UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C. , 20460


## 'JUN 11 2014 OFFICE OF CHEMICAL SAFETY AND POLLUTION

PREVENTION

MEMORANDUM SUBJECT: FROM:

THRU:

TO: Use/Usage Refinement in Support ofRegistration Review ofTrinexapac-Ethyl Sunil Ratnayake, Biologist (

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# ·r**~ ~**  Biological Analysis Branch _, Ov \ Stephen Smearman, Economist

# ~**~** Economic Analysis Branch Claire Paisley-Jones, Environmental Protection Specialist,.ftr Science Information and Analysis Branch Biological and Economic Analysis Division (7503P) Arnet Jones, Chief 

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# / /J _,----. Biological Analysis Branch

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# -»z-..-**~ v~**  J

## ~5 Tim Kiely, Chief 

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# ,(? Economic Analysis Branch

## ~**~** Diann Sims, Chief

# ~~**--­** Science Information and Analysis Branch Biological and Economic Analysis Division (7503P) Kaitlin Keller, Chemical Review Manager Neil Anderson, Chief Risk Management and Implementation Branch I Product Re-evaluation Division (7508P)

Product Review Panel: June 4, 2014

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### BACKGROUND Trinexapac-ethyl is in the proposed decision making phase ofregistration review. As part ofthe registration reviewprocess, BEAD is providing information onthe benefits oftrinexapac-ethyl to support risk management decisions. This document provides an overview ofthe use of trinexapac-ethyl on non-agricultural use sites. Trinexapac-ethyl is a plant growth regulator (PGR) that was registered in 1993 (USEPA 2008) for homeowner and professional applicator use to manage the growth ofturfgrass and several cereal grain crops. Trinexapac-ethyl inhibits the biosynthesis ofthe phytohormone gibberellin that promotes growth ofgrasses. In turfgrass, applications oftrinexapac-ethyl help to minimize the frequency ofmowing and clipping, and suppress seed head formation. In cereal grains, trinexapac-ethyl use reduces the length ofinternodes. This produces sturdier plants and that are less prone to lodging, and thus minimizes yield loss (Zagonel 2002).



### USAGE INFORMATION Use Sites: Non-Agricultural Ornamental Grasses and Turfincluding: residential, commercial/industrial, and recreational lawns; golfcourse turf, sod farms, as well as fencerows/hedgerows. Application around ornamental trees, shrubs, and flower beds is permitted. 

### Agricultural Growth Management in grasses grown for seed, wheat, triticale, barley, oats, and sugarcane. Two SLNs are registered for growth management in clover grown for seed in the state ofOregon (OR130009, and OR120007). 

### Usage information: BEAD has limited proprietary data on usage oftrinexapac-ethyl, which provides usage in terms ofpounds AI applied in 2011. Based on the data available, trinexapac-ethyl appears to be widely used inprofessional turfand horticulture management, which includes golfcourses, institutional turffacilities, turffarms, as well as professional lawn care and landscape management. In 2011, approximately 90,000 lbs oftrinexapac-ethyl were applied, accounting for over 30% ofthe total PGR usage inprofessional turfand horticulture management (US EPA Proprietary data 2012). The vast majority ofthis usage takes place on golfcourses, where it is the second most commonly used PGR (over 60,000 lbs AI, 30% oftotal the PGRuse). While fewer total pounds oftrinexapac-ethyl are used on institutional turffacilities (approximately 8,000 lbs AI), trinexapac-ethyl appears to be quite important to this sector, as it accounts for over 55% oftotal the PGRuse in these facilities, and is the most commonly used AI. Similarly, nearly 100% of PGRusage on turffarms is comprised oftrinexapac-ethyl (less than 7,000 lbs AI). Page2Trinexapac-ethyl is also used by lawn care operators and landscape contractors, but appears to be ofless importance to these sectors. Among lawn care operators, use ofless than 8,000 lbs AI was reported in 2011, which accounts for less than 7% ofthe total PGRuse in this market. Landscape contractors reported usage ofless than 500 lbs AI in 2011, which accounts for less than 1% of the PGRmarket in this sector (US EPA Proprietary data 2012). Again, because this data represents only one year ofusage, itprovides only a snapshot oftrinexapac-ethyl's importance. Publicly available trinexapac-ethyl usage data are also limited. Data from the California Department ofPesticide Regulation (CADPR) indicate approximately 5,200 lbs AI was applied annually in California, with approximately 95% used in landscape maintenance ( 4,900 lbs AI) (CADPR 2012). Additional data from CADPR and the US Department ofAgriculture National Agricultural Statistics Service (NASS) indicate limited usage oftrinexapac-ethyl by cut flower and bedding plant operations. This accounted for less than 1% ofthe operations based onthe USDA NASS 2009 and 2006 data. Currently, BEAD has no available agricultural usage data for this chemical.

CONCLUSION Plant growth regulators, including trinexapac-ethyl, slow foliage growth inturf, which can decrease costs by reducing mowing and other maintenance activities. Based onthe limitedusage information described above, trinexapac-ethyl is more widely used by weight than other PGRs in professional turfand horticulture management. This suggests that turfmanagers have found benefits from using trinexapac-ethyl as a PGR especially inthe golfcourse and turffarm markets. Additionally, proprietary information suggests that trinexapac-ethyl is relatively inexpensive compared to other PGRs on costper acre basis (US EPA Proprietary Data 2012). However, because BEAD does not have information regarding total acres treated nationally with PGRs, EPA cannot fully ascertain its overall importance in the turfand horticulture PGRmarket.

Page 3REFERENCES: CADPR. 2013. CaliforniaPesticide Information Portal. Online Database. Available at: http://calpip.cdpr.ca.gov/main.cfm

. Accessed on May 22, 2014. USDA. 2013. National Agricultural Statistic Service. Online Database. Available at: http://guickstats.nass.usda.gov/

. Accessed on May 22, 2014. US EPA Proprietary Data. 2012. US EPA. 2008. Trinexapac-ethyl Summary Document Registration Review. Online Publication. Available at: http://www.regulations.gov/#!documentDetail;D=EP A-HQ-OPP-2008-0657- 0008;oldLink=false. Accessed on May 27, 2014. US EPA. 2012. First Food Use Registrations ofTrinexapac-ethyl on Cereal Grains, Sugarcane, and Grasses Grown for Seed. Online Publication. Available at: http://www.epa.gov/pesticides/chem search/ppls/000100-00727-20120217.pdf. Accessed on May 27,2014 Zagonel J., Venancio W.S. Kunz R.P. 2002. Effect ofgrowth regulator on wheat crop under different nitrogen rates and plant densities. Planta Daninha 20: 471-476.

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