UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MAY 0 7 2014 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

TO: 

BEAD Chemical Profile (BCP) for Registration Review: Cyhalofop-butyl 

(082583) 

Bill Phillips, Agronomist / 

Biological Anal~ B~~ch · 

~£:~~~ental Protection Specialist 

Science Information and Analysis Branch 

Economic 

Derek Berwald, 

Analysis 

Economist 

Branch 

f-rK R( --, 

V/j 

.J- vv.._ ~ Biological and Economic Analysis Division (7503P) 

Biological 

Arnet Jones, 

Analy

Chief 

sis Branch ~r. 

a ... ~~ ~ U 

Sc

Diann 

ience 

Sims, 

Information 

Chief ~~ and Analysis Branch 

Timothy 

Economic Kiely, Analysis 

Chief 

Branch 

fr 

vvv 

I~~.~~~ Biological and Economic Analy Division (75 

Jolene Trujillo, Chemical Review Manager 

Risk Management and Implementation Branch 5 

Pesticide Re-evaluation Division (7508P) 

Peer Review Panel date: 2 April2014 

1 
SUMMARY 

Cyhalofop-butyl is an herbicide that is labeled for grass weed control in rice only. Grass weed 

control is difficult to achieve in a grass crop such as rice. However, cyhalofop-butyl is a 

selective herbicide that makes controlling difficult to manage weeds possible without damaging 

rice crops in which it is applied. Most of the use of cyhalofop-butyl is in Arkansas and 

California, the two largest rice producing states. While these states account for the majority of 

the herbicide use, nationally, between 2008 and 2012 15% of the total rice crop was treated with 

this herbicide. BEAD concludes that there are important uses for this herbicide. In rice 

production there are a few key weeds that pose significant problems for growers. Cyhalofopbutyl is used in combination with other herbicides to control some of these key weed species, 

including herbicide resistant biotypes. 

INTRODUCTION 

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

overview of the pest management roles and quantitative usage information for cyhalofop-butyl. 

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

use and usage data for cyhalofop-butyl to describe the role of this chemical in pest management. 

Additional information on use is available in the cyhalofop-butyl Label Data Report and 

Screening Level Usage Analysis (SLUA). Information provided in this BEAD Chemical Profile 

(BCP) may be used by stakeholders (e.g., users and registrants), OPP risk and benefit assessors, 

and OPP risk managers, and the general public during the Registration Review process of this 

pesticide. 

USE SITES 

Cyhalofop-butyl is registered for use on rice only. There are no other uses (agricultural or nonagricultural) for this chemical. 

FORMULATIONS AND APPLICATION METHODS 

Cyhalofop-butyl is formulated as an emulsifiable concentrate, soluble concentrate, granular, and 

ready-to-use solution. This chemical can be broadcast aerially or by foliar application with 

ground equipment. This herbicide is applied postemergence in both flooded and dryland rice 

crops to control annual grass. 

HISTORY OF CYHALOFOP-BUTYL AND BEAD PRODUCTS 

The only BEAD work on cyhalofop-butyl was for two Section 18 emergency exemption requests 

from the early part of this century. The use was requested to control weeds in rice for Louisiana 

(EPA 2002) and California (EPA 2001). In both cases the use was requested for control of 

emerging weed problems for which the states did not have efficacious alternatives. BEAD agreed 

with this assessment. Later cyhalofop-butyl was registered for these uses. 

2 
USAGE 

Usage Trends 

For years 2003-2012, cyhalofop-butyl annual usage averaged 103,000 pounds of active 

ingredient (A.I.) treating an annual average of 406,000 thousand acres, for an overall average 

application rate of 0.25 pounds A. I. per acre. As shown in Figures 1 and 2, use, both in terms of 

pounds AI. and total area treated peaked in 2005, and has decreased overall until the most recent 

years for which data is available (Proprietary Data, 2003-2012). Some of this decline can be 

attributed to the decline in rice acreage, but acreage treated with cyhalofop-butyl has decreased 

more than acreage has. 

Application Rates 

From 2008 - 2012, an average of 81,000 pounds of cyhalofop-butyl was used on rice. The 

average total acres treated1 for the same period was 311,000 for an average application rate of 

0.26 pounds A.l. per acre (Proprietary data, 2008-2012). 

Figure 1. Avera e Pounds ofC 2003-2012 

200,000 .,...-----------------------

< 

"0 "' c: 

~ 

0 

Q. 

0 +--~--r--~-~r--.---.--.----.---. 

2003 2004 2oos 2006 2oo1ea~oos 2009 2010 2011 2012 

Source: Proprietary Data, 2003-2012 

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

3 
Figure 2. Total Area Treated 

800,000 .------------------------

0 +--~--r--~-~~-~-~--~-~-~ 

2003 2004 2005 2006 200te ~008 2009 2010 2011 2012 

As shown in Table 1, use is only seen in the rice growing states, and most of the use is 

concentrated in Arkansas and California, the two largest production states. These two states 

account for about 70% of the total use of cyhalofop-butyl in the nation, both in the early period 

and from 2008 - 2012. While these states account for the majority of the herbicide use, 

nationally, between 2004 and 2012 15% ofthe national rice crop was treated with this herbicide 

(SLUA). California's share of national use is somewhat higher than the share of national rice 

production, indicating that cyhalofop-butyl is more important there than in other states. This can 

also be seen in Table 2, which shows the percent of the rice crop treated with cyhalofop-butyl by 

state. In both time periods, the states with the highest percentage of the crop treated are 

California and Mississippi. Note, however, that the percent treated is much higher in the earlier 

period than from 2008 - 2012. This matches the general use pattern shown in Figures 1 and 2, 

which show the cyhalofop-butyl has declined over time. 

Table 1. Comparison of States with Highest Use of Cyhalofop-butyl Percent of Total Lbs. 

Applied Between the 2003-2007 and 2008-2012 Timeframes 

2003-2007 2008-2012 

% ofTotal % ofTotal 

State Pounds Applied State Pounds Applied 

Nationallv Nationally 

Arkansas 41 Arkansas 41 

California 29 California 29 

Louisiana 14 Mississippi 12 

Mississippi 10 Louisiana 10 

Missouri 4 Texas 5 

Texas 2 Missouri 3 

Source: Proprietary Data, 2003-2012 

4 
Table 2. Percent of Crop Treated by State, 2003-2007 and 2008 - 2012 

2003-2007 2008-2012 

Average Average Average Average Percent Total Percent Total 

State of Crop Area Total State of Crop Area Total 

Pounds Pounds Treated Treated AI Treated Treated AI (Acres) (Acres) 

Arkansas 13 203,000 50,000 Arkansas 5 127,000 33,000 

California 27 146,000 35,000 California 10 92,000 24,000 

Louisiana 12 69,000 18,000 Louisiana 5 30,000 8,000 

Mississippi 22 53,000 13,000 Mississippi 11 37,000 10,000 

Missouri 9 19,000 5,000 Missouri 2 9,000 2,000 

Texas 7 12,000 3,000 Texas 6 16,000 4,000 

Source: Proprietary Data, 2003-2012 

Geographic Distribution of Cyhalofop-butyl Use 

Another measure of usage is the agricultural use intensity. In this analysis, the use intensity is 

expressed as the average annual amount (in pounds) of the active ingredient applied per 1,000 

acres of crop acres grown. This differs from the application rate, which is expressed as the 

pounds a.i. applied per treated area. Figure 3 spatially represents cyhalofop-butyl's use intensity 

in the U.S. from 2008 - 2012. Because cyhalofop-butyl is only used on rice, the map is showing 

the major rice producing states, with relatively high intensity in the two states with the highest 

production Arkansas and California. Although Mississippi has a relatively high percentage of the 

crop treated with cyhalofop-butyl, use intensity is lower than, for example, Arkansas, because 

there is relatively little rice acreage there. For more information about this map, see Appendix 

A. 

5 
Figure 3. Cyhalofop-butyl Usage by Crop Reporting District (2003-2012) 

Pounds Active Ingredient 

per 1,000 Crop Acres Grown 

D o.o 

0 <0.2 

- 0.2-1 .5 

. 1.6 - 1.7 

- >1 .8 

CYHALOFOP-BUTYL AND USE CHARACTERISTICS 

Cyhalofop-butyl is an aryloxphenoxy propionate herbicide in the Weed Science Society of 

America herbicide mechanism of action group one, with the mechanism of action of inhibiting 

the enzyme acetyl CoA carboxylase (ACCase). This herbicide is applied postemergence in both 

flooded and dry land rice crops to control annual grass weeds along with seedling perennial grass 

weeds. 

ROLE OF CYHALOFOP-BUTYL IN PEST MANAGEMENT 

Grass weed control is difficult to achieve in a grass crop such as rice. Herbicides that control 

grass weeds usually control or damage grass crops such as rice. However, cyhalofop-butyl is a 

selective herbicide that makes controlling difficult to manage weeds possible without damaging 

rice crops in which it is applied. 

Cyhalofop-butyl controls grasses that can result in yield losses in rice crops. Weeds controlled 

by this herbicide include such difficult to control grass weeds as barnyardgrass (Echinochloa 

crus-galli) and sprangletop (Leptochloa dubia) (Fischer 2010). In California barnyardgrass has 

been found to have biotypes that are reported to be resistant to this herbicide. However, the 

predominant weed in this state in rice production is sprangletop, which cyhalofop-butyl is often 

6 
used in tank mixes to control (Fischer 201 0). In Arkansas this herbicide is important in the 

control of barnyard grass. This species has biotypes that are resistant to three of the most 

commonly used herbicides in rice production for the control of barnyard grass; clomazone, 

propanil and quinclorac (Wilson et al. 201 0). Overall, because of its ability to control the 

herbicide resistant weed barnyardgrass in Arkansas and sprangletop in California, cyhalofopbutyl can be an important part of an integrated weed management program. 

DATA NEEDS 

The Agency currently does not have important information on cyhalofop-butyl. Obtaining the 

following information may improve future assessments conducted by the Agency related to the 

use and importance of cyhalofop-butyl. 

Agricultural Use 

• Information on any additional niche weeds that this herbicide is used specifically to 

control. 

REFERENCES 

BEAD, 2014. Cyhalofop-butyl Screening Level Usage Analysis. Biological and Economic 

Analysis Division, Office of Pesticide Programs, US Environmental Protection Agency. 

February, 2014 

EPA, 2001. Dietrich, Virginia and Frank Hernandez, Review of Request for Emergency 

Exemption for Use of Cyhalofop-butyl (ClincherTM) on Rice to Control Bearded Sprangletop in 

California (01-CA-15) [DP Barcodes 02733377, and 0273379], April 5, 2001 

EPA, 2002. Werling, Virginia and Frank Hernandez, Review of Request for Emergency 

Exemption for Use of Cyhalofop-butyl (ClincherTM) to Control Perennial Grasses Including 

K.notgrass in Rice in Louisiana (02-LA-03) [OP Barcode 0281087], March 27, 2002. 

Fischer, A., et al. California weed control strategies. 2010. Available at: 

http://www.ricefarming.com/home/issues/20 11-03/20 11_ MarStrategies.html 

Nickerson, C., R. Ebel, A. Borchers, and F. Carriazo. 2011. Major Uses of Land in the 

United States, 2007. USDA/ERS. Economic Information Bulletin Number 89. 

Proprietary Data. 2003-2012. (pesticide usage data) 

US Census. 2012. Statistical Abstract of the United States 2012. Table 358 

7 
USDA, 2006-2010. NASS Crop Reporting Districts (shape file ofCRDs). Available at: 

http://www.ers.usda.gov/br}efing/arms/resourceregions/resourceregions.htm#nass. 

USDA, 2006-2010. NASS Crop Reporting Districts. Available at: 

http://www.nass.usda.gov/Data and Statistics/County Data Files/Frequently Asked Questi 

ens/county list.txt 

USDA, 2007. Census of Agriculture. Available at: 

http://www.agcensus.usda.gov/Publications/2007/index.asp. 

USDA, 2007. Census of Agriculture. (for Land in Farms data). Available at: 

http://www.agcensus.usda.gov/Publications/2007/index.asp. 

Wilson, M., J. Norsworthy, D. Johnson, R. Scott, and C. Starkey. 2010. Herbicide programs 

for managing herbicide-resistant barnyard grass in Arkansas rice. Available at: 

http:/ /arkansasagnews. uark.edu/591-26.pdf 

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 amount (in 

pounds) of the active ingredient applied per 1,000 acres of"land in farms" . These data are 

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

across farmland. Because of the definition of Land in Farms, as discussed below, the calculated 

values presented in the map are not equivalent to an application rate (lbs ai/ A). 

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

consider the underlying data and the associated limitations carefully. 

The smallest areas shown on t4e maps within each state are Crop Reporting Districts (CRD). 

CRDs are defined by USDA and each consists of multiple counties that have similar soils, 

growing conditions, and farming practices. The CRDs within many states have roughly the same 

area. Because it is not feasible to conduct an agricultural survey that samples every county in the 

United States, the use of CRDs allow for a sample to be collected that represent a much larger 

area with relatively homogeneous agricultural characteristics. 

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, 2007-2011). 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, there 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 \Yith very small acreages are not included in the survey 

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

amount of the active ingredient being used. 

The denominator (1,000 Acres ofland in farms) was selected from the Census of Agriculture 

(USDA, 2007) to represent agricultural acreage that is actively managed and includes most of the 

9 
areas treated with pesticides. The category "Land in Farms" is defined by the Census of 

Agriculture as being made up of four components: 

• Total cropland 

• Permanent pasture 

• Total woodland 

• Land in farmsteads, buildings, livestock facilities, ponds, roads, wasteland, etc. 

This category includes land in the various USDA conservation programs. It should be noted that 

the Census of Agriculture does not include grazing land rented (on a per-animal basis) from the 

Bureau of Land Management or Forest Service, thus it is an underestimate of the land being 

managed for agricultural purposes. 

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. 

Scale and units of measurement do matter and may be different between maps. 

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