UNITED STATES ENVIRONMENTAL PROTECTION AGENC Y WASHINGTON, D

. C

. 20460 

## JJUl l 0 2014

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION
MEMORANDUM
SUBJECT :
FROM:

THRU:

TO: B EAD Chemica l Profile for Registration Review: Imazapic (129041) and Imazapic-ammonium ( 12894 ?Yir 3) Sunil Ratnayake, Biologist Biological Analysis Branch Cynthia Doucoure, Environmental Protection Specialist Science Information and Analysis Branch Elizabeth Hill, Economist Economic Analysis Branch Biological and Economic Analysis Divi sion (750 Arnet Jones, Chief Biological Analysis Bra h Diann Sims , Chief

# ~ Science Information and

### An~alysis**Branch~** Timo thy Kiely, Chief Economic Analysis Branch 

# \AA Biological and Economic An Division ( 0 P) Ricardo Jones, Chemical Review Manager Risk Management and Implementation Branch V Pest icide Re-evaluation Division (7508P)
Product Review Panel date: June 11, 2014

Page 1 ofllSUMMARY Imazapic (imazapic and imazapic ammonium) is a systemic herbicide used for the control of certain annual and perennial grasses and broadleafweeds in non-crop lands. This includes utility plant sites, airports, and turf areas (industrial lands, golf courses, recreation and non-residential). Imazapic and imazapic-arnmonium are also registered for weed management in peanuts, lands under conservation reserve programs, pasture and rangeland. The predominant agricultural use of imazapic is on peanuts. Based on available data from 2004- 2012, over half of the peanut crop in the U.S. was treated with imazapic- 55 percent crop treated (PCT). Available data also shows that recently (2008-2012) over 98% of the total imazapic pounds a.i. applied was on peanuts, primarily in the states of Georgia, Alabama, and Florida, which represents nearly a slight increase in comparison to use from 2003-2007
. Use of imazapic on pastureland rose sharply early on, peaking in 2002, but declined steadily afterwards. Recently, less than one percent of the site is treated with imazapic. As for use of imazapic in the non-agricultural market, available proprietary data show reported use by consumers, but the exact figures are not available.
INTRODUCTION The purpose of this document is to convey usage information and a broad overview of the pest management roles of pesticides that are beginning to undergo registration review. The anticipated audience consists of the team of EPA staff currently evaluating the registration status of imazapic, and eventually the general public. This document builds upon the data
. BEAD provides in the Label Use Information System (LUIS) reports and the Screening Level Usage Analysis (SLUA) to Registration Review teams. The document is based on information and data available to BEAD as of April2014.
HISTORY OF BEAD ASSESSMENTS FOR IMAZAPIC Imazapic was registered in 1994. BEAD prepared a Screening Level Usage Analysis (SLUA) in Apri l 2014 based on available data from 2004 to 2012 that showed that imazapic is used on over halfof the peanut crop in the U.S. (55% PCT) and only a small percentage ofpastureland (<1% PCT). The average annual pounds a.i. applied on peanuts was 40,000 and on pastureland was 1,000. BEAD has not conducted any reviews ofrequests for Section 18 Emergency Exemptions for the use of imazapic in the past ten years. This should not be interpreted as a lack of benefits derived from imazapic. COMMON FORMUL ATIONS AND APPLICATION METHODS Imazapic products are formulated as granules, water dispersible granules (dry flowable), soluble concentrates , as well as ready-to-use solutions. Page 

### 2 ofllUSE SITES Agricultural Use Sites: Imazapic is registered for use peanuts, pastureland/rangeland, and land under conservation reserve programs. Non

-Agricultural Use Sites: Imazapic is registered for use on non-crop areas including rights-of-way, non-residential turf, and wildlife habitat management.
IMAZAPIC USAGE Agricultural Usage Trend According to proprietary market research surveys, imazapic is reported to be used predominantly on peanuts and pastureland during the 1998-2012 time period. Reported use ofimazapic on peanuts was variable throughout these years resulting in an indiscernible trend; pastureland use spiked in 2002 and decreased afterwards. Similar trends were found for the total area treated with imazapic as shown in Figure 2. During this period, the overall average annual pounds a.i. applied on peanuts was 38,000 lbs. used to treat an average of 680,000 acres at an overall application rate of0.06lb a.i. per acre. Recently, however, as shown in Table 1, the average annual pounds a.i. applied increased to 42,600. The maximum labeled application rate for peanuts is 0.063 lb a.i. per acre. On pastureland during this period, an average of3,800 pounds a.i. were applied annually on 47,000 acres at an overall application rate of 0.08 lb a.i. per acre. Recently, however, as shown in Table 1, the average annual pounds a.i. applied decreased significantly to 600. The maximum labeled application rate for pastureland is 0.199 lb a.i. per acre.

Page 

### 3 ofllFigure 1. Imazapic Usage on Peanuts and Pastureland: Pounds AI Applied, 1998-2012

"C .!!:! 0.. a. <( <i. 

### "' "C c: :J 0**~** 60000

0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Year

- Pasturel and

- Peanuts Source : EPA Proprietary Data, 1998-2012 Figure 2: Imazapic Usage on Peanuts and Pastureland: Total Area Treated, 1998-2012

"C <II -ro <II 

## ... 1- ro <II 

### ... <( ro

### ~ 1200000

0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Year

- Pastureland - Peanuts Source: EPA Proprietary Data, 1998-2012 Page 

### 4 ofllAgricultural Usage: Top Crops Imazapic is used primarily on peanuts and accounts for over 98% of the total pounds a.i
. applied in recent years (2008-2012), which represents a slight increase in comparison to use between 2003-2007. Imazapic use on pastureland has decreased by over 80% in recent years. The average a.i. rate of application increased sligh tly on pastureland but remained the same on peanuts during both periods while the number of applications for all sites remained the same as shown in Table 1.
Table 1. Imazapic: Comparison ofUsage on Crops between 2003-2007 and 2008

-2012 Timeframes. 2003-2007 ,J 2008

- 2012 Avg Annual Lbs A.I. Applied, Avg Annual Lbs A.l. Applied: Peanuts

- 42,000 Peanuts- 42,600 Pastureland- 3,600 Pastureland

- 600 Crop Avg. A
. I
. #of Crop Avg. A.I. Proportion Rate of Apps Proportion Rate of

of Total Application of Total Application Lbs A.l
. of (lb Lbs A.I. of (lb

Applied a. i./acre) Applied a.i./acre) Peanuts 92% 0.06 1.0 Peanuts 98.6% 0.06 Pastureland 8% 0.09 1.0 Pastureland 1.4% 0.14 Source: Propnetary Data, 2003-2012 Agricultural Usage: Top States #of Apps

1.0 1.0

Imazapic is used primarily in Georgia on peanuts during the 2003-2012 time period where in recent years over 50% of total pounds a.i. were applied. Alabama and Florida follow, each with 15% of the total pounds a.i. applied. In the earlier period, the proportion of total pounds a.i. applied in Texas was significant at 11% but decreased in more recent years to less than 5%
. This is attributed to no reported use on pastureland and decreased use on peanuts. Usage of imazapic in South Carolina picked up slightly in more recent years, accounting for 7% of the pounds a.i. applied.

Page 5 ofllTable 1. Imazapic: Comparison of Usage in States between 2003-2007 and 2008-2012 Timeframes. 2oo3-2oo1 1 2008-2012 Avg Annual Lbs A .I. Appliedt Avg Annual Lbs A.I. Applied: Peanuts- 42,000 Peanuts

- 42,600 Pastur:eland- 3,600 Pastureland

- 600 State Avg. A.I. #of Crop Avg. A. I. Proportion Rate of Apps Proportion Rate of

of Total Application of Total Application Lbs A.I. of (lb Lbs A.I. of (lb

Applied a.i./acre) Applied a. i./acre) Georgia 49% 0.05 1.0 Georgia 53% 0.06 Alabama 13% 0.05 1.0 Alabama 15% 0.05 Florida 12% 0.05 1.0 Florida 15% 0.06 Texas 11% 0
.07 1.0 South 7% 0.06 Carolina Other* 15% 0.02-0.17 1.0 Other 10% 0.04-0.1 9 #of Apps

1.0 1.0 1.0 1.0 1.0 Other states include AR, ID, KS , MT, NE, Other states include ID, KS, MS, MT, NE, NM, NC, ND, OK, SC, SD, UT, VA, and WY NC, ND , OK, SD, TX, VA, and WY Source: Propnetary Data , 2003-2012 Agricultural Use Intensity oflmazapic Use in the U.S. Another measure of usage is the use intensity. In this analysis, the use intensity is expressed as the average annual amount (in pounds) of the active ingredient applied per 1 ,000 acres ofcrop acres grown. This differs from the application rate, which is expressed as the pounds a.i. applied per treated area. Figure 3 spatially represents imazapic's use intensity in the U .S. in the Southeast states of Georgia, Florida, Alabama, and South Carolina on peanuts . For more information about this map, see Appendix A.

Page 6 ofll

### Figure 3
. Annual Average Agricultural Use Intensity of Imazapic (2008-2012)
.

Pounds Active Ingredient per 1.000 Crop Acres Grown CJ N o O

ata CJ <ODG

. 0
. 06 · 0. 27

. 0
.28 ·1
.65

- >1
.65 (Source: Proprietary Data, 2008-2012)

Non

-Agricultural Usage BEAD reviewed available data and found that there is reported use of imazapic by consumers but the data are not quantified and exact figures were not available (Proprietary Data, 2010, 2012).

Page 7 ofllBIOLOGICAL ASPECTS RELEVANT TO IMAZAPIC Imazapic belongs to the imidazolinone family of herbicides. It is a systemic herbicide registered for the control of certain annual and perennial grasses and broadleaf weeds. Imazapic can be applied as pre-and post-emergence treatments and is active at low rates. For example, for roadside vegetation management the typical application rate used was 0.09 lbs a.i. per acre per year (Washington State Dept. of Transportation (Undated). The maximum labeled application rate for non-crop areas including roadsides is 0.19 lbs a.i. per acre (Washington State Dept. of Transportation (Undated). According to the Weed Science Society ofAmerica (WSSA) classification ofmechanism of action of herbicides, imazapic is classified as a Group 2 herbicide (ALS inhibitors) (WSSA, 2013). The mechanism of action of Group 2 herbicides is inhibition ofthe enzyme acetolactate synthase (ALS), which is also called the acetohydroxy acid synthase (AHAS). It is an enzyme involved with the biosynthesis of branched chain amino acids such as leucine, isoleucine, and valine (WSSA, Undated)
. Imazapic is absorbed by roots and foliage ofweed species and rapidly translocated to the growing points. Growth of susceptible weeds is inhibited withi n a few hours after the application of imazapic and injury symptoms appear 1 to 2 weeks after the application. Major injury symptoms include chlorotic meristematic areas fo llowed by general foliar chlorosis and necrosis (Herbicide Handbook, 2007). The availability of soil moisture is important for the activity of imazapic
. When adequate soil moisture is available, imazapic provides residual activity on susceptible germinating weeds (Herbicide Handbook, 2007). Depending on the application rates, rotational restrictions are applied on certain crops up to 48 months after the application of imazapic. For example, if imazapic is applied at a rate of 9 to 12 ounces ofproduct per acre for weed control in Conservation Reserve Program (CRP) lands, for crops such as canola, potatoes, or sugar beets a minimum plant back interval of48 months is recommended (Imazapic 2SL, Product Label, Undated). The long rotational intervals of imazapic may interfere with some crop rotations.
ROLE OF IMAZAPIC IN PEST MANAGEMENT Imazapic is applied for the control of annual and perennial grasses and broadleaf weeds in noncrop lands, pasture and range lands, and conservation reserve programs. Imazapic is registered for the control of certain annual and perennial grasses and broadleaf weeds in non-agricultural lands which include: lands in CRP, pasture and range lands, utility plant sites, airports, and turf areas (industrial lands, golf courses, recreation and non-residential)
. Also, imazapic is registered for weed management in peanuts. In pasture and rangelands, annual weeds are effectively controlled with pre-emergence applications of imazapic up to small, actively growing plants (Prather, 2013).

Page 

### 8 ofllFrom 2003 to 2012, over 90% ofimazapic (lbs a.i.) was applied on peanuts (Table 1). When applied as early post-emergence treatments for weed contro l in peanuts , imazapic provides excellent control of many broadleaf and grass weeds, including both purple and yellow nutsedge (Marshall, 20 12). This observation, plus the relatively high usage in peanuts, suggests that imazapic is important in peanut weed control. Imazapic is used for vegetation management of roadsides. It is used to control selected annual and perennial grasses and broadleaf weeds and is applied for roadside vegetation management as a pre-emergent treatment to control undesirable grass species (Washington State Roadside Vegetation Management Plan, 2012). Of the total of 144 weed species ident ified with resistance to different modes of action of herbicides in the United States, 46 were found to have developed resistance to ALS inhibitors (Heap, Undated ( 1)). This is primarily due to the extensive use of many ALS inhibiting herbicides in crop production fields the U nited States. However, the only weed that has developed resistance to imazapic is Palmer amaranth (Amaranthus palmeri) (Heap, Undated (2)); therefore, the weed resistance does not seem to be a serious problem for imazapic users. INFORMATION THAT MAY BE USEFUL FOR BEAD'S FUTURE WORK ON IMAZAPIC The Agency currently does not have important information on imazapic. Obtaining the following usage information may improve future assessments conducted by the Agency related to the use and importance of imazapic :
• Pounds a.i. applied by consumers, on non-residential turf, and in non-crop areas • Typical rates of application rates on non-residential turf and non-crop areas

REFERENCES Cadre® Product LabeL 2012. BASF Corporation. Online Publication. Avai lable at: http: //agproducts .basf.us/products/label-and-msds/cadre-herbicide-label.pdf
. Accessed on May 19, 2014. EPA , lmazapic Screening Level Usage Analysis (SLUA) , Apri l 20 14 EPA Proprietary Data, 1998-2012 Heap, I. Undated (l) .The International Survey ofHerbicide Res istant Weeds. Online Publication. 20 14. Available www.weedscience.org. Accessed on Feb 12, 2014. Heap , I. Undated (2). The International Survey of Herbicide Resistant Weeds. Weeds Resistant to the Herbicide Imazapic. Online Publication. Available at: http: //www.weedscience.org/summary /ResistbyActive.aspx
. Accessed on April 7, 2014. Page 9 ofllHerbicide Handbook. 2007. Weed Science Society of America. 9 1h Edition. Imazapic. pp. 82

- 84. Imazapic 2SL Product Label. Undated
. Nufarm Inc. Burr Ridge , Il 60527. Online Publication. Avail able at: http: //www.cdms.net/LabelsMsds/LMDefault.aspx ? pd= 11734&t=1,2,3,4
. Accessed on April 9, 2014. Marshall, M. 2012. South Carolina Pest Management Handbook for Field Crops- 2012. Online Publication. Availab le at: https : / /www.clemson.edu/ extension/rowcrops/pest/files/20 12%20PMH%20Web%20Page %20Version /2012%20PMH PEANUTWC.pdf
. Accessed on June 6, 2014. Prather, T. 20 13. Weed Control in Pasture and Rangelands. Pacific Northwest Weed Management Handbook. A Pacific Northwest Extension Publication. Available at: shttp://pnwhandbooks.org/weed/other-areas/pasture-and-rangeland/weed-control-pastureand-range land. Accessed on April 7, 2014. Shinn, S. L. , and D. C. Thill. 2002. The response of Yellow Starthistle (Centaurea solstitialis) , Annual Grasses and Smooth Brome (Bromus inerrnis) to Imazapic and Picloram
. Weed Technology. Vol. 16 (2) pp. 366

- 370. Sudianto, E. , Beng-Kah, S., Ting-Xiang, N , . Saldain, N , E. , Robert C. Scott, R, C. , and N. R. Burgos 20 13. Clearfield® rice: Its development, success , and key challenges on a global perspective. Crop Protection 49:40-51. Online Publication. Available at: http: //www.researchgate.net/publication/257085079 Clearfield rice Its development su ccess and key challenges on a global perspective. Accessed on April 8, 2014. Summary of Herbicide Mechanism ofAction. Undated. Weed Science Society of America. Avai lable at: http://wssa.net/wp-content/ uploads/WSSA-Mec hani sm-of-Action. pdf. Accessed on March 31, 2014. Imazapic Washington State Department ofTransportation. Undated. Roadside Vegetation Management Herbicide Fact Sheet. Online publication. Available at:http://www.wsdot.wa.gov/nr/rdonlyres/67f89cb7-d919-47dd-890febabbbd32e6e/O/imazapic.pdf. Accessed on May 19, 2014. Integrated Roadside Vegetation Management Plan. 2012. Washington State Department of Transportation . Online Publication. Avai lable at: http: //www. wsdot.wa.gov/NR/rdonlyres/C7DDC83D-C8DA-416C-AC09- 36EBAB243329/0/Herbicide List.pdf. Accessed on May 16 , 2014. WSSA, (Weed Science Society ofAmerica). Undated. Summary of Herbicide Mechanism of Action. Online Publication. Available at: http: //wssa.net/wp

-content/uploa ds/WSSAMechanism-of

-Action.pdf
. Accessed on March 20 , 2014.

Page 

### 10 of 11APPENDIX 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 ai/ 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 ofpesticide 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 ofthe 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 ofthese limitations is that states that show no usage may actually have a small amount ofthe 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 in 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 ofall ofthe surveyed crops. This value is independent ofpesticide usage and pesticide registration. 

### It is important to note that the surveyed crops (about 60) are sampled from states that are major producers ofeach 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.

Page 11 ofll