UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OC12 2 20\4 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: BEAD Chemical Profile (BCP) for Registration Review: Propoxycarbazone 

sodium (122019) 

FROM: 

THRU: 

TO: 

Carl Chen, Plant Pathologist 

Biological Analysis Branch 

Science 

Cynthia 

Information 

Doucoure, Environmental 

and Analysis Branch 

Protection Specialist (j · ~ 

Stephen Smearman, Economist -- "'J •. _ )w._ 

Economic Analysis Branch ~ u.~ 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Branch 

Science 

Diann Sims, 

Information 

Chief~ and Analysis Branch 

TimothyKiely,Chief 

Economic Analysis Branch ~A~ '-....J 

Biological and Economic Analysis ivision ( 03 ) 

Wilhelmena Livingston, Chemical Review Manager 

Risk Management and Implementation Branch IV 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel date: October 8, 2014 

Page 1 of9 
SUMMARY 

Propoxycarbazone sodium, an herbicide that controls certain post-emergent grasses and 

broadleafweeds in wheat, triticale, rangeland, and pastures was initially registered in June 2004. 

There are currently 6 active Section 3 registrations for propoxycarbazone sodium, including one 

technical. Based on available proprietary usage data, the predominant use of propoxycarbazone 

sodium is on winter wheat. The average annual pounds a.i. applied to winter wheat during the 

2005-2012 period was 30,000, while the average annual pounds a.i. applied to spring wheat was 

3,000. The available data shows that overall use ofpropoxycarbazone on winter wheat has 

decreased since 2005. For spring wheat, use ofpropoxycarbazone has remained relatively low. 

The average percent crop treated (PCT) for winter wheat is 5% while the PCT for spring wheat is 

<2.5%. 

INTRODUCTION 

The purpose of this document is to convey usage information and a broad overview of the pest 

management roles of pesticides that are beginning to undergo registration review. The 

anticipated audience consists of the team of EPA staff currently evaluating the registration status 

ofpropoxycarbazone sodium, and eventually the general public. This document builds upon the 

data BEAD provides in the Label Use Information System (LUIS) reports and the Screening 

Level Usage Analysis (SLUA) to Registration Review teams. The document is based on 

information and data available to BEAD as of July 2014. 

HISTORY OF BEAD ASSESSMENTS FOR PROPOXYCARBAZONE SODIUM 

BEAD prepared a Screening Level Usage Analysis (SLUA) for propoxycarbazone in July 2014 

based on available data from 2004 to 2012 which showed that the primary use of this chemical in 

the U.S. is on winter wheat. Approximately 5 percent of the winter wheat crop is reportedly 

treated using an average annual amount of 30,000 pounds a.i. Propoxycarbazone is used less on 

spring wheat. Less than 2.5 percent of the spring wheat is reportedly treated using an average 

annual amount of3,000 pounds a.i. 

Benefits Assessments- A search of BEAD's Official Records data base for BEAD benefits 

assessments specifically for propoxycarbazone sodium did not find any records of prior BEAD 

assessments specifically for this chemical in the last 10 years. 

Emergency Exemptions- A search of BEAD's Official Records did not find any Section 18s 

requests for propoxycarbazone sodium 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. 

Page 2 of9 
COMMON FORMULATIONS AND APPLICATION METHODS 

Propoxycarbazone sodium is formulated as a water dispersible granule and applied as a preplant, pre-emergence and postemergence application via ground or aerial application equipment. 

USE SITES 

Agricultural Use Sites: 

Propoxycarbazone sodium is registered for use on wheat, triticale, rangeland, pastures, and 

Conservation Reserve Program. 

Non-Agricultural Use Sites: 

There are no non-agricultural use sites registered for propoxycarbazone sodium. 

PROPOXYCARBAZONE SODIUM USAGE 

Agricultural Usage Trend 

Propoxycarbazone sodium is reportedly used on spring and winter wheat in the U.S. Since 2005, 

overall use of propoxycarbazone sodium on winter wheat has declined over the seven year period 

(2005-2012), while use on spring wheat which accounts for approximately 10 percent of the total 

pounds of propoxycarbazone applied (Figure 1) has remained relatively steady but significantly 

lower compared to winter wheat as shown in Figure 1. In terms of area treated, the number of 

winter wheat acres has declined slightly over the same seven year period while the number of 

acres of spring wheat has increased slightly as shown in Figure 2. When comparing the trend in 

the number of acres treated to the number of pounds applied, the continued use of 

propoxycarbazone indicates that growers of both spring and winter wheat still find benefits from 

using it to control various weed pests. Approximately 130,000 lb a.i. are applied annually on 

average to 5,609,000 acres at an overall application rate of 0.023 lb a.i. per acre. The average a.i. 

rate of application on winter wheat is slightly higher (0.026 lb a.i. per acre) than the overall 

average a.i. rate while the average a.i. rate of application on spring wheat is lower (0.011 lb a.i. 

per acre) as shown in Table 1. 

The top states, in terms of the percentage of the total pounds a.i. applied, are Washington (26%), 

Kansas (24%), and Oklahoma (21 %). Washington, Kansas and Oklahoma also have higher than 

average a.i. application rates than other states as shown in Table 2. 

Page 3 of9 
Figure 1. Propoxycarbazone Sodium Usage: Pounds AI Applied, 2005-2012 

., 

.!!! 

'ii. 

a. 

c:t 

.( 

"' ., 

c 

:I 

0 

1:1. 

60,000 

0 

2005 2006 

Source: Proprietary Data, 2005-2012 

2007 2008 2009 2010 

Year 

Wheat, Spring ...-wheat, Winter 

Figure 2: Propoxycarbazone Sodium Usage: Total Area Treated, 2005-2012 

2,000,000 

0 

2005 2006 . 2007 2008 2009 2010 

Year 

Wheat, Spring ...-wheat, Winter 

Source: Proprietary Data, 2005-2012 

Page 4 of9 

2011 

2011 

2012 

2012 
T bl e 1 P a ropoxycar b azone s o d" tum u sage on Wh ea, t 2005 -2012 

Crops Proportion of Proportion of Avg AI. Rate 

Total Pounds AI. Total Area (lb a.i./acre) 

Applied Treated 

Wheat, spring 10% 20% 0.011 

Wheat, winter 90% 80% 0.026 

Source: Propnetary Data, 2005-2012 

T a e bl 2 T op St a t es fi or U se o f P ropoxycar b azone s o dtum, " 2005 -2012 

Top States Proportion of Proportion of A vg A. I. Rate 

Total Pounds AI. Total Area (lb a.i./acre) 

Applied Treated 

Washington 26% 20% 0.029 

Kansas 24% 20% 0.028 

Oklahoma 21% 18% 0.027 

Montana 10% 11% 0.022 

Oregon 7% 7% 0.024 

Other* 0.2-5% 0.5-12% 0.008-0.029 

*Other states include CO, ID, NE, ND, SD, and TX. 

Agricultural Use Intensity ofPropoxycarbazone Sodium Use in the U.S. 

Another measure of usage is the 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 propoxycarbazone sodium's use intensity in the 

U.S. in Washington, Kansas, Oregon, Oklahoma, and Montana show significant use intensity 

compared to other states where propoxycarbazone is used. For more information on Figure 3, 

see Appendix A. 

Page 5 of9 
Figure 3: Annual Average Agricultural Use Intensity ofPropoxycarbazone, 2008-2012 

Pounds Active Ingredient 

per 1 ,000 Crop Acres Grown 

D No Data 

0 <0.02 

D o.o2 -o.1 

- 0.1 - 0.25 

. 0.25 - 0.5 

- >0.5 

Source: Proprietary Data, 2008-2012 

BIOLOGICAL ASPECTS RELEVANT TO PROPOXYCARBAZONE SODIUM 

Propoxycarbazone sodium belongs to the chemical family of sulfonylaminocarbonyltriazolinone. Its site of action is to inhibit acetolactate synthase (ALS) classified by the 

Herbicide Resistance Action Committee (HRAC) and coded as HRAC Group B. It is listed by 

the Weed Science Society of America (WSSA) as a WSSA Group 2 herbicide. In general, the 

Group 2 or ALS inhibiting herbicides are associated with the highest rank of risk on occurrence 

of resistance (WSSA, 2010). Some genera composed ofweeds such as pigweed targeted by 

propoxycarbazone sodium are also associated with the highest rank of resistance risk (WSSA, 

2010; Heap, 2010). 

Page 6 of9 
ROLE OF PROPOXYCARBAZONE SODIUM IN PEST MANAGEMENT 

Propoxycarbazone sodium is an herbicide that can be applied preplant, preemergence, or 

postemergence, and was used mainly in postemergence applications (Proprietary Data, 2011-

2012). It is registered to control a number of grasses and broadleafweeds including cheat grass, 

downy brome, jointed goatgrass, pigweed, and wild oat or mustard in crops such as wheat and 

triticale. 

The major agricultural use of propoxycarbazone sodium is on wheat. Approximately five 

percent of winter wheat in the United States is treated with propoxycarbazone sodium (SLUA, 

2014). In the Pacific Northwest region, approximately 7.7% of winter wheat was treated in 

Washington during the period of2011-2012. The use in Oregon increased from approximately 

6% in 2011 to 17% in 2012 of winter wheat treated (Proprietary data, 2011-2012). 

Section 2(ee) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) allows that a 

pesticide may be mixed with another pesticide not prohibited by the label to control a target pest 

not specified on the label if the application is to the crops specified on the label. The single 

active ingredient product of propoxycarbazone sodium has received several Section 2( ee) 

recommendations for use in over 10 states such as CO, ID, KS, MT, MN, NE, ND, OK, OR, SD, 

WA, and WY. It has a supplemental label for a preplant/pre-emergence bum-down application 

tank-mixed with glyphosate in the fall for control or suppression of Bromus species in winter 

wheat (CDMS, 2014). Propoxycarbazone sodium is also co-formulated with mesosulfuronmethyl, both of which are Group 2 herbicides, for postemergence control of certain grasses and 

broadleaf weeds. 

INFORMATION THAT MAY BE USEFUL FOR BEAD'S FUTURE WORK ON 

PROPOXYCARBAZONESODIUM 

The Agency currently does not have important information on propoxycarbazone sodium. 

Obtaining the following usage information may improve future assessments conducted by the 

Agency related to the use and importance of propoxycarbazone sodium: 

• Propoxycarbazone sodium typical usage information (pounds a.i. applied, average 

application rate and average number of applications) for triticale, rangeland, pastures, and 

Conservation Reserve Program. 

REFERENCES 

CDMS. 2014. Crop Data Management Systems. Accessed August 2014. 

EPA, Propoxycarbazone sodium Screening Level Usage Analysis (SLUA), July 2014 

Page 7 of9 
Heap, I. 2010. International Survey ofHerbicide Resistant Weeds. Online: 

http://www.weedscience.org. Accessed March 2014. 

· Proprietary Data, 2005-2012 

WSSA, 2014. Summary of Herbicide Mechanism of Action. Weed Science Society of America. 

Online: http:/ /wssa.net/wp-content/uploads/WS SA-Mechanism-of-Action. pdf. Accessed March 

2014. 

Page 8 of9 
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 ail 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, 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 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 of9