UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

JUN 07 20ll 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: BEAD Chemical Profile for Registration Review: Prohexadione Calcium 

(112600) 

FROM: Monisha 

Biological 

Kaul, 

Analysis 

Biologist 

Branch 

~h.aJ ~ 

THRU: 

TO: 

Rafael Prieto, Environmental Protection spe i 'st ~ 

Science Information and Analysis Branch V( 

John 

Economic 

Faulkner, 

Analysis 

Economist 

Branch 

~ 

Biological and Economic Anal sis Division (7503 

Arnet Jones, Chief 

Biological Analysis Br 

. 1 

Diann Sims, Chief Jti. . ~~(J-C,""",,~ 

Science Information and Analysis Branch 

Timothy Kiely, Chief fl- ~ r~ Economic Analysis Branch ~ J \ 

Biological and Economic Analysis Division 3P) 

Katie Weyrauch, Chemical Review Manager 

Risk Management and Implementation Branch 5 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel date: May 2, 2012 

INTRODUCTION 

The purpose of the BEAD Chemical Profile 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 prohexadione calcium, a plant growth regulator that controls vegetative 

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growth, 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 April 17, 

2012. 

COMMON FORMULATIONS AND APPLICATION METHODS 

Prohexadione calcium is formulated as a dry flowable and may be applied by aerial and ground 

spray, and by spot treatment. 

USE SITES 

Agricultural Use Sites 

Prohexadione calcium is registered for use on apples, sweet cherries, peanuts, pears, and grasses 

grown for seed. 

Non Agricultural Sites 

Prohexadione calcium is registered for use on sod farms, ornamental lawns and turf. 

USAGE 

Based on private market pesticide usage data, prohexadione's annual agricultural usage averaged 

13,000 pounds of active ingredient (A.I.) treating an average of51,000 acres from 2006-2010. 

The average application rate is about 0.25 pounds active ingredient per acre. 

(Proprietary data, 2006-2010) 

According to proprietary data, between 2000 and 2010, the only crop with any usage for this 

chemical was apples. A new tolerance was established for sweet cherries in 2011 therefore no 

usage is available as of this date. Usage data on peanuts, pears, grasses grown for seed, 

ornamental lawns, and turf were not reported. 

The states with the most agricultural usage in terms of both pounds A. I. and total area treated 

were Washington and Michigan (Table 1). (Proprietary data, 2006-2010) 

T a bliP e . ereen t 0 fT oa t I U sage b ,y St a t e. 

State Pound A.I. (%) Total Area Treated (%) 

Washington 63 51 

Michigan 19 24 

New York 8 13 

Pennsylvania 8 I 10 

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USE TRENDS 

In terms of pounds applied, the use of prohexadione on apples was relatively constant except for 

a spike in 2008 (Proprietary data, 2000-2010). See Figure 1 below. 

Fi re 1. Total Pounds Re orted on Prohexadione's Use on Ales, 2000-2010. 

30,000 

o 

o 

o 

o 

N 

.-t 

o 

o 

N 

N 

o 

o 

N 

Source: Proprietary Data, 2000-2010 

,." 

o 

o 

N 

ADDITIONAL USAGE INFORMATION 

~ 

o 

o 

N 

Lf') 

o 

o 

N 

Year 

...... 

o 

o 

N 

00 

o 

o 

N 

o 

..... 

o 

N 

Another measure of usage is the use intensity. The use intensity is expressed as the average 

pounds A. I. applied per 1,000 acres of land in farms. This differs from the application rate, 

which is expressed as the pounds A. I. applied per treated acre. Figure 2 spatially represents 

prohexadione's use intensity in the US on apples, and that use intensity is relatively high in the 

northwest and in Michigan, regions with significant apple production. 

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Figure 2. Prohexadione Calcium Usage on Apples by Crop Reporting District (2006-2010). 

Average Pounds Per 

1,000 Acres of Farmland 

_ <0 :05 

0.05 - 0.10 

D 0.11- 0.34 

0.35 - 0.80 

_ 0.81-1.17 

Proprietary Data, 2006-2010. 

USDA, 2006-2010. 

USDA, 2007. 

This is a map of agricultural pesticide usage at the Crop Reporting District (CRD) level. CRDs are 

boundaries created by USDA NASS which are aggregates of counties-(USDA, 2010). Pesticide usage is 

displayed as average pounds (for the years 2006-2010) per 1,000 acres offarmland in a CRD to normalize 

for the variation in farmland between CRDs. Farmland acreage was obtained from USDA (2007). 

Usage is based on private market surveys of pesticide use in agriculture (proprietary Data, 2006-2010). 

The survey data are limited to the states that represent the top 80-90% of acreage for the individual crops, 

therefore, use may be occurring in regions outside the scope of the survey. CRDs showing no usage of 

pesticides may be due to either the lack of pesticide use in the region or non-participation in the 

agricultural surveys. In addition, across the years, there may be variations in the specific crops included in 

the CRD survey. This may result in a lower annual average for the CRD. 

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BIOLOGICAL ASPECTS RELEVANT TO PROHEXADIONE CALCIUM 

Prohexadione calcium is a plant growth regulator (PGR) that reduces vegetative growth by 

inhibiting the synthesis of gibberellins, a natural plant growth hormone. Gibberellin regulates 

cell elongation and reducing its production decreases the length of shoot internodes. 

Prohexadione calcium is a production management tool. For example, use of this PGR in tree 

crops decreases the amount of pruning needed, allows for more light penetration, may improve 

fruit color, and reduces incidence of fire blight (a bacterial disease of apples and pears). In 

grasses grown for seeds, prohexadione calcium may reduce the potential for lodging because it 

reduces vegetative growth in grasses. In peanuts, the use of prohexadione calcium decreases 

vegetative growth and aids mechanical harvesting. 

HISTORY OF BEAD ASSESSMENTS FOR PROHEXADIONE CALCIUM 

Prohexadione calcium was mentioned in an emergency exemption: "Using a combination of 

copper-based fungicides, streptomycin sulfate, oxytetracycline (under emergency exemption on 

apples), a biological control agent, fosetyl-Al, prohexadione, and pruning, it is possible to 

minimize the economic losses caused by the disease"[fire blight] (Chandgoyal and Rim, 2006). 

The information presented in this emergency exemption indicated that prohexadione calcium is a 

tool that may be used in the management of fire blight under normal weather conditions. 

INFORMATION THAT MAY BE USEFUL FOR BEAD'S FUTURE WORK ON 

PROHEXADIONE CALCIUM 

Obtaining additional information on the following items would improve future BEAD 

assessments of the importance of prohexadione calcium and may be required as part of the 

registration review of this pesticide. 

• Description of prohexadione calcium use sites other than apples (pounds, area treated, 

application method by site). 

• Description of the primary uses ofprohexadione calcium. 

• Description of frequency of use of prohexadione calcium to control fire blight including 

location, crop/si~e, application rates. 

REFERENCES 

Chandgoyal, Tara, and Elisa Rim, 2006. Request for Emergency Exemption Use of Agry-Gent 

10-W (Gentamicin Sulfate) in Michigan (06-MI-Ol, DP # 325345) on Apples for the Control of 

Fire Blight Disease (Erwinia amylorora), February 27,2006. 

Proprietary Data, 2000-2010, and 2006-2010. 

USDA, 2006-2010. NASS Crop Reporting Districts. Online: 

http://www.ers.usda.gov/briefmg/arms/resourceregions/resourceregions.htm#nass. 

USDA, 2007. Census of Agriculture. Online: 

http://www.agcensus.usda.govlPublications/2007/index.asp. 

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