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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 diflubenzuron. This work plan addresses public comments received 

concerning the Preliminary Work Plan (PWP), which was posted in diflubenzuron’s registration 

review docket (EPA-HQ-OPP-2012-0714). Diflubenzuron is an acaricide/insecticide (insect 

growth regulator) registered for use against leaf-eating insect larvae (e.g., gypsy moths, mosquito 

larvae, rust mites). It also acts as an ovicide, killing insect eggs. Diflubenzuron does not affect 

adult insects that have finished molting. It is registered for use in agricultural (e.g., citrus, 

cotton, mushroom) and non-agricultural use sites (e.g., forest, ornamental plants, rangeland).

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 

diflubenzuron’s registration review planned data needs, risk assessments expected to be 

conducted, and the projected registration review timeline. Lastly, there is a discussion of next 

steps.

UPDATES SINCE THE PWP WAS ISSUED

There are no additional updates on diflubenzuron since the PWP.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

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

opened on September 26, 2012 and closed on November 26, 2012, the Agency received two

public comments. One comment was submitted by the diflubenzuron technical registrant 

Chemtura Corporation (Chemtura) and the other from the FIFRA Endangered Species Task 

Force (FESTF). The comments address the planned ecological and human health risk 

assessments and data requirements. 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 on the PWP nor all of the Agency’s 

responses. Summarized below are public comments of a broader regulatory nature. Public 

 1 http://www.epa.gov/oppsrrd1/registration_review/
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comments and EPA responses in their entirety are located in the docket, EPA-HQ-OPP-2012-

0714. Summarized public comments and Agency responses related to the anticipated ecological

risk assessment or data needs are in the Response to Chemtura 60-day Response to September 

26, 2012 Registration Review (PC Code 108201 DP408278).

Comments submitted by Chemtura Corporation in EPA-HQ-OPP-2012-0714-0010.

1. Comment: In response to Guideline (GLN) requirement 850.1735, freshwater invertebrate 

whole sediment, Chemtura commented that two sediment dwelling insect studies involving 

diflubenzuron were submitted to EPA (MRIDs 46369301 and 46369302). Chemtura will be 

providing additional information from the contact laboratory to address EPA comments 

(DERs for these two studies will be needed to provide complete response. DERs have been 

requested from EPA but not received to date).

 Response: The data evaluation records (DERs) and associated cover memos were sent to 

Chemtura in response to their comment.

2. Comment: Chemtura provided an update on the outstanding Reregistration Eligibility 

Decision (RED) DCI data requirements.

Response: The Agency will continue to work with the registrant to address these outstanding 

RED data requirements. 

Comments submitted by FIFRA Endangered Species Task Force in EPA-HQ-OPP-2012-

0714-0011.

3. Comment: The FIFRA Endangered Species Task Force (FESTF) submitted a comment that 

the Agency should ensure any company who is a technical registrant for diflubenzuron, but 

not a member of the FESTF or a company having met its data compensation obligations

provide a formal offer-to-pay to FESTF in conjunction with their support of the active 

ingredient.

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

it conducts the registration review and makes its registration review decision.

PLANNED DATA NEEDS

The table below summarizes the planned data needs for diflubenzuron based on the Registration 

Review: Problem Formulation for the Environmental Fate, Ecological Risk, Endangered

Species, and Drinking Water Exposure Assessments for Diflubenzuron and the Diflubenzuron: 

Human Health Risk Scoping Document in Support of Registration Review. The planned data 

needs have not changed from what was included in the PWP. 
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Planned Data Needs for Diflubenzuron’s Registration Review

Guideline 

Number Study Title Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

850.1735 Freshwater invertebrate – whole sediment TGAI 12

Non-GLN 

(Special 

Study)

Pollinator larval toxicity study TGAI 12

Non-GLN 

(Special 

Study)

Residues in pollen and nectar TGAI 36

Non-GLN 

(Special 

Study)

Pollinator chronic feeding study TGAI 12

The studies listed below were previously required through a generic data call-in (GDCI-108201-17757), 

issued in February 1997, and are still outstanding2. These studies are listed in this document as

background; they will NOT be included in the anticipated Registration Review DCI as they are already 

required through the earlier DCI.

860.1380 Storage stability Residue of 

Concern in review

860.1500 Crop field trials TEP in review

860.1900 Field rotational crops TEP

more 

information 

requested

860.1340b Residue analytical methods PAI in review

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

 2 See page 6 of the Diflubenzuron: Human Health Risk Scoping Document in Support of Registration Review for 

details on specific studies in review.
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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 diflubenzuron. For human health,

EPA will conduct revised residential risk assessment 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.

The table 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.

Planned Risk Assessments for Diflubenzuron’s 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 

Yes

Incidents Yes For a discussion of diflubenzuron’s reported 

ecological incidents, see page 17 of the Problem 

Formulation.

Human Health

Dietary

Food No Absent any new toxicity, residue chemistry, or 

exposure data; changes to the standard operating 

procedures; or default exposure assumptions that 

could impact the overall risk conclusion, an updated 

dietary (food and drinking water) assessment is not 

anticipated to be needed for registration review.

Drinking water No

Occupational

Handlers (mixers, loaders, 

applicators)

No Absent any new toxicity or exposure data; changes to 

the standard operating procedures; or default exposure 

assumptions that could impact the overall risk 

conclusion, an updated occupational assessment is not 

anticipated to be needed in registration review.

Post-application No

Residential

Handlers Yes

Post-application Yes

Other

Aggregate Yes Evaluates the combined risk from dietary and 

residential exposures.
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Type of Risk Assessment Conduct? Notes

Cumulative No Diflubenzuron is not assumed to have a common 

mechanism of toxicity with other substances.

Tolerances Yes Tolerance expression needs to be updated

Incidents No For a discussion of diflubenzuron’s reported human 

incidents, see page 12 of the Scoping Document.

TIMELINE

EPA has created the following estimated timeline for the completion of diflubenzuron’s

registration review. The projected timeline has not changed since the PWP.

Registration Review for Diflubenzuron – Projected Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and Public Comment Period 2012 – September

Close Public Comment 2012 – November 

Case Development

Final Work Plan 2013 – February

Issue DCI 2013 – Oct-Dec.

Data Submission 2016 – Oct-Dec. 

Open Public Comment Period for Draft Risk Assessments 2018 – April-June 

Close Public Comment Period 2018 – July-Sept.

Registration Review Decision

Open Public Comment Period for Proposed Registration Review 

Decision 

2018 – Oct-Dec.

Close Public Comment Period 2019 – Jan-March 

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

Total (years) 7

NEXT STEPS

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

effects studies for diflubenzuron through a data call-in, expected to be issued in 2013.