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INTRODUCTION

This is the Environmental Protection Agency’s (EPA or the Agency) Final Work Plan (FWP) for 

the registration review of pymetrozine. This work plan addresses public comments received 

concerning the Preliminary Work Plan (PWP), which was posted in the pymetrozine registration 

review docket (EPA-HQ-OPP-2013-0368). Pymetrozine is a pyridine azomethine insecticide 

that is currently registered for use on ornamental plants, non-bearing fruit and nut trees in 

nurseries, Christmas trees, and a variety of agricultural crops. This group of insecticides exhibits 

a unique mode of action characterized as neural inhibition of feeding behavior in its target pests 

(i.e., insects in the order Homoptera, including aphids, whiteflies, and leafhoppers). Pymetrozine 

has residual activity in the plant and is intended to control pests that move onto the plant after 

spraying.

The Agency is implementing the registration review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered 

pesticide every 15 years to determine whether it continues to meet the FIFRA standard for 

registration. Changes in science, public policy, and pesticide use practices occur over time. The 

registration review program is intended to make sure that, as the ability to assess risk evolves and 

as policies and practices change, all registered pesticides continue to meet the statutory standard. 

The public phase of registration review begins when the initial docket is opened for each case. 

Information on this program is provided on the Agency’s website.

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The FWP begins with any updates since the PWP was issued. Next is a summary of substantive 

comments received during the public comment period for the PWP concerning anticipated data 

needs, expected risk assessments, or the estimated timeline identified in the PWP, and a 

summary of the Agency’s responses to those comments. This section is followed by registration 

review planned data needs, risk assessments expected to be conducted, and the projected

registration review timeline for pymetrozine. Lastly, there is a discussion of next steps.

UPDATES SINCE THE PWP WAS ISSUED

After further review and based on a weight-of-evidence approach, the Agency has concluded that 

the immunotoxicity study is not required at this time for the registration review of pymetrozine. 

Additionally, as a result of public comments received, Guidelines 835.2120, Hydrolysis and 

835.6100, Terrestrial Field Dissipation studies have also been removed. More details are 

provided in the following section.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60-day public comment period on the Pymetrozine Preliminary Work Plan, which 

opened on June 26, 2013 and closed on August 26, 2013, the Agency received two public 

comments. Comments were submitted by Syngenta Crop Protection, LLC (Syngenta) and the 

FIFRA Endangered Species Task Force (FESTF). The comments do not address the timeline 

described in the PWP, but they do address the planned ecological and endangered species risk 

assessments. The majority of Syngenta’s comments addressed the Agency’s review of 

 1 http://www.epa.gov/oppsrrd1/registration_review/
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previously-submitted environmental fate studies, citing additional information on degradates for 

use in the planned ecological risk assessment. EPA will review the additional fate information 

cited by Syngenta upon submission to the Agency. Syngenta also submitted a comment 

regarding the planned endangered species assessment, which is addressed in the

Environmental Fate and Effects Division's Response to Public Comments on Registration 

Review: Preliminary Problem Formulation for Pymetrozine. In the PWP, EPA also solicited 

comments on the specific topics of environmental justice, water quality concerns, and trade 

irritants, but no comments or information were received on those issues.

This section does not capture every comment made about the PWP nor all of the Agency’s 

responses. Summarized below are public comments that resulted in changes to the anticipated

registration review data needs, risk assessments, or timeline, or are of a broader regulatory 

nature. Public comments and EPA responses in their entirety are located in the docket, EPAHQ-OPP-2013-0368. Summarized public comments and Agency responses related to the 

anticipated ecological risk assessment or data needs are in the Environmental Fate and Effects 

Division's Response to Public Comments on Registration Review: Preliminary Problem 

Formulation for Pymetrozine.

Comments submitted by FESTF in EPA-HQ-OPP-2013-0368-0009

1. Comment: The FIFRA Endangered Species Task Force commented that Syngenta is a 

current member of FESTF and, as such, is entitled to the FESTF data on federally-listed 

threatened and endangered species. 

Response: The Agency thanks FESTF for their comment and will consider this information 

during registration review.

Comments submitted by Syngenta in EPA-HQ-OPP-2013-0368-0011

1. Comment: Syngenta cites additional information that was not considered in the EFED 

Problem Formulation regarding the storage stability of degradates detected in several 

terrestrial field dissipation studies. Syngenta believes that this information is sufficient to 

support the ecological risk assessment. 

Response: EPA reviewed the additional cited information and will consider it in the 

ecological risk assessment. While this information does not address all of uncertainties 

associated with the storage stability of pymetrozine degradates, requiring additional storage 

stability data is not expected to eliminate uncertainties. Therefore, Guideline 835.6100, 

Terrestrial Field Dissipation (storage stability data) has been removed from the list of data 

needs.

2. Comment: While results are not consistent among the three submitted hydrolysis studies, 

Syngenta believes that sufficient information exists regarding the degradation rate at pH 5. 

Response: EPA reexamined the previously submitted hydrolysis studies and recalculated 

half-life values at pH 5. While the inconsistencies remain regarding degradation rates, 

additional data is not expected to eliminate uncertainties. Therefore, Guideline 835.2120, 
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Hydrolysis has been removed from the list of data needs. In the absence of new data, the 

Agency will assume a hydrolysis half-life of 28 days at pH 5. 

PLANNED DATA NEEDS

Table 1 below summarizes the planned data needs for pymetrozine based on the Registration 

Review: Preliminary Problem Formulation for Pymetrozine, Pymetrozine. Human Health 

Assessment Scoping Document in Support of Registration, and the Environmental Fate and 

Effects Division’s Response to Public Comments on Registration Review: Preliminary Problem 

Formulation for Pymetrozine. The table has been updated since the PWP to reflect changes to 

the data needs, specifically the removal of the immunotoxicity, hydrolysis, and terrestrial field 

dissipation studies.

Table 1: Planned Data Needs for the Pymetrozine Registration Review

Guideline 

Number2 Study Title2

Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

835.4300 Aerobic Aquatic Metabolism TGAI 24

850.6100

Environmental Chemistry Methods and Associated 

Independent Laboratory Validation for soil and 

water

TGAI 12

850.2100 Avian oral toxicity (passerine species) TGAI 12

850.4100 Terrestrial plant toxicity, seedling emergence TEP 12

850.4150 Terrestrial plant toxicity, vegetative vigor TEP 12

NonGuideline Semi-field Toxicity Test with Honey Bee TGAI 24

TGAI = technical grade active ingredient; TEP = typical end-use product;

 2 On June 27, 2012, EPA announced certain revisions in harmonized guideline series 850 – Ecological Effects Tests 

– including renumbering and other designations or changes for some guideline studies. See “Final Test 

Guidelines; OCSPP 850 Series; Notice of Availability” 77 FR 38282, June 27, 2012. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0154-0028
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RISK ASSESSMENTS FOR REGISTRATION REVIEW

During registration review, the Agency will conduct a comprehensive ecological risk assessment, 

including an endangered species assessment, for all uses of pymetrozine. For human health,

EPA will conduct revised dietary, residential, and occupational risk assessments during

registration review. If toxicological endpoints or points of departure are revised based on the 

data that are required for registration review, they will be considered in the new assessments, as 

well as any changes to the standard operating procedures or default exposure assumptions.

Table 2 below summarizes the planned registration review risk assessments based on the EFED 

Problem Formulation and HED Scoping Document and the planned assessments have not 

changed from what was included in the PWP.

Table 2: Planned Risk Assessments for the Pymetrozine Registration Review

Type of Risk Assessment Conduct? Notes

Ecological and Environmental Fate

Comprehensive ecological 

(species to be assessed 

include terrestrial and 

aquatic organisms), 

including endangered 

species 

Y The registration review assessment will consider 

the 5 major degradates estimated to exhibit 

approximately equal toxicity to the parent 

pymetrozine (CGA 359009, CGA 215525, GS 

23199, CGA 249257, and CGA 300407).

Incidents Will check 

for updates

No incidents were reported. See page 24 of the 

Problem Formulation.

Human Health

Dietary

Food Y EPA will incorporate updated percent crop treated 

estimates in accordance with Agency policies 

regarding the use of anticipated residues for 

dietary risk assessment. The major degradate 

CGA 359009 is currently considered a residue of 

concern in drinking water. In the last dietary 

assessment, water was considered the key dietary 

risk driver. As drinking water will likely be the 

primary risk driver in the new dietary assessment, 

a revised drinking water assessment will be 

performed.

Drinking water Y

Occupational

Handlers (mixers, loaders, 

applicators)

Y The Agency will need to conduct an occupational 

assessment to update doses and endpoints, 

maximum rates for applications to ornamentals 

using handheld equipment, along with chemicalspecific dislodgeable foliar residue data (DFR), 

and updated transfer coefficients and activity data.

Post-application Y

Residential
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Handlers Y A residential assessment will be needed due to 

updated doses and endpoints, revisions to the 

HED Residential SOPs, and the available 

chemical-specific DFR data.

Post-application Y

Other

Aggregate Y Evaluates the combined risk from dietary and 

residential exposures.

Cumulative N/A Pymetrozine is not a member of a cumulative 

group.

Tolerances Y EPA expects to revise the tolerance expression.

Incidents Will check 

for updates

For a discussion of reported human incidents for 

pymetrozine, see page 10-11 of the Scoping 

Document and the Pymetrozine: Review of Human 

Incidents. Between 2007 and 2012, two moderate 

severity and two low-severity incidents were 

reported.

TIMELINE

EPA has created the following estimated timeline for the completion of the pymetrozine

registration review in Table 3 below. The projected timeline has not changed since the PWP.

Table 3: Projected Pymetrozine Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and 60-day Public Comment Period June 2013 – Completed

Close Public Comment August 2013 –

Completed

Case Development

Final Work Plan Dec. 2013 - Completed

Issue DCI 2014: Jan. - March

Data Submission 2016: Jan. - March

60-day Public Comment Period for Draft Risk Assessments[1] 2017: July – Sept.

Registration Review Decision

60-day Public Comment Period for Proposed Registration Review 

Decision

2018: Jan. - March

Registration Review Decision and Begin Post-Decision Follow-up 2019

Total (years) 6

 [1] The regulations governing Registration Review generally require the Agency to provide a public comment period 

of at least 30 calendar days for draft risk assessments; see 40 CFR Part 155.53(c). For conventional pesticides, the 

Agency plans to provide a 60 calendar day public comment period generally for draft risk assessments.
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NEXT STEPS

As noted previously, the Agency plans to require several environmental fate, ecological effects, 

and human health studies for pymetrozine through a Data Call-In Notice, expected to be issued 

in early 2014.