UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

APR 05 2012 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

TO: 

BEAD Chemical Profile for Registration Review: Rimsulfuron (129009) 

Sunil Ratnayake, Biologist 

Biological Analysis Branch (kJ-\~ Cynthia 

Science Information 

Doucoure, Environmental 

and Analysis Branch 

Protection Specialist ~ 

Economic 

Stephen Smearman, 

Analysis Branch 

Economist ~~ 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Branch 

Diann Sims, Chief /1t~ Science Information and Analysis Branch 

Timothy 

Economic Kiely, Analysis 

Chief 

Branch 

91 \1\1\ 

V\I \ ~ 

Biological and Economic Analysis ivision (7 

Jose Gayoso, Chemical Review Manager 

Risk Management and Implementation Branch 2 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel date: March 7, 2012 

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 

of rimsulfuron, and eventually the general public. This document builds upon the data already 

provided in the "Usage and Label Use Data Packages" that are also provided to Registration 

Review teams by BEAD. The document is based on information and data available to BEAD as 

of March 5, 2012. 
BACKGROUND 

Rimsulfuron was ftrst registere,d as an herbicide in the U.S. in 1994. This herbicide belongs to 

the sulfonylurea herbicide family and mode of action of this herbicide is inhibition of the activity 

of acetolactate synthase (ALS) enzyme which is important for synthesis of branched chain amino 

acids (leucine, isoleucine, and valine). Rimsulfuron is a selective herbicide applied as fallow, 

pre-plant, pre-emergence, and post-emergence treatments to control broadleaf and grassy weeds 

on crops described below. Rimsulfuron is absorbed by leaves and roots of susceptible weeds and 

provides effective weed control at very low application rates compared to many other herbicides. 

USE SITES 

Agricultural Use Sites , 

Rimsulfuron is labeled for use on grapes, vineyards, citrus fruits, nut crops, pome fruits, stone 

fruits, tropical and sub-tropical fruits, fruiting vegetables, root crop vegetables, seed and pod 

vegetables, com, cotton, orchards, fruit trees, soybeans, chicory, chinquapin, and farmyards 

(including fuel storage areas, uncultivated areas, fallow land and barrier strips). 

Non-Agricultural Use Sites 

Rimsulfuron is also labeled for non-residential use on rangeland, ornamental lawns and turf, 

ornamental trees, drainage systems, and uncultivated non-agricultural areas (airports, rights-ofway, roadsides, utility substations, pipeline pumping stations, sewage disposal areas, industrial 

sites, lumber yard,tank farms, and fencerows). 

COMMON FORMULATIONS AND APPLICATION METHODS 

Rimsulfuron is formulated as water dispersible granules (dry flowable), emulsifiable 

concentrates, and soluble concentrates/solids. This herbicide can be applied using the following 

application methods: ground and aerial applications, broadcast applications (followed in some 

instances by soil incorporation), band applications, and chemigation. 

USAGE 

Agricultural Use Trends. 1998-2010 

Rimsulfuron use in terms of average pounds a.i. applied in the U.S., as reported in private market 

research surveys, fluctuated between 1998 and 2010, with a steep decline in usage after 2004, 

followed by a slight upward trend in recent years (Figure 1). Similar results were found in terms 

of total acres treated. The top agricultural crops treated with rimsulfuron (pounds applied) 

during this period were com (84%), potatoes (6%), tomatoes (5%), and almonds (2%). Figure 2 

shows the use pattern of rimsulfuron use on the major crops. During this period, on average, 

92,000 pounds of rimsulfuron were applied to 7,404,000 acres per year at an overall average 

application rate of 0.OI2Ibs/acre. 

2 
Figure 1. Rimsulfuron Use Trend: Pounds A.I. Applied, 1998-2010 

120,000 

...: 

- RIMSULFURON 

0 i ---r 

co (i'I 0 ..-t N fB g II) 

~ l' co C'l 0 

C'l (i'I 0 0 0 0 0 0 0 ..... O"l CTI 0 0 0 0 0 0 0 0 0 0 0 

.-I ..... N N N N N N N N N N N 

Years 

Source: Proprietary Data, 1998-2010 

Figure 2. Rimsulfuron Use Trend: To Markets for Pounds A, I. A lied,1998-201O 

120,000 

I I 

"2" 

~ 

~ ~ 

<II 

=a 

Do 

IV 

.-ra 

:9 

--_ ........ _-

o 

-Corn (left axis) 

T 24,000 

- - Potato 

----Tomato 

••••••• Almond 

- Other 

: ....... . .;. 

: '-... .... ::-.... _-_.. I 

• T j 0 

i 

Q, 

... 

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 

Year 

Source: Proprietary Data, 1998-2010 

"Other" crops include almonds, apples, apricots, cantaloupes, celery, cherries, cotton, dry beans/peas, grapes (raisin, 

table, and wine), lemons, oranges, peaches, pears, pistachios, plums/prunes, soybeans, sunflowers, sweet com, and 

walnuts. 

3 
Agricultural Use, 2006-2010 

Based on private market pesticide usage data from 2006-2010, agricultural usage of rimsulfuron 

averaged approximately 79,000 pounds annually and was applied on average to approximately 

5,355,000 acres at an overall average application rate of 0.015 lbs per acre, a 25% increase over 

the 1998-2010 average application rate. Decreased use of rimsulfuron, particularly on com, 

continued at the beginning of this period followed by a slight increase in usage in rece~t years 

due in part to the increased use of rimsulfuron on potatoes, tomatoes, almonds and other crops. 

The top agriCUltural crops in terms of pounds of rimsulfuron during this period were com (72%), 

potatoes (8%), tomatoes (7%), and almonds (4%) as shown in Figure 3. Similar results were 

found in terms of total acres treated. 

F~e 3. Rimsulfuron: Top Crops for Pounds A.1. Applied, 2006-2010 

Almonds 

Source: Proprietary Data, 2006-2010 

The states with the most agricultural usage of rimsulfuron in terms of pounds a.i. applied were 

California (20%), Iowa (15%), Missouri (8%) and lllinois (7%). However, in terms of total acres 

treated, the top states are Iowa (19%), Missouri (10%), lllinois (9%), California (7%), Nebraska 

(7%), and Minnesota (6%) as shown in Figure 4. Rimsulfuron is also used on a variety of other 

crops in over 30 additional states and accounts for 50% of pounds a.i. applied and 55% of total 

acres treated during this period. 

4 
Figure 4. Rimsulfuron: Top States, 2006-2010 

Other, 

50% 

Ib applied 

8% 

Source: Proprietary Data, 2006-2010 

Other 

55% 

acres treated 

"Other" states include AL, AR, CO, DE, FL, GA, ID, KS, KY, LA, ME, MD, MI, MN, MT, NJ, 

n~~~~~~~~~m~~~m~~ 

Agricultural Usage by Crop Reporting District 

a 

7% 

Iowa 

19% 

Another measure of usage is the ilse intensity. In this analysis, the use intensity is expressed as 

the pounds a.i. applied per acre of land in farms. This differs from the application rate, which is 

expressed as the pounds a.i. applied per treated acres. Figure 6 spatially represents rimsulfuron's 

use intensity in the U.S., which is relatively greater in California, Iowa, Minnesota, Missouri, 

Michigan, and Maryland. 

5 
Figure 6. Rimsulfuron Usage by Crop Reporting District (2006 - 2010) 

Average Pounds Per 

1,000 Acres of Farmland 

• <O.OB 

0. OB - 0.17 

0 0.1B-O.31 

. 0. 32-0.8 

. 0. 61-1.25 

Source: Proprietary Data (2006-2010) 

This is a map of agricultural pesticide usage at the Crop Reporting District (CRO) level. CROs 

are boundaries created by USDA NASS which are aggregates of counties (USDA, 2010). 

Pesticide usage is displayed as average pounds (for the years 2006-2010) per 1,000 acres of 

farmland in a CRO to normalize for the variation in farmland between CROs. Farmland acreage 

was obtained from USDA (2007). 

Usage is based on private market surveys of pesticide use in agriculture (Proprietary Data, 2006-

2010). The survey data are limited to the states that represent the top 80-90% of acreage for the 

individual crops, therefore, use may be occurring in regions outside the scope of the survey. CROs 

showing no usage of pesticides may be due to either the lack of pesticide use in the region or nonparticipation in the agricultural surveys. In addition, across the years, there may be variations in 

the specific crops included in the CRD survey. This may result in a lower annual average for the 

CRO. 

6 
Non-Agricultural Use 

No available national-level usage data were found for use of rimsulfuron on non-agricultural use 

sites. 

BIOLOGICAL ASPECTS RELEVANT TO RIMSULFURON 

Rimsulfuron belongs to the family of sulfonylurea herbicides and the mode of action of this class 

of herbicides is inhibition of acetolactate synthase (ALS) enzyme. The presence of 44 weed 

species resistant to ALS inhibitors has been reported in the United States (Heap et al. 2011). 

However, according to this database, no reports were found on development of resistance 

specifically for rimsulfuron. The control of weed species resistance to ALS inhibitors can.be 

achieved by tank mixing compatible registered herbicides with a different mode of action to 

rimsulfuron. The investigations on postemergence applications of rimsulfuron plus 

thifensulfuron-methyl with various acetolactate synthase (ALS)- and non-ALS-inhibitor 

herbicides for weed control in com has reported a greater control (95%) of giant foxtail (Setaria 

faberi) and common lambsquarters (Chenopodium album) by tank mixing rimsulfuron with 

thifensulfuron-methyl (Isaacs et al., 2002). 

IDSTORY OF BEAD ASSESS:MENTS FOR RIMSULFURON 

In March 2011 there were two Section 18 requests for the use of rimsulfuron mixed with 

thifensulfuron to control broadleaf weeds in chicory production in the BEAD Official Records 

data base. The BEAD reviews of the Section 18 Emergency Exemption Requests from 

Nebraska (11 NE-03, 11-NE-04) (DP# 386264, DP# 386265) and Wyoming (11 -WY-02,11-

WY -03) (DP# 386266, DP# 386267) determined that the requests did not qualify as urgent and 

non-routine situations under FIFRA Section 18 guidelines because there were sufficient 

alternatives already registered and available. 

There were no other assessments or Section 18 requests in the BEAD Official Records data base 

for rimsulfuron. 

CONCLUSION 

The rimsulfuron usage trend is mixed. The major use market for rimsulfuron, com, decreased 

based on proprietary data. It appears that rimsulfuron is not as beneficial as it once was for com 

growers as glyphosate has absorbed market share ·once held by rimsulfuron. Even though there 

is increasing resistance to glyphosate, it is not certain that the rimsulfuron market will return for 

com. The number of rimsulfuron pounds of active ingredient used on com dropped nearly 50% 

in the period from 2004 to 2010 while the total number of pounds ai of glyphosate applied to 

com annually has increased in the same time period. However, rimsulfuron is seeing an increase 

in use on other crops as more sites are approved for registration. For almond growers and other 

nut and fruit tree producers, increase in usage suggests that rimsulfuron has become a very 

beneficial tool. Its use in terms of pounds a.i. applied on almonds has increased by over 350% 

in the period between 2008 and 2010. For field crops such as potatoes and tomatoes, 

rimsulfuron's use has remained constant during the time period from 1998-2010 so growers still 

have a need for rimsulfuron on these two and similar crops. 

7 
INFORMATION THAT MAY BE USEFUL FOR BEAD'S FUTURE WORK ON 

RIMSULFURON 

Obtaining additional usage information on non-agricultural uses of rimsulfuron would assist 

BEAD with improving future assessments regarding the importance of rimsulfuron. Usage 

information may also be required as part of the registration review of this pesticide. 

REFERENCES 

Heap, I, H. Glick, L Glasglow, and W. Vencill. 2011. Herbicide Resistant Weeds by Country 

and Site of Action. 2011. http://www.weedscience.orglsummary/countrysummary.asp . 

Isaacs, M. A., H. P. Wilson, and J. E. Toler. 2002. Rimsulfuron Plus Thifensulfuron-Methyl 

Combinations with Selected Post Emergence Broadleaf Herbicides in Corn (Zea mays). 

Weed Tehnology 16:3, pp. 664-668. 

Proprietary Data, 1998-2010. 

Ratnayake, S., and J. Faulkner. 2011. Review of Section 18 Emergency Exemption Requests from 

Nebraska (11 NE-03, I I-NE-04) (01 '# 386: 164,01' # 386265) and Wyoming (11 -WY-02, 

ll-WY-03) (01'# 386266,01'# 386267) for Use of Basis· (Thifensulfuron and Rimsulfuron) to 

Control BroadleafWeeds in Chicory Production. 

USDA, 2006-2010. NASS Crop Repprting Districts. Online: 

http://www.ers.usda.govlbriefing/arms/resourceregions/resourceregions.htm#nass. 

USDA, 2007. Census of Agriculture. Online: 

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

8