UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON

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OFFICE OF CHEMICAL SAFETY ANn Pnl I IIT i nN PI'II=\/I=NTinN MEMORANDUM
SUBJECT: FROM:

THRU:

TO: BEAD Chemical Profile (BCP) for Registration Review: Thidiazuron (120301) Sunil Ratnayake, Biologist

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_ Biological Analysis Branch

### ~**··~ ~g..,** **~** Cyntnia Doucoure, Environmental Protection Specialist 

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### ~ Science Information and Analysis Branch Stephen Smearman,

# Economist~~ Economic Analysis Branch Biological and Economic Analysis Division (7503P) Arnet Jones , Chlef Biological Analysis Branch Diann Sims, Chief

# ~ Science Information and Anutalysis

### Branch~~ Timothy Kiely, Chief Economic Analysis Branch

# ~ Biological and Economic Analysis Division 3P) Khue Nguyen, Chemical Review Manager Risk Management and Implementation Branch IV Pesticide Re-evaluation Division (7508P)
Product Review Panel date: November 26,2014

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### 1 of8SUMMARY Thidiazuron was first registered in the U.S. in 1982. This pesticide is used as a pre-harvest treatment (trea tment applied before harvesting) on cotton as a defolian t to reduce the foliage and immature fruiting structures which contribute to the staining ofharvested cotton. Applications of thiadiazuron also facilitates cotton harvesting and reduces the pieces of dry leaves and other inert matter in harvested cotton. During the 2008-2012 time frame, an average of approximately 250,000 pounds a.i
. of thidiazuron were applied annually to 3
. 8 million acres at an overall average application rate of 0.07 lb a.i. per acre. The top states, in terms ofthe percentage ofthe total pounds a.i. applied, were Georgia, Texas, Mississippi, and Arkansas
. The average percent crop treated (PCT) for use ofthidiazuron on cotton during 2004-2012 was 30 percent. According to 2008 to 2012 usage data, the highest usage ofthidiazuron was observed in Georgia and Texas. These two states account for 46 percent ofthe cotton acreage treated with thidiazuron. INTRODUCTION The purpose of this document is to convey usage information and a broad overview ofthe pest management roles ofpesticides that are beginning to undergo registration review. The anticipated audience consists of the team ofEPA staffcurrently evaluating the registration status of thidiazuron, 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 September 2014. HISTORY OF BEAD ASSESSMENTS FOR PROPOXYCARBAZONE SODIUM BEAD prepared a Screening Level Usage Analysis (SLUA) for thidiazuron in September 2014 based on avai lable data from 2004 to 2012 which shows that the average percent crop treated for cotton was approximately 30 percent and the average annual pounds a.i. applied was 300,000. A search of BEAD's Official Records data base for BEAD benefits assessments specifically for · thidiazuron did not find any records ofprior BEAD assessments specifically for this chemica l in the last 10 years. Emergency Exemptions

- A search of BEAD 's Official Records did not find any Section 18s requests for thidiazuron in the last 1 0 years. Emergency exemptions may indicate that there is a need for a particular chemica l 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 Section 18 assessments by BEAD does not specifically indicate the relative importance ofthe chemical.

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### 2 of8COMMON FORMULATIONS AND APPLICATION METHODS Thidiazuron is formulated as wettable powder in water soluble bags, or as suspension and emulsifiable concentrates and applied as a pre-harvest application via ground or aerial application equipment. This product is not to be applied using any type ofirrigation system. USE SITES Agricultural Use Sites: Thidiazuron is regi stered for use as a cotton defoliant. Non-Agricultural Use Sites: There are no non-agricultural use sites registered for thidiazuron
THIDIAZURON USAGE Agricultural Usage Trend Based on the available proprietary data for the time period from 1998 through 2012, thidiazuron use on cotton in the U.S. fluctuated with a significant decrease in 2008 followed by a significant increase in use for the remainder ofthe time period through 2012 as shown in Figure 1. The long term use trend has remained positive, gradually increasing over the period from 1998 through 2012. Similar patterns were seen for the total area tr eated with thidiazuron as shown in Figure 2. During this period, an average of approximately 255 ,000 pounds a.i
. were applied annually to 4.2 million acres at an overall average application rate of 0.06 lb a.i. per acre. In recent years (2008-2012), use ofthidiazuron on cotton in terms ofboth total pounds and acres treated has recovered to pre-2007 levels as seen in Figure 1 and Figure 2. For this time period, an average of approximately 250,000 pounds a.i. were applied annually to 3.8 million acres at an overall average application rate of0.07 lb a.i. per acre. The top states, in terms ofboth the percentage ofthe total pounds a.i. applied and acre treatments are Georgia, Texas , Mississippi, and Arkansas as shown in Table 1. The maximum labeled application rate for thidiazuron use on cotton is 0.2 lb a.i. per application and 0.3 lb a.i. per year.

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### 3 of8Figure 1
. Thidiazuron Usage on Cotton: Pounds AI Applied, 1998-2012 400,000

0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Year Source: Proprietary Data, 1998-2012 Figure 2: Thidiazuron Usage on Cotton: Total Area Treated, 1998-2012
6,000,000

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

### Source: Proprietary Data, 1998-2012 Page 4 of8T bl 1 T S a e op tates 

### fi U fThid. or se o tazuron on 

# cotton, 2008 20 12 

### - Top States Percentage of Percentage of Avg A. I. Rate Total Pounds 

### A. I. Total Area (lb a. i./acre) Applied Treated Georgia 22% 23% 0.06 Texas 23% 23% 0.06 Mississippi 12% 11% 0.07 Arkansas 8% 8% 0.06 *Othe r 35% 35% 0.07 *Other states include AL, AZ, CA, FL, KS, LA, MO , NC , OK, SC, and TN
. Agricultural Use Intensity ofThidiazuron Use on Cotton in the U .S. Another measure ofusage is the use intensity. In this analysis, the use intensity is expressed as the average annual amount (in pounds) ofthe active ingredient applied per I ,000 acres of crop acres grown. This differs from the application rate, which is expressed as the pounds a.i. applied per treated area. Figure 3 spatially represents thidiazuron' s use intensity in the U.S. in Georgia, Texas, Mississippi and Arkansas. For more information on Figure 3, see Appendix A.

Page 5 of8Figure 3: Annual Average Agricultural Use Intensity of Thidiazuron 2008*2012

Pounds Active I ngredient per 1,000 Crop Acres Grown 0 No0 ata 

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-5

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- >10 Source: Proprietary Data, 2008*2012 USE OF THIDIAZURON IN COTTON PRODUCTION Thidiazuron is a hormonal type cotton defoliant applied as a pre-harvest treatment to reduce the plant foliage to facilitate harvesting. Also, this chemical reduces the amount oftrash in harvested cotton and improves the lint grade
. Generally cotton**d~foliants** are applied in the field when 60 percent ofthe cotton boll s in a plant are open (Dodds et al., 2014). Chemicals used as defoliants can injure the cotton plant and cause it to produce ethylene. Ethylene production promotes formation of an abscission layer and separation of the leaf from the plant resulting the leaf drop (Dodds et al. , 2014). Tribufos , carfentrazone, pyraflufen-ethyl, glyphosate, and paraquat are some of the chemicals that can be used as alternatives to thidiazuron. Tank mixing thidiazuron with tribufos, as well as the addition of silicone surfactants or ammonium sulfate have been shown to increase uptake of thidiazuron in drought stressed cotton. Also, compared to some other defoliants , thidiazuron has 

### shown an 

### excellent ability to prevent regrowth which makes it easy for harvesting. (Dodds et al., 2014). Page 6 of8REFERENCES Arysta LifeSciences. North America, LLC. Undated. Thiadiazuron 4 SC. Product Label. 15401 Weston Parkway, Suite 150. Carry, NC27513
. Online Publication. Available at: http: //www.agrian.com /pdfs/Thidiazuron 4 SC Labell.pdf. Accessed on Nov. 14, 2014. Dodds, D
. M
. , Reynolds, D. B., Barber, L.T., and T. B. Raper. 2014. Mid-South Cotton Defoliation Guide : Online Publication. Availa ble at: http ://www.mississippicrops.com /wp-content/uploads /20 14/09/20 14-Cotton-Defoliation-Guide Final.pdf Accessed on Dec.23, 2014. EPA, Thidiazuron Screening Level Usage Analysis (SLUA), September 2014. Propr ietary Data, 1998-2012. USEPA. 2005. Registration Eligibility Decision ofThiadiazuron. Online Publication. Available at: http: //www.epa.gov/oppsrrd1/REDs/thidiazuron red.pdf. Accessed on Nov. 17,2014
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Page 7 of8APPENDIX 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 ofthe average annual amount (in pounds) of the active ingredient applied per 1,000 acres ofcrop 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. IA). The data used to make these maps have severa l 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 m,ajority of the crop . Although the surveys capture most ofthe use of a particular active ingredient in agriculture, there are severa l limitations to these surveys.
• States with minor production of a surveyed crop are not sampled • Not all types ofpesticides 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 show 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 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 of all of the 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 sta tes 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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