UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON. D.C. 20460 

SEP 2·0 2011 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

BEAD Chemical Profile for Registration Review: Mepiquat Chloride (109101) 

Sunil Ratnayake, Biologist /I 1_ 0 

Biological Analysis Branch l W\.. v'f \ ~ 

Sepebr 

Science 

Haddad, 

Information 

Environmental 

and Analysis 

Protection 

Branch 

Specialist I I J1 

If 

/ ~ 

John Faulkner, Economist ~ ~ .. d h Nt /I A 

Economic Analysis Branch ~ W \ 

Biological and Economic Ana ysis Division (7503P) 

THRU: Arnet Jones, Chief /J.. tIJ.J 

Biological Analysis Branch ~.,. i ., 

Diann Sims, Chief 

Science Information and Analysis Branch , 

Timothy Kiely, Chief ~ \ A /I ' 

Economic Analysis Branch . VV~ \ 

Biological and Economic Analy' ivision (750 

TO: Carissa Cyan, Chemical Review Manager 

Risk Management and Implementation Branch 1 

Pesticide Reevaluation Division (7508P) 

Product Review Panel date: July 20, 2011 

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 me pi quat chloride (109101), and eventually the general public. This document builds upon the 

data already provided in the "Usage and Label Use Data Packages" that are also provided to 

Registration Review teams by BEAD. The document is based on information and data available 

to BEAD as of July 13, 2011. 

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· , , 

Mepiquat chloride is a systemic, foliar applied plant growth regulator extensively used in cotton 

production as a harvest-aid. In addition, there is also a minor usage on wine grapes. The active 

ingredient of this chemical was first registered in the United States in 1980 (EPA, 1997). 

Mepiquat chloride is a gibberellic acid suppressant and it is absorbed by the green portions of 

plants. This plant growth regulator reduces cell elongation, and plant height (York, 1983a & 

Kerby, 1985) and has been associated with enhancing earliness of fruiting and fruit development 

(Walter, et al., 1980; York, 1983b; Kerby, 1985). 

USE SITES 

Agricultural Use Sites 

Mepiquat chloride is used as a plant growth regulator and registered for use on cotton and 

grapes. 

Non-Agricultural Use Sites 

Mepiquat chloride is not registered for non-agricultural use. 

COMMON FORMULATIONS AND APPLICATION METHODS 

Mepiquat chloride is formulated as pelletedltabletted, water dispersible granules, water soluble 

and emulsifiable concentrate. Application methods include water spray, oil spray, and aerial 

application. 

USAGE 

Based on private market usage data from 1998-2010, usage averaged approximately 400,000 

pounds active ingredient (a.i.) for 14 million acres treated (Proprietary Data, 1998-2010). The 

average a.i. rate over this time period has remained fairly constant at approximately 0.03 pounds 

a.i./acre. Figure 1 presents mepiquat chloride usage over the 1998-2010 timeframe for cotton, 

the major use (over 99.5%). Minor mepiquat chloride usage (less than 1 %) has been reported on 

wine grapes, while minor usage has also been reported on tobacco, which is not a registered site. 

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· . 

FIGURE 1. Mepiquat Chloride Usage on Cotton (1998-2010) 

700,000 

"U 

.!! 

ii 

D. 

ct 

<i. 

"U '"

C 

~ 

0 

GO 

Years 

Source: Proprietary Data, 1998-2010 

Between 1998-2010, the states with the most agricultural usage in terms of pounds a.i. applied 

were Texas (18%), Georgia (15%), Arkansas (13%) and Mississippi (11 %). Usage has also 

been reported in North Carolina, Tennessee, Missouri, California, Louisiana, and Alabama each 

with less than 10%. (Figure 2). The "other states" (7%) in Figure 2 include Arizona, South 

Carolina, Florida, Oklahoma, and Virginia. 

FIGURE 2. States with Highest Usage on Cotton (1998-2010) 

ALABAMA 

5% 

CALIFORNIA 

5% 

MISSOURI 

6% 

TENNESSEE 

7% 

CAROLINA 

9% 

Source: Proprietary Data, 1998-2010 

11% 

As shown in Figure 1, between 1998 and 2010, the lowest use of me pi quat chloride was reported 

in 1998, while use reached a peak in 2005. In 2005, the total area treated was also the highest 

during the 1998-2010 period. Use has been increasing steadily each year from 2008 through 

3 
2010. Figure 3 presents the states with the highest pounds a.i. used from 1998-2000, as 

compared to the states with the highest pounds a.i. used from 2008-2010. As shown in Figure 3, 

use in Texas and Georgia has increased significantly within the last decade (total area treated has 

increased in these two states by more than 50%), while use in California has decreased during 

the same period from approximately 12% to only 3% of total pounds a.i. applied, and use in 

Tennessee has decreased by 50% during the same timeframe. 

FIGURE 3. Comparison of States with Highest Usage Between 1998-2000 and 2008-2010 

Timeframes 

5% 

TENNESSEE 

5% 

NORTH 

7% 

1998-2000 

11% 

2008·2010 

11% 

Source: Proprietary Data, 1998-2010 

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BIOLOGICAL ASPECTS RELEVANT TO MEPIQUAT CHLORIDE 

The cotton plants treated with mepiquat chloride become shorter and narrower with thicker, 

smaller leaves. This will result in better early boll retention and/or larger bolls. Mepiquat 

chloride can also reduce the boll rot and improve defoliation. It allows the grower to manage the 

cotton plant for short-season production, reducing yield and quality losses due to a delayed and 

prolonged harvest. Mepiquat chloride is a gibberellic acid suppressant and it is absorbed by the 

green portions of the plant. It has been reported that leaves and stems of glyphosate resistant 

cotton are more resistant to glyphosate compared to the cotton fruits and treatments with 

mepiquat chloride has produced greater portion of cotton bolls in lower parts of the plant and 

improved the fiber quality (Nuty et aI., 2006). 

HISTORY OF BEAD ASSESSMENTS FOR MEPIQUAT CHLORIDE 

Emergency exemptions were approved in 1998 for the use of mepiquat chloride in New York, Ohio 

and Pennsylvania on grapes to enhance fruit set to overcome frost damage. These exemptions imply 

that mepiquat chloride had benefits on grapes that were not provided by the alternatives. No other 

BEAD assessments were found. 

DATA NEEDS RELEVANT TO BEAD'S FUTURE WORK ON MEPIQUAT CHLORIDE 

There are no data gaps identified by BEAD at this time. 

REFERENCES 

1). EPA. 1997. Re-registration Eligibility Decision(RED) Mepiquat Chloride. 

http://www.epa.gov/oppsrrdl/REDs/2375red.pdf 

2). Kerby, T.A. 1985. Cotton response to mepiquat chloride. Agron. J. 77:515-518. 

3). Nuti, R. T., Viator, R. P., Casteel, S., Edmisten, K., and R. Well. 2006. Effect of planting 

date,. mepiquat chloride, and glyphosate application to glyphosate resistant cotton in 

North Carolina. Agron. J. 98:1627-1633. 

4), Proprietary Data, 1998-2010. 

5). Walter, H., H.W. Gausman, F.R. Rittig, L.N. Namken, D.E. Escobar, and R.R. Rodriguez. 

1980. Effect of mepiquat chloride on cotton plant leaf and canopy structure and dry 

weights of its components. p. 32-35. In J.M. Brown (ed.) Proc. Beltwide Cotton Prod. 

Res. Conf., St. Louis, MO. 6-10 Jan. 1980. National Cotton Council of America. 

Memphis, TN. 

6). York, A.C. 1983a. Cotton cultivar response to mepiquat chloride. Agron. J. 75:663-667. 

7). York, A.C. 1983b. Response of cotton to mepiquat chloride with varying N rates and plant 

populations. Agron. J.75:667-672. 

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