Docket Number EPA- HQ-OPP-2014-0771 

www.regulations.gov 

Dikegulac Sodium Preliminary Work Plan 

Registration Review: Initial Docket 

Case Number 3061 

Approved by: 

D ate: 

December 2014 

~QNOL.P~~~ 

Richard P. Keigwin,Jr. 

Director 

Pesticide Re-evaluation Division 
2

Dikegulac Sodium Preliminary Work Plan – Table of Contents 

OVERVIEW ................................................................................................................................... 3

ANTICIPATED DATA NEEDS ................................................................................................... 4

STATUTORY AND REGULATORY AUTHORITY .................................................................... 5

CHEMICAL FACTS ....................................................................................................................... 5

USE AND USAGE INFORMATION ............................................................................................ 6

RECENT ACTIONS ...................................................................................................................... 7

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW ................................. 7

TIMELINE ..................................................................................................................................... 9

NEXT STEPS ............................................................................................................................... 10

Appendix – Additional Areas Considered in the Dikegulac Sodium Registration Review ........... 11

References:

This Preliminary Work Plan summarizes the Environmental Protection Agency's current position 

based on the following documents: 

1. EFED Registration Review Problem Formulation for Dikegulac-sodium. Arnold, Elyssa. October, 27 

2014. 

2. Dikegulac Sodium. Human Health Scoping Document and Preliminary Risk Assessment. Bobowiec, 

Bridgett. September 10, 2014. 

3. BEAD Chemical Profile for Registration Review: Dikegulac Sodium (109601). Chen, Carl. 

November 17, 2014. 

These and other supporting documents for the dikegulac sodium registration review case may be 

found in the docket EPA- HQ-OPP-2014-0771 at http://www.regulations.gov. 
3

OVERVIEW 

The docket for dikegulac sodium is now open, initiating the first public comment period for this 

registration review (docket number EPA-HQ-OPP-2014-0771). Dikegulac-sodium is a plant growth 

regulator that was first registered in 1978. It is registered for use on ornamentals, nursery crops, and 

trees to reduce growth, flowering, and/or fruit set. There are residential uses of dikegulac sodium. 

Three end-use products containing dikegulac-sodium are currently registered for use in the United 

States. Dikegulac-sodium was previously assessed at the time of the development of the 

Reregistration Eligibility Decision (RED) in 2007. This Preliminary Work Plan (PWP) document 

explains what EPA's Office of Pesticide Programs knows about dikegulac sodium, highlighting 

anticipated data and assessment needs, identifying the types of information that would be especially 

useful to the Agency in conducting the review, and providing an anticipated timeline for completing 

the registration review for dikegulac sodium. 

 

The registration review process was designed to include a public participation component to solicit 

input from interested stakeholders. The Agency intends, by sharing this information in the docket, 

to inform the public of what it knows about dikegulac sodium and what types of new data or other 

information would be helpful for the Agency to receive as it moves toward a decision on dikegulac 

sodium. The Agency encourages all interested stakeholders to review the PWP and Appendix and 

to provide comments and additional information that will help the Agency’s decision-making 

process for this chemical. In addition to general areas on which persons may wish to comment, 

there are some areas identified in the PWP and Appendix about which the Agency specifically seeks 

comments and information. Interested stakeholders could include: environmental non-profit or 

interest groups; pesticide manufacturers; agricultural labor or commodity groups; commercial, 

institutional, residential, and other users of pesticides; or the public at large. 

The Preliminary Work Plan begins by listing the anticipated data needs for dikegulac sodium. Next, 

it discusses the statutory and regulatory authority for Registration Review. Then the document 

provides chemical facts, use and usage information, recent actions, the anticipated risk assessments, 

and a projected registration review timeline for dikegulac sodium. Finally, the Appendix to this 

document includes identification and discussion of some areas that are considered generally in 

Registration Review along with some additional chemical case-specific information. 

 
4

ANTICIPATED DATA NEEDS 

Table 1 below summarizes anticipated data needs for dikegulac sodium. For additional discussion of 

the anticipated data needs, see the EFED Registration Review Problem Formulation for Dikegulac-sodium.

Table 1: Anticipated Data Needs for the Dikegulac Sodium Registration Review 

Guideline 

Number1 Study Title1 

Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI)

Anticipated Data Needs for the Parent Dikegulac Sodium

Nonguideline 

Honey bee acute oral toxicity TGAI 12 

Nonguideline 

Honey bee acute larval toxicity TGAI 12 

Nonguideline 

Honey bee chronic larval toxicity TGAI 12 

Nonguideline 

Honey bee adult chronic 10-day toxicity TGAI 12 

TGAI = technical grade active ingredient 

 

 

1 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 
5

STATUTORY AND REGULATORY AUTHORITY 

The Food Quality Protection Act (FQPA) of 1996 mandated a registration review program. All 

pesticides distributed or sold in the United States (U.S.) generally must be registered by the 

Environmental Protection Agency (EPA or the Agency), based on scientific data showing that they 

will not cause unreasonable risks to human health or the environment when used as directed on 

product labeling. 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 of no unreasonable adverse effects to human health or 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 

change occurs, products in the marketplace can be used safely. Information on this program is 

provided on EPA’s website.2

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. The 

regulations governing registration review begin at 40 CFR 155.40. The Agency will consider benefits 

information and data as required by FIFRA. The public phase of registration review begins when 

the initial docket is opened for each case. The docket is the Agency’s opportunity to state what it 

knows about the pesticide and what additional risk analyses and data or information it believes are 

needed to make a registration review decision. After reviewing and responding to comments and 

data received in the docket during this initial comment period, the Agency will develop a Final Work 

Plan (FWP) and anticipated schedule for the registration review of dikegulac sodium. 

CHEMICAL FACTS 

Table 2 provides a summary of the chemical facts for dikegulac sodium. 

Table 2: Chemical Facts for Dikegulac Sodium

PC code 109601 

Case Number 3061 

CAS Number 52508-35-7 

Year first registered 1978 

Pesticide Type Plant growth regulator 

Chemical class Not applicable 

Reregistration Eligibility 

Decision (RED) 

The RED was completed in 2007 

Tolerance Reassessment 

Eligibility Decision 

(TRED) 

Not applicable. There are no food uses for dikegulac sodium. 

Cumulative group Dikegulac sodium has not been identified as a member of a 

cumulative group that shares a common mechanism of toxicity. 

40 CFR Citation There are no established tolerances for dikegulac sodium. 

 

2 http://www.epa.gov/oppsrrd1/registration_review/ 
6

Table 2: Chemical Facts for Dikegulac Sodium

Dual-use Dikegulac sodium is registered for conventional pesticidal uses only 

and has no registered antimicrobial or biopesticidal uses. 

Non-pesticidal uses There are no identified non-pesticidal uses of dikegulac sodium. 

Pesticide Re-evaluation 

Division, Chemical Review 

Manager 

Matthew Manupella, manupella.matthew@epa.gov, (703) 347-0411 

Registration Division, 

Product Manager 

Tony Kish, kish.tony@epa.gov, (703) 308-9443 

USE AND USAGE INFORMATION 

Table 3 summarizes the use and usage information for dikegulac sodium. Please see the BEAD 

Chemical Profile for Registration Review: Dikegulac Sodium (109601) in the registration review docket for 

more details. 

Table 3: Dikegulac Sodium Use and Usage Information

Summary of Use Dikegulac sodium, a plant growth regulator, is registered for use on 

ornamental plants in greenhouses, nurseries, and on landscapes, as 

well as deciduous evergreen and conifer tree farms. 

Use Sites Agricultural Use Sites: Dikegulac sodium is registered for use on 

farms for deciduous evergreen and conifer trees, including 

Christmas trees. 

Non-Agricultural Use Sites: Dikegulac sodium is registered for use 

in greenhouses, nurseries, and on landscape trees, hedges, shrubs, 

groundcovers, flowering plants and other ornamentals. Landscape 

areas include parks, school campuses, city streets, and similar 

recreational, institutional, or industrial areas. 

Summary of Usage EPA reviewed available data sources and found that only the 

Department of Agriculture National Agricultural Statistics Service 

reported national use of dikegulac sodium in the nursery and 

floriculture sector in 2006, where approximately 400 lbs a.i. were 

applied at an average a.i. rate of 2.057 lbs a.i. per acre. California 

Department of Pesticide Regulation, however, reported use of 

dikegulac sodium in higher amounts in recent years (2008-2012), 

particularly for landscape maintenance, where an average of 1,400 

lbs a.i. were applied annually. 

Formulation Type(s) Dikegulac sodium is formulated as soluble and emulsifiable 

concentrates, as well as liquid ready-to-use. 

Application Method(s) Dikegulac-sodium is applied as a foliar spray, soil drench, tree trunk 

injection, or tree trunk spray band 

Technical Registrant(s) PBI/Gordon Corporation, Arborsystems Inc. 
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Table 3: Dikegulac Sodium Use and Usage Information

No. of Registrations 3 Section 3 products3

Restricted Use No 

Guidance for Commenters: The Agency currently does not have certain important 

information on dikegulac sodium. Obtaining the following information may improve future 

assessments conducted by the Agency related to the use and importance of dikegulac sodium. 

 Current usage information (pounds a.i. applied, average a.i. rate of application and 

number of application) on all sites. 

 Geographic distribution of dikegulac sodium use in the U.S. 

RECENT ACTIONS 

There are no recent actions for dikegulac sodium. 

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW 

The most recent comprehensive human health and ecological risk assessments for dikegulac sodium 

were completed in 2006 in preparation for the Reregistration Eligibility Decision. Findings and 

conclusions from these risk assessments are summarized in the Dikegulac Sodium: Human Health 

Scoping Document and Preliminary Risk Assessment and the EFED Registration Review Problem Formulation 

for Dikegulac-sodium. 

During registration review, the Agency anticipates the need for additional data to allow for a more 

comprehensive evaluation of potential effects to honey bees. For human health, no new data are 

expected to be required to support the registration review of this pesticide. There are no hazards 

associated with dikegulac sodium at doses relevant to humans; therefore, a qualitative approach to 

risk assessment is appropriate. The Dikegulac Sodium Human Health Scoping Document and Preliminary 

Risk Assessment is expected to serve as the preliminary risk assessment for the purpose of registration 

review. EPA believes that there are no human health risks associated with the currently registered 

uses of dikegulac sodium. 

Table 4 below summarizes the anticipated registration review risk assessments based on the EFED 

Problem Formulation and HED Scoping Document. 

 

3 Section 3 product labels can be obtained from the Pesticide Product Label System (PPLS) website 

(http://oaspub.epa.gov/pestlabl/ppls.home). 
8

Table 4: Anticipated Risk Assessments for the Dikegulac Sodium Registration Review 

Type of Risk Assessment Conduct? Notes 

Ecological and Environmental Fate 

Comprehensive ecological 

(species to be assessed include 

terrestrial and aquatic 

organisms) 

No Ecological risk conclusions in the RED are unchanged 

and will not be reassessed. The RED determined that all 

potential risks to aquatic organisms and plants were 

below the Agency’s level of concern (LOC). All 

potential risks to terrestrial organisms were also below 

the Agency’s LOC, except for semi-aquatic non-listed 

and listed plants. However, a more comprehensive 

evaluation of potential effects to honey bees is 

anticipated. Risks to federally listed species will be 

reevaluated. 

Incidents Will check for 

updates 

As of July 2014, there were no ecological incidents 

reported in EIIS or AIMS for dikegulac-sodium. There 

were also no minor incidents reported in aggregate 

incident reports. 

Human Health 

Dietary 

Food No Dikegulac sodium does not have any agricultural or 

food production uses, as such it is designated and 

classified as a “non-food” use chemical. Based on the 

low hazard concern from the available studies, no 

endpoints of toxicological concern have been identified. 

Due to the hazard profile drinking water assessments 

are not needed. In addition, because dikegulac sodium 

is not used on any agricultural food and/or feed 

commodities and is classified as a “non-food” use 

chemical and metabolized to non-toxic substances; a 

dietary risk assessment is not required. 

Drinking water No 

Occupational 

Handlers (mixers, loaders, 

applicators) 

No While there are uses that could result in occupational 

handler and post-application exposure, due to the (very) 

low systemic toxicity of dikegulac sodium, a quantitative 

occupational risk assessment is not warranted for any 

type, or duration of exposure. 

Post-application No 

Residential 

Handlers No Dikegulac sodium is used in small quantities by the 

professional landscaping industry, and is not marketed 

to homeowners. Residential post application exposure 

is possible from occupational application to residential 

use sites however, due to the (very) low systemic 

toxicity of dikegulac sodium, a residential quantitative 

risk assessment is not warranted for any type, or 

duration of exposure. 

Post-application No 

Other 
9

Aggregate No Evaluates the combined risk from dietary and 

residential exposures. 

Cumulative No Unlike other pesticides for which EPA has followed a 

cumulative risk approach based on a common 

mechanism of toxicity, EPA has not made a common 

mechanism of toxicity finding with dikegulac sodium. 

Dikegulac sodium does not appear to produce a toxic 

metabolite produced by other substances. 

Tolerances No There are no tolerances to be assessed for dikegulac 

sodium. 

Incidents Will check for 

updates 

As of September 2014, there are no incident cases 

reported for dikegulac sodium in either the Main or 

Aggregate Incident Data System (IDS) module, Poison 

Control Centers (PCCs), California Department of 

Pesticide Regulation, National Pesticide Information 

Center (NPIC) and National Institute of Occupational 

Safety and Health’s Sentinel Event Notification System 

for Occupational Risks. 

TIMELINE 

EPA has created the following estimated timeline for the completion of the dikegulac sodium 

registration review in Table 5 below. 

Table 5: Projected dikegulac sodium Registration Review Timeline

Activities Estimated Date

Opening the Docket 

Open Docket and 60-day Public Comment Period December 2014 

Close Public Comment February 2015 

Case Development 

Final Work Plan June 2015 

Issue DCI July-September 2015 

Data Submission July-September 2016 

60-day Public Comment Period for Draft Risk 

Assessments4

January-March 2017 

Registration Review Decision 

60-day Public Comment Period for Proposed 

Registration Review Decision 

June-September 2017 

Registration Review Decision and Begin Post-Decision 

Follow-up 

January-March 2018 

Total (years) 4 years 

 

4 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. 
10

NEXT STEPS 

After the 60-day public comment period closes, the Agency will review and respond to any 

comments received in a timely manner and then issue a Final Work Plan for the registration review 

of dikegulac sodium. 

 
11

Appendix – Additional Areas Considered in the Dikegulac Sodium 

Registration Review 

PUBLIC COMMENTS AND FEEDBACK: 

Guidance for Commenters: The areas below highlight topics of special interest to the Agency 

where your comments, data submissions, or reference to sources of additional information could be 

of particular use.

Trade Irritants: 

Through the registration review process, the Agency intends to solicit information on trade irritants 

and, to the extent feasible, take steps toward facilitating irritant resolution. The Agency will work to 

harmonize tolerances and international maximum residue limits (MRLs) and may modify tolerance 

levels to do so, when possible. Growers and other stakeholders are asked to comment on any 

trade irritant issues resulting from lack of MRLs or disparities between U.S. tolerances and MRLs in 

key export markets, providing as much specificity as possible regarding the nature of the concern. 

Because dikegulac sodium is not registered for food/feed uses in the U.S., it has no U.S. tolerances; 

therefore, the Agency does not anticipate any trade irritant issues for it. 

Water Quality: 

Dikegulac sodium is not identified as a cause of impairment for any water bodies listed as impaired 

under section 303(d) of the Clean Water Act.5

 In addition, no Total Maximum Daily Loads 

(TMDL) have been developed for dikegulac sodium.6 More information on impaired water bodies 

and TMDLs can be found at the Agency’s website.7 The Agency invites submission of water 

quality data for this pesticide. To the extent possible, data should conform to the quality 

standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired Water Body and 

Other Water Quality Data in OPP’s Registration Review Risk Assessment and Management Process8 in order to 

ensure they can be used quantitatively or qualitatively in pesticide risk assessments. 

Environmental Justice: 

EPA seeks to achieve environmental justice, the fair treatment and meaningful involvement of all 

people, regardless of race, color, national origin, or income, in the development, implementation, 

and enforcement of environmental laws, regulations, and policies. To help address potential 

environmental justice issues, the Agency seeks information on any groups or segments of the 

population who, as a result of their location, cultural practices, or other factors, may have atypical, 

unusually high exposure to dikegulac sodium compared to the general population. Please 

comment if you are aware of any sub-populations that may have atypical, unusually high 

exposure compared to the general population.

 

5 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885 6http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_g

roup_name=PESTICIDES 7 http://www.epa.gov/owow/tmdl/

8 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
12

ENDANGERED SPECIES: 

A risk assessment that supports a complete endangered species determination has not been 

conducted for dikegulac sodium. The ecological risk assessment planned during registration review 

will allow the Agency to determine whether use of dikegulac sodium has “no effect” or “may affect” 

federally listed threatened or endangered species (listed species) or their designated critical habitats. 

When an assessment concludes that a pesticide’s use “may affect” a listed species or its designated 

critical habitat, the Agency will consult with the U.S. Fish and Wildlife Service and/or National 

Marine Fisheries Service (the Services), as appropriate. 

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, 

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 its 

reregistration decision for dikegulac sodium, 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), dikegulac sodium 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, 20139 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. 

 

9

 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals. 
13

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.10

 

10 http://www.epa.gov/endo/