UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

DEC. 0 2 2014 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

BEAD Chemical Profile (BCP) for Registration Review: Cycloate (041301) 

Biological 

Sunil Ratnayake, 

Analysis 

Biologist 

Branch ~ 

/1. ~ · ..} "' ~ Oi - j 

Sepehr Haddad, Environmental Protection Specialist IJ 'f./~ Science Information and Analysis Branch 

Stephen Smearman, Economist 

Economic Analysis Branch 

Biological and Economic Analysis Division (7503P) 

Arne! Jones, Chief /J "'~ Biologi~al Analysis Branch ~u . . ~ 

D1ann Stms, Chtef jj-: ~ jlf. ~ ~v 0) 

Science Information and Analysis Branch t/ 

Timothy Kiely, Chief gj: \A 1\~ Economic Analysis Branch ·v\. 

Biological and Economic Analysi ivision (7 ) 

TO: Matthew Manupella, Chemical Review Manager, RMIB II 

Pesticide Re-evaluation Division (7508P) 

Peer Review Panel date: November 5th, 2014 
SUMMARY 

Cycloate was first registered in the United States in 1967 (USEPA, 2004). Cycloate belongs to 

the herbicide family of thiocarbamates. It is a systemic, broad-spectrwn, and pre-emergent 

herbicide registered for control of certain grasses and broadleaf weeds in table beets, spinach, 

and sugarbeets. A Re-registration Eligibility Decision (RED) was completed for cycloate in 

2004. Based on private market usage data from 1998-2012, usage averaged approximately 

220,000 pounds active ingredient (a.i.) applied annually approximately on 100,000 acres treated. 

The average application rate over this time period was 2.2 lbs a.i./acre. A Screening Level 

Usage Analysis (SLUA) was prepared by BEAD for this chemical in 2014 that provides the 

percent crop treated data over the 2004-2012 timeframe. For sugarbeets and spinach these 

percent crop treated values were 5 and 40 percent, respectively. There are no non-agricultural 

uses of cycloate. 

INTRODUCTION 

The Biological and Economic Analysis Division (BEAD) Chemical Profile (BCP) provides an 

overview of the pest management roles and quantitative usage information for cycloate. The 

BCP includes summaries of previous BEAD products and available public and/or private use and 

usage data for cycloate to describe the role of this chemical in pest management. Additional 

information on use is available the Screening Level Usage Analysis (SLUA). Information 

provided in this BCP may be used by stakeholders (e.g., users and registrants), OPP risk and 

benefit assessors, OPP risk managers, and the general public during the Registration Review 

process of this pesticide. 

USE SITES 

Agricultural Use Sites 

Cycloate registered agricultural use sites are table beets, sugarbeets and spinach. 

FORMULATIONS AND APPLICATION METHODS 

Cycloate is formulated as an emulsifiable concentrate liquid. As pre-plant or at plant treatments, 

cycloate is applied using ground spray equipment and then incorporated into the soil 

mechanically or by sprinkler irrigation ( chemigation). 

HISTORY OF CYCLOATE and BEAD PRODUCTS 

Cycloate was first registered in the United States for use as a selective herbicide on sugarbeets 

and spinach in 1967 (USEPA, 2004). A Re-registration Eligibility Decision (RED) was 

completed for cycloate in 2004. 

Page2 
A search of BEAD's Official Records database for BEAD benefits assessments specifically for 

cycloate did not find any records of prior BEAD assessments specifically for this chemical in the 

last 10 years. 

A Screening Level Usage Analysis (SLUA) was prepared by BEAD for cycloate in 2014 that 

provides the percent crop treated data over the 2004-2012 timeframe for spinach (average 40 

percent) and sugarbeets (average 5 percent). 

No results were found in a search of BEAD's Official Records and the OPP Section 18 

(emergency exemption) database for any Section 18 requests for cycloate in the last 10 years. 

Emergency exemptions may indicate that there is a need for a particular chemical that is not 

registered for use on a particular site. An emergency exemption request may yield information 

about a particular chemical's importance or value that is not found in other EPA records. 

However, a lack of Section 18 assessments by BEAD does not specifically indicate the relative 

importance of the chemical. 

USAGE 

Agricultural Usage 

Based on private market usage data from 1998-2012, average annual usage was approximately 

220,000 pounds active ingredient (a.i.) on 100,000 acres treated. The average a.i. rate over this 

time period was pounds 2.2 lbs a.i./acre. Figure 1 presents cycloate usage in pounds a.i., and 

Figure 2 shows total area treated in acres over the 1998-2012 timeframe (Proprietary Data, 1998-

2012). Figures 1 and 2 show that over this time period in terms of pounds applied and acres 

treated there has been a sharp decrease in use. 

FIGURE 1. Cycloate Usage in Pounds Active Ingredient (1998-2012) 

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Source: Proprietary Data, 1998-2012 

Page 3 
FIGURE 2. Cycloate Total Area Treated in Acres (1998-2012) 

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Years 

Source: Proprietary Data, 1998-2012 

Since the RED was issued in 2004, Table 1 shows a comparison oftimeframes before and after 

the issuance of the document. The crop with the most pounds applied during the 2001-200~ 

timeframe was sugarbeets while in the 2008-2012 timeframe the top crop was spinach with 98 

percent of total pounds applied. The average annual usage in pounds a.i. applied has decreased . 

sharply from approximately 237,000 lbs (a.i.) in the earlier timeframe to approximately 45,000 

lbs/year (a.i.) in the 2008-2012 timeframe, a drop in usage of more than 80 percent. However, 

most of this decline is due to reduction of use on sugarbeets. The development of genetically 

modified sugarbeet varieties with resistance to gylphosate may have contributed to the reduction 

of cycloate usage on sugarbeet production. 

Table 1. Comparison of Crops with Highest Use of Cycloate- Percent of Total Lbs. Applied 

(2001-2005 and 2008-2012) 

2001-2005 2008-2012 

Average annual= 237,000 lbs/yr Average annual= 45,000 lbs/yr 

Crop %Lbs Crop %Lbs 

Sugarbeet 76% Sugarbeet 2% 

Spinach 24% Spinach 98% 

TOTAL 100% TOTAL 100% 

Source: Proprietary Data, 2001-2012. 

As shown in Table 2, Idaho, California and Michigan were the top states with the highest use of 

cycloate during the 2001-2005 timeframe accounting for approximately 75 percent oftotal 

pounds applied, while in the latter 2008-2012 timeframe, California was the top state with the 

highest use (92 percent of total pounds applied). However, total usage in pounds a.i. applied has 

declined more than 80 percent between the two periods. 

Page4 
Table 2. Comparison of States with Highest Use of Cycloate- Percent of Total Lbs. 

AJ!Piied (2001-2005 and 2008-2012) 

2001-2005 2008-2012 

Average annual= 237,000 lbs/yr Average annual= 45,000 lbs/yr 

State %Lbs State %Lbs 

Idaho 41% California 92% 

California 23% New Jersey 3% 

Michigan 10% Arizona 3% 

Other 26% Nebraska 2% 

TOTAL 100% TOTAL 100% 

Other states in the 2001-2005 time period includes 13 additional states. 

Source: Proprietary Data, 2001-2012 

Application Rates and Percent Crop Treated 

The average a.i. rate for the top crop, spinach, which accounts for 98 .Percent of total use in 2008-

2012 in terms of pounds a.i. applied was 2.3 lbs a.i./acre as shown in Table 3. 

T a e bl 3 C . ;yc I oa t e U se on T C op rops: A vera2e A I R . . a t e, 2008 -2012 

Annual Average Annual Average A vg. A.I. Rate (lbs Crop Total Acres Pounds Treated* a.i./acres) 

Spinach 44,200 19,200 . 2.30 

*Total Acres Treated sums all acres treated for a crop, mcludmg those acres that receive multiple treatments. 

Source: Proprietary Data, 2008-2012 

Geographic Distribution of Cycloate Use 

Figure 3 provides a very broad geographical view of the average annual amount (in pounds) of 

cycloate applied per 1,000 acres of crop acres grown. The calculated values presented in the 

map are not equivalent to an application rate (lb a.i./A), therefore, the map may show areas of 

high use intensity that do not necessarily correspond to the states listed in Table 2. However, in 

this case, California and New Jersey are the states that use approximately 95 percent of the total 

pounds a.i. used and are also the states that show high use intensity as depicted in the map. 

Please see Appendix A for a more detailed explanation of the information presented on the map. 

Page 5 
FIGURE 3. Annual Average Agricultural Use Intensity of Cycloate (2008-2012) 

Pounds Active Ingredient 

per 1 ,000 Crop Acres Grown 

0 <0.1 

0 o.1-1.4 

. 1.5-4.8 

- >4.8 

UNo Data 

BIOLOGICAL ASPECTS RELEVANT TO CYCLOATE 

Cycloate belongs to the family ofthiocarbamate (Group 8) herbicides. It is a broad-spectrum, 

pre-emergence herbicide used for the control of certain grasses and broadleaf weeds in table 

beets, spinach, and sugarbeet production. 

The mechanism of action of this herbicide is inhibition of the enzyme fatty acid elongase. 

Inhibition of this enzyme interferes with the biosynthesis of long-chain fatty acids and lipids. 

Fatty acid and lipids are essential constituents of plant waxes and suberin (Magnucka et al., 

2009). Following the application of cycloate, susceptible weeds fail to emerge as the coleoptile 

of grass weed species or hypocotyl ofbroadleafweed species cease growth beneath the soil 

(Herbicide Handbook, 2014). 

Page 6 
ROLE OF CYCLOATE IN PEST MANAGEMENT 

Cycloate is registered as a pre-emergence herbicide for control of certain grasses, broadleaf 

weeds, and sedges (Cyperus spp.) in beets and spinach. Major grassy weed species controlled by 

cycloate are barnyardgrass (Echinochloa spp.), crabgrass (Digitaria spp.), foxtails (Setaria spp.) 

and wild oats (Avenafatua). Also, cycloate is applied for control ofbroadleafweeds such as 

black nightshade (Solanum nigrum), hairy nightshade (Solanum villosum), henbit (Lamium spp.), 

lambsquarters, (Chenopodium album), purslane (Portulaca oleracea), redroot pigweed 

(Amaranthus retrojlexus), shepherd's-purse (Capsella bursa-pastoris), and small stinging nettle 

(Urtica urens) (Cycloate Herbicide Profile, 1985). 

Compared to the timeframe of2001 to 2005, use of cycloate on sugarbeets declined significantly 

from 2008 to 2012 (Table 1). The development of genetically modified sugarbeet varieties with 

resistance to gylphosate may have contributed to the reduction of cycloate usage on sugarbeet 

production. From 2008 to 2012, 98 percent of total average annual usage of cycloate was on 

spinach, with about 92 percent of average yearly usage of cycloate was in California spinach. 

About 40 percent of the crop is treated with cycloate, suggesting that this herbicide is important 

in U.S. spinach production. 

Stinging nettle (Urtica urens), annual bluegrass (Poa annua), sowthistle (Sonchus oleraceus), 

prickly lettuce (Lactuca serriola), little mallow (Malva parviflora), London rocket (Sisymbrium 

irio) shepherd's-purse (Capsella bursa-pastoris) and pigweeds (Amaranthus spp.) are some of 

the troublesome weeds found in spinach production (Univ. of California, 2011). Ofthese weeds, 

little mallow (Malva parviflora), purslane (Portulaca oleracea), shepherd's-purse (Capsella 

bursa-pastoris), and redroot pigweed (Amaranthus retrojlexus) are the main weed species 

targeted by cycloate (Proprietary data, 2014). 

In California spinach production, several herbicide options are available as alternatives to 

cycloate. Of these herbicides, S-metolachlor is used as a pre-emergent herbicide. The weeds 

controlled by S-metolachlor are similar to those controlled by cycloate. However, S-metolachlor 

has a 50 day pre-harvest interval which limits the use of S-metolachlor in fresh market spinach. 

However, S-metolachlor may be useful in longer season processing spinach where a 50-day preharvest interval does not preclude its use (Univ. of California, 2014 b). Other alternatives to 

cycloate include metam sodium (soil fumigant) and herbicides such as glyphosate, pelargonic 

acid (pr~-plant foliar applied herbicides) and post-emergent foliar applied herbicides such as 

sethoxydim, and clethodim which are registered for grass weed control in California spinach 

(Univ. of California, 2014 b). 

According to the International Survey of Herbicide Resistant Weeds, biotypes of five weed 

species have developed resistance to· the mechanism of action ofthiocarbamates in the United 

States. These weed species ~e: wild oats (Avenafatua), barnyardgrass (Echinochloa crus-galli), 

early water grass (Echinochloa oryzoides), late watergrass (Echinochloa phyllopogon), and 

annual ryegrass (Poa annua) (Heap, Undated). 

Page 7 
DATA NEEDS 

The Agency currently does not have complete information for cycloate. Obtaining the following 

information may improve future assessments conducted by the Agency related to the use and 

importance of this herbicide: 

Use and usage information of cycloate on table beets may be needed for risk assessments. 

REFERENCES 

BEAD. 2014. Cycloate Screening Level Usage Analysis. Biological and Economic 

Analysis Division, Office ofPesticide Programs, US Environmental Protection 

Agency. 

Cycloate Herbicide Profile. 1985. Online Publication. Available at: 

http://pmep.cce.cornell.edu/profiles/herb-growthreg/cacodyliccymoxanillcycloate/herb-prof-cycloate.html. Accessed on Oct. 14, 2014. 

Heap, I. (Undated). The International Survey of Herbicide Resistant Weeds. Online 

Publication. Available at: 

http://www. weedscience.org/summary/CountrySummary.aspx. Accessed on 

October 17, 2014. 

Herbicide Handbook. 2014. lOth edition. Weed Science Society of America. Cycloate. 

Pp 123-124. 810 E. lOth Street, Lawrence, KS 66044-8897. 

Magnucka E.G., Suzuki Y., Pietr S.J., Kozubek A., and R. Zarnowski. 2009. Cycloate, 

an inhibitor of fatty acid elongase, modulates the metabolism ofvery-long-sidechain alkyl resorcinols in rye seedlings. Online Publication. Available at: 

http://www.ncbi.nlm.nih.gov/pubmed/19479950. Accessed on Oct. 14, 2014. 

Proprietary Data. 1998-2012. 

University of California. 2011. Spinach Production in California. Publication number 

7212. Online Publication. Available at: http://anrcatalog.ucdavis.edu/pdf/7212.pdf 

Accessed on Oct. 01, 2014. 

University of California. IPM Online. 2014a. Information about Herbicides in Spinach. 

Spinach. Online Publication. Available at: 

http://www.ipm.ucdavis.edu/PMG/r73270041l.html. Accessed on Oct. 22, 2014. 

University of California. IPM Online. 2014b. Information about Integrated Weed 

Management in Spinach. Online Publication. Available at: 

http://www.ipm.ucdavis.edu/PMG/r732700111.html Accessed on Oct. 22, 2014. 

USEP A.2004. Reregistration Eligibility Decision (RED) for Cycloate. Online 

Publication. Available at: 

http://www.epa.gov/oppsrrdl/REDs/factsheets/cycloate red fs.pdf. Accessed on 

Oct. 17, 2014. 

Page 8 
APPENDIX A. 

The map included herein is primarily for the use of the risk assessors in the Environmental Fate 

and Effects Division. The map provides a very broad geographical view of the average annual 

amount (in pounds) of the active ingredient applied per 1,000 acres of crop acres grown. These 

data are included in the maps because risk assessors are interested in the amount of a pesticide 

used across agricultural land. The calculated values presented in the map are not equivalent to 

an application rate (lb a.i./ A). · 

The data used to make these maps have several limitations. Any interpretation of the maps 

should consider the underlying data and the associated limitations carefully. 

The numerator (annual average pounds applied) is based on private market surveys of pesticide 

use in agriculture averaged over the last five years (Proprietary Data, 2008-2012). These surveys 

cover about 60 crops and are targeted in states that produce the majority of the crop. Although 

the surveys capture most of the use of a particular active ingredient in agriculture, ther~ are 

several limitations to these surveys. 

• States with minor production of a surveyed crop are not sampled 

• Not all types of pesticides are surveyed in every crop in every year 

• Many specialty crops with very small acreages are not included in the survey 

The result of these limitations is that states that show no usage may actually have a small amount 

of the active ingredient being used. In some cases the displayed use intensity may be distorted 

because the surveyed crops and the reported pesticide usage may not accurately represent the 

actual pesticide usage on the crops produced in the state. 

The denominator (1 ,000 crop acres grown) was also obtained from the same private market 

survey database. The "Crop Acres Grown" variable represents the total acres grown in a given 

state of all of the surveyed crops. This value is independent of pesticide usage and pesticide 

registration. It is important to note that the surveyed crops (about 60) are sampled from states 

that are major producers of each crop. Therefore, there are cases where the actual crop acreage in 

a state is higher than that reported by crop acres grown in the survey because either that state 

and/or crop was not included in the survey. 

The reader should pay particular attention to the figure legends and realize that a map prepared 

for a particular chemical is not directly comparable to a map prepared for a different chemical as 

the legend bins will likely be different. 

Page 9