UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON , D.C. 20460

MAY 23 2011

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

MEMORANDUM

SUBJECT: BEAD Chemical Profile for Registration Review: Orthosulfamuron (108209)

FROM: Sunil Ratnayake, Botanist

Biological Analysis Branch

Stephen Smearman, Economist

Economic Analysis Branch

Biological and Economic Analysis Division (7503P)

THRU:

TO:

Arnet Jones, Chief

Biological Analysis Branch

Diann Sims, Chief A1~f1v~. J;rMScience Information and Analysis~ranch

Timothy Kiely, Chief

Economic Analysis Branch · J

Biological and Economic Analys Division (7 )

James Parker, Chemical Review Manager

Risk Management and Implementation, Branch 1

Pesticide Reevaluation Division (7508P)

Product Review Panel date: May 18,2010

INTRODUCTION

The purpose ofthis document is to convey usage information and a broad overview ofthe pest

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

anticipated audience consists ofthe team ofEPA staff currently evaluating the registration status

of Orthosulfamuron, 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

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

to BEAD as ofMay 5, 2011.

Brief description ofthe pesticide, including chemical class, mode of action, and main target

pests.

Orthosulfamuron, a member ofthe sulfonylurea family, is a systemic herbicide that can be

used for the control of annual and perennial broadleaf weeds and sedges in rice production

fields. Orthosulfamuron inhibits the activity of aceolacte synthase enzyme (ALS) which is

important for the synthesis of branched chain amino acids {leucine, isoleucine, and valine) in

susceptible weeds. Orthosulfamuron is applied as an early post-emergence treatment and has a

broad spectrum ofselectivity at a very low rate. It is rapidly absorbed through leaves and roots

and translocated in to the other plant tissues. Selectivity mechanism involves the differential

rates ofmetabolism in different weed species (Isagro, 2011). Orthosulfamuron is suitable for

weed control in both water seeded and dry seeded rice production (orthosulfamuron Technical

Bulletin, 2010).

USE SITES

Agricultural Use Sites

This herbicide is recommended for the control of annual and perennial grasses, sedges, and

broadleaf weeds found in rice fields.

COMMON FORMULATIONS AND APPLICATION METHODS

Orthosulfamuron is formulated as water dispersible granules and emulsifiable concentrate. This

herbicide can be applied using ground (tractor mounted sprayers and spreaders) and aerial

equipment.

USAGE

Agricultural Usage

Orthosulfamuron was registered for use on rice in 2007. Approximately 3 million acres ofrice is

grown in the United States. Based on private market usage data from 2007-2010, usage averaged

approximately 3,000 pounds active ingredient (a.i.) for 45,000 acres treated on rice, the only

registered use site, as shown in Figure 1. Since 2007 the use oforthosulfamuron on rice has

steadily increased through 2010. Orthosulfamuron is typically applied one time per year at a rate

of 0.06Ibs. a.i. per acre (Proprietary Data, 2007-2010).

The states with the most agricultural usage for the years 2007- 2010 in terms of pounds a.i.

applied were Arkansas (69%) and Missouri (30%) as shown in Figure 2. Minor use was also

reported in California (1%) (proprietary Data, 2007-2010).

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FIGURE 1. Orthosulfamuron Usa e

6,000 ...-----------------------

o

2007 2008 2009 2010

Years

2007-2010, Proprietary Data

FIGURE 2.

2007-2010, Proprietary Data

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Non-Agricultural Usage

BEAD reviewed available data sources, but there was no information on orthosulfamuron nonagricultural use.

BIOLOGICAL ASPECTS RELEVANT TO ORTHOSULFAMURON

Description of other unique issues including resistance, plant health claims, and public health

issues.

Presence of 43 weed species resistant to ALS inhibitors has been reported in the United States

(Heap et al. 2011). However, no reports could be found on the herbicide resistant weeds,

specifically, to orthosulfamuron in rice production fields in the U.S. Halosulfuron,

penxosulam, bensulfuron, bispyribac sodium, and propanil are the most competitive

registered post-emergence herbicides to orthosulfarnuron. Except propanil, mode of action

ofthese herbicides is similar to orthosulfamuron. Compared to orthosulfamuron, and

halosulfuron, penoxsulam has a greater efficacy on water hyssop (Bacopa spp). However, it is

less effective on controlling alligator weed (Alternanthera philoxeroides). Compared to

orthosulfamuron, bispyribac sodium, and propanil have a greater activity on watergrass

species and they are less effective on weed species such as ducksalad (Heteranthera spp.)

and yellow nutsedge (Cyperus esculentus). Also, bensulfuron provides a poor control of

watergrass species (Echinochloa spp.) (Texas Rice Production Guidelines, 2010).

mSTORY OF BEAD ASSESSMENTS FOR ORTHOSULFAMURON

EAB searched the BEAD data base for previous assessments for orthosulfamuron. The search

results found only one document in the BEAD Official Records which was a Public Interest

Finding in which BEAD determined that the availability of orthosulfamuron would be in the

public interest (Ratnayake, 2006). Orthosulfamuron was considered as an alternative to control

watergrass weeds resistant to propanil, cyhalofop and fenoxoprop in rice fields in California

(Ratnayake, 2006).

There were no other documents found in BEAD's Section 18, QUA or Use and Usage Request

data bases.

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

ORTHOSULFAMURON

BEAD specific Registration Review issues, as relevant, including BEAD data gaps needed for

future assessments and BEAD work plan. There are no data gaps identified by BEAD at this

time.

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REFERENCES

2007-2010, Proprietary Data.

2010. Texas Rice Production Guidelines.

http://beaumont.tamu.edu/eLibrary/Bulletins/2010 Rice Production Guidelines.pdf

Orthosulfamuron Technical Bulletin. ISAGRO.

http://www.isagro.com/images/stories/file/PDF/Orthosulfamuron%2OTechnical%20Bulle

tin%20may2010.pdf. Accessed on May 5, 2011.

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

and Site ofAction. http://www.weedscience.org/summary/countrysummary.asp

Ratnayake, S. 2006. Review ofPublic Interest Documentation for the Registration of

Orthosulfamuron Herbicide for Control of Sedges, Broadleaf, and Aquatic

Weeds in Rice Production. DP # 327089. A Publication ofEnvironmental Protection

Agency.

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