UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

DEC 0 4 2014 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: BEAD Chemical Profile (BCP) for Registration Review: Penoxsulam 

(119031) 

FROM: Sunil Ratnayake, Biologist fl ~ L · Biological Analysis Branch l ~ ~ 

Sepehr Haddad, Environmental Protection Specialist fiJ__... /""' -~ 

THRU: 

Science Information and Analysis Branch r~ 

Stephen Smearman, Economist 

Economic Analysis Branch 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Branch 

,":), 

Diann Sims, Chief 

Science Information and Analysis Branch 

Timothy 

Economic 

Kiely, 

Analys

Chi

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ef 

Branch \) 

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Biological and Economic Analysts Division ( P) 

TO: Khue Nguyen, Chemical Review Manager, RMIB III 

Pesticide Re-evaluation Division (7508P) 

Peer Review Panel date: November 19,2014 
SUMMARY 

Penoxsulam was first registered in the United States as an herbicide in 2004 (USEPA, 2004). 

This herbicide belongs to the triazolopyrimidine family of herbicides. It is applied as a postemergence treatment to control annual grasses, sedges, and broad leaf weeds in agricultural 

and non-agricultural use sites described below. 

Based on private market usage data from 2005-2012, usage averaged approximately 6,500 

pounds active ingredient (a.i.) applied annually on approximately 207,000 acres treated. The 

average application rate over this time period was pounds 0.03 lbs a.i./acre. A Screening 

Level Usage Analysis (SLUA) was prepared by BEAD for this chemical in 2014 that 

provides the percent crop treated for six crops (almonds, pecans, pistachios, plums, rice and 

walnuts). During the timeframe of 2004-2012, usage of penoxsulam on rice averaged 6,000 

lbs a.i. with an average 5 percent crop treated, and for almonds, usage averaged 1,000 lbs. a.i. 

with an average of 5 percent crop treated. For the remainder of the crops listed in the SLUA 

(pecans, pistachios, plums, and walnuts) the average pounds a.i. was less than 500 lbs each 

over this timeframe. 

INTRODUCTION 

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

an overview of the pest management roles and quantitative usage information for 

penoxsulam. The BCP includes summaries of·previous BEAD products and available public 

and/or private use and usage data for penoxsulam to describe the role of this chemical in pest 

management. Additional information on use is available the Screening Level Usage Analysis 

(SLUA). Information provided in this BCP may be used by stakeholders (e.g., users and 

registrants), OPP risk and benefit assessors, OPP risk managers, and the general public 

during the Registration Review process of this pesticide. 

USE SITES 

Agricultural Use Sites 

Registered agricultural use sites of penoxsulam include: Fruit trees (non-bearing), conifer 

seed orchards, nut trees, rice, and vineyards. 

Non-Agricultural Use Sites 

Registered non-agricultural use sites of penoxsulam include: ornamental lawns and turf, 

eucalyptus, non-crop areas, paved and unpaved areas, ponds, reservoirs, rights-of-way, sports 

arenas, and wetlands. 

Page 2 
FORMULATIONS AND APPLICATION METHODS 

Penoxsulam is formulated as a foliar spray on dry-seeded rice crops or as a foliar spray or 

granular formulation on water-seeded rice crops. The granular formulation is only 

recommended for use on flooded rice paddies. It is also formulated as soluble 

concentrate/liquid, and ready to use (RTU). Application methods include ground and aerial. 

HISTORY OF PENOXSULAM and BEAD PRODUCTS 

Penoxsulam was first registered in the United States as an herbicide in 2004 (USEPA, 2004). 

A Screening Level Usage Analysis (SLUA) was prepared by BEAD for this chemical in 

2014 that provides the percent crop treated for six crops (almonds, pecans, pistachios, plums, 

rice and walnuts). For penoxsulam, during the SLUA timefrarne of2004-2012, usage for 

rice averaged 6,000 lbs a.i. with an average 5 percent crop treated, and for almonds, usage 

averaged 1,000 lbs. a.i., also with an average percent crop treated of 5 percent. For the 

remainder of the crops listed in the SLUA (pecans, pistachios, plums, and walnuts) the 

average pounds a.i. was less than 500 lbs each over this timeframe. 

A search of BEAD's Official Records did not find any BEAD benefits assessments over the 

last 10 years or emergency exemption requests for penoxsulam in the last 8 years. 

Emergency exemptions may indicate that there is a need for a particular chemical that is not 

registered for use on a particular site. An emergency exemption request may yield 

information about a particular chemical's importance or value that is not found in other EPA 

records. However, a lack of emergency exemption assessments by BEAD does not 

specifically indicate the relative importance of the chemical. 

USAGE 

Agricultural Usage 

Based on private market usage data from 2005-2012, usage averaged approximately 6,500 

pounds active ingredient (a.i.) applied annually on approximately 207,000 acres treated. The 

average a.i. rate over this time period was pounds 0.03 a.i./acre. Figure 1 presents 

penoxsulam usage in pounds a.i., and Figure 2 shows total area treated in acres over the 

2005-2012 timeframe (Proprietary Data, 2005-2012). Figures 1 and 2 show that over this 

time period in terms of pounds applied and acres treated there has been an increase in use 

from 2005 through 2012, and especially between 2010 and 2011 . 

Page 3 
FIGURE 1. Penoxsulam Usage in Pounds Active Ingredient (2005-2012) 

14,000 

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a. 

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2005 2006 2007 2008 2009 2010 2011 2012 

Years 

Source: Proprietary Data, 2005-2012 

FIGURE 2. Penoxsulam Total Area Treated in Acres (2005-2012) 

500000 

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2005 2006 2007 2008 2009 2010 2011 2012 

Years 

Source: Proprietary Data, 2005-2012 

Table 1 shows that the crop with the most pounds applied during the 2008-2012 timeframe 

has been rice accounting for approximately 90 percent of total pounds applied. The average 

annual usage in pounds during this timeframe has been approximately 8,600 lbs/year. 

Page 4 
Table 1. Crops with Highest Use ofPenoxsulam- Percent of Total Lbs. Applied (2008-

2012) 

2008-2012 

Average annual = 8,600 lbs/yr 

Crop %Lbs 

Rice 89% 

Almonds 6% 

Other* 5% 

*Other crops include walnuts, pecans, and plums 

Source: Proprietary Data, 2008-2012. 

As shown in Table 2, between 2008 and 2012, California was the top state with the highest 

use of penoxsulam accounting for approximately 70 percent of total pounds applied, 

followed by Louis·iana (15 percent) and Arkansas (11 percent). 

Table 2. States with Highest Use of Penoxsulam- Percent of Total Lbs. Applied (2008-

2012) 

2008-2012 

Average annual = 8,600 lbs/yr 

State %Lbs 

California 68% 

Louisiana 15% 

Arkansas 11% 

Other* 6% 

TOTAL 100% 

*Other states include Texas, Missouri, and New Mexico 

Source: Proprietary Data, 2008-2012 

Application Rates and Percent Crop Treated 

The average a.i. rate for the top crop (rice) in terms of pounds a.i. applied was lbs 0.037 

a .i./acre as shown in Table 3. 

Table 3. Penoxsulam Use on Top Crop (Rice): Average A.I. Rate, 2008-2012 

Annual Average Annual Average A vg. A.I. Rate (lbs Crop Pounds Total Acres 

a. i./acres) Treated* 

Rice 8,600 231 ,000 0.037 

*Total Acres Treated sums all acres treated for a crop, mcludmg those acres that receive multiple treatments. 

Source: Proprietary Data, 2008-2012 

Geographic Distribution of Penoxsulam Use 

Figure 3 provides a very broad geographical view of the average annual amount (in pounds) 

of penoxsulam applied per 1,000 acres of crop acres grown. The calculated values presented 

in the map are not equivalent to an application rate (lb a.i./A), therefore, the map may show 

areas of high use intensity that do not necessarily correspond to the states listed in Table 2 

Page 5 
since those are the states with the highest use of penoxsulam based on pounds active 

ingredient applied. However, in this case, the map does demonstrate that California and 

Louisiana which account for more than 70 percent of penoxsulam usage in terms of pounds 

a.i. applied are also the states with the highest use intensity because of application to rice 

fields. Please see Appendix A for a more detailed explanation of the information presented 

on the map. 

FIGURE 3. Annual Average Agricultural Use Intensity of Penoxsulam (2008-2012) 

Pounds Active Ingredient 

per 1,000 Crop Acres Grown 

:::::J < 0.02 

c::::J o.o2 - 0.10 

. 0.11 - 0.25 

- >0.25 

0 NoData 

Non-Agricultural Usage 

Non-agricultural data for penoxsulam is limited. The only available national level data from 

public or private databases show less than 200 lbs a.i. used on turf and ornamental lawns in 

2011 (Proprietary Data, 20 12). 

Page 6 
BIOLOGICAL ASPECTS RELEVANT TO PENOXSULAM 

Penoxsulam belongs to the triazolopyrimidine family of herbicides. It is a systemic herbicide 

which provides a broad spectrum of weed control, including grasses, sedges, and broadleaf 

weeds. Similar to imidazolinone and sulfonylurea herbicides, penoxsulam inhibits the 

activity of acetolactate synthetase (ALS) enzyme. Inhibition of this enzyme interferes with 

the production of branched chain amino acids (valine, leucine and isoleucine) in susceptible 

weed species. 

Penoxsulam is absorbed by leaves, shoots, and roots. Injury symptoms can be observed 7 to 

14 days after foliar applications. Visual injury symptoms are inhibition of growth, chlorosis 

at growing points, and necrosis of terminal buds (Herbicide Handbook, 20 14). 

ROLE OF PENOXSULAM IN PEST MANAGEMENT 

Penoxsulam is used for weed control in agricultural use sites such as rice, orchards, and 

vineyards. Penoxsulam is also applied on non-agricultural use sites as described previously. 

Penoxsulam is a broad spectrum herbicide applied as a post-emergence treatment for weed 

control in rice production. Penoxsulam effectively controls weeds found in rice production 

such as ducksalad (Heteranthera limosa), rice flatsedge (Cyperus iria), barnyardgrass 

(Echinochloa crus-galli), jointvetch (Aeschynomene spp.), and hemp sesbania (Sesbania 

exaltata) (University of Arkansas, Undated). 

During the 2008 to 2012 timeframe, the highest average annual usage (approximately 90 

percent), was in rice production (Table 1 ). During the same timeframe, the highest average 

annual usage (68 percent) was observed in California (Table 2). Use of penoxsulam is 

increasing significantly since the year 20 l 0 in the United States (Figures l and 2). 

Penoxsulam is used for the control of herbicide resistant biotypes of barnyard grass in rice 

production (Talbert and Burgos, 2007). This may be a factor that contributed to the increased 

use of penoxsulam. 

Penoxsulam also applied for weed control on warm-season turfgrasses such as Bermuda 

grass (Cynodon dactylon), centipede grass (Eremochloa ophiuroides), kikuyu grass 

(Pennisetum clandestinum), St. Augustine grass (Stenotaphrum secundatum), and zoysia 

grass (Zoysiajaponica), (Turfcare Supply Corp., (Undated)). Furthermore, in Florida, foliar 

or in-water applications of penoxsulam are made for the control of aquatic and invasive 

weeds such as hydrilla (Hydrilla verticillata), water hyacinth (Eichhornia crassipes), 

mosquito fern (Azolla pinnata), duck weed (Spirodela spp.), water meal (Wolffia 

columbiana) and salvinia (Salvinia spp.) (Univ. of Florida, 2014 ). Penoxsulam is the only 

aquatic herbicide that can be applied to exposed sediment after drawdown to inhibit the 

regrowth of susceptible weeds (Masser et al., 20 13). 

Page 7 
In the United States, 46 weed species have developed resistance to ALS inhibiting herbicides 

(Heap, Undated (1)). Although penoxsulam is also an ALS inhibitor, only rice flatsedge 

(Cyperus iria) has developed resistance to penoxsulam (Heap, Undated (2)). 

DATA NEEDS 

The Agency currently does not have complete information for penoxsulam. Obtaining the 

following information may improve future assessments conducted by the Agency related to 

the use and importance of this herbicide: 

Data on non-ag usage such as turf and ornamental lawns in terms of pounds a.i. 

applied and application timing and rates. 

REFERENCES 

BEAD (Biological and Economic Analysis Division). 2014. Penoxsulam Screening Level 

Usage Analysis. Biological and Economic Analysis Division, Office of Pesticide 

Programs, US Environmental Protection Agency. 

Heap, I. Undated (I ).The international Survey of Herbicide Resistant Weeds. Online 

Publication. 2014. Available at: www.weedscience.org. Accessed on Nov. 6, 2014. 

Heap, I. Undated (2). The International Survey of Herbicide Resistant Weeds. Weeds 

Resistant to the Herbicide Penoxsulam. Online Publication. Available at: 

http://www. weedscience.org/summary/ResistbyActive.aspx. Accessed on Nov. 7, 

2014. 

Masser, M.P., Murphy T. R., and J. L. Shelton. 2013. Aquatic Weed Management: 

Herbicides. Southern Regional Aquaculture Center. Online Publication. Available 

at: http://www2.ca.uky.edu/wkrec/361 aqplant.pdf. Accessed on Nov. 6, 2014. 

Proprietary Data. 2005-2012. 

Proprietary Data. 2012. 

Talbert, R.E. and N. R. Burgos. 2007. History and Management of Herbicide Resistant 

Barnyardgrass (Echinochloa Crus-galli) in Arkansas Rice. Weed Technology 21 

(2):324-33 1. 

Turf Care Supply Corp. Product Label. (Undated). Online Publication. Available at: 

http://www.turfcaresupply.com/upload/documents/label/900621.pdf. Accessed on 

Nov. 3, 2014. 

University of Arkansas Research and Extension. (Undated). Arkansas Rice Production 

Handbook. Publication Number MP 192. Online Publication. Available at: 

http://www.uacx.edu/publications/pdf/mp 192/mp 192.pdf Accessed on Nov. 6, 

2014. 

Page 8 
University ofF1orida. 2014. Plant Management in Florida Waters: An Integrated Approach. 

Extension Center for Aquatic and Invasive Plants. Online Publication. A vai1able at: 

http://plants.ifas.ufl.edu/manage/deve1oping-management-p1ans/herbicideconsiderations/penoxsulam-considerations. Accessed on Nov. 4, 2014. 

USEPA.2004. EPA Fact Sheet for Penoxsulam. Online Publication. Available at: 

http://www .epa.gov/pesticides/chem search/reg actions/registration/fs PC119031 27-Sep-04.pdf. Accessed on Nov. 7, 2014. 

Page9 
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 average 

annual amount (in pounds) of the active ingredient applied per 1,000 acres of crop acres 

grown. These data are included in the maps because risk assessors are interested in the 

amount of a pesticide used across agricultural land. The calculated values presented in the 

map are not equivalent to an application rate (lb a.i./A). 

The data used to make these maps have several limitations. Any interpretation of the maps 

should consider the underlying data and the associated limitations carefully. 

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, 2008-2012). 

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 states that sh9w no usage may actually have a small 

amount of the active ingredient being used. In some cases the displayed use intensity may be 

distorted because the surveyed crops and the reported pesticide usage may not accurately 

represent the actual pesticide usage on the crops produced ill the state. 

The denominator (1 ,000 crop acres grown) was also obtained from the same private market 

survey database. The "Crop Acres Grown" variable represents the total acres grown in a 

given state of all of the surveyed crops. This value is independent of pesticide usage and 

pesticide registration. It is important to note that the surveyed crops (about 60) are sampled 

from states that are major producers of each crop. Therefore, there are cases where the actual 

crop acreage in a state is higher than that reported by crop acres grown in the survey because 

either that state and/or crop was not included in the survey. 

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 as the legend bins will likely be different. 

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