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 of Registration Review ofTrinexapac-Ethyl 

Biological 

Sunil Ratnayake, 

Analysis 

Biologist 

Branch 

( 

_, 

~ Ov ·r ~ \ ~ 

Economic 

Stephen Smearman, 

Analysis Branch 

Economist ~ ~ 

Claire Paisley-Jones, Environmental Protection Specialist,.ftr 

Science Information and Analysis Branch 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief /2/2 ~ / /J _,----. 

Biological Analysis Branch /~ -»z-..- ~ v~ J ~ 5 

Tim Kiely, Chief \I.A.__ ' ,(? 

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 of registration review. As part of the 

registration review process, BEAD is providing information on the benefits of trinexapac-ethyl 

to support risk management decisions. This document provides an overview of the 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 of turfgrass and several 

cereal grain crops. Trinexapac-ethyl inhibits the biosynthesis of the phytohormone gibberellin 

that promotes growth of grasses. In turfgrass, applications oftrinexapac-ethyl help to minimize 

the frequency of mowing and clipping, and suppress seed head formation. In cereal grains, 

trinexapac-ethyl use reduces the length of internodes. 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 Turf including: residential, commercial/industrial, and recreational 

lawns; golf course 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 of Oregon 

(OR130009, and OR120007). 

Usage information: 

BEAD has limited proprietary data on usage of trinexapac-ethyl, which provides usage in terms 

of pounds AI applied in 2011. Based on the data available, trinexapac-ethyl appears to be widely 

used in professional turf and horticulture management, which includes golf courses, institutional 

turf facilities, turf farms, as well as professional lawn care and landscape management. In 2011, 

approximately 90,000 lbs of trinexapac-ethyl were applied, accounting for over 30% of the total 

PGR usage in professional turf and horticulture management (US EPA Proprietary data 2012). 

The vast majority of this usage takes place on golf courses, where it is the second most 

commonly used PGR (over 60,000 lbs AI, 30% of total the PGR use). While fewer total pounds 

oftrinexapac-ethyl are used on institutional turf facilities (approximately 8,000 lbs AI), 

trinexapac-ethyl appears to be quite important to this sector, as it accounts for over 55% of total 

the PGR use in these facilities, and is the most commonly used AI. Similarly, nearly 100% of 

PGR usage on turf farms is comprised of trinexapac-ethyl (less than 7,000 lbs AI). 

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Trinexapac-ethyl is also used by lawn care operators and landscape contractors, but appears to be 

of less importance to these sectors. Among lawn care operators, use of less than 8,000 lbs AI was 

reported in 2011, which accounts for less than 7% of the total PGR use in this market. Landscape 

contractors reported usage of less than 500 lbs AI in 2011, which accounts for less than 1% of 

the PGR market in this sector (US EPA Proprietary data 2012). Again, because this data 

represents only one year of usage, it provides only a snapshot oftrinexapac-ethyl's importance. 

Publicly available trinexapac-ethyl usage data are also limited. Data from the California 

Department of Pesticide 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 of Agriculture National 

Agricultural Statistics Service (NASS) indicate limited usage oftrinexapac-ethyl by cut flower 

and bedding plant operations. This accounted for less than 1% of the operations based on the 

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 in turf, which can 

decrease costs by reducing mowing and other maintenance activities. Based on the limited usage 

information described above, trinexapac-ethyl is more widely used by weight than other PGRs in 

professional turf and horticulture management. This suggests that turf managers have found 

benefits from using trinexapac-ethyl as a PGR especially in the golf course and turf farm 

markets. Additionally, proprietary information suggests that trinexapac-ethyl is relatively 

inexpensive compared to other PGRs on cost per 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 turf and horticulture PGR market. 

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REFERENCES: 

CADPR. 2013. California Pesticide 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/000 100-00727-20120217 .pdf. Accessed on 

May 27,2014 

Zagonel J., Venancio W.S. Kunz R.P. 2002. Effect of growth regulator on wheat crop under 

different nitrogen rates and plant densities. Planta Daninha 20: 471-476. 

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