (special study renamed as honey bee larval 

chronic oral toxicity study)

o Field testing for pollinators (OCSPP 850.3040, Tier III)

o Field trial of residues in pollen and nectar (special study, Tier II)

o Semi-field testing for pollinators (special study, Tier II). 

Note that it is possible to conduct the larval chronic oral study in such a way as to derive both 

an LD50 (acute endpoint of interest) and a NOAEC (chronic endpoint of interest) from a 

single study. If the chronic larval toxicity study is conducted in such a way that it derives 

 1 (Guidance for Assessing Pesticide Risks to Bees, 06.23.2014; signed by Donald Brady, Director, EFED; 

http://www2.epa.gov/sites/production/files/2014-

06/documents/pollinator_risk_assessment_guidance_06_19_14.pdf)
both an LD50 and NOAEC, then a separate acute larval toxicity study is not needed. For 

pollinator studies without finalized OECD guidelines, protocols should be submitted for EPA 

review and comment prior to study initiation.

Tier II and III studies are reserved pending the results of Tier I tests. 
1

Preliminary Environmental Fate and Ecological Risk

Assessment in Support of the Registration Review of 

Azoxystrobin

Methyl(E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-

methoxyacrylate

CAS Registry Number: 13160-33-8

PC Code: 128810

Prepared by:

Stephen Carey, Biologist

William P. Eckel, Senior Science Advisor U. S. Environmental Protection Agency

 Office of Pesticide Programs

 Environmental Fate and Effects Division

 Environmental Risk Branch VI

 1200 Pennsylvania Ave., NW

 Mail Code 7507P

 Washington, DC 20460

Reviewed by:

Amy Blankinship, Senior Biologist

Ibrahim Abdel-Saheb, Environmental Scientist 

Monica Wait, RAPL

Mark Corbin, ERB6 Chief

December 10, 2015

Office of Chemical Safety 

and Pollution Prevention
2

EXECUTIVE SUMMARY........................................................................................................... 3

POTENTIAL RISKS TO NONTARGET TERRESTRIAL AND AQUATIC ANIMALS AND 

PLANTS 3

CONCLUSIONS – EXPOSURE CHARACTERIZATION 6

CONCLUSIONS – EFFECTS CHARACTERIZATION 6

II. PROBLEM FORMULATION............................................................................................... 8

II.1. Nature of Regulatory Action 8

II.2. Mode of Action 8

III. ANALYSIS ..................................................................................................................... 9

III.1Use Characterization 9

III.2. Exposure Characterization 11

III.2.1. Environmental Fate and Transport Characterization.........................................................11

III.1.3. Measures of Terrestrial Exposure ......................................................................................23

III.1.3.1. Exposure Modeling for Terrestrial Vertebrates..............................................................23

III.2.3.3. Exposure Modeling for Terrestrial Invertebrates............................................................30

III.3. Ecological Effects Characterization 30

III.3.1. Aquatic Effects Characterization.........................................................................................31

III.3.2. Terrestrial Effects Characterization.....................................................................................37

IV. RISK CHARACTERIZATION ........................................................................................... 47

IV.1. Risk Estimation - Integration of Exposure and Effects Data 47

IV.1.1. Non-target Aquatic Organisms...........................................................................................49

IV.1.2 Terrestrial Animals...............................................................................................................64

IV.1.3. Terrestrial Plants in Dry and Semi-aquatic Environments...................................................71

IV.2. Risk Description 72

IV.2.1. Risks to Aquatic Organisms and Plants...............................................................................73

IV.2.2. Risks to Terrestrial Animals and Plants...............................................................................79

V. FEDERALLY THREATENED AND ENDANGERED (LISTED) SPECIES CONCERNS.................... 84

V.1. Endocrine Disruptor Screening Program 85
3

EXECUTIVE SUMMARY

Azoxystrobin is registered as a systemic fungicide for agricultural, commercial, outdoor, 

residential, indoor, and antimicrobial uses with aerial and ground applications, chemigation, and 

seed treatments. Foliar application rates range from 0.1 to 0.55 pounds of active ingredient per 

acre (lb a.i./A) per application with seasonal maximum application rates ranging from 0.45 to 5.0 

lb a.i./A. Maximum seed treatment rates range from 0.00062 lb a.i./A to 0.012 lb a.i./A. As a 

materials preservative, liquid formulations of azoxystrobin are added during manufacturing to 

paper, building materials, fibers, rubber and plastics.

POTENTIAL RISKS TO NONTARGET TERRESTRIAL AND AQUATIC ANIMALS AND 

PLANTS 

Taxa for which risk were identified at or above the Agency’s levels of concern for foliar 

applications and seed treatments are summarized below in Tables 1 and 2. 

For antimicrobial uses, exposure to aquatic taxa from process water created from manufacturing 

and leaching of azoxystrobin during in-service use of manufactured products is expected to be 

low; further, these uses are not expected to result in exposure to terrestrial taxa. In summary, risk 

to these taxa exposed to process water is expected to be negligible. 

Table 1. Potential for Direct Effects on the Foliar Use of Azoxystrobin1.

Taxa Exposure Duration 

and Endpoint Maximum RQ

Potential for 

Direct Effects? Data gaps/ 

Refinements/

Listed Lines of evidence Nonlisted

Aquatic vascular 

plants Frond Count 0.2 No No None

Aquatic nonvascular plants Measures of biomass 7.5 (listed)

3.1(non-listed) Yes Yes None

Dicot terrestrial 

plants Measures of biomass 1.1 (listed)<0.1 (non-listed) Yes No Monocots not adversely affected and only two dicot 

species affected >25%; 

however,

incident data on plants

Monocot terrestrial 

plants Measures of biomass <0.1 No No

Freshwater fish

Acute: mortality 0.32 Yes No

None

Chronic: Reduced body 

length 1.0 Yes

Estuarine/ marine 

fish

Acute: mortality 0.22 Yes+ No

Chronic: NOAEC 

extrapolated using ACR 

for freshwater fish

0.72 No

Freshwater 

invertebrates

Acute: mortality 0.58 Yes Yes

None Chronic: Reduced 

number of 

young/adult/day 

3.5 Yes

Acute: mortality 2.7 Yes Yes None
4

Table 1. Potential for Direct Effects on the Foliar Use of Azoxystrobin1.

Taxa Exposure Duration 

and Endpoint Maximum RQ

Potential for 

Direct Effects? Data gaps/ 

Refinements/

Listed Lines of evidence Nonlisted

Estuarine/ marine 

Invertebrates

Chronic: Reduced 

young/adult/day and 

mortality

16 Yes

Mammals

Acute oral dose:

No mortality Not calculated No No

None

Chronic: decreased 

growth in F1 and F2 pups

8 Yes

Birds

Acute oral dose:

Sub-Acute dietary:

No mortality 

Not calculated No No

Chronic: number of 

eggs laid; 3-wk 

hatchlings; 14-day 

survivors

0.2 No

Terrestrial 

invertebrates

Individual survival:

No mortality Not calculated No Tier 1 larval acute and 

chronic larval and adult

data are not available to 

evaluate risk. 

Individual survival:

Chronic dietary No data

Brood Size and success:

Acute and chronic larval No data

ACR=Acute-to-chronic; RQ=risk quotient; LOC=level of concern; E/M=estuarine/marine; NOAEC=No observable adverse 

effect concentration; BCF=bioconcentration factor; EEC=estimated environmental concentration

1 ‘Taxa’ cells and ‘potential for direct effects’ cells are shaded as follows: 

- red indicates high confidence in a high likelihood of direct adverse effects (e.g., multiple lines of evidence, RQs 

exceed LOCs, RQs based on reliable data and exposure estimate);

- yellow indicates lower confidence in a high likelihood of direct adverse effects (e.g., low confidence in data used to 

calculate RQs, lack of data, or few lines of evidence support the conclusion); and

- green indicates a high confidence in a low likelihood of direct adverse effects (e.g., full data set, high confidence in 

exposure estimates and toxicity dataset). 

- When data were not available to evaluate risk and there are no lines of evidence suggesting a potential for direct 

effects, the cell was not shaded.

Table 2. Potential for Direct Effects on the Seed Use of Azoxystrobin1.

Taxa Exposure Duration 

and Endpoint Maximum RQ

Potential for 

Direct Effects? Data gaps/ 

Refinements/

Listed Lines of evidence Nonlisted

Aquatic vascular 

plants Frond Count <0.1 No No None

Aquatic nonvascular plants Measures of biomass <0.1 No No None

Dicot terrestrial 

plants Measures of biomass <0.1 No No

None Monocot terrestrial 

plants Measures of biomass <0.1 No No

Freshwater fish Acute: mortality 0.01 No No None
5

Table 2. Potential for Direct Effects on the Seed Use of Azoxystrobin1.

Taxa Exposure Duration 

and Endpoint Maximum RQ

Potential for 

Direct Effects? Data gaps/ 

Refinements/

Listed Lines of evidence Nonlisted

Chronic: Reduced body 

length <0.1 No

Estuarine/ marine 

fish

Acute: mortality <0.01 No No

Chronic: NOAEC 

extrapolated using ACR 

for freshwater fish

<0.1 No

Freshwater 

invertebrates

Acute: mortality 0.02 No No

None Chronic: Reduced 

number of 

young/adult/day 

0.14 No

Estuarine/ marine 

Invertebrates

Acute: mortality 0.1 Yes No

Chronic: Reduced 

number of 

young/adult/day and 

mortality

0.6 No

Mammals

Acute oral dose:

No mortality Not calculated No No

Chronic: decreased 

growth in F1 and F2 pups

15 Yes

Birds

Acute oral dose:

Sub-Acute dietary:

No mortality 

Not calculated No No

Chronic: number of 

eggs laid; 3-wk 

hatchlings; 14-day 

survivors

2 Yes

Terrestrial 

invertebrates

Individual survival:

No mortality Not calculated No Tier 1 larval acute and 

chronic larval and adult 

data are not available to 

evaluate risk. 

Individual survival:

Chronic dietary No data

Brood Size and success:

Acute and chronic larval No data

ACR=Acute-to-chronic; RQ=risk quotient; LOC=level of concern; E/M=estuarine/marine; NOAEC=No observable adverse 

effect concentration; BCF=bioconcentration factor; EEC=estimated environmental concentration

1 ‘Taxa’ cells and ‘potential for direct effects’ cells are shaded as follows: 

- red indicates high confidence in a high likelihood of direct adverse effects (e.g., multiple lines of evidence, RQs 

exceed LOCs, RQs based on reliable data and exposure estimate);

- yellow indicates lower confidence in a high likelihood of direct adverse effects (e.g., low confidence in data used to 

calculate RQs, lack of data, or few lines of evidence support the conclusion); and

- green indicates a high confidence in a low likelihood of direct adverse effects (e.g., full data set, high confidence in 

exposure estimates and toxicity dataset). 

- When data were not available to evaluate risk and there are no lines of evidence suggesting a potential for direct 

effects, the cell was not shaded.
6

CONCLUSIONS – EXPOSURE CHARACTERIZATION

Azoxystrobin is relatively persistent, but not highly mobile. The dissipation of azoxystrobin is

predominantly dependent on aquatic photodegradation and to a lesser extent microbial-mediated 

degradation, and limited mobility into ground and surface waters. The low mobility in soil was 

confirmed in the field studies where azoxystrobin dissipated slowly on the surface (0-6 inch) of 

non-flooded soils. No azoxystrobin residue was found in soil layers deeper than 6 inches (TFD 

studies, Table III.1). Since photodegradation is a major route of degradation for azoxystrobin, the 

dissipation of azoxystrobin is expected to be dependent on condition of the water (e.g., sediment 

loading, depth, etc.) affecting sunlight penetration. Although azoxystrobin has limited mobility 

and is subject to photolysis, the compound has been detected in federal and state surface water 

monitoring studies.

CONCLUSIONS – EFFECTS CHARACTERIZATION

Available toxicity data classifies azoxystrobin as highly toxic to freshwater and estuarine/marine 

fish and freshwater invertebrates, but is very highly toxic to estuarine/marine invertebrates on an 

acute exposure basis. Freshwater fish serve as surrogates for aquatic-phase amphibians in the 

absence of amphibian-specific data; therefore, azoxystrobin is classified as highly toxic to 

aquatic-phase amphibians. Chronic exposure resulted in impaired growth in freshwater fish and 

invertebrates and reproductive effects in estuarine/marine invertebrates. In the absence of data, 

an acute-to-chronic ratio (ACR) was used to estimate the chronic toxicity endpoint for estuarine/

marine fish. Toxicity data show that of the degradates of azoxystrobin, three degradates 

(compounds 2, 28 and 30) are practically nontoxic to freshwater fish and invertebrates and to 

aquatic nonvascular plants; the other degradates’ (i.e. compounds 9 (Z-isomer)) toxicity to 

aquatic organisms is unknown as data are not available. Thus, the only stressor of concern for 

ecological effects is azoxystrobin, the parent compound. Studies conducted with a typical end

use product (TEP) co-formulated with the fungicide chlorothalonil, indicate that that product is 

very highly toxic to freshwater fish and that aquatic non-vascular plants are more sensitive to the 

TEP than to technical grade azoxystrobin because chlorothalonil contributes to the toxicity of the 

formulated product.

For terrestrial wildlife, azoxystrobin is practically nontoxic to birds on both an acute oral and 

subacute dietary exposure basis. Since birds serve as surrogates for reptiles and terrestrial-phase 

amphibians in the absence of taxa-specific data, azoxystrobin is classified as practically nontoxic 

to reptiles and terrestrial-phase amphibians on an acute exposure basis. Chronic exposure 

resulted in reproductive effects in birds. 

Azoxystrobin is practically nontoxic to mammals on an acute oral basis. Chronic exposure 

resulted in impaired growth of offspring.

Azoxystrobin is classified as practically non-toxic to adult honey bees (Apis mellifera) on an

acute contact and oral exposure basis. A formulated product was also tested and is practically 

non-toxic to adult honey bees as well.
7

Effects to terrestrial plants were limited to the seedling emergence in which dicotyledonous 

plants were the only species to be inhibited 25% or more. None of the monocotyledonous plants 

tested were impacted.
8

II. PROBLEM FORMULATION 

In 2009, the Environmental Fate and Effects Division of the Office of Pesticide Programs 

completed a preliminary problem formulation1 for the ecological risk and drinking water 

assessments for azoxystrobin, which was then released for comment. The preliminary problem 

formulation provides a more detailed discussion of ecosystems potentially at risk, assessment 

endpoints evaluated in the risk assessment, conceptual model, and risk hypothesis associated 

with the uses of azoxystrobin. An analysis plan was also articulated, and the reader is referred to 

that document.

II.1. Nature of Regulatory Action

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), all pesticides distributed 

or sold in the United States must be registered by the United States Environmental Protection 

Agency (EPA or the Agency). To determine whether a pesticide can be registered, the EPA 

evaluates the product’s safety to non-target species based on a wide range of environmental and 

health effects studies. In 1996, FIFRA was amended by the Food Quality Protection Act 

(FQPA), and EPA was mandated to implement a new program for the periodic review of 

pesticides, i.e., Registration Review2

. The registration review program is intended to ensure that 

as the ability to assess risk evolves and as policies and practices change, all registered pesticides 

continue to meet the statutory standard of no unreasonable adverse effects to human health and 

the environment. Changes in science, public policy, and pesticide use practices will occur over 

time. Through the registration review program, the Agency periodically reevaluates pesticides to 

make sure that as changes occur, products in the marketplace can be used safely.

Additionally, potential effects to Federally-listed endangered and threatened species (hereafter 

referred to as “listed”) and their designated critical habitat are also considered under the 

Endangered Species Act (ESA) in order to ensure that the continued registration of azoxystrobin

is not likely to jeopardize the continued existence of listed species or adversely modify their 

critical habitat. In order to meet the requirements of FIFRA and the ESA, this assessment 

follows EPA guidance on conducting ecological risk assessments (USEPA, 1998) and Office of 

Pesticide Program’s Overview Document, which contains guidance for assessing pesticide risks 

to non-listed and listed species (USEPA, 2004).

II.2. Mode of Action

Azoxystrobin is a fungicide in a class of compounds called β-methoxyacrylates, which are 

derived from the naturally occurring strobilurins. Their biochemical mode of action is inhibition 

of electron transport.

 1 http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2009-0835-0008 2 http://www2.epa.gov/pesticide-reevaluation
9

III. ANALYSIS 

In order to address the risk hypothesis in the Problem Formulation (EPA-HQ-OPP-2009-0835-

0008), the potential for adverse effects on the environment is estimated. The use pattern, 

environmental fate, and ecological effects of azoxystrobin are characterized and integrated to 

assess the risks. This is accomplished using a risk quotient (ratio of exposure concentration to 

effects concentration) approach. Although risk is often defined as the likelihood and magnitude 

of adverse ecological effects, the risk quotient-based approach does not provide a quantitative 

estimate of likelihood and/or magnitude of an adverse effect. However, as outlined in the 

Overview Document (USEPA 2004), the likelihood of effects to individual organisms from 

particular uses of azoxystrobin is estimated using the level of concern (discussed below), lines of 

evidence, or actual calculated risk quotient value.

III.1 Use Characterization

Initially registered in 1997, azoxystrobin is used as a fungicide on a wide variety of terrestrial 

food and feed crops and terrestrial non-food crops. As an antimicrobial pesticide, it is also used 

as a fungicidal materials preservative for a variety of building materials, textiles and plastics.

There are currently 95 active Section 3 product registrations for azoxystrobin (Tables III.1 and

III.2). Other non-agricultural uses include turf, ornamentals, and both indoor and outdoor 

residential uses. Based on the most recent usage data provided by the Biological and Economic 

Analysis Division (BEAD) in the October 9, 2014 Screening Level Usage Analysis (SLUA), on 

average, roughly 1.1 million pounds of azoxystrobin are applied annually to agricultural crops. 

This represents a 42.8% increase in usage relative to what was reported in the April 9, 2009 

SLUA (778,000 lbs).

Azoxystrobin is formulated as a water dispersible granule, dry flowable, emulsifiable 

concentrate, flowable concentrate, granular, dust, and liquid. Azoxystrobin applications are made 

pre-plant, at-plant, pre-transplant, at-emergence, spring, early summer, summer, crown, foliar, 

post-plant, at bud break-through, early jointing, early bloom, bloom, petal fall, tillering, boot, 

cutting, pre-harvest, post-harvest, delayed dormant through foliar, and seed treatment.

Application methods include aerial and ground spray, chemigation (drip irrigation, sprinkler 

irrigation), pump sprayer, soil in-furrow treatment, band, basal spray treatment, dip treatment, 

drench, injection treatment, high volume spray (low concentration), low volume spray (high 

concentration), high and low volume ground sprayer, and seed treatment (slurry and mist-type 

seed treater). Indoor uses are surface treatments with hand held spray wand, pump-up sprayer, 

package applicator, and pressure sprayer.

Azoxystrobin end-use products can be co-formulated with other pesticide active ingredients such 

as chlorothalonil, difenoconazole, cyproconazole, fludioxonil, propiconazole, thiamethoxam, 

lambda-cyhalothrin, mefenoxam, tetraconazole, acibenzolar-S-methyl, and abamectin.
10

Table III.1. Overview of Fungicidal Uses of Azoxystrobin

Crop Grouping Representative Use

Agricultural uses 

Almonds, artichoke (globe), asparagus, bananas (& plantains), barley, oats, rye, 

bushberries, caneberries, cranberries, low growing berries, dry beans, dry and 

succulent beans, brassica head and stem, brassica (cole) leafy vegetables, 

brassica leafy greens, bulb vegetables, canola, carrots, celery, chickpeas, citrus 

fruits, corn (field, pop and seed), corn (sweet), cotton, cucurbits, filberts, fruiting 

vegetables, grapes and other vine climbing small fruits, herbs & spices, leafy 

vegetables, legume vegetables, dry and succulent and legume vegetables, foliage 

of any cultivar of bean and field pea, mint, nongrass animal feeds (forage, 

fodder, straw and hay), oilseed crops, onion (green and bunching), onion (dry 

bulb), peanuts, pecans, pepper/eggplant/okra, pistachios, potatoes, rice, 

sorghum, soybean & immature soybean seeds (edamame), stone fruits, 

strawberries, sugarbeet, sugarcane, Ti palm, tobacco, tomatoes & tomatillos, tree

nuts, tropical fruits, root and tuber vegetables, tuberous and corm vegetables,

watercress, cereals, and wild rice.

Outdoor Uses

Golf course turf, ornamentals, recreational areas/lawns, Christmas tree 

plantations, grasses grown for seed, ornamental sod farms, seed orchard trees, 

and trees such as softwood/conifers, cypress, fir, juniper, red cedar, and spruce.

Residential Uses

(Indoor/Outdoor)

Domestic dwellings/premises, carpets, residential lawns and ornamentals.

Antimicrobial Uses 

Materials preservative added during manufacturing to: Paper, building 

materials, fibers, rubber and plastics. wallboard (drywall and gypsum board) 

and paperboard products, ceiling tiles, water-based paints, stains, and coatings, 

latex caulks, sealants, adhesives, and binders, natural and synthetic fibers 

(textiles, fabrics, canvas and cordage which are not for apparel, but may include 

building materials such as awnings, boat covers, carpets (carpet backing only), 

cordage, tents, tarpaulins and wall-covering yarn), rubber and plastic products.

Commercial (Indoor/Outdoor) Institutional/industrial premises/equipment, hospitals, storage/warehouses, 

transportation facilities, automobiles, industrial lawns.

Table III.2. Registered Uses and Application Rates for Azoxystrobin

Use

Range of Max. Single 

Application Rates

(lbs a.i./A)1

Maximum Seasonal 

Application Rate

(lbs a.i./A)

Grapes, pecans, peaches, bananas, wheat, bulb 

vegetables, cotton, tropical fruits

Up to 0.25 up to 1.5

Citrus fruits, Root & Tuber Vegetables, Strawberry, 

mint, watercress, Grasses grown for seed, Leafy 

Brassica and Turnip greens, Bushberries, Peppers, 

Okra, Eggplant, Artichoke, Head and Stem Brassica, 

Asparagus, Herbs

Max rates range from 0.2 

to 0.33

0.8 to 2

Wild Rice 0.1 – 0.3 0.7

Leafy Vegetables & Cilantro, Corn, Peanuts, 

Soybeans, Tomatoes

0.1 – 0.4 0.4 to 2

Turf 0.55 5

Barley 0.1 – 0.2 0.4

Herbs 0.25 1.5
11

Table III.2. Registered Uses and Application Rates for Azoxystrobin

Use

Range of Max. Single 

Application Rates

(lbs a.i./A)1

Maximum Seasonal 

Application Rate

(lbs a.i./A)

Spices 0.25 1.5

Seed Production 0.11 to 0.23 0.45

Tobacco 0.2 0.52

Fruiting vegetables 0.1 to 0.25 1.0

Forage, fodder, straw, and hay grass and non-grass, 

legume vegetables

0.1 to 0.25 0.75 to 1.5

Clover, Cotton – Aerial Spray 0.15 0.45

Sorghum, Sugarcane – Ground/Aerial Spray 0.2 0.8

Seed Treatment – Head/Stem Brassica Crops 0.00198

(3.08 fl oz/cwt)

0.00198

Seed Treatment – Sorghum 0.00048

(3.75 fl oz/cwt)

0.00048

1 lbs a.i./A = pounds of active ingredient per acre

III.2. Exposure Characterization

III.2.1. Environmental Fate and Transport Characterization

Azoxystrobin is relatively persistent and mobile to moderately mobile. The primary route of 

degradation for azoxystrobin is through photolysis in water and on soil and to a lesser extent by 

microbial-mediated degradation in soil. The compound is stable to hydrolysis. Since 

photodegradation is a major route of degradation for azoxystrobin, the dissipation of azoxystrobin 

is expected to be dependent on conditions of the water affecting sunlight penetration (e.g., 

sediment loading, depth, etc.). Table III.3 lists the environmental fate properties of azoxystrobin

as identified in the submitted environmental fate and transport studies. 

Table III.3. Environmental fate properties of azoxystrobin, the 

degradation/transformation products and the residues of concern.

Study

(Guideline Numbers) Value 

Degradation/Transformat

ion Products1

(maximum % of applied 

radioactivity)

MRID#

Henry’s Constant (at 20 oC) 7.3 x 10-14 atm m3 mol-1 NA

Vapor Pressure 8.2 x 10-13 torr (mm Hg) NA

(161-1, 835.2120) 

Hydrolysis T1⁄2 (at 25 °C) 

stable at pH5, 7, 9 NA 43678172

(161-2, 835.2240)

Direct Aquatic Photolysis

T1⁄2 = 11 and 17 days Compound 9 (15.0%)

Compound 13 (1.7%)

43678173

44150904
12

Table III.3. Environmental fate properties of azoxystrobin, the 

degradation/transformation products and the residues of concern.

Study

(Guideline Numbers) Value 

Degradation/Transformat

ion Products1

(maximum % of applied 

radioactivity)

MRID#

T1⁄2 Compound 21 (<5.6%) 

Compound 24 (<2.6%)

Compound 28 (<8.9%)

Compound 30 (<2.4%)

CO2 (5.9%)

(161-3, 835.2410)

Soil Photolysis

T1⁄2 = 17.6 to 28.4 days Compound 3 (0.7%)

Compound 9 (9.0%)

Compound 13 (<3.5)

Compound 19 (<6.0%)

Compound 24 (<3.2%)

Compound 28 (<6.5%)

Compound 30 (<5.0%)

U13 (<5.2%)

CO2 (<17 to 24%)

43678174

(162-1, 835.4100)

Aerobic Soil Metabolism 

T1⁄2

72, 85, 164 days Compound 2 (28%)**

Compound 3 (3.1%)

Compound 28 (3.1%)

Compound 30 (<2.8%)

Compound 36 (2.8%)

CO2 (18 to 27%)

43678175

44046801

(162-2, 835.4200)

Anaerobic Soil Metabolism 

T1⁄2

DT50 – 49-56 days Compound 2 (68%)**

Compound 3 (0.6%)

Compound 28 (4.2%)

Compound 30 (<2.8%)

Compound 36 (1.1%)

CO2 (<5%)

43678175

44046801

(162-4, 835.4300)

Aerobic Aquatic 

Metabolism T1⁄2

138 (SFO)/609(IORE)

to 206 days(SFO)

49112201

(162-3, 835.4400)

Anaerobic Aquatic 

Metabolism, T1⁄2

50 to 59 days

(soil-water system)

62.3 90 % upper bound

43678175
13

Table III.3. Environmental fate properties of azoxystrobin, the 

degradation/transformation products and the residues of concern.

Study

(Guideline Numbers) Value 

Degradation/Transformat

ion Products1

(maximum % of applied 

radioactivity)

MRID#

(164-1, 835.6100) 

Terrestrial Field 

Dissipation T1⁄2

65 days

85 days

60 days

28-32 days

Compounds 2, 9, 28

Compounds 28, 29

Compounds 2, 9

Compounds 28, 30

Compound 2 (6.7%)

Compound 28 (3.7%)

Compound 30 (0.5%)

Compound 30

Compound 28, 30

Compounds 28, 30

43678184

43678185

43678186

43678187

44058709

44058711

44058712

44058713

(163-1, 835.1240) 

Mobility (Freundlich 

Sorption Coefficients) Kfads

1.5 to 23 mL/g

0.35 to 6.8 mL/g

0.76 to 11 ml/g

0.27 to 4.2 ml/g

Azoxystrobin

Compound 2

Compound 28

Compound 30

43678178 

43678181

43678179

43678177

43678180

1 Structures and chemical names are given in Appendix 1. Table1. 

 * Residue of concern. ** Major degradation products (>10%).

SFO: single first-order kinetics; IORE: Indeterminate order rate equation kinetics.

In terms of abiotic routes of degradation, azoxystrobin is stable to hydrolysis at pH 5, 7, and 9 at 

25 °

C; however, the dissipation half-life (T1⁄2) of azoxystrobin by photolysis on soil is 34.4 days 

and in surface water is 12.5 days. The Z-isomer ((methyl (Z)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]-phenyl}-3-methoxyacrylate); Compound 9)) of azoxystrobin, a 

transformation product only formed during photolysis, was previously determined by the Health 

Effects Division (HED) to be a residue of concern for dietary exposure. For drinking water, a

total toxic residue (TTR) half-life was calculated for photolysis in surface water of 15.4 days

based on residues of the parent compound combined with the Z-isomer; however, for the 

ecological aspect of the risk assessment, only the parent compound was used in the calculations

because the Z-isomer does not form in soil metabolism studies.

With respect to biotic routes of degradation, azoxystrobin is expected to slowly undergo 

biotransformation in aerobic and anaerobic soils. The aerobic soil metabolism half-lives range 

from 72 to 164 days; therefore, azoxystrobin is expected to be moderately persistent to persistent 

in aerobic mineral soils. 

A new aerobic aquatic metabolism study (MRID 49112201) was submitted since the 2009 

Problem Formulation; the aerobic aquatic metabolism half-life ranged from 138 to 206 days.
14

Transformation Products

Nine degradation or transformation products were identified in the photolysis studies. Only the

Z-isomer of azoxystrobin and parent azoxystrobin have been identified as residues of concern in

drinking water. Five degradation products were identified in laboratory metabolism studies 

(aerobic and anaerobic). In the terrestrial field dissipation studies, five degradation/ 

transformation products were identified (including the Z-isomer).

The major degradation or transformation processes which act on azoxystrobin are photolysis in 

water and on soil and biotransformation in soil and water. Six degradation or transformation 

products (Appendix 1, Table 1) plus CO2 were identified in the aqueous photolysis study. They 

are compounds 9 (percent of applied 15.0%), 13 (1.7%), 21 (<5.6%), 24 (<2.6%), 28 (<8.9%), 

and 30 (<2.4%). Only compound 9 (Z isomer: methyl (Z)-2-{2-[6-(2-cyano-phenoxy)pyrimidin4-yloxy]-phenyl}-3-methoxyacrylate) which is an isomer of azoxystrobin has been determined to 

be an degradation or transformation product of concern. A similar distribution of transformation 

products was identified in the soil photolysis study.; compounds 9 (percent of applied 9.0%), 3 

(0.7%), 13 (<3.5%), 19 (<6.0%), 24 (<3.2%), 28 (<6.5%), and 30 (<5.0%), and U13 (<5.2%).

In the aerobic soil metabolism degradation products identified were compounds 2 (percent of 

applied 28%), 3 (3.1%), 28 (3.1%), 30 (<2.8%), 36 (2.8%), and CO2 (17-24%). The degradation 

products in the anaerobic studies identified were 2 (68%), 3 (0.6%), 28 (4.2%), 30 (2.8%), 36 

(<1.1%), and CO2 (<5%). Compound 9 was not identified in the aerobic and anaerobic 

metabolism studies (laboratory studies), thus it was not included as a residue of concern. Five

transformation products were identified in the terrestrial field dissipation studies.

Mobility

Based upon organic carbon partition coefficients (Koc) values of 210 to 1610 mL/goc, 

azoxystrobin is classified as mobile to moderately mobile according to the FAO classification 

scheme. The Koc values (21 to 500 mL/goc) for the transformation compounds 2, 28, and 30 

suggest that they are more mobile than azoxystrobin. The soil/water partitioning coefficients 

(Freundlich Kf) for azoxystrobin ranged from 1.5 to 23 mL/g oc. The relatively low mobility was 

confirmed in the field studies where azoxystrobin dissipated slowly on the surface (0-6 inch) of 

non-flooded soils. No azoxystrobin residue was found in soil layers deeper than 6 inches. The 

vapor pressure of azoxystrobin (8.2 x 10-13 torr @ 25 oC) would suggest that it has a low 

potential to volatilize from dry or moist soils or from water.

Bioaccumulation

Based on the low octanol-water partitioning coefficient (Kow= 316), azoxystrobin is not expected 

to bioaccumulate in aquatic organisms. 
15

Table III.4. Summary of environmental fate parameters for azoxystrobin and values 

used for modeling (SWCC, GENEEC, and Rice).

Parameter Value or Range Value Used in Model Source

Molecular Weight 403.4 g/mol 403.4 g/mol

Solubility in water @ 20°C 6.7 mg/L 6.7 mg/L

Vapor Pressure @ 25°C 8.2x10-13 torr 8.2x10-13 torr

Hydrolysis T1⁄2 (at 25 °C)1 Stable @ pH 5, 7, & 9 0 43678172

Aquatic Photolysis T1⁄2 12.5 days1 - parent only

15.4 days

Photolysis Reference Latitude: 

30°

43678173

44150904

Aerobic Soil Metabolism 

T1⁄21

116 days

84.8 days

143 days

142 days3 @ 20°C (SWCC)

100.5 days2,3 @ 25°C

(PRZM-GW)

43678175

44046801

Anaerobic Soil Metabolism 

T1⁄21

46.1 days

57.3 days 62.3 days3 4367817544046801

Aerobic aquatic

Metabolism T1/2 @ 20°C

206 days (SFO)

609 days(IORE) 787.5 days3 49112201

Anaerobic Aquatic 

Metabolism, T1⁄21

46.1 days

57.3 days 62.3 days3 43678175

Sorption Kd 1.5 to 23 mL/g 8.87 43678178

Foliar Dissipation HalfLife1

22.8 days, 13.7 days

7.98 days, 5.26 days,

5.4 days, 10.5 days

14.8 days3 44150911

Application Efficiency -- 0.99 – ground application

0.95 – aerial application

Spray Drift % to pond -- 0.125 – aerial

0.062 - ground (EFED, 2009)

1 Half-lives were recalculated using PestDF (EFED, 2014). IORE half-life value of 609 days used for water 

column metabolism; SFO half-life 138 days, Log-linear half-life 141 days. 2 EFED Input Parameter Guidance: 90th Percentile (EFED, 2009) 3 Half-life values adjusted to 25°C

Monitoring Data

Monitoring data for azoxystrobin were downloaded from the Water Quality Portal database 

(http://waterqualitydata.us/) on May 28, 2015. The Water Quality Portal integrates data from the 

USGS National Water Information System (NWIS), EPA’s STORET data warehouse, and 

USDA ARS STEWARDS platform. A total of 5,581 records were retrieved for the analysis of 

azoxystrobin spanning from 2006 to 2014. The majority of the data comes from the Minnesota 

Department of Agriculture with 2,662 records from the years 2010 to 2014. There were 1,661 

detects with a concentration range from 10.2 to 589 ng/L. The Water Quality portal contained 

data from four additional states; Arizona, Montana, Colorado, and Indiana; however, the samples 

from these states were all non-detects.
16

The USGS National Water Quality Assessment (NAWQA) Program also contains azoxystrobin 

monitoring data (http://cida.usgs.gov/nawqa_queries_public/jsp/mxmaster.jsp) and was also 

accessed on May 28, 2015. The NAWQA database has 84 records from 8 states from the years 

2010 to 2013 (Table III.2) with detections as high as 520 ng/L in surface water.

Table III.2. NAWQA Azoxystrobin Monitoring Results.

State Year Total Records Detects Concentration Range (ng/L)

GA 2010 2 0 --

CA 2012 12 7 7 – 128.3

IA 2013 12 4 3.4 – 86

IN 2013 12 7 6.4 – 86

MO 2013 11 9 7.2 – 99.2

NE 2013 12 10 4 – 520.1

TX 2013 11 0 --

WI 2013 12 6 24.2 – 69.8

Data from California Department of Pesticide Regulation was also accessed for this assessment 

on June 10, 2015. The sampling periods for which azoxystrobin were monitored in surface and 

ground water were 2004-2005, 2007-2008, and 2012. A total of 86 records were retrieved with a 

limit of quantitation of 0.5 ppb for years 2004 -2008 and 0.005 μg/L (parts per billion; ppb) in 

2012. For years 2004-2008, there were 56 records and 5 detections (9% detection frequency)

ranging from 0.53 to 2.67 ppb. In 2012, there were 30 records and 17 detections (57% detection 

frequency) ranging from 0.0062 to 0.012 ppb suggesting that the more sensitive detection limits 

provided a better opportunity to determine the extent to which azoxystrobin is moving into 

surface waters. The CADPR surface water database can be found at: 

http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm.

Data provided by the State of Colorado to the EPA returned 138 results for the year 2010. Two 

of the samples were detects of 0.039 and 0.040 ppb with a detection limit of 0.020 ppb.

None of the monitoring data listed above is a result of sampling targeted to azoxystrobin use. 

That coupled with a less robust sampling frequency would suggest that the monitoring results are 

most likely missing the peak concentrations of azoxystrobin.

Multiple monitoring studies of pesticide residues in honey bee colonies (Mullin, 2010; Pettis, 

2013; Stoner, 2013; Rennich, 2012) have demonstrated detectable quantities of azoxystrobin in 

various hive matrices (e.g., wax, pollen). Residues in comb wax were detected at a maximum of 

278 ppb in wax (limit of detection LOD = 1 ppb) and in pollen as high as 107 ppb (LOD = 1.0 

ppb).

Simulation Modeling

Aquatic exposures are quantitatively estimated for all assessed uses using scenarios that 

represent high exposure sites for azoxystrobin use. Each of these sites represents a 10-hectare 

field that drains into a 1-hectare pond that is 2 meters deep and has no outlet. Exposure estimates 

generated using the standard pond are intended to represent a wide variety of vulnerable water 
17

bodies that occur at the top of watersheds including prairie pot holes, playa lakes, wetlands, 

vernal pools, man-made and natural ponds, and intermittent and first-order streams. As a group, 

there are factors that make these water bodies more or less vulnerable than the standard surrogate 

pond. Static water bodies that have larger ratios of drainage area to water body volume would be 

expected to have higher peak EECs than the standard pond. These water bodies will be either 

shallower or have large drainage areas (or both). Shallow water bodies tend to have limited 

additional storage capacity, and thus, tend to overflow and carry pesticide in the discharge 

whereas the standard pond has no discharge. As watershed size increases beyond 10 hectares, at 

some point, it becomes unlikely that the entire watershed is planted in a single crop and treated 

with the same pesticide. Headwater streams can also have peak concentrations higher than the 

standard pond, but they tend to persist for only short periods of time and residues are then carried 

downstream. 

Surface Water

Models

For surface water assessments, the Tier 2 Surface Water Concentration Calculator (SWCC) 

version 1.106 (EFED, 2014), Tier 1 Generic Estimated Environmental Concentrations 

(GENEEC) version 2.0 (EFED, 2001), and Tier 1 Rice version 1.0 (EFED, 2007) models were

used to estimate environmental concentrations of the active ingredient azoxystrobin in surface 

waters. For further information on these models see: http://www2.epa.gov/pesticide-science-andassessing-pesticide-risks/about-water-exposure-models-used-pesticide.

Scenario Selection

The EECs for a chemical are calculated based on the use parameters that produce the highest 

potential exposures (e.g., highest application rate, minimum reapplication interval, etc.) for the

registered use sites. 

The scenarios used for modeling in this assessment include the use sites that previously resulted 

in the highest EECs (i.e., turf and rice) and uses with the highest application rates according to 

the October 9, 2014 SLUA. These uses include corn, peanuts, wheat, potatoes, and almonds. 

Additionally, sugarcane and leafy vegetable uses are modeled to represent minor crop uses with 

relatively high application rates. A total of 25 standard foliar spray scenarios in the SWCC and 

27 seed treatment scenarios in the GENEEC model and tier I Rice model are available to model 

these use patterns. 

Additionally, the 1999 New Use assessment for leafy vegetables (DP260137) modeled the leafy 

vegetable group as a maximum yearly application rate of 1.5 lbs a.i./A; however, the Use 

Summary Table submitted by the registrant in March 2015 notes that it is possible to for some 

uses to have three crop cycles (planting through harvest) in a year, which would yield a 

maximum yearly application rate of 4.5 lbs a.i./A. It is possible that three successive seasons of 

azoxystrobin applications could occur in one year, either through replanting of the same crop or 

rotation to different crops. Both the single and three crop cycles per year scenarios were modeled 

for this assessment. 
18

Application parameters used for modeling azoxystrobin in SWCC, GENEEC and Rice can be 

found in Table III.3. Application of azoxystrobin was modeled using efficiency and spray drift 

values from foliar application and seed treatments. Inputs used for SWCC and GENEEC 

modeling can be found in Table III.1.

Table III.3. Maximum Application Parameters for Azoxystrobin Modeling

Use site –

application 

method

Max. Single 

Application 

Rate

(lbs a.i./A)

Minimum 

Reapplication 

Interval

(Max. # 

Applications

)

First Application 

Date

Max. Seasonal 

Application 

Rate 

(lbs a.i./A)

SWCC modeling 

Scenario1

Modeling for Azoxystrobin Foliar Sprays (SWWC)

Turf – Ground 0.55 14 days

(9 applications)

Emergence 

Day 0 in SWCC 5 FLturfSTD, PAturfSTD

Corn – Air 0.25 7 days

(4 applications)

V4 – V8 stage

Day 15 in SWCC 2

IAcornstd, ILCornSTD, 

INCornStd, KSCornStd, 

MNCornStd, MScornSTD, 

NCcornESTD, NECornStd,

OHCornSTD, PAcornSTD

Peanuts – Air 0.4 10 days

(2 applications)

At plant

Day (-10) in 

SWCC

0.8 NCpeanutSTD

Wheat – Air 0.2 14 days

(2 applications)

Prior to disease 

development

Day 0 SWCC

0.4 NDwheatSTD

Potatoes – Air 0.33 7 days

(6 applications)

Prior to disease 

development

Day 0 SWCC

2 IDNpotato_WirrigSTD, 

MEpotatoSTD

Almond – Air 0.25 7 days

(6 applications)

When disease 

appears

Day 0 SWCC

1.5 CAalmond_WirrigSTD

Sugarcane –

Air 0.2 14 days

(4 applications)

Prior to rust 

development 

continuing 

throughout season

Day 30 SWCC

0.8 FLsugarcaneSTD

LAsugarcaneSTD

Leafy 

Vegetable –

Air 

0.25

14 days2

(1 CC/year – 6 

applications

3 CC/year – 18 

applications)

Prior to disease 

onset

(Day 0 SWCC)

1.5

4.5 per year

CAlettuceSTD, 

FLpepperSTD, 

ORbeanSTD, 

NJmelonSTD, 

MIasparagusSTD, 

PAtomatoSTD

Modeling for Azoxystrobin Seed Treatments (GENEEC)

Use site –

application 

method

Max. Single 

Application 

Rate

Minimum 

Reapplication 

Interval

First Application 

Date

Max. Seasonal 

Application 

Rate 

SWCC modeling 

Scenario
19

(lbs a.i./A) (Max. # 

Applications)

(lbs a.i./A)

SEED TREATMENT- DYNASTY PRODUCT (9.6% A.I.) EPA Reg No. 100-1159

Brassica crops

0.00062 

(3.75 fl. 

oz./CWT)

None 

(one 

application)

--1 0.00062A --

Rice

0.012 (1.53 

fl. oz./ 

CWT)

None 

(one 

application)

-- 0.012 --

Sorghum

0.00175 

(3.08 fl. 

oz./CWT)

None 

(one 

application) -- 0.00175 --

Soybeans

0.00478 

(0.459 fl. 

oz./CWT)

None 

(one 

application) -- 0.00478 --

Sunflower

0.009 (37.5 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.009 --

SEED TREATMENT- DYNASTY CST PRODUCT (6.64% A.I.) EPA Reg No. 100-1177

Cotton

0.0032 (3.95 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0032 --

SEED TREATMENT- DYNASTY EXTREME PRODUCT (8.33% A.I.) EPA Reg No. 100-1284

Cotton

0.0033 (3.0 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0033 --

SEED TREATMENT- ADAGE DELUXE PRODUCT (0.32% A.I.) EPA Reg No. 100-1449

Soybean

0.0015 (4.29 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0015 --

SEED TREATMENT- ADAGE PREMIER PRODUCT (0.32% A.I.) EPA Reg No. 100-1450

Soybean

0.0015 (4.23 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0015 --

SEED TREATMENT- AVICTA CORN 250 PRODUCT (10.3% A.I.) EPA Reg No. 100-1405

Field corn

0.023 (11.61 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.023 --

Popcorn

0.038 (25.8 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.038 --

Sweet corn

0.046 (20.65 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.046 --

SEED TREATMENT- AVICTA CORN 500 PRODUCT (10.2% A.I.) EPA Reg No. 100-1399

Field corn

0.022 (11.4 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.022 --
20

Popcorn

0.037 (25.2 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.037 --

Sweet corn

0.045 (20.2 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.045 --

SEED TREATMENT- CRUISER EXTREME PRODUCT (0.5% A.I.) EPA Reg No. 100-1208

Field corn

0.00024 

(2.51 fl. oz./ 

CWT)

None 

(one 

application) -- 0.00024 --

Popcorn

0.0004 (5.58 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0004 --

Sweet corn

0.0005 (4.46 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0005 --

SEED TREATMENT- CRUISER MAXX RICE PRODUCT (1.32% A.I.) EPA Reg No. 100-1369

Rice

0.0078 (7.0 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0078 --

SEED TREATMENT- FOUR WAY VAP PRODUCT (0.9% A.I.) EPA Reg No. 100-1384

Foliage of 

Legume Veg. 

Crop Group 7 

(common 

beans) 

0.0029 (3.0 

fl. oz./ 

CWT)

None

(one 

application)

-- 0.0029 --

Legume Veg. 

Crop Group 6 

(succulent or 

dried)

0.0077 (3.0 

fl. oz./ 

CWT)

None

(one 

application)

-- 0.0077 --

Soybean

0.0029 (3.0 

fl. oz./ 

CWT)

None

(one 

application)

-- 0.0029 --

SEED TREATMENT- MAXIM QUATTRO PRODUCT (1.33% A.I.) EPA Reg No. 100-1352

Field corn

0.0003 (1.18 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0003 --

Popcorn

0.0006 (3.07 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0006 --

Sweet corn

0.0006 (2.05 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0006 --

SEED TREATMENT- QUARTET PRODUCT (5.24% A.I.) EPA Reg No. 100-1286

Cotton

0.0026 (4.0 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0026 --

SEED TREATMENT- TRIO CST PRODUCT (6.64% A.I.) EPA Reg No. 100-1285
21

CC = one crop cycle; 3 CC = three crop cycles

1

Scenarios are identified by state and crop

2 GENEEC does not have exposure scenarios or application dates for modeling.

3 Annual application rates in lb a.i./A were calculated through T-REX using its seed treatment worksheet.

Azoxystrobin environmental fate data used for generating model parameters are listed in Table 

III.1. Chemical property input values were chosen in accordance with current input parameter

guidance (USEPA, 2009). The SWCC EECs for foliar sprays are provided in Table III.4; 

GENEEC EECs and Rice EECs for seed treatments are provided in Table III.5.

Table III.4. Estimated Environmental Concentrations (EEC) for Azoxystrobin in 

Standard Farm Pond from Foliar Sprays using SWCC 1-in-10 year Azoxystrobin 

Concentration (μg/L)

Scenario -State Crop Peak 21-Day Average 60-Day Average

FL - Turf 43.7 42 40.3

PA – Turf 32.9 32 31.1

IA – Corn 24.3 23.4 22.1

IL – Corn 30.9 29.7 27.8

IN – Corn 24.9 24.1 23.1

KS – Corn 41.1 39.3 36.6

MN – Corn 29.7 28.6 27.6

MS – Corn 34.2 33.3 31.4

NC – Corn 22.2 21.3 20.2

NE – Corn 33.2 31.7 30.2

OH – Corn 28.9 27.9 26.2

PA – Corn 25.3 24.8 24.8

NC – Peanut 17.4 16.6 15.7

ND – Wheat 10 9.69 9.2

ID – Potato 32.5 32.1 30.9

ME – Potato 52.6 51.3 49.1

CA – Almond 21.5 20.6 19.7

FL – Sugarcane 29.7 28.6 27.2

LA – Sugarcane 31.5 30.5 28.8

CA – Lettuce (3 CC/year)1 82.3 80.9 79.3

CA – Lettuce (1 CC/year) 33.5 32.5 31.1

FL – Pepper2 (3 CC/year) 150 152 151

FL – Pepper2 (1 CC/year) 50.6 49.4 51.1

OR – Bean 2 (3 CC/year) 111 111 110

NJ – Melon2 (3 CC/year) 96.7 95.1 93.1

MI – Asparagus2 (3 CC/year) 60 58.2 56.9

PA – Tomato2 (3 CC/year) 96.5 95.4 92.8 1 Crop cycles per year

Cotton

0.0029 (3.5 

fl. oz./ 

CWT)

None 

(one 

application) -- 0.0029 --
22

2 Leafy vegetable surrogate scenario

Table III.5. Estimated Environmental Concentrations (EEC) for Azoxystrobin in 

Standard Farm Pond from Seed Treatment using GENEEC and tier I Rice

1-in-10 year Azoxystrobin Concentration (parts-per-billion, μg/L)

Crop Peak 21-Day Average 60-Day Average

DYNASTY 

Brassica crops 0.0078 0.0075 0.0071

Sorghum 0.022 0.021 0.020

Rice 6.1 6.1 6.1

Soybeans 0.06 0.058 0.055

Sunflowers 0.113 0.109 0.103

DYNASTY CST

Cotton 0.04 0.039 0.037

DYNASTY EXTREME

Cotton 0.04 0.039 0.037

ADAGE DELUXE

Soybeans 0.019 0.018 0.017

ADAGE PREMIER

Soybeans 0.019 0.018 0.017

AVICTA CORN 250

Field corn 0.288 0.279 0.264

Popcorn 0.476 0.462 0.436

Sweet corn 0.576 0.559 0.523

AVICTA CORN 500

Field corn 0.288 0.279 0.264

Popcorn 0.476 0.462 0.436

Sweet corn 0.576 0.559 0.523

CRUISER EXTREME

Field corn 0.003 0.0029 0.0027

Popcorn 0.005 0.0049 0.0046

Sweet corn 0.0063 0.0061 0.0057

CRUISER MAXX RICE

Rice 4.0 4.0 4.0

FOUR-WAY VAP

Foliage of legume veg crop group 

7 0.036 0.035 0.033

Legume veg crop group 6 0.096 0.094 0.088

Soybean 0.036 0.035 0.033

MAXIM QUATTRO

Field corn 0.0038 0.0036 0.0034

Popcorn 0.0075 0.0073 0.0069

Sweet corn 0.0075 0.0073 0.0069
23

QUARTET

Cotton 0.033 0.032 0.03

TRIO CST

Cotton 0.036 0.035 0.033

III.1.3. Measures of Terrestrial Exposure

III.1.3.1. Exposure Modeling for Terrestrial Vertebrates

Exposure estimates for terrestrial animals assumed to be in the target area or in an area exposed 

to azoxystrobin as a result of spray drift or foraging for seeds are derived using the terrestrial 

exposure (T-REX)

3 model (version 1.5.2.). This model incorporates the Kenaga nomograph, as 

modified by Fletcher et al. (1994), which is based on a large set of actual field residue data. The 

upper-limit values from the nomograph represent an approximation of the highest residue value 

observed in the data set (Hoerger and Kenaga 1972). Consideration is given to different types of 

feeding strategies for mammals and birds, including herbivores, insectivores and granivores. For 

dose-based exposures, three weight classes of birds (20, 100, and 1000 g) and mammals (15, 35, 

and 1000 g) are considered. Acceptable foliar dissipation half-lives of 22.8, 7.98, 13.7, and 5.26 

days were available to determine a reviewer-calculated foliar dissipation half-life of 14.9 days, 

all T-REX EECs are based on the measured half-life value of 14.9 days. 

Ingestion of Food Items Based on Foliar Application

The azoxystrobin application rates are taken from active labels and are used to estimate 

terrestrial exposure for this assessment. The dietary-based EECs on a variety of food items from 

the use of azoxystrobin applied at the maximum label rates for the current uses are provided in 

Table III.6; dose-based EECs are provided in Table III.7.

 3 USEPA. 2013. Pesticides: Science and Policy. Terrestrial Models, T-REX Version 1.5.2. 

http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/models-pesticide-risk-assessment#terrestrial
24

Table III.6. T-REX Calculated Dietary-Based EECs for Azoxystrobin on Food 

Residues.*

Use Pattern (Foliar Application) Food Type Maximum Dietary-based EECs 

(mg/kg-diet)

Turf; 

0.55 lb a.i./A x 14 days interval x 9 

apps

Short Grass 275

Tall Grass 126

Broadleaf plants 155

Fruits/pods/seeds 17

Arthropods 108

Corn; 

0.25 lb a.i./A x 7 days interval x 4 

apps

Short Grass 157

Tall Grass 72

Broadleaf plants 88

Fruits/pods/seeds 10

Arthropods 62

Peanuts; 

0.4 lb a.i./A x 14 days intervals x 2 

apps

Short Grass 146

Tall Grass 67

Broadleaf plants 82

Fruits/pods/seeds 9

Arthropods 57

Wheat; 

0.2 lb a.i./A x 10 days intervals x 2 

apps

Short Grass 78

Tall Grass 36

Broadleaf plants 44

Fruits/pods/seeds 5

Arthropods 31

Potatoes; 

0.33 lb a.i./A x 7 days interval x 6 

apps

Short Grass 245

Tall Grass 112

Broadleaf plants 138

Fruits/pods/seeds 15

Arthropods 96

Almonds; 

0.25 lb a.i./A x 7 days intervals x 6 

apps

Short Grass 185

Tall Grass 85

Broadleaf plants 104

Fruits/pods/seeds 12

Arthropods 73

Sugarcane; 

0.25 lb a.i./A x 14 days interval x 4 

apps

Short Grass 116

Tall Grass 53

Broadleaf plants 65

Fruits/pods/seeds 7

Arthropods 45

Leafy Vegetables

(1 crop cycle per year); 0.25 lb a.i./A x 

14 days interval x 6 apps

Short Grass 123

Tall Grass 56

Broadleaf plants 69

Fruits/pods/seeds 8

Arthropods 48

Leafy Vegetables Short Grass 125

Tall Grass 57
25

(3 crop cycles per year); 0.25 lb a.i./A 

x 14 days x 18 apps

Broadleaf plants 71

Fruits/pods/seeds 8

Arthropods 49

* Based on reviewer-calculated foliar dissipation half life of 14.9 days

Table III.7. T-REX Calculated Dose-Based EECs for Azoxystrobin on Food Residues.*

Use Pattern 

(Foliar 

applications)

Food Type

Dose-based EECs for 

Birds

(mg/kg-bw)

Dose-based EECs for Mammals

(mg/kg-bw)

Small

(20 g)

Medium

(100 g)

Large

(1000 g)

Small

(15 g)

Medium

(35 g)

Large

(1000 g)

Turf; 

0.55 lb a.i./A x 14 

days interval x 9 

apps

Short grass 313 179 80 262 181 42

Tall grass 144 82 37 120 83 19

Broadleaf 

plants 176 100 45 147 102 24

Fruits/pods 20 11 5 16 11 3

Arthropods 123 70 31 103 71 16

Seeds 

(granivore) 4 2 1 4 3 0.6

Corn; 

0.25 lb a.i./A x 7 

days interval x 4 

apps

Short grass 179 102 46 150 104 24

Tall grass 82 47 21 69 47 11

Broadleaf 

plants 101 57 26 84 58 14

Fruits/pods 11 6 3 9 6 2

Arthropods 70 40 18 59 41 9

Seeds 

(granivore) 2 1 0.6 2 1 0.3

Peanuts; 

0.4 lb a.i./A x 14 

days intervals x 2 

apps

Short grass 166 95 42 139 96 22

Tall grass 76 43 19 64 44 10

Broadleaf 

plants 94 53 24 78 54 13

Fruits/pods 10 6 3 9 6 1

Arthropods 65 37 17 54 38 9

Seeds 

(granivore) 2 1 0.6 2 1 0.3

Wheat; 

0.2 lb a.i./A x 10 

days intervals x 2 

apps

Short grass 89 51 23 75 51 12

Tall grass 41 23 10 34 24 5

Broadleaf 

plants 50 29 13 42 29 7

Fruits/pods 6 3 1 5 3 0.8

Arthropods 35 20 9 29 20 5

Seeds 

(granivore) 1 0.7 0.3 1 0.7 0.2

Potatoes; 

0.33 lb a.i./A x 7 

days interval x 6 

apps

Short grass 279 159 71 233 161 37

Tall grass 128 73 33 107 74 17

Broadleaf 

plants 157 89 40 131 91 21

Fruits/pods 17 10 4 15 10 2

Arthropods 109 62 28 91 63 15

Seeds 

(granivore) 4 2 0.99 3 2 0.5
26

Almonds; 

0.25 lb a.i./A x 7 

days intervals x 6 

apps

Short grass 211 120 54 177 122 28

Tall grass 97 55 25 81 56 13

Broadleaf 

plants 119 68 30 99 69 16

Fruits/pods 13 8 3 11 8 2

Arthropods 83 47 21 69 48 11

Seeds 

(granivore) 3 2 0.75 2 2 0.39

Sugarcane; 

0.25 lb a.i./A x 14 

days interval x 4 

apps

Short grass 132 75 34 111 77 18

Tall grass 61 35 15 51 35 8

Broadleaf 

plants 74 42 19 62 43 10

Fruits/pods 8 5 2 7 5 1

Arthropods 52 30 13 43 30 7

Seeds 

(granivore) 2 1 0.47 2 1 0.25

Leafy Vegetable (1 

crop cycle per year); 

0.25 lb a.i./A x 14 

days x 6 apps

Short grass 140 80 36 117 81 19

Tall grass 64 37 16 54 37 9

Broadleaf 

plants 79 45 20 66 46 11

Fruits/pods 9 5 2 7 5 1

Arthropods 55 31 14 46 32 7

Seeds 

(granivore) 2 1 0.50 2 1 0.26

Leafy Vegetables

(3 crop cycles per 

year); 

0.25 lb a.i./A x 14 

days x 18 apps

Short grass 143 81 36 120 83 19

Tall grass 65 37 17 55 38 9

Broadleaf 

plants 80 46 21 67 47 11

Fruits/pods 9 5 2 7 5 1

Arthropods 56 32 14 47 32 8

Seeds 

(granivore) 2 1 0.51 2 1 0.27

* Based on foliar dissipation half-life of 14.9 days estimated by the reviewer

Ingestion of Azoxystrobin-treated Seeds as a Result of Seed Treatment

The azoxystrobin application rates are taken from active labels and are used in T-REX to 

estimate exposure (seed dose-based EECs) as well as dietary-based exposure in terms of the

amount of azoxystrobin available as treated seed on a field for birds and mammals. The dosebased EECs on seed treatment uses applied at the maximum label rates are provided in Table 

III.8; EECs based on azoxystrobin available in the form of treated seed on the field are provided 

in Table III.9.

Table III.8. T-REX Calculated Dose-Based EECs of Azoxystrobin on Seeds.

Use 

(Seed treatment)

Seed 

Application 

Rate (mg 

a.i./kg seed)

Dose-based EECs for 

Birds

(mg a.i./kg-bw/day)

Dose-based EECs for Mammals

(mg a.i./kg-bw/day)

Small

(20 g)

Medium

(100 g)

Large

(1000 g)

Small

(15 g)

Medium

(35 g)

Large

(1000 g)

DYNASTY (9.6% A.I.)

Rice 95.59 24.2 13.8 6.2 20.3 14 3.3
27

Sunflower 2342.8 593 338 151 496 343 80

Soybeans 28.68 7.3 4.1 1.9 6.1 4.2 0.97

Sorghum 192.42 48.7 27.8 12.4 40.8 28.2 6.5

Head/Stems 

Brassica Crops 234.28 59.3 33.8 15.1 49.6 34.3 7.95

DYNASTY CST (6.64% A.I.)

Cotton 170.7 43.2 24.6 11.0 36.2 25.0 5.8

DYNASTY EXTREME (8.33% A.I.)

Cotton 162.6 41.2 23.5 10.5 34.5 23.8 5.5

ADAGE DELUXE (0.32% A.I.)

Soybean 8.9 2.3 1.3 0.6 1.9 1.3 0.3

ADAGE PREMIER (0.32% A.I.)

Soybean 8.8 2.2 1.3 0.6 1.9 1.3 0.3

AVICTA CORN 250 (10.3% A.I.)

Field corn 778 197 112 50 165 114 26

Popcorn 1729 438 250 112 366 253 59

Sweet corn 1384 350 200 89 293 203 47

AVICTA CORN 500 (10.2% A.I.)

Field corn 757 192 109 49 160 111 26

Popcorn 1673 423 241 108 354 245 57

Sweet corn 1341 339 194 87 284 196 46

CRUISER EXTREME (0.5% A.I.)

Field corn 8.2 2.1 1.2 0.5 1.7 1.2 0.3

Popcorn 18.2 4.6 2.6 1.2 3.9 2.7 0.6

Sweet corn 14.5 3.7 2.1 0.9 3.1 2.1 0.5

CRUISER MAXX RICE (1.32% A.I.)

Rice 60 15 8.7 3.9 13 8.8 2.0

FOUR WAY VAP (0.9% A.I.)

Foliage of legume 

vegetables crop 

group 7

17.6 4.5 2.5 1.1 3.7 2.6 0.6

Legume vegetables 

crop group 6 17.6 4.5 2.5 1.1 3.7 2.6 0.6

Soybean 17.6 4.5 2.5 1.1 3.7 2.6 0.6

MAXIMUM QUATTRO (1.33% A.I.)

Field corn 10.2 2.6 1.5 0.7 2.2 1.5 0.4

Popcorn 26.6 6.7 3.8 1.7 5.6 3.9 0.9

Sweet corn 17.7 4.5 2.6 1.2 3.8 2.6 0.6

QUARTET (5.24% A.I.)

Cotton 136 34.5 19.7 8.8 28.9 20.0 4.6

TRIO CST (6.64% A.I.)

Cotton 151 38.3 21.8 9.8 32.0 22.2 5.1

Table III.9. T-REX Calculated EECs of Azoxystrobin

Available on a Field.

Use Pattern 

(Seed treatment)

Maximum Application 

Rate 

(lb a.i./A)

EEC 

(mg a.i./ft2)

DYNASTY (9.6% A.I.)

Rice 0.012 0.129

Sunflower 0.009 0.098

Soybeans 0.0048 0.05
28

Sorghum 0.0018 0.018

Head/Stems Brassica 

Crops 0.0006 0.006

DYNASTY CST (6.64% A.I.)

Cotton 0.003 0.032

DYNASTY EXTREME (8.33% A.I.)

Cotton 0.003 0.032

ADAGE DELUXE (0.32% A.I.)

Soybean 0.0015 0.016

ADAGE PREMIER (0.32% A.I.)

Soybean 0.0015 0.015

AVICTA CORN 250 (10.3% A.I.)

Field corn 0.023 0.24

Popcorn 0.038 0.398

Sweet corn 0.046 0.48

AVICTA CORN 500 (10.2% A.I.)

Field corn 0.022 0.23

Popcorn 0.037 0.38

Sweet corn 0.045 0.46

CRUISER EXTREME (0.5% A.I.)

Field corn 0.00024 0.003

Popcorn 0.0004 0.004

Sweet corn 0.0005 0.005

CRUISER MAXX RICE (1.32% A.I.)

Rice 0.0078 0.08

FOUR WAY VAP (0.9% A.I.)

Foliage of legume 

vegetables crop group 7 0.0029 0.03

Legume vegetables crop 

group 6 0.0077 0.08

Soybean 0.0029 0.03

MAXIMUM QUATTRO (1.33% A.I.)

Field corn 0.0003 0.003

Popcorn 0.0006 0.006

Sweet corn 0.0006 0.006

QUARTET (5.24% A.I.)

Cotton 0.0026 0.027

TRIO CST (6.64% A.I.)

Cotton 0.0029 0.03

III.1.3.2. Exposure Modeling for Terrestrial Plants

Azoxystrobin exposure to terrestrial and semi-aquatic plants is estimated using the Terrestrial 

Plant (TerrPLANT4; version 1.2.2) model. The model generates EECs for plants residing near a 

use area that may be exposed via a combination of surface water runoff and spray drift from 

foliar applications, or via surface water runoff from seed treatments. The EECs are generated 

from one application at the maximum rate for a particular use and compound-specific solubility 

information. Only a single application is considered because it is assumed that for plants, toxic 

 4 USEPA. 2013a. Pesticides: Science and Policy. Terrestrial Models, TerrPlant Version 1.2.2. 

http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/models-pesticide-risk-assessment#terrestrial
29

effects are likely to manifest shortly after the initial exposure and that subsequent exposures do 

not contribute to the response. Hence, the model estimates EECs based on application rate, the 

solubility limit, and default assumptions of drift. The EECs for terrestrial and semi-aquatic 

plants for a single application of azoxystrobin current uses are presented in Table III.10. In 

addition, of the numerous azoxystrobin uses which permit aerial or ground applications, turf uses 

with the highest single and seasonal application rate of all uses do not allow aerial applications 

thus only EECs from ground applications were modeled for turf uses. 

With the AgDRIFT model (v. 2.1.1) available for modeling exposure to plants from spray drift 

alone, the drift EECs in TerrPLANT are no longer used for assessments and are replaced with 

AgDRIFT to better represent the azoxystrobin that is expected to drift downwind off the treated 

areas to non-target plants inhabiting areas adjacent to the treated areas. To characterize potential 

non-target plant exposure from spray drift alone as a result of foliar applications, Tier 1 modules 

in AgDRIFT were used to estimate EECs for off-site spray drift exposure in dry and semiaquatic areas and water bodies (i.e., standard farm pond) (Table III.11) for water-dispersible

granular and flowable/emulsifiable concentrate formulations. For aerial applications, the 

American Society of Agricultural and Biological Engineers (ASABE, formerly ASAE) Fine-toMedium droplet size category is used in modeling. This droplet size category is EFED’s default 

distribution when labels do not specify application parameters. For ground applications, the 

ASABE Very Fine-to-Fine droplet size category is used with a high boom height. Again, this 

droplet size category is EFED’s default distribution when labels do not specify the application 

parameters for ground applications. For seed treatments, EECs are based on surface water runoff 

only since seeds are planted in the ground and no spray drift is produced; thus, spray drift from 

seed treatments was not modeled.

In previous risk assessments, the highest exposure of all scenarios modeled for the current uses

did not resulted in any risks of concern for terrestrial plants exposed to azoxystrobin; thus, EECs 

are estimated with TerrPLANT and AgDRIFT using only the maximum and the 2nd highest 

application rates instead of modeling EECs for all exposure scenarios.

Table III.10. TerrPLANT EECs for Terrestrial Plants Located Adjacent to Azoxystrobin

Treated Sites. 

Max. Single

Application Rate

(lb a.i./A)

Application 

Method

TerrPLANT EECs (lbs a.i./A)

Total Loading to Dry Areas 

Adjacent to Treated Areas1

Total Loading to Semi-Aquatic 

Areas Adjacent to Treated 

Areas2

0.55 Aerial Unincorp. 

Spray

No aerial applications for turf uses

0.4 0.024 0.06

0.55 Ground Unincorp. 

Spray

0.011 0.0605

0.4 0.008 0.044

0.012 Ground Incorp. 

Spray3

0.00008 0.0008

0.009 0.0006 0.006

1 EEC = Sheet Runoff (1:1 ratio) + Drift (0% for seed; 1% for ground; 5% for aerial) 2 EEC = Channelized Runoff (10:1 ratio) + Drift (0% for seed; 1% for ground; 5% for aerial) 3 An incorporation depth of 1.5 inches is assumed for seed treatments.
30

III.2.3.3. Exposure Modeling for Terrestrial Invertebrates

Concentrations of azoxystrobin residues in pollen and nectar resulting from foliar applications of 

azoxystrobin were not calculated for honey bee (Apis mellifera) contact and dietary routes of 

exposure. EECs will be calculated when the complete set of data for honey bees is available. 

III.3. Ecological Effects Characterization 

The effects characterization describes the types of effects (toxicity) a pesticide can have on 

aquatic and terrestrial organisms. This characterization is based on the registrant-submitted 

toxicity data as well as published toxicity data for birds, mammals, fish, invertebrates, and plants 

for azoxystrobin for this phase of Registration Review. 

As described in the Agency’s Overview Document (USEPA 2004), the most sensitive endpoint 

for each taxon is used for risk estimation. For this assessment, evaluated taxa include freshwater 

and estuarine/marine fish (also a surrogate for aquatic phase amphibians), freshwater and 

estuarine/marine invertebrates, aquatic plants, aquatic nonvascular plants, birds (also a surrogate 

for terrestrial-phase amphibians and reptiles), mammals, honey bees, and terrestrial plants. 

Toxicity endpoints are established based on data generated from guideline studies submitted by 

the registrant, and from open literature studies that meet the criteria for inclusion into the 

ECOTOX database maintained by EPA/Office of Research and Development (ORD) (U.S. EPA, 

2004). In general, effects data in the open literature that indicate effects at lower concentrations 

Table III.11. Maximum Drift Loadings at Specific Distances for Terrestrial and SemiAquatic Areas and Ponds Alongside Azoxystrobin Use Areas.

Broadcast 

Application 

Rate

(lb a.i./A)

Application 

Method

Distance from Edge of 

Field

(ft)

AgDRIFT EEC

Dry Areas

(lb a.i./A)

Wetland

(lb a.i./A)

Pond

(μg/L)

0.55 Ground

0 0.55 0.03 1.9

10 0.1 0.02 1.2

50 0.03 0.01 0.6

100 0.01 0.007 0.4

500 0.002 0.002 0.09

997 0.0008 0.0007 0.04

0.4

Aerial

0 0.2 0.05 2.8

10 0.1 0.04 2.4

50 0.07 0.03 1.6

100 0.04 0.02 1.1

500 0.007 0.006 0.4

997 0.005 0.005 0.3

Ground

0 0.4 0.025 1.4

10 0.1 0.015 0.8

50 0.02 0.008 0.4

100 0.01 0.005 0.3

500 0.002 0.001 0.07

997 0.006 0.0005 0.03
31

than the registrant-submitted data are considered. The degree to which open literature data are 

quantitatively or qualitatively characterized is dependent on whether the information is relevant 

to the assessment endpoints (survival, reproduction, and growth). For example, endpoints such as 

behavior modifications are likely to be qualitatively evaluated, because quantitative relationships 

between modifications and reduction in species survival, reproduction, and/or growth are not 

available. On August 31, 2015, of the open literature on azoxystrobin that passed the ECOTOX 

screen that showed effects at lower concentrations than the registrant-submitted studies could be 

not be used quantitatively and thus they are not used in this risk assessment. 

In addition to registrant-submitted and open literature toxicity information, reviews of other 

sources of information including the Ecological Incident Information System (EIIS), are 

conducted to further refine the characterization of potential adverse ecological effects associated 

with exposure to azoxystrobin. A summary of the available aquatic and terrestrial ecotoxicity 

information for azoxystrobin are provided in Section IV.2, respectively.

Ecological effects studies have been submitted for azoxystrobin, its degradates, and the 

formulated end-use products Heritage® Fungicide containing 50% azoxystrobin (EPA Reg. No. 

100-1093) and Renown® Fungicide containing 3% azoxystrobin and 45% chlorothalonil (EPA 

Reg. No. 100-1315). In the ecological effects characterization section, toxicity values are 

expressed based in terms of active ingredient (a.i.) as opposed to formulated product.

III.3.1. Aquatic Effects Characterization

The most sensitive acute and chronic effects measurement endpoints associated with azoxystrobin 

exposure to freshwater and estuarine/marine species are summarized in Table III.13; these values 

are used for estimating risk to aquatic organisms. Selected effects endpoints for the risk assessment 

are from acceptable and supplemental studies for azoxystrobin and are briefly described below. 

Based on the available acute toxicity data, azoxystrobin is classified as highly toxic to most aquatic 

vertebrate and invertebrate organisms; azoxystrobin is classified as very highly toxic to 

estuarine/marine invertebrates. In addition, freshwater fish are surrogates for aquatic-phase 

amphibians in the absence of amphibian-specific data; therefore, using the acute toxicity data with 

freshwater fish, azoxystrobin would be classified as highly toxic to aquatic-phase amphibians. 

Chronic toxicity data were available for fish and invertebrates except for estuarine/marine fish. 

Chronic exposure resulted in reproductive effects in estuarine/marine invertebrates and effects on 

growth in freshwater fish and invertebrates. Acute-to-chronic ratio (ACR) calculations were used 

to estimate the chronic no-observed adverse effect concentration (NOAEC) for estuarine/marine 

fish using acute and chronic toxicity data for freshwater fish. However, the relative sensitivity of 

the fish used in estimating the ACR is uncertain.

Toxicity data show that the azoxystrobin degradates (compounds 2, 28, 30 only) are practically 

nontoxic to freshwater fish and invertebrates and to aquatic nonvascular plants. However, toxicity 

tests with a typical end-use product (TEP) show that it is very highly toxic to freshwater fish and 

aquatic nonvascular plants, indicating that the TEP is more toxic to these aquatic organisms than 

the technical grade active ingredient (TGAI). 
32

Table III.13. Most Sensitive Acute and Chronic Toxicity Data for Aquatic Organisms 

Exposed to Azoxystrobin and its Degradates. 

Exposure 

Scenario Species Test Material

Affected 

Endpoint Toxicity Measurement MRID(Classification)

Freshwater Fish

Acute

Rainbow trout

(Oncorhynchus 

mykiss) 

TGAI

Mortality

96-hr LC50 = 0.47 mg 

a.i./L (no probit slope)

43678115

(acceptable)

Compound 2 

degradate 

96-hr LC50 >150 

mg compound 2/L

44158803

(acceptable)

Renown® 96-hr LC50 = 0.00206 mg 

a.i./L

48860607

(acceptable)

Chronic

Fathead minnow

(Pimephales 

promelas)

TGAI Reduction in 

length

NOAEC = 0.147 mg 

a.i./L

43678120

(acceptable)

Freshwater Invertebrates

Acute Water flea

(Daphnia magna)

TGAI

Immobility

48-hr EC50 = 0.26 mg 

a.i./L (no probit slope)

43678116

(acceptable)

Compound 

28 degradate 

48-hr EC50 >50 mg 

Compound 28/L

44158801 

(acceptable)

Compound 

30 degradate 

48-hr EC50 >50 mg 

Compound 30/L

44158802

(acceptable)

Compound 2 

degradate 

48-hr EC50 >190 mg 

Compound 2/L

44158804

(acceptable)

Chronic TGAI Growth NOAEC = 0.044 mg 

a.i./L 

43678121

(acceptable)

Estuarine/Marine Fish

Acute

Sheepshead minnow

(Cyprinodon 

variegates)

TGAI Mortality 96-hr LC50: 0.67 mg 

a.i./L (no probit slope)

43678117

(acceptable)

Chronic TGAI No data 

available

Estimated NOAEC = 

0.21 mg a.i./L ACR1

Estuarine/Marine Invertebrates

Acute Mysid shrimp 

(Mysidopsis bahia) TGAI Mortality 96-hr LC50 = 0.056 mg a.i./L

43678118

(acceptable)

Chronic TGAI Reproduction NOAEC = 0.0095 mg 

a.i./L

44452302

(acceptable)

Aquatic Plants

7-day 

exposure

Duckweed

(Lemna gibba) TGAI Frond count

7-day EC50 = 3.4 mg 

a.i./L

NOAEC = 0.8 mg a.i./L

43678165

(acceptable)

96-hour 

exposure

Freshwater diatom

(Navicula) TGAI Cell density

96-hr EC50 = 0.049 mg 

a.i./L

NOAEC = 0.02 mg a.i./L

43678164

(acceptable)

Freshwater green 

algae

(Pseudokircheriella 

subcapitata

formerly 

Selenastrum 

capricornutum)

Renown® Cell density

96-hr EC50 = 0.0053 mg 

a.i./L

NOAEC = 0.0026 mg 

a.i./L

48860606 

(supplemental)

1 Estimated value based on ACR method, using rainbow trout acute and fathead minnow chronic data; The ACR of

3.19 is applied to the sheepshead minnow acute toxicity value (LC50 of 0.67 mg/L).
33

Freshwater Fish, Acute Effects

Fish toxicity studies using TGAI, the Compound 2 degradate, and the formulated product 

Renown® Fungicide (containing 3% azoxystrobin and 45% chlorothalonil) were submitted to 

establish the acute toxicity of azoxystrobin to freshwater fish. Results of the acute study with the 

TGAI indicate rainbow trout (Oncorhynchus mykiss) are the most sensitive with an LC50 value of 

0.47 mg a.i./L (Table III.14). As a result, azoxystrobin is categorized as highly toxic to fish on 

an acute exposure basis. The TGAI LC50 is used to estimate potential acute risk of azoxystrobin 

to freshwater fish. The Compound 2 degradate is several orders of magnitude less toxic than the 

azoxystrobin TGAI. When adjusted for percent azoxystrobin in the formulation, Renown® is 

more acutely toxic to fish than TGAI azoxystrobin by several orders of magnitude (Renown® = 

0.002 mg azoxystrobin/L; TGAI = 0.47 mg a.i./L). When the formulation toxicity value is 

adjusted to account for the other active ingredient, chlorothalonil, the resulting value (0.031 mg 

a.i./L) is similar to the acute toxicity value for chlorothalonil TGAI (0.018 mg a.i./L (MRID 

45710219)), indicating that the enhanced toxicity of Renown® compared to TGAI azoxystrobin is 

likely due to the presence of chlorothalonil.

Freshwater Fish, Chronic Effects

A fish early life-stage toxicity study using the TGAI was submitted to establish the chronic 

toxicity of azoxystrobin to freshwater fish. The preferred test species is the most sensitive fish of 

the freshwater fish acute toxicity tests, which is the rainbow trout. However, because a different 

species (fathead minnow; Pimephales promelas) was used instead of the rainbow trout in the 

chronic study, there is uncertainty whether fathead minnows represent the most sensitive test 

species. There are no acute toxicity data available for the fathead minnow and it is unknown 

whether the fish is more or less sensitive than the trout on an acute exposure basis. Results of the 

chronic study with the TGAI on fathead minnow indicate an NOAEC of 0.147 mg a.i./L (Table 

III.15). Thus, the NOAEC of 0.147 mg a.i./L is used to evaluate potential chronic effects of 

azoxystrobin to freshwater fish. 

Table III.14. Freshwater Fish Acute Toxicity Profile for Azoxystrobin, Formulation, and 

its Degradates.

Species % a.i. or 

degradate

LC50

mg a.i./L 

(95% Confidence 

Interval) 

Toxicity 

Category

MRID No.

Author/Year

Study 

Classification

Rainbow trout

(Oncorhynchus 

mykiss)

96.2 0.47

(0.4-0.58 mg a.i./L)

Highly 

toxic

43678115

Craig et al. 1992 Acceptable

DEG

(Compound 2)

98

>150 mg/L Practically 

nontoxic

44158803

Kent et al. 1993 Acceptable

(Renown®)

2.94

0.00206

(0.00169-0.0025 mg 

a.i./L)

Very highly 

toxic

48860607

Bormann 2010 Acceptable

Bluegill sunfish 

(Lepomis 

macrochirus)

96.2

1.1

(0.9-1.7 mg a.i./L)

Moderately 

toxic

43678114

Sankey et al. 1992 Acceptable
34

Table III.15. Freshwater Fish Chronic Toxicity Profile for Azoxystrobin.

Species % a.i.

/ NOAEC / 

LOAEC

(mg a.i./L)

Endpoint 

Affected

MRID No.

Author/Year

Study 

Classification

Fathead minnow

(Pimephales 

promelas)

96.2 0.147/0.193 Length 43678120

Rhodes et al. 1994 Acceptable

Freshwater Invertebrates, Acute Effects

Toxicity studies using the TGAI, Compound 2 degradate, Compound 28 degradate, and 

Compound 30 degradate were submitted to establish the acute toxicity of azoxystrobin and its

degradates to the waterflea (Daphnia magna). Results of the acute study with the TGAI indicate 

an EC50 value of 0.259 mg a.i./L (Table III.16), which categorizes azoxystrobin as highly toxic 

to freshwater invertebrates on an acute exposure basis. Thus, the TGAI EC50 of 0.259 mg a.i./L 

is used to evaluate potential acute effects of azoxystrobin to freshwater invertebrates. Relative 

to the parent compound, the degradates tested yield non-definitive endpoints when testing at

concentrations several orders of magnitude higher than studies with the TGAI. Based on these 

studies, the degradates are categorized as practically nontoxic to freshwater invertebrates on an 

acute exposure basis.

Freshwater Invertebrates, Chronic Effects

A laboratory toxicity study using the TGAI was submitted to establish the chronic toxicity of 

azoxystrobin to freshwater invertebrates. Results of the full lifecycle study with D. magna

indicate a NOAEC value of 0.044 mg a.i./L based on reduced young produced per adult (Table 

III.17). The NOAEC is used to evaluate potential chronic effects of azoxystrobin to freshwater 

invertebrates. 

Table III.16. Freshwater Invertebrate Acute Toxicity Profile for Azoxystrobin and its 

Degradates.

Species % a.i.

EC50

mg a.i./L 

(95% Confidence 

Interval)

Toxicity 

Category

MRID No.

Author/Year

Study 

Classification

Water flea

(Daphnid 

magna)

96.2

0.26

(0.126-0.644 mg a.i./L)

Highly 

toxic

43678116

Rapley et al. 1994 Acceptable

99 >50 mg Compound 28/L Practically 

nontoxic

44158801 & 

44158802

Hamer 1996

Acceptable 98 >50 mg Compound 30/L

98 >190 mg Compound 2/L Practically 

nontoxic

44158804

Kent et al. 1993 Acceptable
35

Table III.17. Freshwater Invertebrate Chronic Toxicity Profile for Azoxystrobin.

Species % a.i.

NOAEC

/LOEAC 

(mg a.i./L)

Endpoint 

Affected

MRID No.

Author/Year

Study 

Classification

Water flea

(Daphnia magna) 96.2 0.044/0.084 Reproduction 

(young per adult)

43678121

Rhodes et al. 1994 Acceptable

Estuarine/Marine Fish, Acute Effects

A study using the TGAI was submitted to establish the acute toxicity of azoxystrobin to the 

estuarine/marine sheepshead minnow (Cyprinodon variegatus). Results of the acute study 

indicate an LC50 value of 0.67 mg a.i./L (Table III.18), which categorizes azoxystrobin as highly 

toxic to estuarine/marine fish on an acute exposure basis. The LC50 value of 0.67 mg a.i./L is 

used to evaluate potential acute effects of azoxystrobin to estuarine/marine fish. 

Estuarine/Marine Fish, Chronic Effects

No chronic toxicity data are available for estuarine/marine fish; therefore, an acute-to-chronic 

(ACR) approach was used to estimate the chronic toxicity to estuarine/marine fish. The ACR 

based on acute and chronic toxicity data for freshwater fish is 3.19 mg ai/L. Applying this ACR 

to the sheepshead acute toxicity value (LC50 of 0.67 mg a.i./L) results in a chronic toxicity

estimate of 0.21 mg a.i./L for estuarine/marine fish. The NOAEC of 0.21 mg a.i./L is used to 

evaluate potential chronic effects of azoxystrobin to estuarine/marine fish. 

Estuarine/Marine Invertebrates, Acute Effects

Toxicity studies using the TGAI were submitted to establish the acute toxicity of azoxystrobin to 

estuarine/marine invertebrates. Results of the acute studies indicate the lowest LC50/EC50 value 

for estuarine/marine invertebrates to be 0.056 mg a.i./L (Table III.19). As a result, azoxystrobin 

is categorized as very highly toxic to estuarine/marine invertebrates. The LC50 of 0.056 mg a.i./L 

was used to evaluate potential acute effects of azoxystrobin to estuarine/marine invertebrates. 

Table III.18. Estuarine/Marine Fish Acute Toxicity Profile for Azoxystrobin.

Species % 

a.i.

LC50

mg a.i./L 

(95% Confidence 

Interval)

Toxicity 

Category

MRID No.

Author/Year

Study 

Classification

Sheepshead minnow

(Cyprinodon variegates)

96.2

0.67

(0.56-0.8 mg a.i./L)

Highly 

toxic

43678117

Sankey et al. 

(1992)

Acceptable
36

Table III.19. Estuarine/Marine Invertebrate Acute Toxicity Profile for Azoxystrobin.

Species % 

a.i.

LC50/EC50

mg a.i./L (95% 

Confidence Interval)

Toxicity 

Category

MRID No.

Author/Year

Study 

Classification

Mysid shrimp

(Mysidopsis bahia) 96.2

0.056

(0.035-0.11 mg a.i./L)

Very highly 

toxic

43678118

Kent et al. 1993 Acceptable

Pacific oyster

[shell deposition]

(Crassostrea gigas)

96.2

1.3 

(1.1-1.4 mg a.i./L)

Moderately 

toxic

43678119

Kent et al. 1993 Acceptable

Estuarine/Marine Invertebrates, Chronic Effects

A laboratory toxicity study using the TGAI was submitted to establish the chronic toxicity of 

azoxystrobin to estuarine/marine invertebrates. Results of the life-cycle study with mysid shrimp 

(Americamysis bahia) indicate a NOAEC of 0.0095 mg a.i./L based on reduced number of young 

produced per adult and reduced survival (Table III.20). The NOAEC is used to evaluate 

potential chronic effects of azoxystrobin to estuarine/marine invertebrates. 

Table III.20. Estuarine/marine Invertebrates Chronic Toxicity Profile for Azoxystrobin.

Species % a.i.

LOEAC / 

NOAEC

(mg a.i./L)

Endpoint 

Affected

MRID No.

Author/Year

Study 

Classification

Mysid shrimp

(Americamysis 

bahia formerly

Mysidopsis bahia)

96.2 0.016 / 0.0095

Reproduction 

(young per adult) 

and survival

44452302

Boeri et al. 1997 Acceptable

Effects to Aquatic Vascular and Non-vascular Plants

Azoxystrobin studies were submitted for a freshwater vascular plant (duckweed, Lemna gibba) 

and four phytoplanktonic nonvascular plants: green algae (Pseudookirchneriella subcapitata), 

cyanobacteria (Anabaena flos-aquae), freshwater diatom (Navicula pelliculosa) and the marine 

alga (Skeletonema costatum) (Table III.21). 

Aquatic plant toxicity studies using the TGAI and a TEP (Renown® Fungicide) were submitted 

to establish the toxicity of azoxystrobin to vascular and non-vascular species. Testing with 

duckweed yielded an EC50 and NOAEC of 3.4 and 0.8 mg a.i./L, respectively (Table III.21).

The most sensitive EC50 for aquatic nonvascular plants studies was for N. pelliculosa with EC50

and NOAEC of 0.049 and 0.02 mg a.i./L, respectively. The most sensitive EC50 and NOAEC 

values for vascular and nonvascular aquatic plants are used to evaluate potential effect of 

azoxystrobin to non-listed and listed aquatic plants, respectively. 

Toxicity testing with TEP indicates that green algae is several orders of magnitude more 

sensitive to Renown® (EC50 = 0.0053 mg a.i./L) compared to the azoxystrobin TGAI (EC50 = 

0.106 mg a.i./L). When the formulation toxicity value is adjusted to the other active ingredient, 

chlorothalonil, the value (0.098 mg a.i./L) is similar to the acute toxicity value for chlorothalonil 
37

TGAI (0.19 mg a.i./L (MRID 42432801)), indicating that the enhanced toxicity of Renown®

compared to TGAI azoxystrobin is likely due to the presence of chlorothalonil.

Table III.21. Aquatic Plant Toxicity Profile for Azoxystrobin and its Formulated Product.

Species % a.i.

EC50

mg a.i./L

(95% Confidence Interval)

NOAEC 

mg a.i./L

MRID No.

Author/Year

Study

Classification

Vascular Plants

Duckweed

(Lemna gibba) 96.2

3.4

(3.0 - 3.9 mg a.i./L) 0.8

43678165

Smyth et al.

1993

Acceptable

Non-Vascular Plants

Freshwater green algae

(Pseudokirchneriella 

subcapitata formerly 

Selenastrum 

capricornutum)

96.2

0.106

(0.092-0.121 mg a.i./L)

<0.025 

(EC05 = 0.023)

43678161

Smyth et al.

1994

Acceptable

TEP

2.94

0.0053

(0.0039-0.007 mg a.i./L)

0.0026 48860606

Dengler 2010 Supplemental1

Freshwater blue-green 

algae

(Anabaena flos-aquae)

96.2

13

(12-14 mg a.i./L)

9

43678162

Smyth et al.

1994

Acceptable

Marine diatom

(Skeletonema costatum) 96.2

0.453

(0.386-0.532 mg a.i./L)

0.1

43678163

Smyth et al.

1994

Acceptable

Freshwater diatom

(Navicula pelliculosa) 96.2

0.049

(0.043-0.058 mg 

a.i./L)

0.02

43678164

Smyth et al.

1994

Acceptable 

1 Only three replicates per level were used; guideline requires 4 replicates per level.

III.3.2. Terrestrial Effects Characterization 

The most sensitive acute and chronic effects measurement endpoints associated with azoxystrobin 

exposure to terrestrial species are summarized in Table III.22. Selected effects endpoints for the 

risk assessment are from acceptable and supplemental studies for azoxystrobin and are described 

below. 

Overall, azoxystrobin is practically nontoxic to birds on an acute oral and subacute dietary

exposure basis. Azoxystrobin caused no significant mortality or sub-lethal effects up to and 

including oral doses of 2,000 mg a.i./kg bw and dietary concentrations of 5200 mg a.i./kg diet. In 

addition, birds also serve as surrogates for reptiles and terrestrial-phase amphibians in the absence 

of taxa-specific data; therefore, using the acute toxicity data for birds, azoxystrobin is classified as 

practically nontoxic to reptiles and terrestrial-phase amphibians on an acute oral and subacute 

dietary exposure basis. Following chronic exposure, reproductive effects were reported at 3000

mg a.i./kg diet; the resulting NOAEL was 1200 mg a.i./kg diet. 
38

Azoxystrobin is practically nontoxic to mammals on an acute oral basis (LD50 >5,000 mg a.i/kgbw). In the chronic 2-generation studies with laboratory rats (Rattus norvegicus), growth effects 

were reported at 165.4 mg a.i./kg/day (NOAEL = 32.3 mg a.i./kg/day), based on decreased body 

weight gains for pups.

Results of the honey bee acute contact and oral tests with azoxystrobin and the formulated product

Heritage® Fungicide (50% azoxystrobin; EPA Reg. No. 100-1093) indicate the active ingredient

content is practically nontoxic to young adult honey bees (LD50 ≥200 μg a.i./bee). No data are 

available to evaluate the toxicity of the TGAI to larval bees. 

Effects to terrestrial plants were limited to the seedling emergence stage. Carrot and rape plants 

were the only species to be inhibited 25% or more resulting in a tier II study. None of the 

monocotyledonous (monocots) plants were impacted. All monocots and dicotyledenous (dicots)

at the true 3-leaf stage (vegetative vigor study) were not affected at the limit treatment level of 1.0 

lb a.i./A, which was tested higher than the maximum labeled rate of 0.55 lb a.i./A. The lowest EC25

and NOAEC value obtained in the tier II study was for dicots (carrots) at 0.59 and 0.5 lb a.i./A, 

respectively.
39

Table III.22. Most Sensitive Endpoints from Acute and Chronic Toxicity Data for 

Terrestrial Animals and Plants Exposed to Azoxystrobin. 

Exposure 

Scenario Species Affected Endpoint Toxicity Measurement

MRID

(Classification)

Mammals

Acute

(Dose-based)

Laboratory rat

(Rattus 

norvegicus)

Mortality LD50 >5000 mg 

a.i./kg-bw

43678122

(acceptable)

Chronic

(Dietary-based)

Decreased pup body 

weight gain

LOAEL = 1500 

ppm (165.4 

mg/kg/day)

NOAEL = 300 ppm 

(32.3 mg/kg/day)

43678144

(acceptable)

Birds

Acute 

(Dose-based)

Northern 

bobwhite quail

(Colinus 

virginianus) Mortality

LD50 >2000 mg 

a.i./kg bw

43678108

(acceptable)

Canary

(Serinus canaria)

LD50 >2000 mg 

a.i./kg bw

49337501

(acceptable)

Acute 

(Dietary-based)

Northern 

bobwhite quail

(Colinus 

virginianus)

Mortality LC50 >5200 mg 

a.i./kg diet 

43678111

(acceptable)

Chronic 

(Dietary-based)

Northern 

bobwhite quail

(Colinus 

virginianus)

Number of eggs laid, 

live 3-week embryos, 

and 14-day old 

survivors

LOAEC = 3000 mg 

a.i./kg diet

NOAEC = 1200 mg 

a.i./kg-diet

43678113

(acceptable)

Terrestrial Plants

Seedling 

emergence

All monocots

Growth

EC25 >1.0 lbs a.i./A 

NOAEC = 1.0 lbs 

a.i./A 43678160

(acceptable) Carrot

(dicot)

EC25 = 0.59 lbs 

a.i./A 

NOAEC = 0.5 lbs 

a.i./A 

Vegetative Vigor All species

EC25 >1.0 lbs a.i./A 

NOAEC = 1.0 lbs 

a.i./A

43678158

43678159

(acceptable)

Terrestrial Invertebrates

Acute (Contactbased)

Honey bee

Mortality via contact LD50 >200 μg 

a.i./bee 43678166 

Acute (acceptable)

(Oralbased) 

Adult

Mortality via oral

LD50 >25 μg 

a.i./bee

Larval No data No data

Chronic 

(Oralbased)

Adult No data No data

Larval No data No data

Birds, Acute Oral

Acute oral toxicity studies using the TGAI are required to establish the acute toxicity of 

azoxystrobin to birds. The submitted acute data indicate that the TGAI is categorized as practically 
40

nontoxic to upland game birds, i.e., Bobwhite quail (Colinus virginianus), and passerines, i.e., 

canaries (Serinus canaria) with LD50 values >2000 mg a.i./kg bw, the maximum dose tested, and 

no effects to waterfowl, i.e., mallard ducks (Anas platyrhynchos), were observed at up to 250 mg 

a.i./kg bw (Table III.23). Thus, with no mortality at doses as high as 2,000 mg a.i./kg-bw in the 

acceptable studies, the LD50s of >2000 mg a.i./kg-bw were used to evaluate potential acute effects 

of the TGAI to birds via the oral route of exposure. The available avian acute oral toxicity data are 

summarized in Table III.23.

Table III.23. Avian Acute Oral Toxicity Profile for Azoxystrobin.

Species % 

a.i.

LD50

(mg a.i./kg 

bw)

Toxicity 

Category

MRID No.

Author/Year

Study 

Classification

Canary

(Serinus canaria) 99.2 >2000 Practically 

nontoxic

49337501

Hubbard PM, Beavers JB. 

2014.

Acceptable

Mallard duck

(Anas platyrhynchos)

96.2 >250

No effects 

up to 250 

mg a.i./kgbw

43678109

Hakin, Johnson, Anderson, 

Dawe (1992)

Supplemental1

Northern bobwhite 

quail

(Colinus virginianus)

96.2 >2000 Practically 

nontoxic

43678108

Hakin, Johnson, Anderson, 

Dawe (1992)

Acceptable

1 Test birds in the three highest treatment groups regurgitated within an hour of dosing. An accurate LD50 could not 

be determined; thus, a LD50 of >250 mg/kg (the lowest dose) since the actual dosage each bird received above 250 

mg/kg is unknown due to vomiting. 

Birds, Subacute Dietary

Dietary studies using the TGAI are required to establish the subacute toxicity of azoxystrobin to 

birds. The submitted data indicate no mortality occurred and the subacute dietary LC50 for duck 

and quail were both >5200 mg a.i./kg diet, the maximum dietary concentrations tested. The TGAI 

is categorized as practically non-toxic to upland game birds and waterfowl on a subacute dietary 

basis (Table III.24). Therefore, the LC50 value of >5200 mg a.i./kg-diet was used to evaluate 

potential effects of the TGAI to birds following subacute dietary exposure. The available avian 

subacute dietary studies are summarized in Table III.24.

Table III.24. Avian Subacute Dietary Toxicity Profile for Azoxystrobin 

Species % 

a.i.

Nominal LC50

(mg a.i./kg diet)

Toxicity 

Category

MRID No.

Author/Year

Study 

Classification

Mallard duck

(Anas platyrhynchos) 96.2 >5200 Practically 

nontoxic

43678111

Hakin et al. 1992 Acceptable

Northern bobwhite quail 

(Colinus virginianus) 96.2 >5200 Practically 

nontoxic

43678110

Hakin et al.1992 Acceptable
41

Birds, Reproduction

Avian reproduction studies using the TGAI are required to establish the chronic toxicity of 

azoxystrobin to birds (Table III.25). A NOAEC of 1200 mg a.i./kg diet for both species is used 

to evaluate potential chronic effects of the TGAI to birds. 

Table III.25. Avian Chronic Toxicity Profile for Azoxystrobin. 

Species % 

a.i.

NOAEC / LOAEC

(mg a.i./kg-diet) Affected endpoints MRID no.Author/Year

Study 

classification

Northern 

bobwhite quail

(Colinus 

virginianus)

96.2 1200/3000

Number of eggs laid, 

eggs set, viable 

embryos, live 3-week 

embryos, normal 

hatchling, and 14-day 

old survivors

44452301

Gallagher et al.

1997

Acceptable

Mallard duck

(Anas 

platyrhynchos)

96.2 1200/3000 Number of eggs laid

43678113

Cameron et al.

1994

Acceptable

Mammals, Acute Oral 

Wild mammal testing is required on a case-by-case basis, depending on the results of lower Tier 

laboratory mammalian studies, intended use pattern and pertinent environmental fate 

characteristics. In most cases, rat or mouse toxicity values obtained from the Agency's Health 

Effects Division (HED) substitute for wild mammal testing. These toxicity values are reported 

below in Table III.26.

Results of the acute oral study with rats indicate azoxystrobin is categorized as practically nontoxic 

(LD50 >5000 mg a.i/kg-bw) to small mammals on an acute oral exposure basis. The LD50 value of 

>5000 mg a.i./kg-bw is used to evaluate potential acute effects to mammals. 

Table III.26. Mammalian Acute Oral Toxicity Profile for Azoxystrobin. 

Species % a.i. Test Type

LD50

(mg a.i./kg bw)

Affected 

Endpoints

MRID No.

Author, Year

Study 

Classification

Rat

(Wistar) 95.2 acute oral LD50 >5000 None

43678122

Robinson (1991) Acceptable

Mammals, Chronic

In a 2-generation study of rats (Table III.27), azoxystrobin (96.2% a.i.) resulted in a treatmentrelated reduction (↓8 - 21%) in adjusted (for initial weight) pup body weights in the F1a and F2a

pups dosed at 1500 ppm (165.4 mg/kg bw/day). The corresponding NOAEL is 300 ppm (32.3 

mg/kg/day). 
42

Table III.27. Mammalian Reproductive Toxicity Profile for Azoxystrobin.

Species % a.i. Test

Type

Toxicity

ppm (mg a.i./kg bw/day)

Affected 

Endpoints MRID No.

Rat

(Wistar) 96.2 2-

generation Reproduction NOAEL = 300 (32.3)

LOAEL = 1500 (165.4)

Decreased pup 

body weight

43678144

(acceptable)

Terrestrial Invertebrates, Acute

Acute contact and oral honey bee studies with adult bees and their larvae exposed to azoxystrobin 

are used to establish the toxicity of the TGAI to terrestrial invertebrates because of outdoor uses 

that will result in exposure. The submitted data (Table III.28) with the TGAI and Heritage®

Fungicide (50% azoxystrobin; EPA Reg No. 100-1093) indicate no significant mortality occurred 

in the studies and the acute contact LD50 for adult bees for both test materials were >200 μg a.i./bee, 

the maximum concentrations tested, while the oral LD50s for adult bees exposed to the TGAI and 

formulated product Heritage® Fungicide were >200 and >25 μg a.i./bee, respectively. The TGAI 

is categorized as practically non-toxic to adult bees on an acute contact and dietary exposure basis, 

and because no definitive endpoint was identified for the formulated product, its relative toxicity 

could not be discerned. Therefore, the acute contact and acute oral LD50 values of >200 μg a.i./bee 

are used to evaluate potential acute effects of the TGAI to bees via contact from foliar sprays and 

through ingestion of residues in pollen and nectar. Although azoxystrobin is practically non-toxic 

to adult bees on an acute exposure basis, there is uncertainty regarding the potential acute effects 

of azoxystrobin on bee larvae. 

Table III.28. Honey bee Acute Toxicity Profile for Azoxystrobin.

Species % a.i. Life 

Stage

LD50 (μg 

a.i./bee)

Toxicity 

Category MRID No. Study Classification

Honey bee

(Apis mellifera)

96.2 Adult

>200 

(contact)

Practically 

nontoxic 43678166

Gough et al. 1993

Acceptable

>25 (oral) Practically 

nontoxic Acceptable

Herita

ge®

51.6

Adult

>200 

(contact)

Practically 

nontoxic 43678167

Gough and 

Jackson 1994

Acceptable

>200 (oral) Practically 

nontoxic Acceptable

N/A Larval No data N/A N/A N/A

Terrestrial Invertebrates, Chronic

Chronic honey bee toxicity studies with larval and adult bees exposed to azoxystrobin are

necessary to establish the toxicity of the TGAI to terrestrial invertebrates because of outdoor uses 

that will result in exposure; however, no chronic toxicity studies with adult or larval honey bees 

have been submitted. Therefore, there is uncertainty regarding the effects of azoxystrobin on both 

adult bees and their brood (larvae and pupae) as a result of chronic (repeat) exposure.
43

Terrestrial Plants

Terrestrial plant studies are required for all terrestrial outdoor pesticides. Tier I terrestrial plant 

toxicity studies were conducted to establish the toxicity of the TEP, Heritage® Fungicide (EPA 

Reg No. 100-1093, 50% azoxystrobin), at the maximum limit dose of 1.0 lb a.i./A to non-target 

terrestrial plants; the TEP was tested at rates higher than the maximum-labeled single application 

rate of 0.55 lb a.i./A. 

The recommendations for seedling emergence and vegetative vigor studies are for testing of (1) 

six species of at least four dicot families, one species of which is soybean (Glycine max), and the 

second of which is a root crop; and, (2) four species of at least two monocotyledonous families, 

one of which is corn (Zea mays). 

In Tier I testing, seedling emergence of most of the test species—except for two dicot species,

carrot (Daucus carota) and rape (Brassica napus)--was not inhibited 25% or more by the 

formulated product, at the limit dose. Emergence of carrot and rape plants in the Tier I seedling 

emergence study were inhibited by more than 25% (Table III.29); Tier II tests were conducted for 

both of these species. EC25 and NOAEC values for the Tier II study is reported in Table III.30.

Since carrots were the most sensitive species tested in that study, the EC25 of 0.59 lb a.i./A and its 

corresponding NOAEC of 0.5 lb a.i./A are used to estimate risks for seedling emergence of nonlisted and listed terrestrial plants in dry and semi-aquatic areas adjacent to sites treated with

azoxystrobin and exposed to residues of azoxystrobin in surface water runoff and spray drift.

In the Tier I vegetative vigor studies, none of the monocot or dicot plants were inhibited 25% or 

more at the limit dose. Testing was repeated with rape (MRID 43678159) because rape plants had 

been treated with another pesticide during the course of the original study. Results of these studies 

are summarized in Tables III.31 and III.32. EC25 values were all >1.0 lb a.i./A and a Tier II 

vegetative vigor study was not necessary. With no significant effects to the tested plants in the 

vegetative vigor study, the limit dose is used as the endpoint to assess risk to non-listed and listed 

terrestrial plants in dry and semi-aquatic areas adjacent to a treated site exposed to azoxystrobin 

residues via downwind spray drift. 
44

Terrestrial Plants, Seedling Emergence

Tier I

Table III.29. Summary of Tier I Seedling Emergence Results for Heritage® Fungicide *

Species

Most 

sensitive 

endpoint

% 

Inhibition

Nominal EC25

(lb a.i./A)

Nominal NOAEC

(lb a.i./A)

Study 

Classification

Corn Dry weight 14.4 >1.0 1.0 Acceptable

Meadow 

fescue Damage 8.6 >1.0 1.0 Acceptable

Purple 

nutsedge Dry weight 5.3 >1.0 1.0 Acceptable

Wheat Dry weight 24.6 >1.0 1.0 Acceptable

Wild oat1 - - >1.0 1.0 --

Carrot Damage 33.2** - -

Cocklebur Damage 16.1 >1.0 1.0 Acceptable

Morning 

glory Dry weight 10.1 >1.0 1.0 Acceptable

Rape Dry weight 27.2** >1.0 1.0 Acceptable

Soybean Damage 10.2 >1.0 1.0 Acceptable

Sugar beet Dry weight 11.2 >1.0 1.0 Acceptable

Velvetleaf Dry weight 14.8 >1.0 1.0 Acceptable

* 48% a.i azoxystrobin, tested at the limit dose of 1.0 lb a.i./A; MRID 43678156, Canning et al. 1994.

** Tier II testing is required for this species for which emergence was inhibited at or greater than 25%.

1 Poor germination at 17% made it difficult to adequate assess inhibition in wild oats; thus, results are not reported. This 

would be considered a data gap; however, because seedling emergence data are required for only 10 species, repeating the 

test with wild oats is not necessary. 

Tier II

Table III.30. Summary of Tier II Seedling Emergence Toxicity Profile for Azoxystrobin. A

Species Most Sensitive 

Endpoint NOAEC EC05 EC25 Study Classification

Carrot Dry weight 0.5 0.37 0.59 Acceptable

Rape Emergence 1.0 0.55 3.2 Acceptable A 51.6% a.i; MRID 43678160, Everett et al. 1995. 
45

Terrestrial Plants, Vegetative Vigor

Tier I

Table III.31. Summary of Tier I Vegetative Vigor Results for Heritage® Fungicide *

Species

Most 

sensitive 

endpoint

% 

Inhibition

Nominal EC25

(lb a.i./A)

Nominal NOAEC

(lb a.i./A)

Study 

Classification

Corn Dry weight 8.7 >1.0 1.0 Acceptable

Purple 

nutsedge Dry weight 2.9 >1.0 1.0 Acceptable

Wheat Dry weight 4.9 >1.0 1.0 Acceptable

Wild oat Dry weight 11.4 >1.0 1.0 Acceptable

Cocklebur Damage 0.3 >1.0 1.0 Acceptable

Morning 

glory None 0.0 >1.0 1.0 Acceptable

Rape Dry weight 6.7 - - Invalid1

Soybean Damage 0.3 >1.0 1.0 Acceptable

Sugar beet Damage 1.3 >1.0 1.0 Acceptable

Velvetleaf Damage 0.7 >1.0 1.0 Acceptable

* 48% a.i azoxystrobin, tested at the limit dose of 1.0 lb a.i./A; MRID 43678158, Canning et al. 1994.

1 Rape plants were treated with primicarb to control aphids; thus, results are not reported. 

Table III.32. Summary of Tier I Vegetative Vigor Results for Azoxystrobin 50 WG *

Species

Most 

sensitive 

endpoint

% 

Inhibition

Nominal EC25

(lb a.i./A)

Nominal NOAEC

(lb a.i./A)

Study 

Classification

Rape Damage 5.7 >1.0 1.0 Acceptable

* 51.6% a.i azoxystrobin, tested at the limit dose of 1.0 lb a.i./A; MRID 43678159; Everett et al. 1995.

Ecological Incidents

A review of the Ecological Incident Information System (EIIS) maintained by the Agency’s Office 

of Pesticide Programs (OPP) indicates a total of 36 reported ecological incidents associated with 

the use of azoxystrobin (Table III.33). The reported incidents involved damage mainly to 

terrestrial plants. Incidents were associated with misuse or registered uses of azoxystrobin as a 

result of off-site spray drift or direct treatments. In addition, there are 40 aggregate incidents

including 3 ‘Other Non-Target’ incidents reported for azoxystrobin that were reported by the 

pesticide registrant. 

There is one incident to birds (bald eagle; Haliaeetus leucocephalus) as a result of indirect 

poisoning. The report states the chemical analysis of the crop contents showed the presence of 

carbofuran and azoxystrobin. The certainty was highly probable for carbofuran and unlikely for 

azoxystrobin; however, it was undetermined if the pesticides were used legally. The Avian Incident 

Monitoring System (AIMS) database also reported the bald eagle incident.
46

Table III.13. Summary of Ecological Incidents Associated with Azoxystrobin Uses, By Crop.

Incident 

# Species Response Exposure Certainty Legality Formulation Appl. Method Magnitude

Plants

 Agricultural Area 

I009314-

004 apple plant damage drift Probable Misuse N/R mist blower 3.5 acres

I009314-

001 apple plant damage drift Possible Undetermined F broadcast 450 trees

I009314-

003 apple plant damage drift Probable Misuse N/R mist blower

150 to 175 

trees

I021500-

071 tobacco plant damage

treated 

directly N/R N/R N/R N/R 6.7 acres

I021500-

072 tobacco plant damage

treated 

directly N/R N/R N/R N/R 32 acres

I021500-

073 tobacco mortality treated directly N/R N/R N/R N/R 12.87 acres

I021500-

074 field corn plant damage N/R N/R N/R N/R N/R N/R

I021500-

075 field corn plant damage

treated 

directly N/R N/R N/R N/R 35 acres

 Apple

I009314-

002 apple plant damage N/R Possible Misuse F spray 16 acres

I020627-

012 apple plant damage drift Highly probable

undetermi

ned N/R N/R 4 acres

 Corn

I019130-

070 corn plant damage carryover Probable Undetermined N/R broadcast 400 acres

 Grape

I009314-

026

imperial 

gala apple

plant 

damage drift Probable Misuse F N/R 15 acres

 N/R

I014597-

001 tobacco plant damage N/R Possible Undetermined F N/R 6 acres

I009314-

022 apple plant damage drift Probable Misuse N/R N/R 27 acres

I009314-

023 apple plant damage drift Possible Misuse N/R N/R 3 acres

I009314-

024 apple plant damage drift Probable Misuse N/R N/R 1.5 acres

I009314-

025 apple plant damage drift Probable Misuse N/R N/R unknown

 Orchards

I008384-

407 apple plant damage N/R Probable Registered Use N/R N/R N/R

I008384-

408 apple mortality N/R Probable Registered Use N/R N/R N/R

I008384-

409 apple mortality N/R Probable Registered Use N/R N/R N/R

I008384-

410 apple mortality N/R Probable Registered Use N/R N/R N/R
47

Table III.13. Summary of Ecological Incidents Associated with Azoxystrobin Uses, By Crop.

Incident 

# Species Response Exposure Certainty Legality Formulation Appl. Method Magnitude

I008384-

411 apple mortality N/R Probable Registered Use N/R N/R N/R

I008384-

412 apple mortality N/R Probable Registered Use N/R N/R N/R

I008384-

413 apple mortality N/R Probable Registered Use N/R N/R N/R

I008384-

414 apple mortality N/R Probable Registered Use N/R N/R N/R

I008384-

415 apple mortality N/R Probable Registered Use N/R N/R N/R

I008384-

416 apple mortality N/R Probable Registered Use N/R N/R N/R

I008384-

417 apple mortality N/R Probable Registered Use N/R N/R N/R

 Ornamentals

I013612-

007 cypress plant damage

treated 

directly Probable Registered Use WDG 434

 Peanut

I016903-

001 peanut plant damage

treated 

directly Possible Registered Use F broadcast 80 acres

 Soybean

I015713-

083 soybean plant damage

treated 

directly Possible Registered Use DF broadcast 88 acres

 Sugar beet

I015713-

001 sugar beet mortality treated directly Possible Registered Use N/R band 222 acres

I015713-

002 sugar beet plant damage

treated 

directly Possible Registered use

N/R band 532 acres

I015713-

003 sugar beet mortality treated directly Possible Registered Use N/R band 664 acres

Terrestrial

 Use site not reported

I018723-

002 bald eagle incapacitation ingestion unlikely Undetermined N/R N/R 1 bird

N/R- not reported; F – flowable; WDG – water dispersible granule; DF – dry flowable

IV. RISK CHARACTERIZATION

Risk characterization provides the final step in the risk assessment process. In this step, exposure 

and effects data are integrated to provide an estimate of risk relative to Agency’s established levels 

of concern (LOCs). The results are then interpreted for the risk manager through a risk description 

and synthesized into an overall conclusion.

IV.1. Risk Estimation - Integration of Exposure and Effects Data 

A deterministic (point estimate) approach is used to evaluate the likelihood of adverse ecological 

effects to non-target species. In this approach, risk quotients (RQs) are calculated by dividing 
48

acute and chronic point estimates of exposure (EECs) by acute and chronic point estimates of 

toxicity for non-target species. 

RQ = EXPOSURE/TOXICITY

RQs are then compared to LOCs used by the Agency to indicate potential risk to non-target wildlife 

and the need to consider regulatory action. Exceedance of the LOC by the RQ indicates that a 

pesticide used as directed has the potential to cause adverse effects on non-target wildlife. LOCs 

currently address the following risk presumption categories: (1) acute risk - potential for acute 

risk to non-target animals which may warrant regulatory action in addition to restricted use 

classification, (2) acute restricted use – potential for acute risk to non-target animals, but may be 

mitigated through restricted use classification, (3) acute listed species – listed species may be 

potentially affected by use, (4) chronic risk – potential for chronic risk may warrant regulatory 

action, listed species may potentially be affected through chronic exposure, (5) non-listed plant 

risk - potential for effects in non-target (non-listed) plants, and (6) listed plant risk – potential 

for effects in listed plants. 

For acute studies on taxa where a definitive LC50/LD50/EC50 is not established due to insufficient 

mortality or no effects were observed, an RQ was not calculated, and the study is discussed further 

in the Risk Description section.

Risk presumptions, along with the basis for deriving RQs and LOCs are tabulated below in 

Tables IV.1, IV.2, and IV.3:

Table IV.1. Risk Presumptions for Terrestrial Animals 

Risk Presumption RQ LOC

Birds:

Acute Risk EEC1/LC50 or LD50/sq ft2 or LD50/day3 ≥0.5

Acute Restricted Use EEC/LC50 or LD50/sq ft or LD50/day (or LD50 < 50 mg 

a.i./kg) ≥0.2

Listed Species EEC/LC50 or LD50/sq ft or LD50/day ≥0.1

Chronic Risk EEC/NOAEC ≥1

Wild Mammals:

Acute Risk EEC/LC50 or LD50/sq ft or LD50/day ≥0.5

Acute Restricted Use EEC/LC50 or LD50/sq ft or LD50/day

(or LD50 < 50 mg a.i./kg) ≥0.2

Listed Species EEC/LC50 or LD50/sq ft or LD50/day ≥0.1

Chronic Risk EEC/NOAEC ≥1

Invertebrates:

Listed Species EEC/LD50 ≥0.4

Chronic Risk EEC/NOAEC ≥1

1 EEC=abbreviation for Estimated Environmental Concentration (mg a.i./kg) on avian/mammalian food items 

2

 mg/ft 3 mg of toxicant consumed/day

 LD50 * wt. of bird LD50 * wt. of bird 

Table IV.2. Risk Presumptions for Aquatic Animals

Risk Presumption RQ LOC

Acute Risk EEC1/LC50 or EC50 ≥0.5

Acute Restricted Use EEC/LC50 or EC50 ≥0.1
49

Table IV.2. Risk Presumptions for Aquatic Animals

Risk Presumption RQ LOC

Acute Listed Species EEC/LC50 or EC50 ≥0.05

Chronic Risk EEC/NOAEC ≥1

EEC = (mg a.i./L or μg a.i./L) in water

Table IV.3. Risk Presumptions for Plants 

Risk Presumption RQ LOC

Terrestrial Plants in Terrestrial and Semi-Aquatic Areas:

Non-Listed Plant Species EEC1/EC25 ≥1

Listed Plant Species EEC/NOAEC or EC053 ≥1

Aquatic Plants:

Non-Listed Plant Species EEC2/EC50 ≥1

Listed Plant Species EEC/NOAEC or EC053 ≥1

1 EEC = lbs a.i./acre 2

 EEC = (μg a.i./L or mg a.i./L) in water

3 An EC05 is only used when a definitive NOAEC is not available.

The following section presents the acute and chronic risk quotients calculated for azoxystrobin

and indicates whether LOCs are exceeded. Further discussion of the risk quotients and 

uncertainties in the assessment is presented in Section IV.2.

IV.1.1. Non-target Aquatic Organisms

Tables IV.4 thru IV.11 list acute and chronic RQs calculated for aquatic organisms (freshwater 

fish are surrogates for aquatic-phase amphibians) exposed to azoxystrobin based on the EECs 

generated from SWCC modeling for foliar sprays and EECs from GENEEC and tier I Rice 

modeling for seed treatments.

Depending on the use site, results of the assessment on aquatic organisms indicate acute and/or 

chronic risk LOC exceedances for fish and/or invertebrates exposed to azoxystrobin via foliar 

applications and seed treatments (Tables IV.4 and IV.5 – freshwater fish, Tables IV.6 and IV.7

– freshwater invertebrates, Tables IV.8 and IV.9 – estuarine/marine fish; and Tables IV.10 and 

IV.11- estuarine/marine invertebrates).

As part of the analysis plan discussed in the preliminary problem formulation, to address the gap 

about the number of crop cycles per year for several use sites, 1 and 3 crop cycles per year were 

modeled for this assessment, each cycle with applications of azoxystrobin. As a result, modeling 

for leafy vegetable uses (i.e., lettuce, pepper, bean, melon, asparagus and tomato) with three crop 

cycles per year yields the highest EECs of all use scenarios. RQs may exceed LOCs for particular 

use sites with three crop cycles per year, but not necessarily for 1 or 2 crop cycles per year. Also, 

if there are no LOC exceedances for leafy vegetables after three application cycles, exceedances 

are not expected for all other uses with lower EECs.

Additionally, for azoxystrobin-treated seeds, modeling for rice yields the highest EECs of all seed 

treatments. Thus, if rice uses do not results in LOC exceedances, there are no LOC exceedances 

for all other uses with lower EECs, which apply to many taxa. 
50

For foliar applications, except for uses on wheat and peanuts, other uses modeled exceed the acute 

risk to listed species LOC (RQ>0.05) of freshwater fish; however, none of the uses modeled exceed 

the acute risk to non-listed species LOC of 0.5 (Table IV.4). Except for use on peppers where 3 

cycles per year were modeled, RQ values are below the chronic risk LOC of 1.0 for freshwater 

fish. Estimated run-off from seed treatments does not exceed acute or chronic risk LOCs (Table 

IV.5)

For listed species, LOC exceedances from foliar sprays require an additional in-depth listed species 

evaluation of the potential co-occurrence of listed species in azoxystrobin-treated areas to 

characterize risks. This step has not been undertaken for this assessment.

The potential adverse effects to fish and invertebrates are discussed further in Section IV.2.
51

Freshwater Fish - Foliar Spray

Table IV.4. Risk Quotients for Freshwater Fish via Foliar Sprays

Crop Scenario

Use Pattern

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-

year

Peak EEC 

(μg/L)

Freshwater Fish

LC50 = 470 μg a.i./L 

1-in-10-year

60-day EEC 

(μg/L)

Freshwater Fish

NOAEC =

147 μg a.i./L

Acute RQs Chronic RQs

Turf

FLturf

0.55 x 14 x 9

43.7 0.09* 40.3 0.3

PAturf 32.9 0.07* 31.1 0.2

Corn

IAcorn

0.25 x 7 x 4

24.3 0.05* 22.1 0.2

ILcorn 30.9 0.07* 27.8 0.2

INcorn 24.9 0.05* 23.1 0.2

KScorn 41.1 0.09* 36.6 0.2

MNcorn 29.7 0.06* 27.6 0.2

MScorn 34.2 0.07* 31.4 0.2

NCcorn 22.2 0.05* 20.2 0.1

NEcorn 33.2 0.07* 30.2 0.2

OHcorn 28.9 0.06* 26.2 0.2

PAcorn 25.3 0.05* 24.8 0.2

Peanuts NCpeanut 0.4 x 10 x 2 17.4 0.04 15.7 0.1

Wheat NDwheat 0.2 x 14 x 2 10 0.02 9.2 0.1

Potato IDpotato 0.33 x 7 x 6

32.5 0.07* 30.9 0.2

MEpotato 52.6 0.11** 49.1 0.3

Almond CAalmond 0.25 x 7 x 6 21.5 0.05* 19.7 0.1

Sugarcane FLsugarcane 0.25 x 14 x 4

29.7 0.06* 27.2 0.2

LAsugarcane 31.5 0.07* 28.8 0.2

Lettuce CAlettuce 

0.25 x 14 x 6

(1 Crop Cycles / 

year)

0.25 x 14 x 18 

82.3

(3 CC/yr) 0.18** 79.3(3 CC/yr) 0.5

33.5 

(1 CC/yr) 0.07* 31.1(1 CC/yr) 0.2

Pepper FLpepper 150

(3 CC/yr) 0.32** 151(3 CC/yr) 1.0†
52

Table IV.4. Risk Quotients for Freshwater Fish via Foliar Sprays

Crop Scenario

Use Pattern

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-

year

Peak EEC 

(μg/L)

Freshwater Fish

LC50 = 470 μg a.i./L 

1-in-10-year

60-day EEC 

(μg/L)

Freshwater Fish

NOAEC =

147 μg a.i./L

Acute RQs Chronic RQs

(3 Crop Cycles / 

year)

50.6

(1 CC/yr) 0.11** 51.1(1 CC/yr) 0.3

Bean ORbean 111 

(3 CC/yr) 0.24** 110(3 CC/yr) 0.7

Melon NJmelon 96.7

(3 CC/yr) 0.21** 93.1(3 CC/yr) 0.6

Asparagus MIasparagus 

60

(3 CC/yr) 0.13** 56.9(3 CC/yr) 0.4

Tomato PAtomato 

96.5

(3 CC/yr) 0.21** 92.8(3 CC/yr) 0.6

*

RQ meets or exceeds the acute risk listed species LOC of 0.05.

**RQ exceeds the acute risk listed species LOC of 0.05 and the acute restricted use LOC of 0.1

† RQ exceeds the chronic risk LOC of 1.0.

Freshwater Fish – Seed Treatment

Table IV.5. Risk Quotients for Freshwater Fish via Seed Treatment

Crop Application Rate 

(lb a.i./A)

Rice 

Model

Peak EEC 

(μg/L)

Freshwater Fish

LC50 = 470 μg a.i./L 

Rice Model

60-day EEC 

(μg/L)

Freshwater Fish

NOAEC =

147 μg a.i./L

Acute RQs Chronic RQs

DYNASTY

Rice1 0.012 6.1 0.01 6.1 <0.1

1 Based on Tier I Rice Model.

Because this use, with the highest EECs of all the seed treatment uses, does not yield RQs greater than the LOCs, we can conclude 

that none of the other seed treatment uses of azoxystrobin will yield RQs greater than the LOCs.

Freshwater Invertebrates - Foliar Spray
53

With the exception of use on wheat, RQ values exceed the acute risk to listed aquatic invertebrate species and the majority of uses 

exceed the restricted use LOC of 0.1 as well (Table IV.6). Use on peppers for 3 cycles per year exceeds the acute risk to non-listed 

species LOC of 0.5; whereas, a single crop cycle for peppers does not exceed the acute risk to non-listed species LOC, but does exceed 

the restricted use LOC. With respect to chronic risk to aquatic invertebrates, potatoes, lettuce, peppers, beans, melons, asparagus and 

tomatoes exceed the chronic risk LOC of 1.0. Estimated run-off from seed treatments does not exceed acute or chronic risk LOCs 

(Table IV.7).

 

Table IV.6. Risk Quotients for Freshwater Invertebrates via Foliar Sprays

Crop Scenario

Use Pattern 

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-year

Peak EEC 

(μg/L)

Freshwater 

Invertebrates

LC50 = 260 μg a.i./L 

1-in-10-year

21-day EEC 

(μg/L)

Freshwater 

Invertebrates

NOAEC =

44 μg a.i./L

Acute RQs Chronic RQs

Turf

FLturf

0.55 x 14 x 9

43.7 0.17** 42 0.95

PAturf 32.9 0.13** 32 0.7

Corn

IAcorn

0.25 x 7 x 4

24.3 0.09* 23.4 0.5

ILcorn 30.9 0.12** 29.7 0.7

INcorn 24.9 0.10** 24.1 0.5

KScorn 41.1 0.16** 39.3 0.9

MNcorn 29.7 0.11** 28.6 0.7

MScorn 34.2 0.13** 33.3 0.8

NCcorn 22.2 0.09* 21.3 0.5

NEcorn 33.2 0.13** 31.7 0.7

OHcorn 28.9 0.11** 27.9 0.6

PAcorn 25.3 0.10** 24.8 0.6

Peanuts NCpeanut 0.4 x 10 x 2 17.4 0.07* 16.6 0.4

Wheat NDwheat 0.2 x 14 x 2 10 0.04 9.69 0.2

Potato IDpotato 0.33 x 7 x 6

32.5 0.13** 32.1 0.7

MEpotato 52.6 0.20** 51.3 1.2†

Almond CAalmond 0.25 x 7 x 6 21.5 0.08* 20.6 0.5
54

Table IV.6. Risk Quotients for Freshwater Invertebrates via Foliar Sprays

Crop Scenario

Use Pattern 

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-year

Peak EEC 

(μg/L)

Freshwater 

Invertebrates

LC50 = 260 μg a.i./L 

1-in-10-year

21-day EEC 

(μg/L)

Freshwater 

Invertebrates

NOAEC =

44 μg a.i./L

Acute RQs Chronic RQs

Sugarcane FLsugarcane 0.25 x 14 x 4

29.7 0.11** 28.6 0.7

LAsugarcane 31.5 0.12** 30.5 0.7

Lettuce CAlettuce

0.25 x 14 x 6

(1 CC / year)

0.25 x 14 x 18

(3 CC / year)

82.3

(3 CC/yr) 0.32** 80.9(3 CC/yr) 1.8†

33.5

(1 CC/yr) 0.13** 32.5(1 CC/yr) 0.7

Pepper FLpepper

150

(3 CC/yr) 0.58*** 152(3 CC/yr) 3.5†

50.6

(1 CC/yr) 0.19** 49.4(1 CC/yr) 1.1†

Bean ORbean 111

(3 CC/yr) 0.43** 111(3 CC/yr) 2.5†

Melon NJmelon 96.7

(3 CC/yr) 0.37** 95.1(3 CC/yr) 2.2†

Asparagus MIasparagus 60

(3 CC/yr) 0.23** 58.2(3 CC/yr) 1.3†

Tomato PAtomato 96.5

(3 CC/yr) 0.37** 95.4(3 CC/yr) 2.2†

*

RQ meets or exceeds the acute risk to listed species LOC of 0.05 .

**RQ exceeds the acute risk to listed species LOC of 0.05 and the acute restricted use LOC of 0.1. 

***

RQ exceeds the acute risk to listed species LOC of 0.05, the acute restricted use LOC of 0.1, and the acute risk to listed 

species LOC of 0.5. 

† RQ exceeds chronic risk LOC of 1.0.

.
55

Freshwater Invertebrates – Seed Treatment

Table IV.7. Risk Quotients for Freshwater Invertebrates via Seed Treatment

Crop Application Rate 

(lb a.i./A)

Rice Model

Peak EEC 

(μg/L)

Freshwater 

Invertebrates

LC50 = 260 μg a.i./L

Rice 

Model

21-day 

EEC 

(μg/L)

Freshwater 

Invertebrates

NOAEC =

44 μg a.i./L

Acute RQs Chronic RQs

DYNASTY

Rice1 0.012 6.1 0.02 6.1 0.14

1 Based on Tier I Rice model.

For foliar applications, with the exception of peanuts and wheat, RQ values for other modeled uses exceed the acute risk to listed species 

LOC for estuarine/marine fish. Use on potatoes, lettuce, peppers, beans, melons and tomatoes also exceed the acute restricted use LOC 

(Table IV.8). None of the uses modeled exceed the chronic risk LOC for estuarine/marine fish. Estimated run-off from seed treatments 

does not exceed acute or chronic risk LOCs (Table IV.9).

Estuarine/marine Fish - Foliar Spray

Table IV.8. Risk Quotients for Estuarine/marine Fish via Foliar Sprays

Crop Scenario

Use Pattern 

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-

year

Peak EEC 

(μg/L)

Estuarine/marine 

Fish

LC50 = 

670 μg a.i./L 

1-in-10-year

60-day EEC 

(μg/L)

Estuarine/marine Fish

ACR calculated NOAEC 

=

210 μg a.i./L

Acute RQs Chronic RQs

Turf

FLturf

0.55 x 14 x 9

43.7 0.07* 40.3 0.19

PAturf 32.9 0.05* 31.1 0.15

Corn

IAcorn

0.25 x 7 x 4

24.3 0.04 22.1 0.11

ILcorn 30.9 0.05* 27.8 0.13

INcorn 24.9 0.04 23.1 0.11

KScorn 41.1 0.06* 36.6 0.17

MNcorn 29.7 0.04 27.6 0.13

MScorn 34.2 0.05* 31.4 0.15
56

Table IV.8. Risk Quotients for Estuarine/marine Fish via Foliar Sprays

Crop Scenario

Use Pattern 

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-

year

Peak EEC 

(μg/L)

Estuarine/marine 

Fish

LC50 = 

670 μg a.i./L 

1-in-10-year

60-day EEC 

(μg/L)

Estuarine/marine Fish

ACR calculated NOAEC 

=

210 μg a.i./L

Acute RQs Chronic RQs

NCcorn 22.2 0.03 20.2 0.10

NEcorn 33.2 0.05* 30.2 0.14

OHcorn 28.9 0.04 26.2 0.12

PAcorn 25.3 0.04 24.8 0.12

Peanuts NCpeanut 0.4 x 10 x 2 17.4 0.03 15.7 0.07

Wheat NDwheat 0.2 x 14 x 2 10 0.01 9.2 0.04

Potato IDpotato 0.33 x 7 x 6

32.5 0.05* 30.9 0.15

MEpotato 52.6 0.08* 49.1 0.23

Almond CAalmond 0.25 x 7 x 6 21.5 0.03 19.7 0.09

Sugarcane FLsugarcane 0.25 x 14 x 4

29.7 0.04 27.2 0.13

LAsugarcane 31.5 0.05* 28.8 0.14

Lettuce CAlettuce

0.25 x 14 x 6

(1 CC / year)

0.25 x 14 x 18

(3 CC / year)

82.3

(3 CC/yr) 0.12** 79.3(3 CC/yr) 0.38

33.5

(1 CC/yr) 0.05* 31.1(1 CC/yr) 0.15

Pepper FLpepper

150

(3 CC/yr) 0.22** 151(3 CC/yr) 0.72

50.6

(1 CC/yr) 0.08* 51.1(1 CC/yr) 0.24

Bean ORbean 111

(3 CC/yr) 0.17** 110(3 CC/yr) 0.52

Melon NJmelon 96.7

(3 CC/yr) 0.14** 93.1(3 CC/yr) 0.44

Asparagus MIasparagus 60

(3 CC/yr) 0.09* 56.9(3 CC/yr) 0.27

Tomato PAtomato 96.5

(3 CC/yr) 0.14** 92.8(3 CC/yr) 0.44

*

RQ meets or exceeds the acute risk to listed species LOC of 0.05 .

**RQ exceeds the acute risk to listed species LOC of 0.05 and the acute restricted use LOC of 0.1.
57

Estuarine/marine Fish – Seed Treatment

Table IV.9. Risk Quotients for Estuarine/marine Fish via Seed Treatment

Crop Application Rate 

(lb a.i./A)

Rice 

Model

Peak EEC 

(μg/L)

Estuarine/marine 

Fish

LC50 = 670 μg 

a.i./L

Rice Model

60-day EEC 

(μg/L)

Estuarine/marine Fish

ACR calculated 

NOAEC =

210 μg a.i./L

Acute RQs Chronic RQs

DYNASTY

Rice1 0.012 6.1 <0.01 6.1 <0.1

1 Based on Tier I Rice model.

For foliar applications, RQ values for all of the uses modeled exceed the acute risk to listed estuarine/marine invertebrate species LOC 

and the acute restricted use LOC; the majority of uses also exceed the acute risk to non-listed species LOC. All of the uses modeled 

also exceed the chronic risk LOC.
58

Estuarine/marine Invertebrates - Foliar Spray

Table IV.10. Risk Quotients for Estuarine/marine Invertebrates via Foliar Sprays

Crop Scenario

Use Pattern 

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-year

Peak EEC 

(μg/L)

Estuarine/marine 

Invertebrates

LC50 = 56 μg a.i./L 

1-in-10-year

21-day EEC 

(μg/L)

Estuarine/marine 

Invertebrates

NOAEC =

9.5 μg a.i./L

Acute RQs Chronic RQs

Turf

FLturf

0.55 x 14 x 9

43.7 0.8*** 42 4.4†

PAturf 32.9 0.6*** 32 3.4†

Corn

IAcorn

0.25 x 7 x 4

24.3 0.4** 23.4 2.5†

ILcorn 30.9 0.6*** 29.7 3.1†

INcorn 24.9 0.4** 24.1 2.5†

KScorn 41.1 0.7*** 39.3 4.1†

MNcorn 29.7 0.5*** 28.6 3.0†

MScorn 34.2 0.6*** 33.3 3.5†

NCcorn 22.2 0.4** 21.3 2.2†

NEcorn 33.2 0.6*** 31.7 3.3†

OHcorn 28.9 0.5*** 27.9 2.9†

PAcorn 25.3 0.5*** 24.8 2.6†

Peanuts NCpeanut 0.4 x 10 x 2 17.4 0.3** 16.6 1.7†

Wheat NDwheat 0.2 x 14 x 2 10 0.2** 9.69 1.0†

Potato IDpotato 0.33 x 7 x 6

32.5 0.6*** 32.1 3.4†

MEpotato 52.6 0.9*** 51.3 5.4†

Almond CAalmond 0.25 x 7 x 6 21.5 0.4** 20.6 2.2†

Sugarcane FLsugarcane 0.25 x 14 x 4

29.7 0.5*** 28.6 3.0†

LAsugarcane 31.5 0.6*** 30.5 3.2†

Lettuce CAlettuce

0.25 x 14 x 6

(1 CC / year)

0.25 x 14 x 18

82.3

(3 CC/yr) 1.5*** 80.9(3 CC/yr) 8.5†

33.5

(1 CC/yr) 0.6*** 32.5(1 CC/yr) 3.4†
59

Table IV.10. Risk Quotients for Estuarine/marine Invertebrates via Foliar Sprays

Crop Scenario

Use Pattern 

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-year

Peak EEC 

(μg/L)

Estuarine/marine 

Invertebrates

LC50 = 56 μg a.i./L 

1-in-10-year

21-day EEC 

(μg/L)

Estuarine/marine 

Invertebrates

NOAEC =

9.5 μg a.i./L

Acute RQs Chronic RQs

Pepper FLpepper

(3 CC / year) 150

(3 CC/yr) 2.7*** 152(3 CC/yr) 16.0†

50.6

(1 CC/yr) 0.9*** 49.4(1 CC/yr) 5.2†

Bean ORbean 111

(3 CC/yr) 2.0*** 111(3 CC/yr) 11.7†

Melon NJmelon 96.7

(3 CC/yr) 1.7*** 95.1(3 CC/yr) 10.0†

Asparagus MIasparagus 60

(3 CC/yr) 1.1*** 58.2(3 CC/yr) 6.1†

Tomato PAtomato 96.5

(3 CC/yr) 1.7*** 95.4(3 CC/yr) 10.0†

**RQ exceeds the acute risk to listed species LOC of 0.05 and the acute restricted use LOC of 0.1. ***RQ exceeds the acute risk to listed species LOC of 0.05, the acute restricted use LOC of 0.1, and the acute risk to listed 

species LOC of 0.5.

† RQ exceeds chronic risk LOC of 1.0.

For Dynasty and Cruiser Max seed treatments on rice, RQ values exceed the acute risk to listed species LOC; Dynasty seed treatment 

on rice also exceeds the acute restricted use LOC (Table IV.11). None of the seed treatment uses modeled exceed the chronic risk 

LOC.
60

Estuarine/marine Invertebrates – Seed Treatment

Table IV.11. Risk Quotients for Estuarine/marine Invertebrates via Seed Treatment

Crop Application Rate 

(lb a.i./A)

GENEEC

Peak EEC 

(μg/L)

Estuarine/marine

Invertebrates

LC50 = 56 μg a.i./L

GENEEC

21-day EEC 

(μg/L)

Estuarine/marine

Invertebrates

NOAEC =

9.5 μg a.i./L

Acute RQs Chronic RQs

DYNASTY

Brassica crops 0.00062 0.0078 <0.01 0.0075 <0.1

Sorghum 0.00175 0.022 <0.01 0.021 <0.1

Rice1 0.012 6.1 0.1** 6.1 0.6

Soybeans 0.00478 0.06 <0.01 0.058 <0.1

Sunflower 0.009 0.113 <0.01 0.109 <0.1

DYNASTY CST

Cotton 0.0032 0.04 <0.01 0.039 <0.1

DYNASTY EXTREME

Cotton 0.0033 0.04 <0.01 0.039 <0.1

ADAGE DELUXE

Soybean 0.0015 0.019 <0.01 0.018 <0.1

ADAGE PREMIER

Soybean 0.0015 0.019 <0.01 0.018 <0.1

AVICTA CORN 250

Field corn 0.023 0.288 <0.01 0.279 <0.1

Popcorn 0.038 0.476 <0.01 0.462 <0.1

Sweet corn 0.046 0.576 0.01 0.559 <0.1

AVICTA CORN 500

Field corn 0.022 0.288 <0.01 0.279 <0.1

Popcorn 0.037 0.476 <0.01 0.462 <0.1

Sweet corn 0.045 0.576 0.01 0.559 <0.1
61

Table IV.11. Risk Quotients for Estuarine/marine Invertebrates via Seed Treatment

Crop Application Rate 

(lb a.i./A)

GENEEC

Peak EEC 

(μg/L)

Estuarine/marine

Invertebrates

LC50 = 56 μg a.i./L

GENEEC

21-day EEC 

(μg/L)

Estuarine/marine

Invertebrates

NOAEC =

9.5 μg a.i./L

Acute RQs Chronic RQs

CRUISER EXTREME

Field corn 0.0024 0.003 <0.01 0.0029 <0.1

Popcorn 0.0004 0.005 <0.01 0.0049 <0.1

Sweet corn 0.0005 0.0063 <0.01 0.0061 <0.1

CRUISER MAXX RICE

Rice1 0.0078 4.0 0.07* 4.0 0.4

FOUR WAY VAP

Crop group 7 0.0029 0.036 <0.01 0.035 <0.1

Crop group 6 0.0077 0.096 <0.01 0.094 <0.1

Soybean 0.0029 0.036 <0.01 0.035 <0.1

MAXIM QUATTRO

Field corn 0.0003 0.0038 <0.01 0.0036 <0.1

Popcorn 0.0006 0.0075 <0.01 0.0073 <0.1

Sweet corn 0.0006 0.0075 <0.01 0.0073 <0.1

QUARTET

Cotton 0.0026 0.033 <0.01 0.032 <0.1

TRIO CST

Cotton 0.0029 0.036 <0.01 0.035 <0.1

*

RQ meets or exceeds the acute risk to listed species LOC of 0.05

**RQ exceeds the acute risk to listed species LOC of 0.05 and the acute restricted use LOC of 0.1.

1 Based on Tier I Rice model.
62

IV.1.2. Aquatic Plants 

RQs for non-listed and listed aquatic plants exposed to azoxystrobin via runoff and spray drift 

from foliar treatments are calculated in Tables IV.12 and IV.14; the RQs for aquatic plants 

exposed to runoff from azoxystrobin-treated seeds are tabulated in Tables IV.13 and IV.15. For 

aquatic vascular plants, RQ values are below the LOC of 1.0 for both non-listed and listed 

species from runoff for both foliar (Table IV.12) and seed treatments (Table IV.13). The 

potential risks to aquatic plants are discussed further in Section IV.2.

Aquatic Vascular Plants - Foliar Spray

Table IV.12. Risk Quotients for Aquatic Vascular Plants via Foliar Sprays

Crop Scenario

Use Pattern 

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-

year

Peak 

EEC 

(μg/L)

Non-listed Aquatic 

Vascular Plants

EC50 = 3400 

μg a.i./L 

Listed Aquatic 

Vascular Plants

NOAEC = 800 μg 

a.i./L

Non-listed RQ Listed RQs

Pepper FLpepper 0.25 x 14 x 18

(3 CC / year) 150 <0.1 0.2

Aquatic Vascular Plants – Seed Treatment

Table IV.13. Risk Quotients for Aquatic Vascular Plants via Seed Treatment

Crop

Application 

Rate 

(lb a.i./A)

Rice Model

Peak EEC 

(μg/L)

Non-listed Aquatic 

Vascular Plants

EC50 = 3400 

μg a.i./L 

Listed Aquatic Vascular 

Plants

NOAEC = 800 μg a.i./L

Non-listed RQ Listed RQs

DYNASTY 

Rice1 0.012 6.1 <0.1 <0.1

1 Based on Tier I Rice model.

Aquatic Non-Vascular Plants - Foliar Spray

For foliar applications, except for uses on peanuts and wheat, all of the RQ values exceed the LOC 

for risk to listed species (Table IV.14). For uses on potatoes, lettuce, beans, melons, asparagus 

and tomatoes, RQs exceed the acute risk to non-listed species LOCs. Run-off from seed treatments 

resulted in RQ values below aquatic plant LOCs (Table IV.15).

Table IV.14. Risk Quotients for Aquatic Non-vascular Plants via Foliar Sprays

Crop Scenario

Use Pattern

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-

year

Peak EEC 

(μg/L)

Non-listed 

Aquatic 

Nonvascular 

Plants

EC50 = 49 μg a.i./L 

Listed Aquatic 

Nonvascular 

Plants

NOAEC = 20 μg 

a.i./L

Non-listed RQ Listed RQs

Turf

FLturf

0.55 x 14 x 9

43.7 0.9 2.2

PAturf 32.9 0.7 1.6

Corn IAcorn 0.25 x 7 x 4 24.3 0.5 1.2
63

Table IV.14. Risk Quotients for Aquatic Non-vascular Plants via Foliar Sprays

Crop Scenario

Use Pattern

(lb a.i./A x days 

interval x no. of 

applications)

1-in-10-

year

Peak EEC 

(μg/L)

Non-listed 

Aquatic 

Nonvascular 

Plants

EC50 = 49 μg a.i./L 

Listed Aquatic 

Nonvascular 

Plants

NOAEC = 20 μg 

a.i./L

Non-listed RQ Listed RQs

ILcorn 30.9 0.6 1.5

INcorn 24.9 0.5 1.2

KScorn 41.1 0.8 2.1

MNcorn 29.7 0.6 1.5

MScorn 34.2 0.7 1.7

NCcorn 22.2 0.5 1.1

NEcorn 33.2 0.7 1.7

OHcorn 28.9 0.6 1.4

PAcorn 25.3 0.5 1.3

Peanuts NCpeanut 0.4 x 10 x 2 17.4 0.4 0.9

Wheat NDwheat 0.2 x 14 x 2 10 0.2 0.5

Potato IDpotato 0.33 x 7 x 6

32.5 0.7 1.6

MEpotato 52.6 1.1 2.6

Almond CAalmond 0.25 x 7 x 6 21.5 0.4 1.1

Sugarcane FLsugarcane 0.25 x 14 x 4

29.7 0.6 1.5

LAsugarcane 31.5 0.6 1.6

Lettuce CAlettuce

0.25 x 14 x 6

(1 CC / year)

0.25 x 14 x 18

(3 CC / year)

82.3

(3 CC/yr) 1.7 4.1

33.5

(1 CC/yr) 0.7 1.7

Pepper FLpepper

150

(3 CC/yr) 3.1 7.5

50.6

(1 CC/yr) 1.0 2.5

Bean ORbean 111

(3 CC/yr) 2.3 5.6

Melon NJmelon 96.7

(3 CC/yr) 2.0 4.8

Asparagus MIasparagus 60

(3 CC/yr) 1.2 3.0

Tomato PAtomato 96.5

(3 CC/yr) 2.0 4.8

A bold cell indicates that the RQ meets or exceeds the plant LOCs of 1.0 for both listed and non-listed plants, 

respectively.
64

Aquatic Nonvascular Plants – Seed Treatment

Table IV.15. Risk Quotients for Aquatic Nonvascular Plants via Seed Treatment

Crop

Application 

Rate 

(lb a.i./A)

Rice Model

Peak EEC 

(μg/L)

Non-listed Aquatic 

Nonvascular Plants

EC50 = 49 μg a.i./L 

Listed Aquatic 

Nonvascular Plants

NOAEC = 20 μg a.i./L

Non-listed RQ Listed RQs

DYNASTY 

Rice1 0.012 6.1 <0.1 <0.1

1 Based on Tier I Rice model.

IV.1.2 Terrestrial Animals 

Brief Description of T-REX Modeling for Birds and Mammals

Foliar spray formulas presented below in Table IV.16 are used to calculate dose-based and 

dietary based risk quotients. Seed treatment formulas in Table IV.17 are used to calculate dosebased and available pesticide acute risk quotients. For seed treatment chronic risk quotients, the 

maximum seed application rate for birds and the dose-based route for mammals were used. The 

potential risks to terrestrial animals are discussed further in Section IV.2.

Table IV.16. Foliar Spray Formulas Used to Calculate Dose-Based and Dietary-Based 

Risk Quotients

Duration Dose or Dietary 

RQ

Surrogate 

Organism Equation

Acute Dose-based Birds and 

mammals

Acute Daily Exposure (mg/kg-bw) / adjusted LD50 (mg/kgbw)1,2

Dietary-based Birds Kenaga EEC (mg/kg-food item) / LC50 (mg/kg-diet)

Chronic

Dietary-based Birds and 

mammals

EEC (mg/kg-food item) / NOAEC (mg/kg-diet)

Dose-based Mammals 

only

EEC (mg/kg-bw) / Adjusted NOAEL (mg/kg-bw)2

1 Adj. Bird LD50 = Bird LD50 (AW/TW) (a-1) 

2 Adj. Mammal LD50 or NOAEL = Mammal LD50 or NOAEL (TW/AW)0.25
65

Table IV.17. Seed Treatment Formulas Used to Calculate Dose-Based and Available 

Pesticide Risk Quotients

Duration Type of RQ Surrogate 

Organism Equation

Acute

Dose-based Birds and 

mammals

Daily Exposure (mg/kg-bw/day) / adjusted LD50 (mg/kgbw)1,2

Available A.I. Birds and 

mammals

mg a.i./ft2 / adjusted LD50 (mg/kg-bw)

Chronic

Seed application 

rate Birds EEC (mg/kg-seed) / NOAEL (mg/kg-bw/day)

Dose-based Mammals Daily Exposure (mg/kg-bw/day) / Adjusted NOAEL 

(mg/kg-bw)2

1 Adj. Bird LD50 = Bird LD50 (AW/TW) (a-1) 

2 Adj. Mammal LD50 or NOAEL = Mammal LD50 or NOAEL (TW/AW)0.25

Risk Quotient Calculations Based on Foliar Application

Birds and mammals foraging short grass with azoxystrobin residues via the dose-based route 

assumes the highest exposure of all scenarios modeled for the current uses (Tables IV.18

(mammal, dose-based), IV.23 (bird, dietary-based), and IV.24 (mammal, dietary-based)). Thus 

exposure for other modeled scenarios is expected to be lower than the maximum scenario modeled 

when heavier vertebrates, use patterns with lower rates, or/and selected food items other than short 

grass are used. With chronic LOC exceedances observed for chronic effects to mammals from 

foraging short grass with the residues, other T-REX food items in order from highest to lowest 

exposure were assessed for exceedances (Tables IV.19 thru IV.22 for dose-based). The food item

resulting in the lowest potential exposure (seeds for granivores) was not tabulated as no LOC 

exceedances occurred. Except for mammals foraging fruits and pods, the majority of uses resulted 

in dose-based RQ values, which exceed the chronic risk LOC for each of the three sizes of listed 

and non-listed mammals evaluated. 

Dosed-based chronic RQs for mammals of different body weight sizes are tabulated below in 

Tables IV.18 thru IV.22. In addition, T-REX does not differentiate between aerial or ground 

applications; thus, T-REX results are based on broadcast foliar applications.

Table IV.18. Dose-Based Chronic Risk Quotients for Mammals of Different Body 

Weight Classes Foraging Short Grass with Azoxystrobin Residues*

Crop

App Rate

in lbs a.i./A / No. of 

Apps / # days interval

Short Grass 

EEC for 15 g / 35 

g / 1000 g 

(mg/kg-bw)

Chronic RQs (dose-based EEC/ 

adjusted NOAEL)

15 g; small 35 g; 

medium 1000 g; large

Turf 0.55 / 9x / 14D 262/181/42 8* 7* 4*

Corn 0.25 / 4x / 7D 150/104/24 5* 4* 2*

Peanuts 0.4 / 2x / 10D 139/96/22 4* 4* 2*

Wheat 0.2 / 2x / 14D 75/51/12 2* 2* 1*

Potato 0.33 / 6x / 7D 233/161/37 7* 6* 3*

Almond 0.25 / 6x / 7D 177/122/28 5* 5* 2*
66

Table IV.18. Dose-Based Chronic Risk Quotients for Mammals of Different Body 

Weight Classes Foraging Short Grass with Azoxystrobin Residues*

Crop

App Rate

in lbs a.i./A / No. of 

Apps / # days interval

Short Grass 

EEC for 15 g / 35 

g / 1000 g 

(mg/kg-bw)

Chronic RQs (dose-based EEC/ 

adjusted NOAEL)

15 g; small 35 g; 

medium 1000 g; large

Sugarcane 0.2 / 4x / 14D 111/77/18 3* 3* 2*

Leafy 

Vegetables

0.25 / 6x / 14D 117/81/19 4* 3* 2*

0.25 / 18x / 14D 120/83/19 4* 3* 2*

* Bold value indicates the RQ exceeds the chronic risk LOC for listed and non-listed mammals.

Table IV.19. Dose-Based Chronic Risk Quotients for Mammals of Different Body 

Weight Classes Foraging Broadleaf Plants with Azoxystrobin Residues*

Crop

App Rate

in lbs a.i./A / No. of 

Apps / # days interval

Broadleaf plant 

EEC for 15 g / 35 

g / 1000 g 

(mg/kg-bw)

Chronic RQs (dose-based EEC/ 

adjusted NOAEL)

15 g; 

small

35 g; 

medium

1000 g; 

large

Turf 0.55 / 9x / 14D 147/102/24 4* 4* 2*

Corn 0.25 / 4x / 7D 84/58/14 3* 2* 1*

Peanuts 0.4 / 2x / 10D 78/54/13 2* 2* 1*

Wheat 0.2 / 2x / 14D 42/29/7 1* 1* 0.6

Potato 0.33 / 6x / 7D 131/91/21 4* 3* 2*

Almond 0.25 / 6x / 7D 99/69/16 3* 3* 1*

Sugarcane 0.2 / 4x / 14D 62/43/10 2* 2* 0.9

Leafy 

Vegetables

0.25 / 6x / 14D 66/46/11 2* 2* 0.9

0.25 / 18x / 14D 67/46/11 2* 2* 0.9

* Bold value indicates the RQ exceeds the chronic risk LOC of 1.0 for listed and non-listed mammals.

Table IV.20. Dose-Based Chronic Risk Quotients for Mammals of Different Body 

Weight Classes Foraging Tall Grass with Azoxystrobin Residues*

Crop

App Rate

in lbs a.i./A / No. of 

Apps / # days interval

Tall Grass EEC 

for 15 g / 35 g / 

1000 g (mg/kgbw)

Chronic RQs (dose-based EEC/ 

adjusted NOAEL)

15 g; 

small

35 g; 

medium 1000 g; large

Turf 0.55 / 9x / 14D 120/83/19 4* 3* 2*

Corn 0.25 / 4x / 7D 69/47/11 2* 2* 0.95

Peanuts 0.4 / 2x / 10D 64/44/10 2* 2* 0.9

Wheat 0.2 / 2x / 14D 34/24/5 1* 0.9 0.5

Potato 0.33 / 6x / 7D 107/74/17 3* 3* 1*

Almond 0.25 / 6x / 7D 81/56/13 2* 2* 1*

Sugarcane 0.2 / 4x / 14D 51/35/8 2* 1* 0.7

Leafy 

Vegetables

0.25 / 6x / 14D 54/37/9 2* 1* 0.8

0.25 / 18x / 14D 55/38/9 2* 1* 0.8
67

Table IV.20. Dose-Based Chronic Risk Quotients for Mammals of Different Body 

Weight Classes Foraging Tall Grass with Azoxystrobin Residues*

Crop

App Rate

in lbs a.i./A / No. of 

Apps / # days interval

Tall Grass EEC 

for 15 g / 35 g / 

1000 g (mg/kgbw)

Chronic RQs (dose-based EEC/ 

adjusted NOAEL)

15 g; 

small

35 g; 

medium 1000 g; large

* Bold value indicates the RQ exceeds the chronic risk LOC of 1.0 for listed and non-listed mammals.

Table IV.21. Dose-Based Chronic Risk Quotients for Mammals of Different Body 

Weight Classes Foraging Arthropods with Azoxystrobin Residues*

Crop

App Rate

in lbs a.i./A / No. of 

Apps / # days interval

Arthropod EEC 

for 15 g / 35 g / 

1000 g (mg/kgbw)

Chronic RQs (dose-based EEC/ 

adjusted NOAEL)

15 g; small 35 g; 

medium

1000 g; 

large

Turf 0.55 / 9x / 14D 103/71/16 3* 3* 1*

Corn 0.25 / 4x / 7D 59/41/9 2* 2* 0.8

Peanuts 0.4 / 2x / 10D 55/38/9 2* 1* 0.8

Wheat 0.2 / 2x / 14D 29/20/5 0.9 0.8 0.4

Potato 0.33 / 6x / 7D 91/63/15 3* 2* 1*

Almond 0.25 / 6x / 7D 69/48/11 2* 2* 0.96

Sugarcane 0.2 / 4x / 14D 43/30/7 1* 1* 0.6

Leafy 

Vegetables

0.25 / 6x / 14D 46/32/7 1* 1*

0.6

0.25 / 18x / 14D 47/32/8 1* 1* 0.7

* Bold value indicates the RQ exceeds the chronic risk LOC of 1.0 for listed and non-listed mammals.

Table IV.22. Dose-Based Chronic Risk Quotients for Mammals of Different Body 

Weight Classes Foraging Fruits and Pods with Azoxystrobin Residues*

Crop

App Rate

in lbs a.i./A / No. of 

Apps / # days interval

Fruits and Pods 

EEC for 15 g / 35 

g / 1000 g 

(mg/kg-bw)

Chronic RQs (dose-based EEC/ 

adjusted NOAEL)

15 g; 

small

35 g; 

medium

1000 g; 

large

Turf 0.55 / 9x / 14D 16/11/3 0.5 0.4 0.2

Corn 0.25 / 4x / 7D 9/6/2 0.3 0.2 0.1

Peanuts 0.4 / 2x / 10D 9/6/1 0.3 0.2 0.1

Wheat 0.2 / 2x / 14D 5/3/1 0.1 0.1 <0.1

Potato 0.33 / 6x / 7D 15/10/2 0.4 0.4 0.2

Almond 0.25 / 6x / 7D 11/8/2 0.3 0.3 0.2

Sugarcane 0.2 / 4x / 14D 7/5/1 0.2 0.2 0.1

Leafy 

Vegetables

0.25 / 6x / 14D 7/5/1 0.2 0.2 0.1

0.25 / 18x / 14D 7/5/1 0.2 0.2 0.1

T-REX results of dietary-based chronic RQs for birds are tabulated below in Table IV.23. No 

chronic risk LOC exceedances were observed for birds foraging on short grass using the maximum 
68

exposure scenario; thus, LOC exceedances for other selected feed items and exposure scenarios 

with lower EECs are not expected.

Table IV.23. Dietary-Based Chronic Risk Quotients for Birds Foraging Short Grass 

with Azoxystrobin Residues

Crop

App Rate

in lbs a.i./A / No. of Apps / # 

days interval

Short Grass EEC 

(mg/kg-bw)

Chronic RQs (dietarybased EEC/ NOAEC)

Turf 0.55 / 9x / 14D 275 0.2

Corn 0.25 / 4x / 7D 179 0.1

Peanuts 0.4 / 2x / 10D 146 0.1

Wheat 0.2 / 2x / 14D 78 <0.1

Potato 0.33 / 6x / 7D 245 0.2

Almond 0.25 / 6x / 7D 185 0.2

Sugarcane 0.2 / 4x / 14D 116 0.1

Leafy 

Vegetables

0.25 / 6x / 14D 123 0.1

0.25 / 18x / 14D 125 0.1

T-REX results of dietary-based chronic RQs for mammals are tabulated below in Table IV.24. 

There were no chronic risk LOC exceedances for mammals foraging on short grass in all current 

use sites; thus, LOC exceedances for other selected feed items and exposure scenarios with lower 

EECs are not expected (Table IV.24).

Table IV.24. Dietary-Based Chronic Risk Quotients for Mammals Foraging Short 

Grass with Azoxystrobin Residues

Crop App. Rate in lbs a.i./A / No. 

of Apps / # days interval

Short grass EEC (mg/kgbw)

Chronic RQs 

(dietary-based EEC / 

NOAEC)

Turf 0.55 / 9x / 14D 275 0.9

Corn 0.25 / 4x / 7D 179 0.5

Peanuts 0.4 / 2x / 10D 146 0.5

Wheat 0.2 / 2x / 14D 78 0.3

Potato 0.33 / 6x / 7D 245 0.8

Almond 0.25 / 6x / 7D 185 0.6

Sugarcane 0.2 / 4x / 14D 116 0.4

Leafy 

Vegetables

0.25 / 6x / 14D 123 0.4

0.25 / 18x / 14D 125 0.4

Risk Quotient Calculations Based on Seed Treatment
69

T-REX results of chronic RQs for birds and mammals foraging azoxystrobin-treated seeds are 

tabulated below in Tables IV.25 and IV.26, respectively. Chronic risk LOC exceedances were 

observed for birds in sunflower and in sweet corn and popcorn use sites and for mammals of all 

weights in field corn, popcorn, and sweet corn use sites, for small (15 g) and medium (35 g)

mammals in head/stem Brassica crops and sorghum use sites, and for 15-g mammals in cotton 

use sites. 

Table IV.25. Chronic Risk Quotients for Birds Exposed via Seed Treatment*

Crop App Rate

in fl. oz./CWT

Seed Application 

Rate

(mg/kg-seed)

Chronic RQs

(mg/kg-seed / NOAEL)

DYNASTY

Brassica crops 3.75 234.28 0.2

Rice 1.53 95.59 0.08

Sorghum 3.05 190.55 0.16

Soybeans 0.459 28.68 0.02

Sunflower 37.5 2342.81 1.95*

DYNASTY CST

Cotton 3.95 170.69 0.14

DYNASTY EXTREME

Cotton 3.0 162.63 0.14

ADAGE DELUXE

Soybean 4.29 8.93 0.01

ADAGE PREMIER

Soybean 4.23 8.81 0.01

AVICTA CORN 250

Field corn 11.61 778.22 0.65

Popcorn 25.8 1729.39 1.44*

Sweet corn 20.65 1384.18 1.15*

AVICTA CORN 500

Field corn 11.4 756.7 0.63

Popcorn 25.2 1672.77 1.39*

Sweet corn 20.2 1340.87 1.12*

CRUISER EXTREME

Field corn 2.51 8.17 0.01

Popcorn 5.58 18.16 0.02

Sweet corn 4.46 14.5 0.01

CRUISER MAXX RICE
70

Table IV.25. Chronic Risk Quotients for Birds Exposed via Seed Treatment*

Crop App Rate

in fl. oz./CWT

Seed Application 

Rate

(mg/kg-seed)

Chronic RQs

(mg/kg-seed / NOAEL)

Rice 7 60.13 0.05

FOUR WAY VAP

Crop group 7 3 17.57 0.01

Crop group 6 3 17.57 0.01

Soybean 3 17.57 0.01

MAXIUM QUATTRO

Field corn 1.18 10.21 0.01

Popcorn 3.07 20.57 0.02

Sweet corn 2.05 17.74 0.01

QUARTET

Cotton 4 136.4 0.11

TRIO CST

Cotton 3.5 151.24 0.13

* Bold value indicates the RQ exceeds the chronic risk LOC of 1.0 for listed and non-listed species.

Table IV.26. Chronic Risk Quotients for Mammals of Body Weight Classes Exposed 

via Seed Treatment*

Crop App Rate

in fl. oz./CWT

Seed EEC for 15 

g / 35 g / 1000 g 

(mg/kg-bw)

Chronic RQs (dose-based EEC/ 

adjusted NOAEL)

15 g; 

small

35 g; 

medium 1000 g; large

DYNASTY

Head/Stem 

Brassica crops 3.75 50/34/8 1.5* 1.3* 0.7

Rice 1.53 20/14/3 0.6 0.5 0.3

Sorghum 3.05 41/28/7 1.2* 1.1* 0.6

Soybean 0.459 6/4/1 0.18 0.16 0.08

Sunflower 37.5 496/343/80 15* 13* 7*

DYNASTY CST

Cotton 3.95 36/25/6 1.1* 0.9 0.5

DYNASTY EXTREME

Cotton 3 34/24/6 1.05* 0.9 0.5

ADAGE DELUXE

Soybean 4.29 2/1/0.3 0.06 0.05 0.03

ADAGE PREMIER
71

Table IV.26. Chronic Risk Quotients for Mammals of Body Weight Classes Exposed 

via Seed Treatment*

Crop App Rate

in fl. oz./CWT

Seed EEC for 15 

g / 35 g / 1000 g 

(mg/kg-bw)

Chronic RQs (dose-based EEC/ 

adjusted NOAEL)

15 g; 

small

35 g; 

medium 1000 g; large

Soybean 4.23 2/1/0.3 0.06 0.05 0.03

AVICTA CORN 250

Field corn 11.61 165/114/26 5* 4.3* 2.3*

Popcorn 25.8 366/253/59 11* 9.5* 5.1*

Sweet corn 20.65 293/203/47 8.9* 7.6* 4.1*

AVICTA CORN 500

Field corn 11.4 160/111/27 4.9* 4.2* 2.2*

Popcorn 25.2 354/245/57 10.8* 9.2* 4.9*

Sweet corn 20.2 284/196/46 8.6* 7.4* 4.0*

CRUISER EXTREME

Field corn 2.51 2/1/0.3 0.05 0.04 0.02

Popcorn 5.58 4/3/0.6 0.12 0.1 0.05

Sweet corn 4.46 3/2/0.5 0.09 0.08 0.04

CRUISER MAXX RICE

Rice 7 13/9/2 0.4 0.3 0.2

FOUR WAY VAP

Crop group 7 3 4/3/0.6 0.11 0.1 0.05

Crop group 6 3 4/3/0.6 0.11 0.1 0.05

Soybean 3 4/3/0.6 0.11 0.1 0.05

MAXIM QUATTRO

Field corn 1.18 2/2/0.4 0.07 0.06 0.03

Popcorn 3.07 6/4/0.9 0.17 0.15 0.08

Sweet corn 2.05 4/3/0.6 0.11 0.1 0.05

QUARTET

Cotton 4 29/20/5 0.88 0.75 0.4

TRIO CST

Cotton 3.5 32/22/5 0.97 0.83 0.45

* Bold value indicates the RQ exceeds the chronic risk LOC of 1.0 for listed and non-listed species.

IV.1.3. Terrestrial Plants in Dry and Semi-aquatic Environments

TerrPLANT modeling yields no LOC exceedances at the maximum exposure scenario using the 

highest single application rate applied via air, ground, or seeds to terrestrial plants inhabiting dry 

and semi-aquatic areas adjacent to a treated site exposed to a combination of surface water runoff 
72

and spray drift; thus, all other exposure scenarios with lower application rates are not expected to 

exceed the plant LOC as well (Table IV.27). 

For spray drift alone using AgDRIFT, the RQ exceeded the LOC for risk to listed terrestrial plants 

exposed to off-site drift from ground applications at the maximum application rate (turf uses). The 

RQs did not exceed the LOC for risk to listed plants inhabiting areas at a distance of 10 feet or 

more from the edge of a treated turf site; the RQs also did not exceeded the LOC for all other uses 

receiving a downwind drift of azoxystrobin residues (Table IV.28).

Unlike T-REX, TerrPLANT and AgDRIFT differentiate between aerial and ground applications 

but turf use labels for azoxystrobin do not allow aerial applications, only EECs from ground 

applications were modeled for turf uses. All other uses were modeled for aerial and ground 

applications; however, because there were no LOC exceedances in previous risk assessments, 

only the maximum application scenario and aerial applications (the method resulting in the 

highest exposure potential) were calculated for any change in its risk conclusion for terrestrial 

plants. The potential risks to terrestrial plants are discussed further in Section IV.2.

Table IV.27. Risk Quotients for Terrestrial Plants1—Spray Drift and Run-off

Crop

App Rate

in lbs a.i./A

(method of app)

EEC (lb a.i./A) RQs

Dry

Areas

Semiaquatic

Areas

Dry Area Semi-aquatic Area

Non-listed 

RQ

Listed 

RQs

Non-listed 

RQ

Listed 

RQs

Turf 0.55 (ground) 0.011 0.0605 <0.1 <0.1 <0.1 0.12

All other Uses 0.4 (aerial) 0.024 0.06 <0.1 <0.1 <0.1 0.12

Rice 0.012 (seed trt) 0.00008 0.0008 <0.1 <0.1 <0.1 <0.1

trt - treatment 1 Based on most sensitive terrestrial plant tested – carrots; the EC25 and NOAEC values were 0.59 and 0.5 lb a.i./A 

respectively.

Table IV.28. AgDRIFT Assessment for Spray Drift Only--Non-target Listed and Nonlisted Terrestrial Plant Species Inhabiting Areas Adjacent to a Treated Site a

No. of Applications and 

Application Rate

(lb a.i/.A)

Distance from 

Edge of Field

EEC

(lb a.i./A)

Non-listed Plant

RQ

Listed

Plant RQ

Spray 

Method

Terrestrial plants inhabiting dry areas

1 @ 0.55 0 feet 0.55 0.9 1.1* Ground 10 feet 0.1 0.2 0.2

1 @ 0.4 0 feet 0.2 0.3 0.4 Aerial a Based on carrot EC25 and NOAEC value of 0.59 and 0.5 lb a.i./A, respectively.

*Value in bold indicates the LOC for risk to plants is exceeded.

IV.2. Risk Description

The risk hypothesis in the Preliminary Problem Formulation written in support of the Registration 

Review stated that the use of azoxystrobin as a fungicide for terrestrial crop sites as a foliar spray 

with aerial and ground-boom equipment or through seed treatment has the potential to adversely 

affect survival, reproduction, and/or growth of non-target aquatic and terrestrial animals and 
73

plants. Based on the available ecotoxicity data and predicted environmental exposures, the 

hypothesis is confirmed for potential adverse effects to fish (and aquatic-phase amphibians), 

aquatic invertebrates, birds (and terrestrial-phase amphibians and reptiles), mammals, terrestrial 

dicot plants, and aquatic non-vascular plants based on the current uses for azoxystrobin and

additionally the presumption of risk to terrestrial invertebrates in the absence of data. Results of 

the risk estimation indicate terrestrial monocot plants and aquatic vascular plants (duckweed) were 

not likely to be adversely affected. The following sections discuss the potential risks of 

azoxystrobin to these taxonomic groups.

IV.2.1. Risks to Aquatic Organisms and Plants 

In the problem formulation, the conceptual model states spray drift and surface runoff/leaching to 

adjacent bodies of water from foliar sprays and surface runoff to adjacent bodies of water from 

seed treatments were predicted as the most likely sources of exposure of azoxystrobin to non-listed

aquatic organisms and plants. Risks to aquatic species (i.e., fish, invertebrates, and plants) were 

assessed based on modeled EECs and available toxicity data. The aquatic EECs were estimated 

using SWCC (Table III.4) for foliar applications and GENEEC/Rice for seed treatment (Table 

III.5). The RQ calculations for each taxonomic group are shown in Tables IV.4 thru IV.11 in 

Section IV.1. Detailed discussions of the potential risks and the magnitude to fish, aquatic 

invertebrates, aquatic plants, and aquatic nonvascular plants can be found below in the subsequent 

sections. 

In summary, AgDRIFT was used to assess risks to non-listed fish, aquatic invertebrates, aquatic 

plants, and aquatic nonvascular plants that inhabit water bodies adjacent or in close proximity to

azoxystrobin-treated sites and to assess the distance from the edge of an application site at which 

RQs for spray drift fall below the acute risk to non-listed species LOC of 0.5 (Table IV.29). The 

RQs were calculated by comparing the amount of deposition (“EEC”) at a specific distance from 

the edge of the field and the respective toxicity endpoints for each taxon. As the deposition distance 

increases, the magnitude of exposures to species outside a treated site decreases. 

This spray drift exposure analysis indicates that when aerial-based application methods are used 

(the method resulting in the highest exposure potential) at the maximum label rate of 0.4 lb a.i./A, 

exposure falls below the LOC for non-listed species beyond the edge of a treated field; thus, risks 

are not of concern. With ground-based applications at the maximum label rate of 0.55 lb a.i./A, 

there were no LOC exceedances from spray drift exposures for non-listed aquatic fauna and flora

inhabiting waterbodies adjacent to the edge of a treated site. Therefore, adverse effects to nonlisted aquatic species in waterbodies adjacent to treated site exposed to spray drift alone are not 

likely. This suggests surface water runoff with azoxystrobin residues contributes more to the risk 

potential than when exposed to off-site spray drift alone. 

Table IV.29. AgDRIFT Assessment for Non-Listed Aquatic Fauna and Flora Species

No. of Applications 

and Application 

Rate

(lb a.i./A)

Distance from 

Edge of Field

EEC in pond

(μg a.i./L)

RQ (EEC/LC50

or EC50)

RQ 

(EEC/ NOAEC)

Spray 

Method

Freshwater fish inhabiting pond a
74

1 @ 0.55 0 feet 1.9 <0.01 <0.1 Ground

1 @ 0.4 0 feet 2.8 <0.01 <0.1 Aerial

Freshwater Invertebrates inhabiting pond b

1 @ 0.55 0 feet 1.9 <0.01 <0.1 Ground

1 @ 0.4 0 feet 2.8 0.01 <0.1 Aerial

Estuarine/marine fish inhabiting pond c

1 @ 0.55 0 feet 1.9 <0.01 <0.1 Ground

1 @ 0.4 0 feet 2.8 <0.01 <0.1 Aerial

Estuarine/marine invertebrates inhabiting pond d

1 @ 0.55 0 feet 1.9 0.03 0.2 Ground

1 @ 0.4 0 feet 2.8 0.05 0.3 Aerial

Aquatic vascular plants inhabiting pond e

1 @ 0.55 0 feet 1.9 <0.1 <0.1 Ground

1 @ 0.4 0 feet 2.8 <0.1 <0.1 Aerial

Aquatic non-vascular plants inhabiting pond f

1 @ 0.55 0 feet 1.9 <0.1 <0.1 Ground

1 @ 0.4 0 feet 2.8 <0.1 0.1 Aerial a Based on trout LC50 of 470 μg a.i./L and fathead minnow NOAEC of 147 μg a.i./L. b Based on a daphnid EC50 of 260 μg a.i./L and NOAEC of 44 μg a.i./L. c Based on sheepshead minnow LC50 of 670 μg a.i./L and ACR-adjusted NOAEC of 210 μg a.i./L. d Based on mysid shrimp LC50 of 56 μg a.i./L and NOAEC of 9.5 μg a.i./L. e Based on duckweed EC50 of 3400 μg a.i./L and NOAEC of 800 μg a.i./L. f Based on marine diatom EC50 and NOAEC of 49 and 20 μg a.i./L, respectively. 

Risk to Fish

IV.2.1.1. Risk to Fish Exposed to Foliar Sprays of Azoxystrobin

Available acute toxicity data indicates that azoxystrobin is highly toxic to freshwater and 

estuarine/marine fish on an acute basis. The most sensitive endpoint derived from the available 

studies for freshwater species (rainbow trout) and the sheepshead minnow study for 

estuarine/marine species were compared to several SWCC for fish inhabiting water bodies 

adjacent to crops treated with azoxystrobin. Acute RQs (RQ range: 0.05 – 0.32 based on aerial 

application for turf and ground application for all other current uses)) for freshwater species of the 

exposure scenarios representative of the current uses modeled except for wheat and peanuts all 

exceeded the acute risk to listed species and restricted use LOCs of 0.05 and 0.1, respectively, 

following foliar applications. The RQs for wheat and peanuts are 0.02 and 0.04, respectively, 

which are below the acute risk to listed species LOC of 0.05. None of the RQ values for fish 

exceeded the acute risk to non-listed species LOC of 0.5.

The freshwater fish acute RQs exceed the acute restricted use LOC of 0.1 and acute risk to listed 

species LOC of 0.05 following azoxystrobin applications to leafy vegetables and potatoes and 

exceed the acute risk to listed species LOC following foliar applications on corn, almond, 

sugarcane, and turf. Estuarine/marine have RQ values(LOC exceedances)similar to the freshwater 

species; however, acute RQs do not exceed the acute restricted use LOC for use on potatoes.

Azoxystrobin was highly toxic to rainbow trout and moderately toxic to the bluegill sunfish with 

LC50 values ranging from 470 to 1100 μg a.i./L. To assess the extent of freshwater species affected 

when exposed to azoxystrobin, a comparison of the least sensitive species (sunfish LC50 of 1100
75

μg a.i./L) and the highest SWCC EEC using the FL pepper scenario after three application cycles 

per year (150 μg a.i./L), the RQ is 0.14 and exceeds the acute risk to listed species LOC of 0.05. 

Thus it is anticipated that freshwater species would be adversely affected when exposed to 

azoxystrobin as a result of foliar sprays; however, more data on freshwater fish species are needed 

to determine the distribution of fish sensitivities to azoxystrobin. With the acute estuarine/marine 

fish toxicity data limited to a single species, the range of estuarine/marine species adversely 

affected to azoxystrobin applications could not be assessed. 

The chronic NOAEC for freshwater fish is 147 μg a.i./L based on reductions of growth. The 

NOAEC for estuarine/marine fish is 210 μg a.i./L is based on an ACR-derived value calculated 

using rainbow trout acute and fathead minnow chronic data. Chronic RQs for both freshwater and 

estuarine/marine fish generally resulted in no exceedance of the chronic risk LOC with the 

exception of freshwater fish for use of azoxystrobin on peppers after three crop cycles per year for 

which the chronic RQ of 1.0 is at the chronic risk LOC of 1.0. 

Risk quotients for freshwater fish indicate that aquatic-phase amphibians are also anticipated to be 

subject to adverse effects from acute exposures to the TGAI as a result of runoff and spray drift to 

adjacent water bodies following azoxystrobin foliar treatments but not following seed treatments. 

Of all the exposure scenarios modeled, the chronic risk LOC was only exceeded for freshwater 

fish inhabiting water bodies adjacent to peppers after a total of three crop cycles per year; thus, 

aquatic-phase amphibians are also anticipated to be at risk when chronically exposed to 

azoxystrobin applied in pepper fields throughout the year. However, none of the other current uses 

exceed the chronic risk LOC including use on pepper where there is a single crop cycle per year. 

IV.2.1.2. Risks to Fish Exposed to Azoxystrobin-treated Seeds

The freshwater and estuarine/marine acute and chronic endpoints were compared to several 

exposure scenarios using GENEEC and Rice models for fish inhabiting water adjacent to use sites 

where azoxystrobin-treated seeds are planted. Acute and chronic RQs (acute RQs <0.01; chronic 

RQs <0.1) for azoxystrobin-treated seed uses are below the acute and chronic risk LOCs of 0.05 

and 1.0, respectively. 

IV.2.1.3. Formulated Product, Degradate, Non-Guideline 

Studies, Etc. 

Acute RQs for freshwater fish exposed to the formulated product and degradate are not calculated. 

Toxicity of a co-formulated product (containing azoxystrobin and chlorothalonil) to the rainbow 

trout indicates the product is more toxic than the azoxystrobin TGAI alone to freshwater fish on 

an acute exposure basis. 

One degradate study with freshwater fish species observed no significant mortality at the limit 

dose of 150 mg/L; therefore, the compound 2 degradate is at least >300 times less toxic than the 

TGAI. 

Acute estuarine/marine fish toxicity data with the TEP and degradate are not available. Chronic 

fish toxicity data (both freshwater and estuarine/marine) with the degradates are not available. 
76

Chronic toxicity data with the TEP are typically not needed as the constituents in the formulation 

would not stay intact but likely dissipate at considerably different rates over time.

IV.2.1.4 Risk Summary for Fish 

Based on the available information, this ecological risk assessment for freshwater and 

estuarine/marine fish suggests potential for adverse effects on survival to freshwater and 

estuarine/marine fish and aquatic-phase amphibians from acute exposure to azoxystrobin as a 

result of foliar applications. There are no concerns on the freshwater fish species from acute 

exposure to the degradate; however, there is a concern from exposure to the co-formulated product 

Renown®, which is more toxic to freshwater fish due to the presence of the other active ingredient,

chlorothalonil. Formulated product and degradate data were not available for estuarine/marine fish.

For seed treatments, the likelihood of adverse effects to fish from exposure to run-off is considered 

low. 

The chronic RQ for adverse effects on reproduction and growth to freshwater fish and aquaticphase amphibians inhabiting in water bodies adjacent to pepper fields after a total treatment of 

three crop cycles equaled the chronic risk LOC; chronic RQs for all other exposure scenarios 

modeled did not exceed the chronic risk LOC, including a single treatment of pepper sites. For 

estuarine/marine species, chronic exposure is expected to be minimal. 

Risk to Aquatic Invertebrates

IV.2.1.5. Risk to Invertebrates Exposed to Foliar Sprays of 

Azoxystrobin

Registrant-submitted studies suggest that azoxystrobin is very highly toxic to estuarine/marine 

invertebrates and highly toxic to freshwater invertebrates. The most sensitive endpoint derived 

from the daphnid study for freshwater invertebrates and from the available studies for 

estuarine/marine invertebrates (mysid shrimp) were compared to SWCC exposure scenarios for 

invertebrates inhabiting adjacent to crops treated with azoxystrobin.

With estuarine/marine invertebrates more acutely sensitive than freshwater invertebrates, the acute 

RQs for estuarine/marine invertebrates exceed the acute risk non-listed species, acute restricted 

use, and acute risk to listed species LOCs following multiple azoxystrobin applications, while the 

LOCs for acute restricted use and acute risk to listed species are only exceeded for freshwater 

invertebrates. The highest acute RQ of 2.7 for estuarine/marine invertebrates from foliar

applications using the highest EEC is 54 times higher than the acute risk to non-listed species LOC 

threshold of 0.05. Only acute RQs for freshwater invertebrates inhabiting waters adjacent to wheat 

use sites did not exceed the acute risk LOCs. In addition, unlike other aquatic taxonomic groups, 

estuarine/marine invertebrates are the only taxonomic group with RQs exceeding the acute risk

LOC for azoxystrobin treatment in wheat use sites. 

Of the acute studies submitted for estuarine/marine invertebrates, the crustacean (mysid) was more

sensitive than the mollusk (Pacific oyster); toxicity values ranged from 56 – 1300 μg a.i./L. To 

assess the extent of estuarine/marine invertebrate species affected when exposed to azoxystrobin, 
77

a comparison of the least sensitive species (oyster EC50 of 1300 μg a.i./L) and the most 

conservative SWCC EEC using the pepper use scenario with three application cycles per year (150

μg a.i./L), the RQ is 0.1 and exceeds the acute restricted use and acute risk to listed species LOCs. 

Thus it is anticipated that a range of estuarine/marine invertebrates would both be adversely 

affected when exposed to azoxystrobin, however, more data on estuarine/marine invertebrates are 

needed to determine the distribution of invertebrate sensitivity to azoxystrobin. With the acute 

freshwater invertebrate toxicity data limited to a single species, the range of freshwater 

invertebrates’ sensitivity is unknown.

Chronic RQ estimations for estuarine/marine invertebrates result in an exceedance of the chronic 

risk LOC for all exposure scenarios, while for freshwater invertebrates the exceedances are limited 

to potatoes and most leafy vegetable use scenarios except for lettuce after a single application crop 

cycle. The highest chronic RQ of 16 based on the most conservative scenario for estuarine/marine

species was 16; whereas, the LOC threshold is 1.0 for chronic risk to non-listed and listed 

freshwater invertebrates. 

IV.2.1.6. Risk to Invertebrates Exposed to Azoxystrobin-treated 

Seeds

The daphnid and shrimp acute and chronic endpoints were compared to exposure scenarios for 

azoxystrobin-treated seeds with GENEEC and Rice models. Using the daphnid data, the highest 

acute RQ of 0.02 and chronic RQ of 0.14 for freshwater invertebrates inhabiting waters adjacent 

to use sites with azoxystrobin-treated seeds are below the acute and chronic risk LOCs of 0.05 and 

1.0, respectively. For estuarine/marine invertebrates using the shrimp data, the acute RQ of 0.07-

0.1 for rice seed use sites exceed the acute restricted use, and acute risk to listed species LOCs; 

while the acute RQs for all other use sites with azoxystrobin-treated seeds do not exceed the acute 

risk LOCs.

IV.2.1.7. Formulated Product, Transformation Products, NonGuideline Studies, Etc. 

RQs for freshwater invertebrates exposed to the degradates are not quantitatively calculated. The 

degradate data indicate the degradates are much less toxic than the TGAI to freshwater 

invertebrates on an acute exposure basis. Three degradate studies with freshwater invertebrate 

species resulted in no significant mortality at doses up to 190 mg/L, which indicate the degradates

are at least 700 times less toxic than the TGAI. 

Toxicity data with the formulated products were not available.

IV.2.1.8. Risk Summary for Aquatic Invertebrates 

Based on the available information, this ecological risk assessment for freshwater and 

estuarine/marine invertebrates suggests a potential for adverse effects on survival, reproduction 

and growth to freshwater and estuarine/marine invertebrates from acute and chronic exposure to 

azoxystrobin as a result of the current label uses. 
78

The likelihood of adverse effect from acute exposure to the degradates is considered low.

For seed treatments, there is a concern for estuarine/marine invertebrates where treated rice seed 

is planted. The likelihood of adverse effects to estuarine/marine invertebrates due to run-off from

other seed treatment sites and for freshwater invertebrates in all seed treatment sites is considered 

low.

Risk to Aquatic Vascular and Non-Vascular Plants

IV.2.1.9. Risk to Aquatic Plants Exposed to Foliar Sprays of 

Azoxystrobin

To evaluate the potential exposure of foliar applications to non-listed aquatic plants, the EC50

derived from the duckweed study for aquatic vascular plants and from the most sensitive aquatic 

non-vascular plants (freshwater diatom) were compared to SWCC exposure scenarios for plants 

inhabiting bodies of water adjacent to crops treated with azoxystrobin. The RQ values for nonlisted aquatic non-vascular plants using the freshwater diatom exceed the LOC of 1 following 

treatments on potatoes (highest RQ = 1.1) and leafy vegetables (highest RQ = 3.1). The RQs for

non-listed aquatic vascular plants using the duckweed were all <0.1 and were below the LOC. 

The most sensitive NOAEC derived from the duckweed study for aquatic vascular plants and from 

available studies for aquatic non-vascular plants (freshwater diatom) were compared to SWCC

exposure scenarios for plants inhabiting bodies of water adjacent to sites treated with azoxystrobin. 

The RQ values for listed aquatic non-vascular plants using the freshwater diatom all exceed the 

LOC of 1 for risk to listed aquatic plants by factors as high as 7.5 following azoxystrobin

applications. Listed plant RQs for aquatic vascular plants using the duckweed were all <0.1 and 

are below the LOC for risk to listed aquatic vascular plants. 

Of the acceptable studies submitted for aquatic non-vascular plants, the freshwater blue-green alga

was the least sensitive (EC50 = 1300 μg a.i./L with its corresponding NOAEC of 900 μg a.i./L); 

overall sensitivities range between 50 to 1300 μg a.i./L for the non-listed plant endpoint and 

between 20 to 900 μg a.i./L for the listed plant endpoint. To assess the range of non-listed and 

listed aquatic non-vascular species affected when exposed to azoxystrobin, a comparison of the 

least sensitive species (blue-green algae EC50 and NOAEC of 1300 and 900 μg a.i./L, respectively) 

and the most conservative SWCC EEC using the pepper use scenario with three application crop 

cycles per year (150 μg a.i./L) results in an RQ of 0.1 and 0.2, which is below the LOC for risk to 

non-listed and listed plants, respectively. Thus it is anticipated that not all aquatic nonvascular 

plants would be adversely affected when exposed to azoxystrobin. Aquatic vascular plants data 

were limited to the duckweed study; therefore, the range of aquatic vascular plants adversely 

affected to azoxystrobin applications could not be assessed. 

IV.2.1.10. Risk to Aquatic Plants Exposed to Azoxystrobin-treated 

Seeds

The toxicity endpoints for evaluating risk to non-listed and listed aquatic vascular and nonvascular 

plant’s non-listed and listed were compared to several exposure scenarios using GENEEC and 
79

Rice models for aquatic flora inhabiting surface water adjacent to sites where azoxystrobin-treated 

seeds are planted. Non-listed and listed RQs are less than 0.1 and are below the LOC of 1.0 for 

risk to non-listed and listed species of aquatic plants. 

IV.2.1.11. Formulated Product, Transformation Products, NonGuideline Studies, Etc. 

The RQs for freshwater green algae exposed to the formulated product are not calculated. Toxicity 

of the TEP Renown® Fungicide (containing azoxystrobin and chlorothalonil) to freshwater green 

algae indicates the product is more toxic than the TGAI to aquatic nonvascular plants due to the 

presence of chlorothalonil, the other active ingredient. Effects of the degradates to freshwater 

diatom, the most sensitive aquatic plant, or to the other nonvascular plant species are not available.

IV.2.1.12. Risk Summary for Aquatic Plants 

This ecological risk assessment for aquatic plants suggests potential for adverse effects on survival 

and growth of non-listed and listed non-vascular plants from exposure to azoxystrobin as a result 

of current uses label uses. The likelihood of adverse effects on vascular aquatic plants from 

exposure to azoxystrobin is considered low. Similarly, the likelihood of adverse effects on 

nonvascular or vascular aquatic plants from exposure to runoff as a result of azoxystrobin-treated 

seeds planted in areas adjacent to surface waters is considered low.

IV.2.2. Risks to Terrestrial Animals and Plants 

In the conceptual model, dietary ingestion of azoxystrobin residues on vegetative matter and 

insects including azoxystrobin-treated seeds on treated areas are considered the most likely sources 

of azoxystrobin exposure to terrestrial animals. Spray drift, runoff and wind erosion of soil 

particles with resulting residues on upland and/or wetland foliage and soil are the most likely 

sources of azoxystrobin exposure to non-target terrestrial plants. Risks to terrestrial species (i.e., 

birds, mammals, terrestrial invertebrates, and plants) are assessed based on modeled EECs and 

available toxicity data. 

To characterize the extent to which RQs for terrestrial wildlife in adjacent habitats are affected by 

distance from an azoxystrobin-treated field, AgDRIFT was used (Table IV.30). The spray drift 

distances were estimated using LOCs divided by risk quotients (calculated based on a single 

application) as the “Fraction of Applied” in AgDRIFT to estimate the spray drift distance for 

terrestrial vertebrates. As the spray drift distance increases, the chance for exposure to non-listed

species outside a treated site increases. Since azoxystrobin is practically non-toxic to bees on an 

acute exposure basis and resulting toxicity values are non-definitive, RQ values for terrestrial 

invertebrates were not calculated; thus, terrestrial invertebrates are not included in the spray drift 

exposure analysis. In addition, the analysis was not performed for birds or mammals from acute 

exposures since azoxystrobin is practically non-toxic to these taxa as well and again toxicity 

estimates were non-definitive and RQs were not calculated. Also, since chronic RQ values are 

below the chronic risk LOC, these were not further analyzed.
80

This spray drift exposure analysis indicates that when aerial-based application methods are used 

(which produces the highest exposures) at the maximum label rate of 0.4 lb a.i./A, there were no

chronic risk LOC exceedances for non-listed mammals beyond the edge of the treated field (0

feet). With ground-based applications at the maximum label rate of 0.55 lb a.i./A, the RQ is

below the chronic risk to non-listed species LOC at a distance of 3 feet off-site from the edge of 

a treated field. Therefore, the likelihood of adverse effects to non-listed terrestrial species in 

untreated areas adjacent to a treated site exposed to off-site spray drift alone is considered low.

Inhalation of Azoxystrobin in Treated Fields

The Screening Tool for Inhalation Risk (STIR v.1.0) was used to calculate an upper-bound 

estimate of wildlife inhalation exposure using azoxystrobin vapor pressure and molecular weight 

as well as the maximum application rate. STIR incorporates results from several toxicity studies 

including the rat acute oral (LD50 >5000 mg/kg-bw) and inhalation toxicity (female LC50 = 0.698 

mg/L) as well as the most sensitive acute oral avian toxicity endpoint (mallard LD50 >2000 mg/kgbw). Based on the results of the STIR model (Appendix 2), exposure through inhalation of spray 

drift or the vapor phase of azoxystrobin is not a potential pathway of concern for either avian or 

mammalian species on an acute exposure basis.

 

Table IV.30. AgDRIFT (Terrestrial) Assessment for Non-Listed Terrestrial Vertebrate 

Species Exposed to Ground Spray at 0.55 lb a.i./A and to Aerial Spray at 0.4 lb a.i./A of 

Azoxystrobin

Taxa Type of Endpoint Highest Risk 

Quotient

Non-listed

Species

LOC

Fraction of 

Applied (Nonlisted LOC/RQ)

Distance from 

Edge of Field 

Where RQ Falls 

below LOC

Aerial Application of 0.4 lb a.i./A

Birds

Acute RQs not calculated due to non-definitive values

Chronic No LOC exceedances

Mammals

Acute RQs not calculated due to non-definitive values

Chronic 2.8 1 0.36 0 feet

Ground application of 0.55 lb a.i./A

Birds

Acute RQs not calculated due to non-definitive values

Chronic No LOC exceedances

Mammals

Acute RQs not calculated due to non-definitive values

Chronic 3.8 1 0.26 3 feet
81

The analysis of the inhalation route in STIR does not consider that aggregation with other exposure 

pathways such as dietary, dermal, or drinking water may contribute to a total exposure that has a 

potential for effects to non-target animals. However, the Agency does consider the relative 

importance of other routes of exposure in situations where data indicate that pesticide exposures 

through other routes may be potentially significant contributors to wildlife risk (USEPA 2004). 

The risk characterization section (Section IV.2), discusses the impact of consideration of other 

routes of exposure that have been identified as potentially important and the degree of certainty 

associated with screening-level risk assessment conclusions. Detailed information about STIR 

v.1.0, as well as the tool, can be found on EPA’s website (http://www2.epa.gov/pesticide-scienceand-assessing-pesticide-risks/models-pesticide-risk-assessment#terrestrial). 

Ingestion of Azoxystrobin through Drinking Water Alone

The Screening Imbibition Program (SIP v.1.0, released June 15, 2010) was used to calculate an 

upper-bound estimate of wildlife drinking water exposure using azoxystrobin solubility (i.e., 6.7 

mg/L at 20oC), and compared to the most sensitive acute and chronic avian and mammalian 

toxicity endpoints. Based on results of the screening model SIP for azoxystrobin, drinking water 

exposure alone is NOT a concern for birds and mammals (Appendix 3). For a sample of the output 

generated by SIP v.1.0, please see Appendix 3. Detailed information about the SIP v.1.0, as well 

as the tool, can be found on the EPA’s website at http://www2.epa.gov/pesticide-science-andassessing-pesticide-risks/models-pesticide-risk-assessment#terrestrial.

Exposure through Ingestion of Aquatic Organisms Containing Azoxystrobin Residues

Azoxystrobin has a low octanol-water partitioning coefficient (Kow = 316), which indicates that 

the likelihood the compound will accumulate in aquatic food chains is low. As of a result, an 

assessment using the Agency’s KABAM model (Kow (based) Aquatic BioAccumulation Model;

v1.0) for piscivorous birds and mammals was unnecessary. 

Risk to Birds

IV.2.2.1 Risk to Birds Exposed to Foliar Sprays of Azoxystrobin

Available avian acute toxicity data indicate that azoxystrobin is practically non-toxic to birds on 

both an acute oral and subacute dietary exposure basis (e.g., LD50>2000 mg a.i./kg bw and 

LC50>5200 mg a.i./kg diet). Due to non-definitive values, the likelihood of adverse effects birds

following acute exposure is anticipated to be low. 

Chronic avian RQs for broadcast spray of azoxystrobin were below the chronic risk LOC of 1, 

with a calculated maximum RQ of 0.2. Chronic avian RQs for seed treatment were below the 

chronic risk LOC of 1, the highest RQ was 0.2.

No mortalities were observed in the acute studies with birds, yet sub-lethal effects were observed 

in the reproduction studies at 3000 mg a.i./kg diet and higher. 

IV.2.2.2. Risk to Birds Exposed to Azoxystrobin-treated Seeds
82

For azoxystrobin-treated seeds, depending on which formulated product was used, the RQs exceed 

the chronic risk LOC for birds of all body weight classes foraging on azoxystrobin-treated popcorn, 

sweet corn and sunflower seeds. The chronic risk LOC is not exceeded for birds for field corn or 

any of the other seed treatments evaluated.

IV.2.2.3 Risk Summary for Birds

There is a potential for adverse effects on reproduction and growth to birds from chronic 

consumption of azoxystrobin-treated seeds in cornfields grown for popcorn and sweet corn and in 

sunflower fields as a result of current seed treatment rates. The adverse effects discussed above 

would be observed for those birds that remain in a treated site and feed exclusively on 

azoxystrobin-treated seeds. However, the likelihood of adverse effects to birds from acute 

exposure to azoxystrobin-treated seeds is considered low. 

No risk concerns are identified for birds exposed to azoxystrobin residues on food resources as a 

result of foliar applications.

The Screening Imbibition Program model (SIP) and the Screening Tool for Inhalation Risk 

model (STIR) indicate low concern for birds and mammals exposed to azoxystrobin through 

drinking water and inhalation.

Risks to Mammals

IV.2.2.4. Risk to Mammals Exposed to Foliar Sprays of 

Azoxystrobin

Available mammalian acute toxicity data indicate that azoxystrobin is practically non-toxic to 

mammals on an acute oral exposure basis. Due to non-definitive values, the likelihood of adverse 

effects to mammals from acute exposure is anticipated to be low. 

Based on the most sensitive mammalian 2-generation NOAEL and upper bound T-REX EECs, the 

dose-based RQs of 1-8 exceed the chronic risk LOC for 15 g, 35 g and 1000 g mammals foraging 

on short grass, tall grass, broadleaves and arthropods following azoxystrobin applications at the 

maximum label rate to turf. Thus, these exceedances indicate mammals there is a potential for 

adverse effects on reproduction and growth from chronic exposure to azoxystrobin as a result of 

the labeled uses of the fungicide when using a reviewer-calculated foliar dissipation half-life of 

14.9 days and the maximum exposure use scenario. Although a shorter foliar dissipation half-life 

did not reduce RQ values below the chronic risk LOC, reducing the number of applications from 

9 applications to 2 applications or less would reduce the RQ to below the chronic risk LOC. In 

addition, none of the dietary-based RQs exceeded the chronic risk LOC for mammals of all body 

weight sizes foraging on any of the selected food items.

IV.2.2.5. Risk to Mammals Exposed to Azoxystrobin-treated 

Seeds
83

For azoxystrobin-treated seeds depending on which formulated product is used, the dose-based

RQs exceed the chronic risk LOC for mammals of all body weight classes foraging exclusively on 

azoxystrobin-treated corn and sunflower seeds; for 15g and 35g mammals foraging on 

azoxystrobin-treated head/stem brassica and sorghum seeds; and for 15g mammals foraging on 

azoxystrobin-treated cotton seeds. The chronic risk LOC is not exceeded for mammals foraging 

on azoxystrobin-treated soybean, rice, and legume vegetable seed treatments.

IV.2.2.6. Risk Summary for Mammals

For mammals, there is a potential for adverse effects from chronic exposure to azoxystrobin as a 

result of current uses label uses, including seed treatments. The likelihood of adverse effects would 

be increased for those mammals that remain in a treated site all the time and forage exclusively on 

food items containing azoxystrobin residues or azoxystrobin-treated seeds. The likelihood of 

adverse effects to mammals from acute exposure following foliar applications or consumption of 

azoxystrobin-treated seed is considered low.

Risk to Terrestrial Plants

IV.2.2.7. Risk to Terrestrial Plants Exposed to Foliar Sprays of 

Azoxystrobin

Based on the available data, monocots were not sensitive to azoxystrobin as none were inhibited 

25% or more in the seedling emergence or vegetative vigor tests. However, two dicots out of 6 

were inhibited more than 25% and tier II testing was conducted on these two dicots to establish 

measurement endpoints. The RQs from TerrPLANT for runoff to semi-aquatic areas result in the 

highest RQs compared to dry areas. This scenario represents a 10-acre area running off into a oneacre area. The highest RQ for a combination of runoff and spray drift from 10 acre into an one acre 

semi-aquatic area is 0.12, resulting from a rate of 0.06 lb a.i./A, which does not exceed the 

Agency’s LOC of 1 for risk to plants. 

For spray drift alone, AgDRIFT indicates that for aerial-based applications at the maximum single 

application rate of 0.4 lb a.i./A did not exceed terrestrial plant LOC beyond the actual treatment

site, while for ground-based applications at the maximum single application rate of 0.55 lb a.i./A, 

the highest RQ of 1.1 drops below the LOC for risk to listed terrestrial plants at approximately 5

feet from the treatment site. This suggests that effects to non-listed terrestrial plants would not

occur outside the site of application.

IV.2.2.8. Risk to Terrestrial Plants Exposed to Azoxystrobintreated Seeds

The phytotoxicity endpoints for non-listed and listed terrestrial plants were compared to several 

exposure scenarios using TerrPLANT for plants inhabiting sites adjacent to use sites with 

azoxystrobin-treated seeds. The RQs for non-listed plants and listed plants are <0.1 for terrestrial 

plants inhabiting in dry and semi-aquatic areas adjacent to use sites with azoxystrobin-treated seeds

and are below the LOC of 1.0. 
84

IV.2.2.9. Risk Summary for Terrestrial Plants

Overall, there is a potential for adverse effects on survival and growth of terrestrial dicots that

inhabit areas adjacent to azoxystrobin-treated fields and which are exposed through spray drift 

alone. The likelihood of adverse effects to terrestrial plants inhabiting both dry and semi-aquatic 

areas subjected to both surface water runoff and spray drift with azoxystrobin residues and to

monocots subjected to spray drift alone is considered low. 

In addition, the incident data reported 35 instances of adverse effects to terrestrial plants as a result 

of being treated directly or from exposure to spray drift. 18 incidents were as a result of registered 

uses, 8 from misuse, and the remaining were undetermined or not reported. 

Risk to Terrestrial Invertebrates

IV.2.2.10. Risk to Terrestrial Invertebrates Exposed to 

Azoxystrobin

The available terrestrial invertebrates toxicity data, based on tests with honey bees, suggest that 

the TGAI is practically non-toxic to adult bees on an acute contact and oral exposure basis. The 

LD50 value was >200 and >25 μg a.i./bee. Terrestrial invertebrates were not assessed quantitatively 

as the acute toxicity values for adult bees are non-definitive. No data are available for assessing 

the acute effects of azoxystrobin on larval bees and no data are available to assess the chronic 

effects of azoxystrobin on either adult or larval bees. Thus, additional data5 on the acute and 

chronic toxicity of azoxystrobin to larval bees and the chronic toxicity to adult bees are needed to 

address the uncertainty. 

IV.2.2.11. Risk Summary for Terrestrial Invertebrates

The complete set of toxicity data for honey bees is not available; until data set is complete, there 

is uncertainty regarding potential risk to terrestrial invertebrates.

V. FEDERALLY THREATENED AND ENDANGERED (LISTED) SPECIES 

CONCERNS

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the National 

Marine Fisheries Service (NMFS) (collectively, the Services), and the U.S. Department of 

Agriculture (USDA) released a summary of their joint Interim Approaches for assessing risks to 

 5 A complete set of toxicity data for honey bee adults and larvae have not been submitted for azoxystrobin and are now needed under EPA’s 

recent guidance on pollinator protection5

. Thus, the following honey bee studies have yet to be submitted for azoxystrobin: 

o Honey bee larval acute [single dose] toxicity study (following OECD 237)

o Honey bee adult 10-day chronic [repeat dose] (special study)

o Honey bee larval [repeat dose] study (special study)

o Field testing for pollinators (OCSPP 850.3040, Tier III)

o Field trial of residues in pollen and nectar (special study, Tier II)

o Semi-field testing for pollinators (special study, Tier II). 

The need for higher Tier semi-field and full field pollinator studies for azoxystrobin will be determined after review of the Tier I studies.
85

listed species from pesticides. The Interim Approaches were developed jointly by the agencies in 

response to the National Academy of Sciences’ (NAS) recommendations and reflect a common 

approach to risk assessment shared by the agencies as a way of addressing scientific differences 

between the EPA and the Services. The NAS report outlines recommendations on specific 

scientific and technical issues related to the development of pesticide risk assessments that EPA 

and the Services must conduct in connection with their obligations under the Endangered Species 

Act (ESA) and FIFRA. 

The joint Interim Approaches were released prior to a stakeholder workshop held on November 

15, 2013. In addition, the EPA presented the joint Interim Approaches at the December 2013 

Pesticide Program Dialogue Committee (PPDC) and State-FIFRA Issues Research and Evaluation 

Group (SFIREG) meetings, and held a stakeholder workshop in April 2014, allowing additional 

opportunities for stakeholders to comment on the Interim Approaches. As part of a phased, 

iterative process for developing the Interim Approaches, the agencies will also consider public 

comments on the Interim Approaches in connection with the development of upcoming 

Registration Review decisions. The details of the joint Interim Approaches are contained in the 

white paper “Interim Approaches for National-Level Pesticide Endangered Species Act 

Assessments Based on the Recommendations of the National Academy of Sciences April 2013 

Report,” dated November 1, 2013. 

Given that the agencies are continuing to develop and work toward implementation of the Interim 

Approaches to assess the potential risks of pesticides to listed species and their designated critical 

habitat, this preliminary risk assessment for azoxystrobin does not contain a complete ESA 

analysis that includes effects determinations for specific listed species or designated critical 

habitat. Although EPA has not yet completed effects determinations for specific species or 

habitats, for this preliminary assessment EPA conducted a screening-level assessment for all taxa 

of non-target wildlife and plants that assumes for the sake of the assessment that listed species and 

designated critical habitats may be present in the vicinity of the application of azoxystrobin. This 

screening level assessment will allow EPA to focus its future evaluations on the types of species 

where the potential for effects exists once the scientific methods being developed by the agencies 

have been fully vetted. This screening-level risk assessment for azoxystrobin indicates potential 

risks of direct effects to listed terrestrial plants. Listed species of plant-dependent taxa may also 

be affected through indirect effects because of the potential for direct effects on listed and nonlisted species upon which such species may rely. Potential direct effects on listed terrestrial plants 

from the use of azoxystrobin may be associated with modification of Primary Constituent Elements 

(PCEs) of designated critical habitats, where such designations have been made. Once the agencies 

have fully developed and implemented the scientific methods necessary to complete risk 

assessments for endangered and threatened (listed) species and their designated critical habitats, 

these methods will be applied to subsequent analyses for azoxystrobin as part of completing this 

registration review. 

V.1. Endocrine Disruptor Screening Program

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 
86

reproductive, and general or systemic toxicity. These studies include endpoints, which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, and 

sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and chronic 

studies that assess growth, developmental and reproductive effects in different taxonomic groups. 

As part of registration review for azoxystrobin, EPA reviewed these data and selected the most 

sensitive endpoints for relevant risk assessment scenarios from the existing hazard database. 

However, as required by FFDCA section 408(p), azoxystrobin is subject to the endocrine screening 

part of the Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide active 

and other ingredients) may have an effect in humans or wildlife similar to an effect produced by a 

“naturally occurring estrogen, or other such endocrine effects as the Administrator may designate.” 

The EDSP employs a two-tiered approach to making the statutorily required determinations. Tier 

1 consists of a battery of 11 screening assays to identify the potential of a chemical substance to 

interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal systems. Chemicals that go 

through Tier 1 screening and are found to have the potential to interact with E, A, or T hormonal 

systems will proceed to the next stage of the EDSP where EPA will determine which, if any, of 

the Tier 2 tests are necessary based on the available data. Tier 2 testing is designed to identify any 

adverse endocrine-related effects caused by the substance, and establish a dose-response 

relationship between the dose and the E, A, or T effect.

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between October 

2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 chemicals, 

which contains 58 pesticide active ingredients and 9 inert ingredients. A second list of chemicals 

identified for EDSP screening was published on June 14, 20136 and includes some pesticides 

scheduled for registration review and chemicals found in water. Neither of these lists should be 

construed as a list of known or likely endocrine disruptors. Azoxystrobin is not on List 1. For 

further information on the status of the EDSP, the policies and procedures, the lists of chemicals, 

future lists, the test guidelines and the Tier 1 screening battery, please visit our website.7

References

U.S. EPA 2009. Registration Review – Preliminary Problem Formulation for the Ecological Risk 

and Drinking Water Exposure Assessments for Azoxystrobin. Dated October 21, 2009. 

D365654.

 6 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals. 7 http://www2.epa.gov/endocrine-disruption/endocrine-disruptor-screening-program-edsp-overview
87

U.S. EPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs. January 23, 2004. Office of Pesticide Programs. Office of Prevention, 

Pesticides, and Toxic Substances. Washington, D.C. 

Guidelines for Ecological Risk Assessment, United States Environmental Protection Agency. 

EPA/630/R-95/002F. April 1998.

Mullin, CA, et al. “High Levels of Miticides and Agrochemicals in North American Apiaries: 

Implications for Honey Bee Health.” PLoS ONE 5.3 (2010): e9754. Web. 

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0009754.doi:10.1

371/journal.pone.0009754

Pettis, J.S., E. M. Lichtenberg, M. Andree, J. Stitzinger, R. Rose, and D. vanEngelsdorp. 2013. 

Crop Pollination Exposes Honey Bees to Pesticides which Alters their Susceptibility to the Gut 

Pathogen Nosema ceranae. PLoS One 8(7): e70182. Doi:10.1371/journal.pone.0070182. 

Stoner, K.A., and B.D. Eitzer. “Using a Hazard Quotient to Evaluate Pesticide Residues Detected 

in Pollen Trapped from Honey Bees (Apis mellifera) in Connecticut” PLoS ONE 8.1 (2013): 

e77550. doi: 10.1371/journal.pone.0077550.

Rennich, K., et al. “2011-2012 National Honey Bee Pests and Diseases Survey Report.” USDA 

Animal Plant and Health Inspection (2012) Available at 

<http://www.aphis.usda.gov/plant_health/plant_pest_info/honey_bees/downloads/2011_Nat

ional_Survey_Report.pdf>.

USEPA. 2013. Pesticides: Science and Policy. Terrestrial Models, T-REX Version 1.5.2. 

http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/models-pesticiderisk-assessment#terrestrial

Fletcher et al. (1994). Literature review and evaluation of the EPA food-chain (Kenaga) 

nomogram in instruments for estimating pesticide residues on plants. Envir. Tox. And 

Chem. 9:1383-1391.

Hoerger and Kenaga, 1972. Pesticides residues on plants: Correlation of representative data as 

basis for estimation of their magnitude in the environment. Envir. Quality. Vol. 1, 

Academic Press, New York, pp. 9-28.
88

Appendix 1. Table 1. .Azoxystrobin and its degradation products in soil and water.

Common Name

Chemical Name

Structure Substrate (maximum % of applied 

radioactivity.

Azoxystrobin

methyl (E)-2-{2-[6-(2-

cyanophenoxy)pyrimidin-4-yloxy]-

phenyl}-3-methoxyacrylate

Parent Compound

Z isomer; Compound 9

methyl (Z)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]-phenyl}-3-

methoxyacrylate

Aqueous photolysis (15.0%)

Soil photolysis (9.0%)

Compound 2

(E)-2-{2-[6-(2-cyanophenoxy)-pyrimidin4-yloxy]phenyl}-3-methoxyacrylic acid

Aerobic soil metabolism (28%)

Anaerobic soil metabolism (68%)

Compound 3

methyl (E)-2-[2-(6-hydroxy-pyrimidin-4-

yloxy)phenyl]-3-methoxyacrylate

Aerobic soil metabolism (3.1%)

Anaerobic soil metabolism (0.6%)

Soil Photolysis (0.7%)

Compound 13

2-hydroxybenzonitrile

Aqueous photolysis (1.7%)

Soil photolysis (<3.5%)

Compound 19

methyl 2-{2-[6-(2-cyanophenoxy)-

pyrimidin-4-yloxy]phenyl}-oxoacetate

Soil photolysis (<6.0%)
89

Appendix 1. Table 1. .Azoxystrobin and its degradation products in soil and water.

Common Name

Chemical Name

Structure Substrate (maximum % of applied 

radioactivity.

Compound 21

Methyl {2-[6-(2-cyanophenoxy) 

pyrimidin-4-yloxy]phenyl}acetate

Aqueous photolysis (5.6%)

Compound 24

methyl 2-{2-[6-(2-cyanophenoxy)-

pyrimidin-4-yloxy]phenyl}glycolate

Aqueous photolysis (<2.6%)

Soil photolysis (<3.2%)

Compound 28

4-(2-cyanophenoxy)-6-hydroxypyrimidine

Aerobic soil metabolism (3.1%)

Anaerobic soil metabolism (4.2%)

Aqueous photolysis (8.9 %) 

Soil photolysis (<6.5%)

Compound 30

2-[6-(2-cyanophenoxy)pyrimidin-4-

yloxy]benzoic acid

Aerobic soil metabolism (2.8%)

Anaerobic soil metabolism (<2.8%)

Aqueous photolysis (2.4%) 

Soil photolysis (<5.0%)

Compound 36

methyl (E)-2-{2-[6-(2-carbamoylphenoxy)pyrimidin-4-yloxy]-phenyl}-3-

methoxyacrylic acid

Aerobic soil metabolism (2.8%)

Anaerobic soil metabolism (<2.8%)

Compound U13

methyl 3-[6-(cyanophenoxy)pyrimidin-4-

yloxy]- 2-methoxy - 3H-3 benzofuroate

Soil Photolysis (<5.2%)
90

Appendix 2: STIR

Input

Application and Chemical Information

Enter Chemical Name azoxystrobin

Enter Chemical Use all

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) ground

Enter Chemical Molecular Weight (g/mole) 403.4

Enter Chemical Vapor Pressure (mmHg) 8.20E-13

Enter Application Rate (lb a.i./acre) 0.55

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 2000

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 5000

Enter Lowest Rat Inhalation LC50 (mg/L) 0.698

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 1.78E-08

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 2.24E-09

Adjusted Inhalation LD50 1.56E+00

Ratio of Vapor Dose to Adjusted Inhalation LD50 1.44E-09 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 5.81E-02

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 3.73E-02 Exposure not Likely Significant

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 1.78E-08

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 2.81E-09

Adjusted Inhalation LD50 4.16E+01

Ratio of Vapor Dose to Adjusted Inhalation LD50 6.77E-11 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 7.31E-02

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 1.76E-03 Exposure not Likely Significant
91

Appendix 3: SIP

Table 1. Inputs

Parameter Value

Chemical name azoxy

Solubility (in water at 25oC; mg/L) 6.7

Mammalian LD50 (mg/kg-bw) 5000

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 15

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) 2000

Avian test species mallard duck

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 1200

Bobwhite quail NOAEC (mg/kg-diet)

NOAEC (mg/kg-diet) for other bird species

Body weight (g) of other avian species

NOAEC (mg/kg-diet) for 2nd other bird 

species

Body weight (g) of 2nd other avian species

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 1.1524 1.1524

Adjusted toxicity value (mg/kg-bw) 3845.8028 11.5374

Ratio of exposure to toxicity 0.0003 0.0999

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Table 3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 5.4270 5.4270

Adjusted toxicity value (mg/kg-bw) 1038.4508 59.5351

Ratio of exposure to acute toxicity 0.0052 0.0912

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for birds

Drinking water exposure 

alone is NOT a potential 

concern for birds

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. 

Therefore, when aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure through 

drinking water may contribute to a total exposure that has potential for effects to non-target animals.