UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

DEC 12 2014 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

TO: 

BEAD Chemical Profile (BCP) for Registration Review: Diclosulam (129122) 

Leonard Y ourman, Biologist 

Biological Analysis Branch 

Rafael 

Science 

A. 

Information 

Prieto, Environmental 

and Analysis 

ProtectiOn 

Branch 

Speciali~ /7""'1Jt:C 

~ , / 

~ 

/l 

Economic 

Derek 

Biological 

Berwald, 

Analysis 

and Economic 

Economist 

Branch 

Analysis 

c;;?'~ 

Division 

~ 

(7503P) 

Arne! 

Biological 

Jones, 

Analysis 

Chief 

Bran,ch 

~~ 1 . 

" ~ A i4~ , Diann Sims, Chief -- It ~ ~ 

Science Information and Analysis Branch 

Timothy Kiely, Chief ~ ~"\ \,~ Economic Analysis Branch ~ 

Biological and Economic Analysis ivision ( ) 

Sue Bartow, Chemical Review Manager 

Risk Management and Implementation Branch 4 

Pesticide Re-evaluation Division (7508P) 

Product Review ~anel: November 26, 2014 

l 
INTRODUCTION 

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

overview of the pest management roles and quantitative usage information for diclosulam. The 

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

usage data for diclosulam to describe the role of this chemical in pest management. Additional 

information on use is available in the diclosulam Label Data Report. Information provided in 

this BEAD Chemical Profile (BCP) may be used by stakeholders (e.g., users and registrants), 

OPP risk assessors, and OPP risk managers, and the general public during the Registration 

Review process of this pesticide. Diclosulam was first registered in 2000. According to the 

Screening Level Usage Analyses (SLUA) (BEAD, 2014) diclosulam is only used on peanut with 

an average of 4,000 pounds active ingredient (a.i.) applied and an average percent crop treated 

(PCT) of20%. There is an active label (Strongarm, 62719-288) allowing use on soybeans in 

some states although BEAD has no usage data for this use site. 

USE SITES 

Diclosulam is used for production of peanuts and is registered in Alabama, Arkansas, Florida, 

Georgia, Illinois, Louisiana, Missouri, Mississippi, North Carolina, South Carolina, Tennessee, 

and Virginia. There are 24(c) Special Local Needs (SLN) registrations indicating a special local 

need for diclosulam to control tropical spiderwort in peanut in Georgia, Florida and Mississippi. 

Diclosulam is labeled for use on soybean in Alabama, Arkansas, Delaware, Florida, Georgia, 

Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Mexico, North Carolina, Oklahoma, 

South Carolina, Tennessee, Texas, and Virginia. A single preplant soil incorporated application, 

soil surface application, or a preemergent incorporation may be made. BEAD has no 

information or usage data suggesting that diclosulam is actually used on soybean fields. 

There are two diclosulam SLN labels for cottonwood plantings in Missouri and Tennessee. 

FORMULATIONS AND APPLICATION METHODS 

Diclosulam is registered as a dry flowable formulation in water soluble packets. Diclosulam is 

labeled for soil applications for most peanut production. It may be applied preplant incorporated 

into soil, preplant surface application, or preemergence through the soil "cracking" phase of the 

peanut emergence (i.e., germinating plant breaking through the soil). For the 24(c) registrations 

to control tropical spiderwort, diclosulam should be applied to the weed at the 1 to 2 leaf stage 

while it is actively growing. For this use, the chemical can be applied from the soil cracking 

phase to the initiation of flowering, but no later than 30 days after planting. 

For soybean, a single preplant soil incorporated application, soil surface application, or a 

preemergent incorporation is indicated on at least one label (Strongarm, 62719-288). 

2 
HISTORY OF DICLOSULAM AND BEAD PRODUCTS 

There is no record of BEAD documents relating to diclosulam. 

USAGE 

For the 2000-2012 timeframe, the annual usage of diclosulam averaged 4,000 pounds a.i. treating 

an annual average of200,000 acres of peanuts, with an overall average application rate of0.02 

pounds a.i. per acre. As shown in Figures 1 and 2, usage for peanut, both in terms of pounds a.i. 

and in terms of total area treated (TAT) has slightly decreased since a minor peak in 2005 

(Proprietary Data, 2000-2012). The SLN labels effective for Georgia (initially in 2004), Florida 

(2007), and Mississippi (2008), which allows applications post-emergence to control tropical 

spiderwort may help to explain some of the higher use after 2003 indicated in Figures 1 and 2. 

According to the SLUA (BEAD, 2014) diclosulam is only used on peanut with 4,000 pounds 

active ingredient (a.i.) applied and an average percent crop treated (PCT) of20%. Georgia and 

Alabama usage constitute over 80% of diclosulam pounds used on peanut fields (Table 1 ). 

BEAD proprietary data show no use for soybean. 

Usage Trends 

FIGURE 1. Diclosulam Total Area Treated in Acres (2000-2012) on Peanuts 

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3 
FIGURE 2. Diclosulam Total Pounds Applied (2000-2012) on Peanuts 

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0 M N m ~ ~ ~ ~ 00 m 0 M N 0 0 0 0 0 0 0 0 0 0 M M M 0 0 0 0 0 0 0 0 0 0 0 0 0 N N N N N N N N N N N N N 

Year 

Source: Proprietary Data, 2000-2012 

TABLE 1. States with Highest Use ofDiclosulam on Peanuts -Share of 

National Use of Diclosulam (2008-2012) 

Share of National Use of Average AI Rate 

State Diclosulam (%) (lbs/acre) 

Georgia 46 0.017 

Alabama 36 0.020 

Florida 8 0.016 

North Carolina 6 0.016 

Virginia 4 0.017 

Source: Propnetary Data, 2008-2012 

4 
Geographic Distribution of Diclosulam Use 

Figure 3 shows the geographic distribution of diclosulam use. The map shows that diclosulam is 

used in states that grow peanuts except in the peanut growing areas of Texas, Oklahoma and 

New Mexico where diclosulam use is prohibited by label. 

Pounds Active Ingredient 

per 1 ,000 Crop Acres Grown 

UNoData 

- <0.001 

- 0.001 - 0.05 

. 0.05-0.1 

- >0.1 

Figure 3. Annual Average agricultural use intensity of diclosulam (2008-2012). 

More information about this map is presented in Appendix A. 

5 
CHEMICAL AND USE CHARACTERISTICS 

Diclosulam is a triazolopyrimidine sulfonanalide chemical of the acetolactate synathase (ALS) 

inhibitor group of herbicides (WSSA Group 2). Therefore, it will not control ALS-resistant 

weeds. It was originally developed for broadleaf weed control in peanut and soybean (Clewis 

and Wilcut, 2004). 

ROLE OF DICLOSULAM IN PEST MANAGEMENT 

Diclosulam is used for broadleaf control-it provides good to excellent control of bristly starbur, 

wild poinsettia, eclipta, and copperleaf. It has provided poor control of sicklepod and 

inconsistent control of nutsedges (Marshall, 20 12). Several herbicides of different chemical 

groups are available for preplant incorporation or pre-emergent application and generally provide 

a range of efficacy against the various problem weeds. For example, imazethapyr (also an ALSinhibitor) is effective against nutsedges. Commonly, more than one herbicide are used to expand 

the range of targeted weeds. 

The product label restricts the use of diclosulam in Oklahoma, Texas, and New Mexico due to 

alkaline soils and the risk of crop injury. In field plot experiments diclosulam applied preemergent resulted in 50% crop injury (Dotray et al., undated). The SLN labels approved for 

Georgia, Florida, and Mississippi for the postemergence use of diclosulam to control tropical 

spiderwort indicate that there is a value for diclosulam with a different use pattern. 

In alkaline soils research in Texas indicated that post-emergence use reduced the incidence of 

crop injury observed in preplant or pre-emergence applications (Dotray et al., undated). 

Currently diclosulam is labeled for preplant or pre-emergence soil application in peanut 

production in Alabama, Arkansas, Florida, Georgia, Illinois, Louisiana, Missouri, Mississippi, 

North Carolina, South Carolina, Tennessee, and Virginia. 

Diclosulam is one among several herbicides that can be used in peanut production. The 

preharvest interval for diclosulam is 30 days. In soils with iron-induced chlorosis the use of 

diclosulam may exacerbate the effect. Soybeans and peanut may be planted without a rotation 

interval restriction after peanut crops where diclosulam has been used. There are substantial 

restrictions on rotations to other crops after the use of diclosulam, however. These range from 

four months for wheat and barley to 30 months for sugarbeets, sunflower, and other crops that do 

not have a specified rotation interval. 

Diclosulum is labeled for use on soybean in Alabama, Arkansas, Delaware, Florida, Georgia, 

Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Mexico, North Carolina, Oklahoma, 

South Carolina, Tennessee, Texas, and Virginia. According to the pesticide label, a single 

preplant soil incorporated application, soil surface application, or a preemergent incorporation 

may be made. A wide range of broadleaf weeds are targeted although additional herbicides may 

be necessary to increase the efficacy against some weeds (e.g., nutsedges). However, BEAD has 

no information that diclosulam is actually used on soybean fields. 

6 
DATA NEEDS 

The Agency currently does not have complete information on use and usage of diclosulam for 

peanut production. Obtaining additional information may improve future assessments conducted 

by the Agency related to the use and importance of diclosulam. For example, BEAD has little 

information as to additional possible niche uses, use patterns, or specific problem weeds where 

diclosulam might fill a need that is currently lacking for growers. The 24( c) labels indicate a 

potential value for postemergence use for tropical spiderwort. On the other hand, the presence of 

ALS-resistant weeds will likely reduce the usefulness of diclosulam where resistant populations 

have developed or where resistant populations develop or spread. Information on changes in use 

and usage as a result of weed resistance may help determine the future use trends for diclosulam 

and ultimately the comparative benefits of the herbicide. 

BEAD information indicates no use of diclosulam in soybean fields in the U.S. Information on 

diclosulam use on soybean fields in general and particularly in Texas, Oklahoma, and New 

Mexico may be valuable. These are areas where use on peanut fields is prohibited and where 

diclosulam-induced injury to peanuts has been observed. 

BEAD has no information on diclosulam SLN uses for cottonwood plantings. Presumably there 

is some benefit not available with other herbicides. Information on particular weed issues may 

be helpful if a benefits assessment is required. 

REFERENCE 

BEAD. 2014. Diclosulam Screening Level Usage Analysis. Biological and Economic Analysis 

Division, Office of Pesticide Programs, U.S. Environmental Protection Agency. 

Clewis, S. B. and Wilcut, J. W. Economic assessment of diclosulam and flumioxazin in stripand conventional-tillage peanut. 26th Southern Tillage Conference. Auburn University Extension. 

http://www.ag.aubum.edu/auxiliary/nsdl/scasc/Proceedings/2004/Clewis3.pdf 

Dotray, P. A., Murphree, T. A., Light, G. G., Grichar, W. J., Keeling, J. W., Baughman, T. A., 

Langston, V. B. (Undated) Weed control systems in peanut with diclosulam postemergence. 

Texas A&M AgriLife Research & Extension Center at Lubbock. 

http://lubbock.tamu.edu/programs/disciplines/weeds/peanut/weed-control-systems-in-peanutwith-diclosulam-postemergence/ 

Marshall, M. 2012. Weed Control in Peanut. South Carolina Pest Management Handbook for 

Field Crops. Clemson University Extension. 

http:/ /www.clemson.edu/extension/rowcrops/pest/files/20 12%20PMH%20Web%20Page%20Ver 

sion/20 12%20PMH PEANUTWC.pdf 

Proprietary Data. 2000-2012. 

7 
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 ofthe 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 the 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 with 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 2007 Census of 

Agriculture 

(http:/ /www.agcensus.usda.gov/Publications/2007 /Full Report/Volume 1, Chapter 1 US/usv 1. 

pdt) to represent agricultural acreage that is actively managed and includes most of the areas 

8 
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. 

9