UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

JUNO 4 2015 OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

TO: 

Sulfentrazone Qualitative Benefits Assessment (PC# 129081). 

Bill Chism, Ph.D., Senior Biologist 

Biological Analysis Branch 

Elizabeth Hill, M.S., Economist 

Economic Analysis Branch 

"'J3e-P /.?-#/ ~ 

~ 

-

Biological and Economic Anal sis Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Branc 

Economic 

Timothy Kiely, 

Analysis 

Chief 

Branch ~ ) · ~ ' 

Biological and Economic Analysis 1 • ision (75 

Christina Scheltema, 

Chemical Review Manager 

Neil Anderson, Chief 

Risk Management and Implementation Branch III 

Pesticide Re-evaluation Division (7505P) 

BEAD Product Review Panel date: May 6, 2015 
SUMMARY 

Sulfentrazone is undergoing registration review by the Pesticide Reevaluation Division (PRD). 

The Biological and Economic Analysis Division (BEAD) conducted a qualitative assessment of 

the benefits of sulfentrazone. Sulfentrazone is registered on field crops, fruits, ornamentals, 

turfgrass, and vegetable crops. This qualitative assessment reviews five example crops to 

demonstrate that sulfentrazone is an affordable and effective tool for the control of herbicide 

resistant and difficult to control weeds in com, dry beans/peas, soybeans, sunflower, and 

tobacco. 

BACKGROUND 

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) authorizes EPA to register 

pesticides under 40 Code of Federal Regulations (CFR) Part 158. FiFRA requires the EPA to 

regulate the use of a pesticide to the extent necessary to prevent unreasonable adverse effects on 

the environment, including human health, where 'unreasonable' is defined as taking into account 

the economic, social, and environmental costs and benefits of the use of the pesticide. 

The primary risk concern for sulfentrazone is risk to non-target plants, primarily from spray drift. 

The risk thresholds for chronic effects to birds and estuarine/marine invertebrates are also 

exceeded. Furthermore, the Agency has significant uncertainty in the risk estimate for 

estuarine/marine invertebrates. The Agency has a risk concern for any workers who handle 

sulfentrazone without wearing chemical-resistant gloves; however, most sulfentrazone product 

labels require use of gloves (EPA, 2015b ). 

Sulfentrazone is a broad spectrum, selective herbicide which can be applied either preplant 

incorporated or preemergence for the control of broadleaf, grass and sedge weeds. It is used on 

field crops, fruits, ornamentals, turf grass, and vegetable crops in many states. Sulfentrazone is a 

ProtoPorphyrinogen Oxidase (PPO) Inhibitor (WSSA Group 14). This herbicide inhibits the 

protoporphyrinogen oxidase enzyme which is important in the production of chlorophyll which 

causes a peroxidation oflipids in the cell membrane, leading to cell leakage (WSSA, 2014). 

PPO herbicides provide growers the option of using an additional mechanism of action for 

herbicide resistant weeds. 

For agricultural uses, sulfentrazone is generally soil directed using ground equipment, with low 

booms and larger droplet sizes. Aerial applications account for 2% of the total soybean acres· 

and 5% of the total sunflower acres treated with sulfentrazone. Aerial treatments occur when 

fields are too wet for ground equipment and when treating large acreage fields. 

QUALITATIVE BENEFITS 

Sulfentrazone is used on alfalfa, asparagus, barley, beans (green), beans (lima), cabbage, com, 

cucumber, dry beans/peas, fallow, peanuts, peas (green), potatoes, rice, soybeans, strawberries, 

sugarcane, sunflowers, tomatoes, tobacco, watermelons, and wheat (Chism et. al., 2015). In 

Page2 
selecting crops for this analysis, percent crop treated and average total acres treated were 

considered. Reviewed crops include com, dry beans/peas, soybeans, sunflowers, and tobacco. 

Table 1. Screening Level Usage Analysis (SLUA) Estimates of Agricultural Uses of 

Sulfentrazone. 

Maximum Average Average Single Annual Total Average 

Crop Application Rate Application Acres Percent Crop 

(lb ai/acre) Treated .. , .. (2008-2012) From Label Treated (2004-2013) Ob ai/acre) (2008-2012) 

Asparagus 0.19 0.38 5,550 15 

Barley 0.09 0.19 150 <l 

Cabbage 0.22 0.38 950 <2.5 

Com 0.06 0.25 28,700 <1 

Cucumbers 0.2 0.25 500 <2.5 

Dry 0.09 0.25 414,000 15 Beans/Peas 

Lima Beans 0.08 0.19 950 10 

Peas 

(Fresh/Green 0.13 0.19 <50 <l 

/Sweet) 

Soybeans 0.15 0.38 3,084,800 5 

Strawberries 0.22 0.38 2,200 5 

Sunflowers 0.11 0.25 1,233,950 50 

Tobacco 0.18 0.38 173,500 45 

Tomatoes 0.11 0.38 - <2.5 

Watermelons 0.11 0.25 400 <2.5 

Wheat 0.06 0.19 - <l 

Source: EPA Proprietary Data, 2004-2013 and 2008-2012. 

Corn 

Sulfentrazone is applied at an average application rate of 0.06 lb/A to approximately 28,700 total 

acres annually, or less than one percent of the com crop (EPA Proprietary Data, 2008-2012). 

Although only applied to a limited number of acres, com was considered in this analysis given 

the overall importance ofthis crop in U.S. agriculture. In com, sulfentrazone is recommended 

for the control of a number of difficult to control weeds such as cominon waterhemp, giant 

ragweed, and marestail (Owen, 2011). Overall, for com sulfentrazone controls several difficult 

to control weeds and is slightly less expensive than several of the competing herbicides. 

Dry beans/peas 

Sulfentrazone is applied at an average application rate of 0.09 lb/A to approximately 415,000 

total acres annually, or 15 percent of the dry beans/pea crop (EPA Proprietary Data, 2008-2012). 

In dry beans/peas, sulfentrazone is used in North and South Dakota for the control of ALS 

Page 3 
resistant kochia, an emerging problem weed, with 6 to 8 weeks ofresidual control (Zollinger, 

2004 and Deneke et. al., 2009). Based on EPA Proprietary Data (2009-2013), sulfentrazone is 

the second most used herbicide for the control of kochia and other resistant weeds. In dry 

beans/peas, sulfentrazone effectively controls ALS resistant kochia and is comparable in price to 

available herbicides. 

Soybeans 

Sulfentrazone is applied at an average application rate of 0.15 lb/ A to over 3 million acres 

annually, or 5 percent of the soybean crop (EPA Proprietary Data, 2009-2013). In soybeans, 

sulfentrazone is recommended as part of a resistance management program for control of 

glyphosate resistant Palmer amaranth which can cause extensive crop loss (Sprague, 2013). Of 

the herbicides used to control Palmer amaranth on soybeans, EPA Proprietary Data show that, on 

average, from 2009 to 2013 sulfentrazone was the sixth most used active ingredient and 

accounted for 9% of total acre applications. Sulfentrazone is applied aerially to 2% of total 

soybean acres nationally (Chism et. al., 2015). In soybeans sulfentrazone effectively controls 

glyphosate resistant Palmer amaranth and is comparable in price to other available herbicides. 

Sunflower 

Sulfentrazone is applied at an average application rate of 0.11 lb/ A to over 1.2 million acres 

annually, or 50 percent of the sunflower crop (EPA Proprietary Data, 2009-2013). In terms of 

percent crop treated, sulfentrazone appears to be an important chemical control in sunflower 

production. In sunflowers, sulfentrazone is recommended in Montana for control of ALS 

resistant kochia, a difficult to control weed (Petroff, 2002). Across the United States, 

sulfentrazone is the most used active ingredient for controlling kochia on sunflowers. 

Sulfentrazone is applied aerially to 5% of sunflower fields (Chism et. al., 2015), effectively 

controls ALS resistant kochia on sunflowers, and is comparable in price to other available 

herbicides. 

Tobacco 

Sulfentrazone is applied at an average application rate of 0.18 lb/A to 174,000 acres annually, or 

45 percent of the tobacco -crop (EPA Proprietary Data, 2009-2013). In terms of percent crop 

treated, sulfentrazone appears to be an important chemical control for tobacco production. In 

tobacco, in North Carolina sulfentrazone is one of the few herbicides recommended for control 

of yellow nutsedge, an aggressive and difficult to control perennial weed (Bailey et al., 2014). 

According to EPA Proprietary Data, sulfentrazone is primarily used against morningglory, 

redroot pigweed, and nutsedge species. In tobacco sulfentrazone effectively controls yellow 

nutsedge and is comparable in price to available herbicides. 

CONCLUSION 

Sulfentrazone is used for control of herbicide resistant weeds and difficult to control weeds in 

corn, dry beans/peas, soybeans, sunflower, and tobacco. In these crops, sulfentrazone is 

comparable in price to other available alternative herbicides. Sulfentrazone is generally soil 

directed using ground equipment with low booms and larger droplet sizes. Aerial applications 

account for 2% of the total soybean acres and 5% of the total sunflower acres treated with 

Page4 
sulfentrazone. Aerial treatments occur when fields are too wet for ground equipment and when 

treating large acreage fields. 

REFERENCES 

Bailey, A., T. Lax, B. Hill. 2014. Comparison of Herbicide Systems for Dark Fire-Cured 

Tobacco. Plant and Soil Sciences Research Report Vol. 3, No. 1, 2014. Accessed online 

on April 20, 2015 at 

http://www.uky.edu/Ag/TobaccoProd/FactSheets/PSSRR/2014/Bailey%20Vol%203%20 

No%201.pdf 

Chism, W., J. Alsadek, E. Hill. 2015. Sulfentrazone Usage Information (PC# 129081). EPA, 

Office of Pesticide Programs, Biological and Economic Analysis Division. 

Deneke, D., M. Moechnig, and L. Wrage. 2009. Weed Control in Pulse Crops 2009. Accessed 

online on April 17, 2015 at http://www.sdstate.edu/ps/extension/weedmgmt/upload/FS525PC.pdf 

EPA. 2015a. Proprietary Data 2009-2013. 

EPA. 2015b. Addendum to the Environmental Fate and Ecological Risk Assessment for 

Sulfentrazone Registration Review. Environmental Fate and Effects Division. 

Owen, M. 2011. 2011 Herbicide Guide for Iowa Corn and Soybean Production. Accessed 

online on April 17, 2014 at 

http://www.weeds.iastate.edu/reference/10%20ACU%20WC94. pdf 

Petroff, R.. 2002. Sunflower Production in Montana. Updated: May 28, 2002. Accessed online 

on April 17, 2015 at http://ipm.montana.edu/MPIN/Cropfiles/sunflower.html 

Sprague, C. 2013. Palmer amaranth management in soybeans. Accessed online on April 17, 

2015 at 

http://www.msuweeds.com/assets/ExtensionPubs/5073 7FINALF actSheetPalmerAmarant 

h-2.pdf 

WSSA. 2014. Herbicide Handbook, Weed Science Society of America, Tenth Edition, 2014. 

Zollinger, R.. 2004. Spartan and dry bean desiccants. Accessed online on April 17, 2015 at 

http://www.northarvestbean.org/BeanDay04/zollinger.pdf 

Page 5