UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C .. 20460 

JUL 0 2 2015 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: BEAD Review of Diquat Dibromide (032201) Use Summary Tables Submitted by 

Syngenta Crop Protection, DP #427305 

FROM: 

THRU: 

TO: 

Science 

Cynthia 

and 

Doucoure, 

Information 

Environmental 

Analysis Branch 

Protection Specialist C ~ 

Biological and Economic Analysis Division (7503P) 

Diann 

Science 

Sims, 

Information 

Chief ~ and Analysis Branch 

Biological and Economic Analysis Division (7503P) 

Bonnie Adler, Chemical Review Manager 

Risk Management and Implementation Branch V 

Pesticide Re-evaluation Division (7508P) 

This memorandum transmits the review of the Diquat Dibromide Use Summary Table (UST) 

submitted by Syngenta Crop Protection. We evaluated the label information for accuracy and 

assessed the following variables to determine if the subset of labels presented in the report are 

representative of the registered use patterns: 

1) Use Sites 

2) Formulations 

3) Methods 

4) Max Application Rates and Number of Applications 

5) Limitations (i.e. Minimum Retreatment Interval, Preharvest Interval, etc.) & Restrictions 

Diquat dibromide cation is an herbicide used in agricultural, residential and 

commercial/industrial locations, as well as aquatic areas. Currently, there are 95 Section 3 

registrations, including two technical registrations (100-1332 and 74530-57), and 24 Section 24 

(c) diquat dibromide registrations. Syngenta submitted one Diquat Dibromide UST with 

agricultural, non-agricultural, and aquatic label data in separate tabs. The UST label data are 

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based on a subset of diquat dibromide active registrations including 3 Section 3 registrations 

(100-1061, 100-1091, and 100-1390) and 8 24(c) registrations (FL000008, -9, and -10, 

PR030001, SC000005, WA040011, ID100006, and OR080025). Overall, the information 

provided in the UST is representative of most of diquat dibromide uses. Syngenta provides very 

detailed information that clearly describes the use patterns for most diquat dibromide use sites. 

However, BEAD found a few discrepancies as described below. 

I. Sites 

BEAD found that all use sites registered by Syngenta are represented in the UST. The 

only discrepancy found was the identification of artichoke, asparagus, and ginseng as 

bearing crops in the UST. These sites are identified as "non-bearing" in the referenced 

label (100-1061). BEAD also found that Source Dynamic, LLC, another registrant, has an 

end-use registration (82542-15) for use of diquat dibromide on two crops (avocado and 

elderberry) not found in Syngenta's UST. 

II. Formulations 

Diquat dibromide products are formulated as soluble concentrates, liquids ready-to-use, 

and oil-in-water emulsion. All Syngenta formulations are represented in this UST except 

liquid ready-to-use (100-1180 and 100-1114) and oil-in-water emulsion (100-1331). 

III. Application Methods 

Most of the diquat dibromide application methods are represented in the UST, including 

broadcast, spot, and directed sprays using ground and aerial boom sprayers, airboats, 

spray handgun, and backpacks. The only missing application type is stump treatment 

( 100-1179 for example) and missing application equipment include hose-end sprayer 

(100-1344), tank sprayer (100-1179 for example) and other hand-held sprayers such as 

pressure, pump-up, trigger sprayer (100-1329 and 100-1115 for example). 

IV. Max Application Rates and Number of Applications 

The application rates in the Diquat Dibromide UST are presented for the active ingredient 

diquat cation, not the dibromide salt. Most of the minimum and maximum single 

application rates provided in the UST for agricultural crops, non-agricultural use sites, 

and aquatic sites accurately reflects the application rates found on the label. For use sites 

that contain missing use patterns (maximum number of applications, application rates per 

crop cycle, crops cycles per year, number of apps per year and yearly application rates), 

Syngenta has provided proposed values with yellow highlights in the UST. 

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Syngenta's UST includes a spot treatment application rate for sites such as fence lines, 

farmyards, and barrier strips (0.5 lb a.i. per acres single max app rate) and a spot 

treatment dilution rate of 0.01 lb a.i. per gal for landscape and commercial greenhouse 

use sites. However, BEAD also found on label 100-1344 a higher single maximum 

application rate of 10 fl oz per 350 sq ft, which converts to 0.97 lb a.i. per acre for several 

outdoor uses including landscape, patio, fencerows, etc. 

V. Limitations & Restrictions 

All pertinent limitations and restrictions were found in the Diquat Di bromide UST. 

Conclusion: 

BEAD reviewed the UST from Syngenta Crop Protection and found that it represents most of the 

diquat dibromide use patterns. Feedback from Syngenta on the labeled "non-bearing" 

designation for artichoke, asparagus, and ginseng and on the missing spot treatment application 

rate, formulations, and application methods are recommended before finalizing the Syngenta 

UST for use in risk assessment. 

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