BIOPESTICIDES REGISTRATION ACTION DOCUMENT 

Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 Proteins and the Genetic Material Necessary for Their 

Production (Plasmid Insert PHP17662) in Event DAS-59122-7 Corn (OECD Unique Identifier: DAS59122-7) 

PC Code: 006490

U.S. Environmental Protection Agency 

Office of Pesticide Programs 

Biopesticides and Pollution Prevention Division
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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Table of Contents

I. OVERVIEW

A. Background 4 

 

B. Use Profile 7 

C. Regulatory History 8 

 

 

II. SCIENCE ASSESSMENT

A. Product Characterization 14 

 

 B. Human Health Assessment 41 

 

C. Environmental Assessment 66 

D. Insect Resistance Management 116 

E. Benefits 179 

 

III. REGULATORY POSITION FOR EVENT DAS-59122-7 CORN

A. Initial Registration (August 31, 2005) 200 

B. 2010 Update 202 

C. Period of Registration 204 

APPENDIX A 206 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 Proteins and the Genetic Material Necessary for Their 

Production (Plasmid Insert PHP17662) in Event DAS-59122-7 Corn Regulatory Action Team

Product Characterization and Human Health

Rebecca Edelstein, Ph.D.

John Kough, Ph.D. 

Annabel Waggoner 

Chris Wozniak, Ph.D. 

Environmental Fate and Effects

Joel Gagliardi, Ph.D. 

Hillary Hill 

Tessa Milofsky 

Robyn Rose 

Zigfridas Vaituzis, Ph.D. 

Annabel Waggoner 

Insect Resistance Management

Jeannette Martinez 

Sharlene Matten, Ph.D. 

Tessa Milofsky 

Alan Reynolds 

Benefits Assessment

Edward Brandt 

Sharlene Matten, Ph.D. 

Tessa Milofsky 

Registration Support

Mike Mendelsohn 

Sheryl Reilly, Ph.D. 

Ann Sibold

Biopesticides Registration Action Document Team Leaders

Jeannine Kausch 

Mike Mendelsohn 

 

Office of General Counsel

Angela Huskey, Esq. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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I. OVERVIEW 

A. Background 

On August 31, 2005, the Environmental Protection Agency (EPA) issued time-limited, conditional 

registrations to Mycogen Seeds c/o Dow AgroSciences LLC (EPA Reg. No. 68467-5) and Pioneer HiBred International, Incorporated (EPA Reg. No. 29964-4) for Event DAS-59122-7 corn, a plantincorporated protectant expressing the active ingredient, Bacillus thuringiensis (Bt) Cry34Ab1 and 

Cry35Ab1 proteins and the genetic material necessary for their production (plasmid insert PHP17662) in 

Event DAS-59122-7 corn (Organization for Economic Cooperation and Development (OECD) Unique 

Identifier: DAS-59122-7). Event DAS-59122-7 corn, at the time of 2005 registration, expressed only the 

second plant-incorporated protectant (PIP) active ingredient to offer protection against corn rootworm, 

and expectations were that adaptation of this new technology would result in further reduction of 

conventional insecticide use by growers attempting to control the highly destructive corn rootworm and 

maintain their crop yields. Prior to registration and after extensive review of copious amounts of 

data/information submitted by the applicants, the Agency determined that the use of this pesticide was in 

the public interest and that it would not cause any unreasonable adverse effects on the environment 

during the period of time-limited (5 year), conditional registration. 

Subsequent to registration of the single-trait products in 2005, the Agency registered stacked and/or 

pyramided plant-incorporated protectants (PIPs), expressing Cry34/35Ab1 along with other proteins, 

and two seed blends for either commercial or limited breeding purposes. A complete list of the currently 

registered products expressing Cry34/35Ab1—including their respective registration numbers, product 

names, registrants, initial dates of registration, proteins (or active ingredients) expressed, and any 

limitations/special notes—can be found in Appendix A. In conjunction with the 2010 evaluation 

(explained in the paragraphs that follow), the Agency has attempted to better detail and describe product 

characterization, human health, environmental effects, and insect resistance management data that were 

submitted to support the registrations of the following stacked and/or pyramided products expressing 

Cry34/35Ab1: 

(1) Herculex® XTRA Insect Protection Corn (EPA Reg. Nos. 68467-6 and 29964-5) 

(2) 1507 x 59122 x MON 810 (EPA Reg. No. 29964-8) 

(3) 59122 x MON 810 (EPA Reg. No. 29964-9) 

When the first products containing Cry34/35Ab1 were registered by the Agency, Mycogen Seeds c/o 

Dow AgroSciences LLC and Pioneer Hi-Bred International, Incorporated were issued time-limited, 

conditional registrations under section 3(c)(7)(C) of the Federal Insecticide, Fungicide, and Rodenticide 

Act (FIFRA). Along with several requirements for further product characterization, environmental 

effects, and insect resistance management data, the registration notices also clearly established an 

absolute expiration date of September 30, 2010. The follow-on stacks and/or pyramids, specifically 

mentioned above, all have this same expiration date with the exception of 1507 x 59122 x MON 810 and 

59122 x MON 810, which both expire on October 31, 2010. The registrants for the Cry34/35Ab1 singletrait and combination PIPs, due to expire on either September 30, 2010 or October 31, 2010, have 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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formally requested that the Agency amend their associated products to extend the current expiration 

dates. 

On October 1, 2009, EPA announced a new policy to provide a more meaningful opportunity for the 

public to participate on major registration decisions before they occur. According to this new policy, 

EPA intends to provide a public comment period prior to making a registration decision for, at 

minimum, the following types of applications: new active ingredients; first food uses; first outdoor uses; 

first residential uses; and other actions for which the Agency anticipates that there will be significant 

public interest. 

Consistent with the policy of making registration actions more transparent, the proposed amendments to 

the expiring Cry34/35Ab1 corn products are subject to a 30-day comment period because the Agency 

believes, given past experiences with PIPs in general, these actions are of significant public interest. 

While a final decision on amending the expiring Cry34/35Ab1 corn products is contingent upon review 

and consideration of public comments received, the Agency maintains that, based on all data submitted 

in support of the expiring Cry34/35Ab1 corn registrations (both for initial registrations and as responses 

to conditions of registration), it is in the best interest of the public and the environment to amend the 

currently existing Cry34/35Ab1 registrations by extending the current expiration dates. The basis for this 

preliminary decision can be found in the risk assessment for the expiring Cry34/35Ab1 corn products, 

which is characterized throughout this Biopesticides Registration Action Document (BRAD). After all 

scientific reviews of Cry34/35Ab1 conditional data were completed, this BRAD was updated 

appropriately to reflect the most current information available to and evaluated by the Agency regarding 

these particular registrations. 

All data and findings for the expiring Cry34/35Ab1 corn products are presented within the standard 

BRAD configuration for PIPs (i.e., information is placed into separate and distinct chapters according to 

scientific discipline or regulatory focus), as this should be the most familiar format to outside 

stakeholders interested in providing comments on these actions. In addition to the expiring Cry34/35Ab1 

corn products, there are other Bt corn PIPs, expressing different proteins effective in controlling corn 

borers or corn rootworm, that expire in 2010, and for which the associated registrants have formally 

requested an extension to the current expiration dates. Therefore, within the same docket (EPA-HQOPP-2010-0607) as this document, the following informationa

 is also available for public examination: 

● Cry1F and Cry1Ab BRAD 

● Cry3Bb1 BRAD 

● mCry3A BRAD 

● Cry1A.105 and Cry2Ab2 BRAD 

● Optimum® AcreMaxTM B.t. Seed Blends BRAD 

● Current Registration Terms and Conditions for Bt Corn Registrations Set to Expire in 2010 

● Proposed Registration Terms and Conditions for Bt Corn Registrations Set to Expire in 2010 

 

a

 Each of the Biopesticides Registration Action Documents available for public comment in this action are modified from 

previous versions to account for data/information submitted to fulfill terms and conditions of registration. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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EPA has made the preliminary decision to amend the registrations of twenty-two (22) expiring Bt corn 

PIP registrations to extend the expiration dates. We have conducted comprehensive assessments of each 

of these registrations, considering all toxicity and environmental effects data, data from insect resistance 

monitoring, and insect resistance refuge compliance reports, received and obtained since the last 

comprehensive evaluation of these products in 2001. Based upon our comprehensive assessment, we 

have reached significant conclusions regarding the positive environmental impact of Bt corn PIPs, and 

we are proposing several actions to strengthen the insect resistance management requirements to ensure 

continued success in the prevention of the evolution of resistance in target pests. 

Since the commercialization of Bt crops, there have been a significant number of published field studies 

that, combined with the post-registration field studies required to be submitted to the Agency, have 

demonstrated that non-target invertebrates are generally more abundant in Bt cotton and Bt corn fields 

than in non-transgenic fields managed with chemical insecticides. Thus, these published and registrantproduced studies demonstrate that, not only are the Bt crops not causing any unreasonable adverse 

effects in the environment, but, arthropod prevalence and diversity is greater in Bt crop fields. Although 

no effects have been observed in the environment, the Agency is requiring additional aquatic 

invertebrate data in light of published laboratory studies showing reduced growth in shredding caddis 

flies exposed to Cry1A protein corn litter. 

To strengthen insect resistance management of these corn PIPs and to address reports that compliance 

with the mandated refuge requirements has been decreasing, EPA is proposing to require enhanced 

compliance assurance programs (CAPs), and a phased requirement for seed bag labeling that clearly 

shows the refuge requirements. Also, given the increasing variety of PIP products and combinations, and 

the differing risk of resistance evolution that the various products represent, we are proposing to grant 

registrations for the corn PIP products for different timeframes, based on assessments of their likelihood 

of forestalling the evolution of insect resistance. We are registering differing categories of products for 

differing time periods to reflect the assessed level of risk of resistance posed by the various corn PIP 

products. The scheme that we propose to follow will include registration periods generally of five, eight, 

and twelve years; with the possibility of a fifteen-year registration period for products that are 

demonstrated to meet specified criteria. We retain, however, the discretion to register products for time 

periods differing from these defaults where circumstances warrant. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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B. Use Profile 

Pesticide Name: Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins and the genetic 

material necessary for their production (plasmid insert PHP17662) in Event 

DAS-59122-7 corn (OECD Unique Identifier: DAS-59122-7) 

Trade and Other 

Names: Event DAS-59122-7 Corn, Herculex® Rootworm Insect Protection, Herculex® 

RW Insect Protection, Herculex® RW Rootworm Protection, Herculex® RW 

 

OPP Chemical Code: 006490

Basic Manufacturers: Mycogen Seeds c/o Dow AgroSciences LLC 

 9330 Zionsville Road 

 Indianapolis, IN 46268-1054 

 Pioneer Hi-Bred International, Incorporated 

 7100 N.W. 62nd Avenue 

 P.O. Box 1000 

 Johnston, IA 50131-1000

Type of Pesticide: Plant-Incorporated Protectant

Use: Field Corn 

Target Pests: western corn rootworm (Diabrotica virgifera virgifera), northern corn 

 rootworm (Diabrotica barberi), and Mexican corn rootworm (Diabrotica 

 virgifera zeae)

Products Expressing 

This Pesticide: See complete list in Appendix A. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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C. Regulatory History 

Date Action Type Description 

March 7, 2003 Federal Register 

Publication 

(Notice of Filing) 

Notice of Filing summarizing information submitted and cited by Mycogen 

Seeds c/o Dow AgroSciences LLC in support of a request for establishment 

of a temporary exemption from the requirement of a tolerance for residues 

of the plant-incorporated protectant, Bacillus thuringiensis Cry 34/35Ab1 

insecticidal crystal protein and the genetic material necessary for its 

production in corn. 

(68 Federal Register (FR) 11100) 

March 13, 2003 Federal Register 

Publication 

(Notice of Receipt) 

Notice announcing receipt of applications 68467-EUP-3, 68467-EUP-5, 

68467-EUP-T, 68467-EUP-I, 29964-EUP-1, 29964-EUP-3, 29964-EUP-U, 

and 29964-EUP-L from Mycogen Seeds c/o Dow AgroSciences LLC and 

Pioneer Hi-Bred International, Incorporated requesting experimental use 

permits and experimental use permit amendments for the following: 

(1) Bacillus thuringiensis Cry34/35Ab1protein and the genetic material 

necessary for its production (from the insert of plasmid PHP 14352) in corn 

(2) Bacillus thuringiensis Cry34/35Ab1 protein and the genetic material 

necessary for its production (from the insert of plasmid PHP 12560) in corn 

(3) Bacillus thuringiensis Cry34/35Ab1 protein and the genetic material 

necessary for its production (from the insert of plasmid PHP 17662) in corn 

(4) Bacillus thuringiensis Cry34/35Ab1 protein and the genetic material 

necessary for its production (from the insert of plasmid PHP 17658) in 

corn 

(68 FR 12073) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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Date Action Type Description 

July 7, 2003 Federal Register 

Publication 

(Final Rule) 

The following temporary exemption from the requirement of a tolerance 

was established under 40 Code of Federal Regulations (CFR) § 180.1242: 

“Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins and the 

genetic material necessary for their production in corn are temporarily 

exempted from the requirement of a tolerance when used as plantincorporated protectants in the food and feed commodities of field 

corn, sweet corn and popcorn. This temporary exemption from the 

requirement of a tolerance will permit the use of the food commodities 

in this paragraph when treated in accordance with the provisions of the 

experimental use permits 68467-EUP-3, 68467-EUP-5, 68467-EUP-T(7), 

68467-EUP-I(8), 29964-EUP-1, 29964-EUP-3, 29964-EUP-U(4), and 

29964-EUP-L(5) which may be issued and amended/extended under the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), as amended 

(7 U.S.C. 136). This temporary exemption from the requirement of a 

tolerance expires and is revoked April 30, 2006. This temporary 

exemption from the requirement of a tolerance may be revoked at any 

time if the experimental use permit is revoked or if any experience 

with or scientific data on this pesticide indicate that the tolerance 

is not safe.” 

(68 FR 40178) 

January 6, 2004 Federal Register 

Publication 

(Notice of Issuance) 

Notice announcing issuance of experimental use permits to Mycogen Seeds 

c/o Dow AgroSciences LLC (68467-EUP-7) and Pioneer Hi-Bred 

International, Incorporated (29964-EUP-5). Each permit allowed for use of 

Bacillus thuringiensis Cry34/35Ab1 proteins and the genetic material 

necessary for their production (from the insert of plasmid PHP17662) in 

corn on 624 acres of field corn and was effective from June 24, 2003 to 

May 1, 2004. 

(69 FR 658) 

March 10, 2004 Federal Register 

Publication 

(Notice of Receipt) 

Notice announcing receipt of applications from Mycogen Seeds c/o Dow 

AgroSciences LLC and Pioneer Hi-Bred International, Incorporated 

requesting amendments/extensions to their experimental use permits 

(68467-EUP-7 and 29964-EUP-5, respectively). 

(69 FR 11431) 

August 31, 2004 Federal Register 

Publication 

(Notice of Filing) 

Notice of Filing summarizing information submitted and cited by Mycogen 

Seeds c/o Dow AgroSciences LLC in support of a request for the 

establishment of a permanent exemption from the requirement of a 

tolerance for residues of the plant-incorporated protectant, Bacillus 

thuringiensis Cry 34Ab1 and Cry35Ab1 proteins and the genetic material 

necessary for their production in corn. 

(69 FR 53060) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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Date Action Type Description 

September 1, 2004 Federal Register 

Publication 

(Notice of Receipt) 

Notice announcing receipt of the following applications for products 

containing new active ingredients: 

(1) File Symbol: 29964-U. Applicant: Pioneer Hi-Bred International, 

A DuPont Company, 7250 N.W. 62nd Ave., P.O. Box 552, Johnston, IA 

50131-0552. Product Name: Pioneer Brand B.t. Cry34/35Ab1 Insect 

Resistant Corn Seed. Plant-incorporated protectant. Active Ingredient: 

Bacillus thuringiensis Cry34/35Ab1 insecticidal crystal protein and the 

genetic material for its production (plasmid insert PHP 17662) in event 

DAS-59122-7 corn. 

(2) File Symbol: 68467-L. Applicant: Mycogen Seeds c/o Dow 

AgroSciences LLC, 9330 Zionsville Road, Indianapolis, IN 46268. Product 

Name: Mycogen Brand B.t. Cry34/35Ab1 Construct 17662 Corn. Plantincorporated protectant. Active Ingredient: Bacillus thuringiensis 

Cry34/35Ab1 insecticidal crystal protein and the genetic material for 

its production (plasmid insert PHP 17662) in event DAS-59122-7 corn. 

(69 FR 53434) 

December 22, 2004 

Federal Register 

Publication 

(Notice of Issuance) 

Notice announcing extension/amendment of experimental use permits 

previously approved for Mycogen Seeds c/o Dow AgroSciences LLC 

(68467-EUP-7) and Pioneer Hi-Bred International, Incorporated (29964-

EUP-5). 

(1) 68467-EUP-7: For use of 0.94 pounds of Bacillus thuringiensis

Cry34/35Ab1 proteins and the genetic material necessary for their 

production (from the insert of plasmid PHP17662) in corn on 1,177 acres 

of field corn; Effective from April 29, 2004 to April 30, 2005. 

(2) 29964-EUP-5: For use of 3.97 pounds of Bacillus thuringiensis

Cry34/35Ab1 proteins and the genetic material necessary for their 

production (from the insert of plasmid PHP17662) in corn on 4,690 acres 

of field corn; Effective from April 29, 2004 to April 30, 2005. 

(69 FR 76732) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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Date Action Type Description 

June 3, 2005 Federal Register 

Publication 

(Notice of Receipt) 

Notice announcing receipt of the following applications for products 

containing new active ingredients: 

(1) File Symbol: 29964-L. Applicant: Pioneer Hi-Bred International, 

A DuPont Company, 7250 N.W. 62nd Ave., P.O. Box 552, Johnston, IA 

50131-0552. Product Name: Herculex Xtra Insect Protection. Plantincorporated protectant. Active Ingredient: Bacillus thuringiensis 

Cry34/35Ab1 insecticidal crystal protein and the genetic material for 

its production (plasmid insert PHP 17662) in event DAS-59122-7 corn and 

Bacillus thuringiensis Cry1F protein and the genetic material for its 

production (plasmid insert PHI 8999) in corn. 

(2) File Symbol: 68467-A. Applicant: Mycogen Seeds c/o Dow 

AgroSciences LLC, 9330 Zionsville Road, Indianapolis, IN 46268. Product 

Name: Mycogen Seeds Herculex Xtra Insect Protection. Plant-incorporated 

protectant. Active Ingredient: Bacillus thuringiensis Cry34/35Ab1 

insecticidal crystal protein and the genetic material for its 

production (plasmid insert PHP 17662) in event DAS-59122-7 corn and 

Bacillus thuringiensis Cry1F protein and the genetic material for its 

production (plasmid insert PHI 8999) in corn. 

(70 FR 32610) 

August 10, 2005 Federal Register 

Publication 

(Notice of Issuance) 

Notice announcing extension/amendment of experimental use permits 

previously approved for Mycogen Seeds c/o Dow AgroSciences LLC 

(68467-EUP-7) and Pioneer Hi-Bred International, Incorporated (29964-

EUP-5). 

(1) 68467-EUP-7: For use of 2,734.85 grams Cry34Ab1 and 10.88 grams 

Cry35Ab1 of the insecticides Cry34/35Ab1 proteins and the genetic 

material necessary for their production (from the insert of plasmid 

PHP17662) in corn on 3,096 acres of field corn; Effective from January 21, 

2005 to April 30, 2006. 

(2) 29964-EUP-5: For use of 1,813.6 grams Cry34Ab1 and 47.2 grams 

Cry35Ab1 of the insecticides Cry34/35Ab1 proteins and the genetic 

material necessary for their production (from the insert of plasmid 

PHP17662) in corn on 5,115 acres of field corn; Effective from January 21, 

2005 to April 30, 2006. 

(70 FR 46510) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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Date Action Type Description 

August 31, 2005 Registration The Agency issued time-limited, conditional registration notices (under 

FIFRA section 3(c)(7)(C)) for Event DAS-59122-7 corn to Mycogen Seeds 

c/o Dow AgroSciences LLC (EPA Reg. No. 68467-5) and Pioneer Hi-Bred 

International, Incorporated (EPA Reg. No. 29964-4). 

*Expiration Date: September 30, 2010 

September 21, 2005 Federal Register 

Publication 

(Final Rule) 

The following permanent exemption from the requirement of a tolerance 

was established under 40 CFR § 174.457: 

“Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins and the 

genetic material necessary for their production in corn are exempted 

from the requirement of a tolerance when used as plant-incorporated 

protectants in the food and feed commodities of corn; corn, field; 

corn, sweet; and corn, pop.” 

(70 FR 55254) 

October 27, 2005 Registration The Agency issued time-limited, conditional registration notices (under 

FIFRA section 3(c)(7)(A)) for Herculex® Xtra Insect Protection to 

Mycogen Seeds c/o Dow AgroSciences LLC (EPA Reg. No. 68467-6) and 

Pioneer Hi-Bred International, Incorporated (EPA Reg. No. 29964-5). 

*Expiration Date: October 15, 2008 

April 25, 2007 

Federal Register 

Publication 

(Direct Final Rule) 

The tolerance exemption for Cry34/35Ab1 proteins was redesignated from 

40 CFR § 174.457 to 40 CFR § 174.506 and changed to the following: 

“Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in 

corn are exempted from the requirement of a tolerance when used as plantincorporated protectants in the food and feed commodities of corn; corn, 

field; corn, sweet; and corn, pop.” 

(72 FR 20431) 

August 15, 2007 Federal Register 

Publication 

(Notice of Issuance) 

Notice announcing conditional approval of two products (Herculex® 

Rootworm Insect Protection, EPA Reg. No. 29964-4; Herculex® RW 

Insect Protection, EPA Reg. No. 68467-5) containing Bacillus 

thuringiensis Cry34Ab1 and Cry35Ab1 proteins and the genetic material 

necessary for their production (plasmid insert PHP17662) in Event DAS59122-7 corn, an active ingredient not included in any previously 

registered product. 

(72 FR 45807) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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Date Action Type Description 

October 8, 2008 Amendment 

The Herculex® Xtra Insect Protection registrations (EPA Reg. Nos. 29964-

5 and 68467-6) were amended by the Agency to extend the expiration date 

set forth in the original registration notices. 

*New Expiration Date: September 30, 2010 

July 2009–April 

2010 

Registration 

The Agency registered several combination PIP products expressing 

Cry34/35Ab1 and another protein(s), as well as two seed blends. See 

Appendix A for the complete list. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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II. SCIENCE ASSESSMENT 

The classifications that are found for each data submission are assigned by Environmental Protection 

Agency (EPA) science reviewers and are an indication of the usefulness of the information contained in 

the documents for risk assessment. A rating of “ACCEPTABLE” indicates the study is scientifically 

sound and is useful for risk assessment. A “SUPPLEMENTAL” rating indicates the data provide some 

information that can be useful for risk assessment. The studies may have certain aspects determined not 

to be scientifically acceptable (“SUPPLEMENTAL: UPGRADABLE”). If a study is rated as 

“SUPPLEMENTAL: UPGRADABLE,” EPA always provides an indication of what is lacking or what 

can be provided to change the rating to “ACCEPTABLE.” If there is simply a “SUPPLEMENTAL” 

rating, the reviewer will often state that the study is not required by the current 40 Code of Federal 

Regulations (CFR) Part 158. Both “ACCEPTABLE” and “SUPPLEMENTAL” studies may be used in 

the risk assessment process as appropriate. An “UNACCEPTABLE” rating indicates that the study is 

not useful for risk assessment and cannot be upgraded. 

A. Product Characterization

1. Event DAS-59122-7 Corn (Organization for Economic Cooperation and Development 

 (OECD) Unique Identifier: DAS-59122-7) Expressing Cry34Ab1 and Cry35Ab1 

a. Data Cited/Submitted for Initial Registrations of Event DAS-59122-7 Corn (Prior to 

 August 2005)

The Agency’s detailed assessment of the product characterization for Bacillus thuringiensis (Bt) 

Cry34/35Ab1 corn is found in U.S. EPA (2004). Portions of the product characterization data were also 

reviewed in U.S. EPA (2001a, 2002, 2003a, 2003c, 2003d, and 2003e). Bacillus thuringiensis

Cry34/35Ab1 corn was produced by Agrobacterium tumefaciens-mediated transformation of public corn 

line (Hi-II) with the transfer deoxyribonucleic acid (T-DNA) from plasmid PHP17662a

, which contains 

cry34Ab1, cry35Ab1, phosphinothricin acetyltransferase (pat), and regulatory sequences necessary for 

the expression of the genes. The cry34Ab1 and cry35Ab1 transgenes were optimized for expression in 

maize, but the amino acid sequence of the expressed proteins is identical to the native proteins from Bt. 

Characterization of the deoxyribonucleic acid (DNA) isolated from Bt Cry34/35Ab1 corn, using 

restriction enzyme digests and Southern blot analysis (Master Record Identification Numbers (MRID 

Nos.) 461239-08 and 461239-09; reviewed in U.S. EPA (2004)), indicated that the T-DNA from 

plasmid PHP17662 inserted as a single, intact copy into the corn genome. In addition, DNA analysis 

indicated stability and inheritance of the inserted DNA within and across several generations. 

Protein characterization data demonstrated that the plant-produced proteins have characteristics and 

activities that are equivalent to those of the proteins produced in Pseudomonas fluorescens transformed 

to produce Cry34Ab1 and Cry35Ab1 (MRID Nos. 461239-05 and 461239-06; reviewed in U.S. EPA 

 

a

 Early in the development of this product, other plasmids were used and other events tested. Event DAS-59122-7, where 

plasmid PHP17662 was used, has been chosen for commercialization. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

15

(2004)). The following techniques were used to characterize and compare the plant-produced proteins 

and the microbially produced proteins: sodium dodecyl sulfate polyacrylamide gel electrophoresis 

(SDS-PAGE), N-terminal amino acid sequencing, matrix-assisted laser desorption/ionization time-offlight mass spectrometry (MALDI-TOF-MS), glycosylation analysis, enzyme-linked immunosorbent 

assays (ELISAs), and western blot analysis. Glycosylation analysis indicated that the Cry34Ab1 and 

Cry35Ab1 proteins are not glycosylated. Biological activity of the plant-produced and P. fluorescensproduced proteins was also assessed and compared; Cry34Ab1 and Cry35Ab1 from both sources 

displayed similar insecticidal activity to western corn rootworm larvae. These analyses justified the use 

of microbially produced proteins in toxicity studies. 

Studies on the mode of action of Cry34Ab1 and Cry35Ab1 indicated that, similar to other Bt deltaendotoxins, Cry34Ab1 and Cry35Ab1 appear to target midgut epithelial cells in susceptible larvae 

(Master Record Identification Number (MRID No.) 457906-01; reviewed in U.S. EPA (2003c)). 

Cry34Ab1 appears to cause pore formation in phospholipid membranes, and addition of Cry35Ab1 

resulted in pores remaining open longer and improved membrane permeability (Masson et al. 2004). 

Ribosomal inhibition activity was also investigated (MRID No. 461239-10; reviewed in U.S. EPA 

(2004)). The results demonstrated that the insecticidal activity of Cry34Ab1 and Cry35Ab1 is not 

associated with the inhibition of protein synthesis. 

Submitted studies on heat stability of the Cry34Ab1 and Cry35Ab1 proteins demonstrated that these 

proteins are inactivated at 90C and 60C, respectively (MRID Nos. 453584-01, 455845-01, 458086-01, 

and 458602-01; reviewed in U.S. EPA (2001a, 2002, and 2003a)). 

Data on expression levels of the proteins in transgenic corn tissues were also provided for both inbred 

and hybrid lines from several different events (MRID No. 461239-04; reviewed in U.S. EPA (2004)). 

The protein expression levels were comparable between hybrid and inbred lines. Data on expression 

levels in a hybrid line are summarized in Table 1. 

Table 1. Mean Expression Levels of Cry34Ab1 and Cry35Ab1 in Plant Tissues from a Hybrid 

 Line Containing Event DAS-59122-7. 

Tissue Cry34Ab1 

(ng/mg tissue dry weight +

standard deviation)* 

Cry35Ab1 

(ng/mg tissue dry weight + standard 

deviation)*

Leaf 50 + 8 – 220 + 38 41 + 7 – 85 + 19 

Root 37 + 9 – 50 + 20 3 + 2 – 8 + 3 

Whole Plant 32 + 16 – 77 + 10 7 + 2 – 14 + 2 

Pollen 74 + 7 0.02 + 0.04 

Stalk 33 + 4 10 + 2 

Forage 53 + 19 12 + 3 

Grain 50 + 16 1 + 0.3 

* Ranges reflect the range of means at different growth stages. 

The product characterization studies that were submitted in support of Event DAS-59122-7 corn are 

summarized in Table 2. Some of the studies were conducted on events other than DAS-59122-7, and 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

16

some of the studies refer to the Cry34Ab1 and Cry35Ab1 proteins as PS149B1 13.6- or 14-kiloDalton 

(kDa) and 43.8- or 44-kDa insecticidal crystal proteins. The term, PS149B1 proteins, was used prior to 

the proteins receiving their Bt toxin nomenclature designations (Crickmore et al. 2010). The PS149B1 

13.6-kDa or 14-kDa proteins and 43.8-kDa or 44-kDa proteins are the same as the Cry34Ab1 and 

Cry35Ab1 proteins, respectively. 

Table 2. Product Characterization Data for Event DAS-59122-7 Corn (Reviewed in U.S. EPA 

 (2004) Unless Otherwise Noted). 

Study Title Summary MRID No.

Product Characterization 

Data for Bacillus 

thuringiensis PS149B1 

13.6 kDa and 43.8 kDa 

Insecticidal Crystal 

Proteins Expressed in 

Transgenic Maize 

Plantsb

 

Maize immature embryo tissues were transformed using a linearized 

fragment from plasmid PHP12560 encoding two insecticidal crystal protein 

(ICP) genes, 8v6 (13.6 kDa) and 7v7 (43.8 kDa), each driven by the maize 

ubiquitin promoter, and the pat gene, driven by the CaMV 35S promoter. 

The two ICP genes from Bt PS149B1 are modified in coding sequence to 

optimize for plant expression. Amino acid sequences are, however, 

identical to the bacterial source proteins. Microprojectile bombardment of 

tissues, followed by selection on glufosinate, produced plants expressing 

the two insecticidal crystal proteins (ICPs) of PS149B1 and PAT. Maize 

plants expressing these genes were also produced by Agrobacterium -

mediated transformation of immature embryos. Western corn rootworm 

(WCRW) bioassays were used to assess the bioactivity of the expressed 

ICPs. Within 48 hours of feeding on transgenic maize plants, WCRW 

larvae had midgut symptoms consistent with feeding on delta-endotoxins 

(e.g., swelling, lysis, blebbing, or vacuolization). WCRW feeding on 

control plants did not show pathological changes in midgut epithelium. The 

two ICPs were also tested for adenosine diphosphate (ADP)-ribosylating or 

glucosylating activities as well as other enzymic activities, but none were 

detected. 

Classification: Acceptable 

452422-01 

Characterization of 

Inserted DNA of Event 

5639 Transgenic Corn 

Plants – Interim Reportb

Based upon the Southern blot data presented, the most likely conclusion is 

that there are three insertions of the 8v6, 7v7, and pat genes into Event 

5639, although only one may be fully intact. The complexity of the 

hybridization patterns does not allow one to say with certainty that three 

insertions are present at this time. A more detailed analysis of gene 

insertion will be required as this product develops to fully ascertain the 

nature of the integration events. Data indicated that Event 5639 does not 

contain a kanr

 sequence. 

Classification: Acceptable 

452422-02 

 

b

 Reviewed in U.S. EPA (2001a) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

17

Study Title Summary MRID No.

Equivalency of 

Microbial- and MaizeExpressed PS149B1 

proteinsc

Biochemical, molecular, and serological data presented indicate that the 

proteins produced in the P. fluorescens system are equivalent to the 

proteins produced in transgenic maize plants. Relative molecular mass and 

serological reactivity to polyclonal antibodies were the same for the 14-

kDa proteins produced in either system. SDS-PAGE and western blots 

indicated identity between the two production systems. This was also true 

for the 44-kDa protein and its proteolytic cleavage product, the 42-kDa 

protein. The 44-kDa protein predominated in the fresh plant material and in 

the P. fluorescens production system. Storage of leaf material led to the 

production of the 42-kDa protein as the predominant form due to 

proteolytic processing. No glycosylation was detected on either protein 

from the maize system. Tryptic digestion of PS149B1 proteins and 

subsequent analysis by MALDI-TOF-MS, N-terminal sequencing, and 

electrospray ionization tandem mass spectrometry (ESI MS/MS) spectra all 

indicated that PS149B1 proteins produced by P. fluorescens and the 

transgenic maize are equivalent for toxicological testing to be performed 

with proteins from either source. In insect bioassays, proteins produced in 

the transgenic maize system and the microbial system both showed activity 

against the southern corn rootworm (SCRW) and WCRW larvae. While the 

transgenic maize assay indicated no reduction in damage from European 

corn borer (ECB) feeding, the diet-based overlay with the microbially 

produced protein indicated some slight inhibition of growth for ECB 

larvae. Additionally, the PS149B1 maize plants sustained greater leaf 

damage from ECB, based upon visual estimates, than the control plants. It 

is not clear if this difference was statistically significant since there was no 

analysis provided. 

Classification: Acceptable

452422-03 

Microbial PS149B1 

Binary Delta-Endotoxin: 

Maize-Insect-Pest 

Susceptibility Studyc

 

The relative sensitivity of the test insects in the feeding bioassays suggests 

that larvae of coleopteran species are far more sensitive to the 14-kDa and 

44-kDa proteins of PS149B1 than the lepidopteran or homopteran larval 

insects evaluated. Adult WCRW were not sensitive to the delta-endotoxins, 

however. Rootworms (northern corn rootworm (NCRW), WCRW, and 

SCRW) were the most susceptible to the PS149B1 proteins. European corn 

borer and corn earworm (CEW) demonstrated some inhibition of growth at 

higher concentrations of the test substance than the rootworm larvae. Black 

cutworm (BCW) was the least sensitive of the lepidopteran species tested. 

No activity was seen against the corn leaf aphid (CLA), a homopteran. 

Relative susceptibilities of the insect species to PS149B1, based upon the 

more sensitive measure of 50% growth inhibition (GI50), were as follows: 

(most susceptible) WCRW, NCRW, SCRW > ECB, CEW >> WCRW 

adult, CLA, BCW (least susceptible). 

Classification: Acceptable

452422-04 

 

c

 Reviewed in U.S. EPA (2001a) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

18

Study Title Summary MRID No.

Quantitative ELISA 

Analysis of PS149B1 

Protein Expression 

Levels in Hybrid and 

Inbred Lines of Maize 

Event TC5639d

Leaf, pollen, root, and senescent whole plant tissue samples were taken 

from field-grown plants cultured in the U.S. corn belt. Both test hybrid and 

inbred lines of Event 5639 and control hybrid and inbred lines were 

compared for expression of the 14-kDa and 44-kDa PS149B1 proteins. 

Leaf, pollen, root, and senescent whole plant tissues expressed the 14-kDa 

and 44-kDa proteins at measurable levels in the modified maize lines. 

Hybrid and inbred lines had comparable levels of expression of these 

proteins when analyzed on a dry weight basis. On a total extractable 

protein basis, though, root tissues had the highest expression and pollen 

had the lowest expression. Control tissues were negative for the presence 

of the 14-kDa or the 44-kDa proteins. Coefficients of variation (CVs) were 

lacking for data presented and need to be included in order to adequately 

assess the results of the ELISAs. The use of samples spiked with known 

quantities of the two proteins separately is also needed to assess the 

possible influence of maize tissue extracts on the enzyme-linked 

immunosorbent assay (ELISA) values observed. These data and an 

evaluation of possible cross-reactivity of the primary antibody with other 

Cry proteins will be needed for Section 3 registration. 

Classification: Acceptable

452422-13 

Lateral Flow Test Kit 

for the Detection of the 

PS149B1 Protein in 

Maize Graine

The double antibody sandwich format of the lateral flow test strip from 

Strategic Diagnostics was capable of correctly detecting 48 positive 

aliquots of 24 extracts from 24 single kernel samples of PS149B1 maize. 

Conversely, 48 aliquots of 24 extracts from 24 kernels of a non-PS149B1 

inbred line all tested negative, as expected. Ratios of positive (PS149B1) 

and negative (control) kernels were mixed and extracted. When 0.5% or 

greater PS149B1 kernels were present in the mixture, they were correctly 

detected as containing Cry34Ab1 protein. No ratios of positive to negative 

below 0.5% were evaluated in this study. 

Classification: Acceptable

453834-01 

 

d

 Reviewed in U.S. EPA (2001a) 

e

 Reviewed in U.S. EPA (2003b)
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

19

Study Title Summary MRID No.

Characterization of 

Cry34Ab1 and 

Cry35Ab1 from 

Recombinant 

Pseudomonas 

fluorescens and 

Transgenic Maizef

 

Cry34Ab1 and Cry35Ab1 proteins were separated from maize leaf extracts 

and from microbial production sources on SDS-PAGE gels and then 

blotted to nitrocellulose for serological detection. Both proteins were 

detected on the western blots by polyclonal antibody preparations and 

appeared at the appropriate Mr for both proteins on individual blots (i.e., 14 

kDa - Cry34Ab1; 44 kDa - Cry35Ab1). A second protein band reacted with 

the Cry35Ab1-specific antibody in the microbially produced protein 

preparation at approximately 40 kDa, which is presumably a degradation 

product from protease activity. This band or signal was noted in the 

western blot of 3 of 6 maize leaf extracts representing the 6 events but at 

reduced amounts relative to the microbial preparation. Both Cry proteins 

from the maize extracts migrated very similarly to the Cry proteins 

produced in the microbial production system and, by this criterion (i.e., 

mobility in SDS-PAGE), are considered as indistinguishable. 

Classification: Acceptable

457904-01 

 

f

 Reviewed in U.S. EPA (2003c) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

20

Study Title Summary MRID No.

Characterization of 

DNA Inserted into 

Transgenic Corn Events 

E4497.42.1.34, 

E4497.45.2.16, 

E4497.59.1.10, 

E4497.66.1.27, 

E4497.71.1.29, and 

E4497.71.1.33g

 

Southern blots were used to discern the number of insertions from the 

plasmid constructs, PHP17662 and PHP17658, used in the transformation 

of maize. An analysis of integration sites in Events E4497.42.1.34, 

E4497.45.2.16, and E4497.59.1.10 indicated a single integration of the TDNA sequence into the maize genome. Each reactive band present in the 

blot resulted from the XhoI cleavage of the incorporated T-DNA region 

(containing cry34Ab1, cry35Ab1, and pat from PHP17622 in a single 

fragment) and a second XhoI restriction site in the adjacent maize genome. 

Hence, the bands represented individual, unique integrations of T-DNA in 

the maize genome. The size of the reactive bands cannot be determined a 

priori since the size of the flanking or border fragment is not known as it is 

determined by the distance from the single XhoI site within the T-DNA 

region. Events E4497.42.1.34 and E4497.45.2.16 each had single reactive 

hybridization events (bands) on the blot, indicating the presence of a single 

T-DNA insertion. The commonality of band sizes (i.e., 9.4 or >22 kilobase 

(kb)) suggests that the T-DNA insertion is the result of a single insertional 

event. A 9.4 kb signal in E4497.59.1.10 also indicates the integration of 

one full T-DNA containing cry34Ab1, cry35Ab1, and pat. The presence of 

a second hybridizing signal (7.4 kb) in the blot of genomic DNA from 

E4497.59.1.10 probed with cry35Ab1 suggests that a partial construct 

insertion occurred containing only the cry35Ab1 portion and not cry34Ab1

or pat. StuI cuts once in PHP17658 and was used to define integration sites 

in Events E4497.66.1.27, E4497.71.1.29, and E4497.71.1.33. Events 

E4497.71.1.29 and E4497.71.1.33 appear to both contain a single T-DNA 

insertion based on the reactive band signals being present at 11 and 8.3 kb 

for all three probes. Additionally, there was a reactive band at 14 kb and 

2.7 kb for the pat-probed blots of E4497.71.1.29 and E4497.71.1.33, 

respectively. The second reactive band in the pat- probed blots was a 

consequence of the position of the cleavage site for the StuI enzyme being 

within the pat open reading frame (ORF). Genomic DNA from control 

plants (non-transgenic) was spiked with restricted plasmid DNA of 

PHP17661 and PHP17657 at a concentration of one copy per genome 

equivalent to serve as positive controls. 

Classification: Acceptable

457904-02 

 

g

 Reviewed in U.S. EPA (2003c) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

21

Study Title Summary MRID No.

Product Characterization 

Data for Bacillus 

thuringiensis Cry34Ab1 

and Cry35Ab1 Proteins 

Expressed in Transgenic 

Maize Plants 

(PHP17662)h

Genes encoding the PAT, Cry34Ab1, and Cry35Ab1 proteins were 

transferred into the T-DNA region of the disarmed A. tumefaciens strain 

LBA4404. This Ti-plasmid was then referred to as PHP17662 and is 

approximately 50 kb in size. This strain carrying PHP17662 was used to 

transform immature maize embryo tissues by co-cultivation for 6 days. 

Coding sequences for the Cry34Ab1 (14-kDa) and Cry35Ab1 (44-kDa) 

proteins were synthesized from the native sequence to optimize expression 

in maize. The PAT protein produced from a synthetic gene is not altered in 

its amino acid sequence as compared to the native protein. The gene and 

protein are considered as inert ingredients in this plant-incorporated 

protectant. Gut cells of the control maize-fed insects and the starved insects 

appeared normal, although the latter group showed some collapse of the 

gut lumen. After 48 hours of feeding on the transgenic maize plants, 

WCRW larvae had evidence of cell lysis, blebbing, and vacuolization, as 

would be expected from intoxication with delta-endotoxins in a susceptible 

insect. Subsequently, the gut tissues showed further collapse and more 

fragmentation. Enzyme assays were evaluated to determine if either 

Cry34Ab1 or Cry35Ab1 proteins were capable of activity: glucosylating or 

ADP-ribosylating of midgut proteins, protease at acid and neutral pH, 

neuraminidase (sialidase), acid and alkaline phosphatase activity. Protein 

synthesis inhibition of an in vitro system was also tested. All assays were 

negative for their corresponding enzyme activities. Amino acid sequences 

of the three proteins and micrographs of histopathological midgut 

responses were presented. 

Classification: Acceptable

457906-01 

 

h

 Reviewed in U.S. EPA (2003c) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

22

Study Title Summary MRID No.

Quantitative ELISA 

Analysis of Cry34Ab1 

and Cry35Ab1 Proteins 

Expressed in Maize 

Plants Transformed with 

the Vector PHP17662i

ELISA was used to determine the quantity of the two ICPs present in leaf, 

pollen, root, and seed of transgenic maize from three separate 

transformation events (E4497.42.1.34, E4497.45.2.16, and E4497.59.1.10). 

Direct double antibody sandwich ELISA was used to quantify the 

Cry34Ab1 and Cry35Ab1 present in plant samples. The primary antibodies 

raised against Cry34Ab1 and Cry35Ab1 were used to capture the proteins 

(individually in separate reactions) in the microplate well, and a second 

specific antibody was used to detect the protein that was bound. This 

second antibody was conjugated to biotin, which was detected using 

streptavidin linked to alkaline phosphatase (AP). The colorimetric reaction 

catalyzed by the AP provides for a means of measuring optical density or 

absorbance and correlating it to the amount of target protein present based 

upon comparison to a standard curve generated from reference standards. 

The values obtained from the ELISA readings are converted to amounts of 

Cry34Ab1 or Cry35Ab1 protein and expressed as nanograms Cry34Ab1 

protein per milligram total extractable protein (TEP). Since data for water 

content exists for the tissue types sampled, the conversion to nanograms 

Cry34Ab1 protein per milligram dry tissue is possible with conversion 

factors. Reference standards used to generate the standard curve were run 

in triplicate within each 96-well microplate. For Cry34Ab1, the magnitude 

of expression for tissue types was as follows in descending order: leaf, 

pollen, kernel, and root. All control tissues were negative for the 

expression of Cry34Ab1. Due to the Mendelian segregation of the 

transgenes, approximately 50% of the seeds were found to be expressing 

Cry34Ab1. For Cry35Ab1, the magnitude of expression for tissue types 

was as follows in descending order: leaf, root, and kernel. All control 

tissues were negative for the expression of Cry35Ab1. Cry35Ab1 protein 

was not detected in pollen. Due to the Mendelian segregation of the 

transgenes, approximately 50% of the seeds were found to be expressing 

Cry35Ab1. Seeds that were observed to contain no Cry proteins by ELISA 

were not included in the summary statistics since they represent segregants 

from the heterozygous populations of the three events. Mean values are 

presented in tabular format for all three events for each tissue type. 

Classification: Acceptable 

458332-01 

 

i

 Reviewed in U.S. EPA (2003c) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

23

Study Title Summary MRID No.

Probe MOA Studies to 

Assess Potential for 

Protein Synthesis 

Inhibition by Bacillus 

thuringiensis PS149B1 

Cry34Ab1/Cry35Ab1 

Proteins in a Rabbit 

Reticulocyte Assay: ReExamination of Lab 

Notebook Dataj

Two experiments were performed in order to assess the potential for 

ribosomal inhibition activity by either Cry34Ab1 or Cry35Ab1. The first 

experiment concluded, based upon a sensitive luciferase 

(chemiluminescence) assay, that the Cry 34Ab1 and Cry35Ab1 proteins 

did not show the properties of ribosomal inhibition proteins (RIPs). This 

was largely based upon comparison to a bovine serum albumin (BSA) 

control and phosphate buffered saline (PBS) buffer control. A second 

experiment, with a different treatment regime and altered protocol, 

concluded that there was some ribosomal inhibition protein (RIP) activity 

associated with the PS149B1 proteins. Further, digesting the 14-kDa 

protein with trypsin may have also reduced translation a little. The two 

experiments used different amounts of BSA (i.e., 1x and 2x), and this 

added variable further confounded the interpretation of results. The lack of 

proper controls and different treatment regimes in the experiments made 

any assessment of the potential RIP activity dubious. The experiments 

would also have benefitted by including a greater number of samples per 

treatment (at least triplicate) and appropriate controls. A positive control 

(i.e., a protein with known RIP activity) is crucial to the interpretation of 

results. Note that the source (lot) of the proteins used for the two 

experiments was different as well. It is also probable that confounding 

stabilization reagents (e.g., glycerol, azide) were present in the reaction 

during the second experiment, further complicating any analysis of results. 

It is not possible, given the present data set and variance in methodologies, 

to assess the results accurately. The RIP assay has not been considered as a 

typical part of the submission process for plant-incorporated protectants. 

There is no a priori reasoning or similarity between the delta-endotoxins of 

Bt or Bacillus sphaericus insecticidal toxins and proteins with known RIP 

activity to expect Cry34Ab1 or Cry35Ab1 to exhibit such action. Proteins 

with this activity also require a means of intracellular vectoring in order to 

reach the ribosome target. 

Classification: Supplemental

459428-01 

Thermolability of 

PS149B1 Binary DeltaEndotoxink

 

Results indicate that the PS149B1 proteins, or at least one of them, are 

inactivated after exposure to 60C for 30 minutes, based upon activity 

against the southern corn rootworm. It is possible that shorter times or 

lower temperatures may have also denatured the protein(s), but these were 

not tested. With the current protocol design, it is not possible to determine 

if one or both proteins are inactivated following heat treatment. To address 

this issue, the applicant should consider repeating the study under a method 

that would allow this distinction to be made as part of the submission for 

Section 3 registration. 

Classification: Acceptable

453584-01 

 

j

 Reviewed in U.S. EPA (2003d) 

k

 Reviewed in U.S. EPA (2001a)
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

24

Study Title Summary MRID No.

Heat Lability of 

Individual Proteins of 

the PS149B1 Binary 

ICPl

The percent growth inhibition of larvae, as observed in a southern corn 

rootworm feeding assay, was used as a measure or indicator that the 

Cry34Ab1 and Cry35Ab1 proteins were degraded to a point they have lost 

insecticidal activity. The decrease in growth inhibition activity following 

heating of the 14-kDa and 44-kDa mixture suggests that heat treatment at 

60C for 30 minutes is sufficient to denature at least one of the necessary 

components of the ICP. No mortality effect was seen with the Cry protein 

treatments, as expected. The author suggested that the degree of inhibition 

(30 to 42% larval growth inhibition) seen following heat treatment of the 

mixture is typical of an inactive protein preparation as observed in previous 

assays. This difference between the larval weights observed with the ICPtemperature treatments and the buffer control was a non-specific effect 

attributable to the presence of proteins in the diet irrespective of the amino 

acid sequence and conformation of the ICPs. The 44-kDa protein in the 

ICP was denatured by treatment at 60C and higher temperatures. The 

decrease in insect growth inhibition, seen in the 44-kDa spike of the heated 

ICP as temperature of incubation was increased, indicates that the 14-kDa 

protein was more heat stable than the 44-kDa protein. The concomitant 

decrease in insect activity (i.e., growth inhibition) with temperature 

increase shows the relative stability of this protein at 60C and 75C but its 

denaturation to background levels (i.e., 36% growth inhibition compared to 

buffer control) at 90C. 

Classification: Supplemental

455845-01 

 

l

 Reviewed in U.S. EPA (2002) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

25

Study Title Summary MRID No.

Summary of Heat 

Lability Studies with 

Cry34Ab1/Cry35Ab1m

Slide Presentation 

Summarizing 

Cry34Ab1/Cry35Ab1 

Heat Inactivation 

Studiesm

Using an insect bioassay as the detection method for PS149B1 proteins 

(Cry34Ab1, Cry35Ab1) provides for a qualitative assessment of the 

protein(s) remaining after treatment but does not allow for quantitation. 

This assay utilized the decrease in growth of larval SCRW, measured as 

mass, as a means of assessing activity remaining in the Cry protein(s) but 

did not give a direct correlation with protein concentration. Nonetheless, 

the assay provided for a determination as to the conformational changes 

(denaturation) that occur following heat treatment. The two studies 

previously submitted (MRID Nos. 455845-01 and 453584-01), regarding 

heat stability of the Cry34Ab1 and Cry35Ab1 proteins, demonstrated that 

these proteins are inactivated at <90C and <60C, respectively. The two 

current submissions served to clarify the lability of the proteins to heat. 

However, differences in the execution of the two studies complicated the 

interpretation and comparison of the results. The feeding bioassays, using 

the southern corn rootworm, indicated that the proteins are no longer active 

following their respective heat treatments. This is taken as evidence of 

protein denaturation. The SCRW assay was based upon growth inhibition 

of the larvae and not mortality. A different diet formulation was used in 

each study with a greater than 10-fold increase in larval growth occurring 

in control insects with the artificial diet in the second study (MRID No. 

455845-01). Additionally, the presence of salts and buffer impurities from 

the purification process used for the synthesis of the test substance 

(Cry34Ab1 and Cry35Ab1 proteins from a bacterial production system) 

resulted in experimental variance not expected or attributable to the 

insecticidal proteins being tested. Both Cry proteins evaluated herein are 

susceptible to heat denaturation under the conditions tested, albeit with 

different denaturation profiles. 

Classification: Acceptable

458086-01 

458602-01 

Independent Laboratory 

Validation of Pioneer 

Hi-Bred International, 

Incorporated ELISA 

Method for the 

Quantification of 

Cry34Ab1 Protein from 

Transgenic Plants 

This study was conducted to provide independent laboratory validation 

(ILV) data for the determination of Cry34Ab1 insecticidal crystal protein 

in corn matrices and to support the stated limit of quantitation (LOQ) of 

0.072 nanograms per milligram (ng/mg). The reported data satisfied the 

requirements of U.S. EPA Guideline Office of Chemical Safety and 

Pollution Prevention (OCSPP) 860.1340(c)(6) and the study protocol. 

Individual recovery values for each fortified control sample were within 

the range of 70 – 120% and averaged 78% and 98% at the LOQ and 2x the 

LOQ, respectively. The relative standard deviation (RSD) of replicate 

recovery measurements did not exceed 20% at or above the LOQ, and 

interferences were minor. 

Classification: Acceptable

461239-01 

 

m Reviewed in U.S. EPA (2003a) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

26

Study Title Summary MRID No.

Independent Laboratory 

Validation of Dow 

AgroSciences Method 

GRM 03.13, 

“Determination of 

Cry35Ab1 Insecticidal 

Protein in Maize Tissue 

by Enzyme-Linked 

Immunosorbent Assay” 

This study was conducted to provide ILV data for the determination of 

Cry35Ab1 insecticidal crystal protein in corn matrices and to support the 

stated LOQ of 0.06 ng/mg. The reported data satisfy the requirements of 

U.S. EPA Guideline OCSPP 860.1340(c)(6) and the study protocol. 

Individual recovery values for each fortified control sample were within 

the range of 70 – 120% and averaged 93 and 101% at the LOQ and 2x the 

LOQ, respectively. The RSD of replicate recovery measurements did not 

exceed 20% at or above the LOQ, and interferences were minor. 

Classification: Acceptable 

461239-02 

Cry34/Cry35 Protein 

Distribution and 

Familiarity 

DNA hybridization and polymerase chain reaction (PCR) analysis of total 

genomic DNA from collections of strains of Bt showed that homologs of 

cry34/35 genes were present in strains from North and South America and 

from Australasia taken from a variety of environments. The overall rate of 

occurrence of cry34/35 genes in Bt strains was 1.2%; this rate of 

occurrence is comparable to that of the cry3Aa gene, which encodes a 

previously registered insect control protein (EPA Registration Number 

524-474). Sequence comparisons demonstrated that the Cry35 protein has 

some homology (26 to 29%, respectively) to the 42- and 51-kDa 

mosquitocidal proteins from B. sphaericus strain 2362 (B. sphaericus

H5a5b strain 2362 is a registered biopesticide). 

Classification: Acceptable

461239-03 

Agronomic 

Characteristics, 

Quantitative ELISA and 

Nutrient Composition 

Analysis of Hybrid 

Maize Lines Containing 

the cry34Ab1, 

cry35Ab1, and pat

Genes: Chile Locations 

The data from this study indicated that control and transgenic lines 

(containing Events DAS-45216-6, DAS-59122-7, and DAS-45214-4) are 

similar with respect to agronomic characteristics and nutrient composition. 

Expression levels of Cry34Ab1, Cry35Ab1, and PAT proteins were 

analyzed by ELISA for various plant tissues at different growth stages for 

transgenic hybrid and inbred lines and compared with control lines for both 

herbicide-sprayed plants and non-sprayed plants. On a dry weight basis, the 

concentrations found for Cry34Ab1 ranged from a low of 31 ng/mg in R1 

stalks to a high of 500 ng/mg in R4 leaves; concentrations for Cry35Ab1 

ranged from a low of 0.01 ng/mg in pollen to a high of 120 ng/mg in R4 

leaves; and concentrations for PAT ranged from 0 ng/mg in pollen to 36 

ng/mg in R1 leaves. Transgenic protein levels were independent of 

spraying status, comparable between hybrid and inbred lines, and the 

proteins were not detected in any control samples. 

Classification: Acceptable

461239-04 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

27

Study Title Summary MRID No.

Biological Equivalency 

of Cry34Ab1/Cry35Ab1 

Insecticidal Crystal 

Protein in Transgenic 

Plants and Derived from 

Transgenic 

Pseudomonas 

fluorescens

Three transgenic corn lines (DAS 45214-4, 45216-6, and 59122-7), 

carrying the cry34Ab1 and cry35Ab1 genes that produce a binary 

insecticidal protein, and control (non-transgenic) corn were field-tested for 

their resistance to damage from western corn rootworm, northern corn 

rootworm, black cutworm, and European corn borer. The transgenic corn 

lines were all shown to have a statistically significant effect against western 

and northern corn rootworm but were not effective against European corn 

borer and black cutworm. These results are consistent with the efficacy 

profiles observed in previous studies on other corn events expressing the 

same insecticidal protein (DAS Report 000367) and with the efficacy 

profiles obtained with purified binary insecticidal protein isolated from P.

fluorescens (DAS Report 000366). 

Classification: Acceptable

461239-05 

Characterization of 

Cry34Ab1 and 

Cry35Ab1 Proteins 

Derived from 

Transgenic Maize Event 

E4497.59.1.22 (DAS59122-7) 

Selected biochemical properties of Cry34Ab1 and Cry35Ab1 proteins, 

isolated from leaf tissue from Bt transgenic corn Event E4497.59.1.22 

(DAS-59122-7) [59.1.22], were evaluated and compared to biochemical 

properties of the proteins obtained from a P. fluorescens bacterial 

expression system containing the two Bt transgenes. The results were also 

compared with results from a previously submitted study on Cry34Ab1 and 

Cry35Ab1 isolated from Bt transgenic corn Event 5638. SDS-PAGE and 

western blot analysis indicated the relative molecular weights of Cry34Ab1 

and Cry35Ab1 from all sources were ~14 kDa and ~44 kDa, respectively. 

In addition, the Cry35Ab1 protein from both transgenic corn (Event 5638) 

and P. fluorescens has been shown previously to be proteolytically 

degraded to a 40-kDa form (with an intact N–terminus), and the Cry35Ab1 

protein isolated from corn Event 59.1.22 also showed a 40-kDa 

degradation product. Glycosylation analysis indicated that Cry34Ab1 and 

Cry35Ab1 derived from Event 59.1.22 are not glycosylated; this result was 

consistent with the earlier studies of these two proteins derived from corn 

Event 5638 and from P. fluorescens. MALDI-TOF-MS and N–terminal 

sequencing provided additional evidence that Cry34Ab1 and Cry35Ab1 

proteins derived from corn Event 59.1.22 are identical to those produced by 

the P. fluorescens bacterial expression system and by corn Event 5638. 

Classification: Acceptable

461239-06 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

28

Study Title Summary MRID No.

Characterization of 

Phosphinothricin 

Acetyltransferase (PAT) 

Derived from 

Transgenic Maize Event 

E4497.59.1.22 

SDS-PAGE, western blot analysis, and ELISA were used to compare PAT 

protein derived from transgenic maize plant Event E4497.59.1.22 with 

PAT protein from a recombinant Escherichia coli expression system. SDSPAGE demonstrated that the E. coli-produced PAT protein had the 

expected molecular weight. Leaf extract samples from Event 

E4497.59.1.22 showed an immunoreactive band in the western blot 

analysis that corresponded to the expected molecular weight for the PAT 

protein and comigrated with the E. coli-produced PAT. ELISA results 

demonstrated similar expression of the PAT protein in all of the transgenic 

leaf samples tested. The control plants did not contain immunoreactive 

proteins. Results were consistent with earlier studies of PAT protein 

derived from E. coli and from transgenic maize Event 5638, which used 

MALDI-TOF-MS peptide mass fingerprinting (Korjagin 2000). The 

present study further supports the use of microbe-derived PAT protein as 

an appropriate surrogate for the PAT protein produced in maize plants.

Classification: Acceptable

461239-07 

Characterization of 

DNA Inserted into 

Transgenic Corn Events 

DAS-45216-6 and DAS59122-7 

Southern blot analysis was used to characterize the DNA inserted in 

transgenic corn Events DAS-45216-6 and DAS-59122-7. The restriction 

enzyme fragments observed in the Southern blots matched the predicted 

fragments, indicating that a single, intact T-DNA from plasmid PHP17662 

was integrated into the corn genome at a single locus. The data also 

demonstrated the absence of the tetracycline and spectinomycin resistance 

genes, the virG gene, and vector backbone DNA regions immediately 

outside of the left and the right T-DNA border, indicating that only DNA 

contained within the T-DNA borders was integrated into the transgenic 

corn. Identical fragment sizes were observed for all samples (two distinct 

generations, four plants each), indicating stability of inheritance across and 

within generations. 

Classification: Acceptable 

461239-08 

Detailed 

Characterization of 

DNA Inserted into 

Transgenic Corn Events 

DAS-45216-6 and DAS59122-7 

Southern blot analysis was used to analyze the inserted DNA in Events 

DAS-45216-6 and DAS-59122-7 and to develop detailed restriction 

enzyme maps of the insertions. Fragments of the expected sizes were 

observed, indicating that a single, intact T-DNA inserted into the corn 

genome at one locus without any rearrangements of the inserted DNA. 

Classification: Acceptable 

461239-09 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

29

Study Title Summary MRID No.

Evaluation of MicrobeDerived Cry34Ab1 and 

Cry35Ab1 Proteins for 

Protein Synthesis 

Inhibition Activity 

The rabbit reticulocyte assay was used to determine if Cry34Ab1 and 

Cry35Ab1 proteins inhibit protein synthesis. Ricin, used as a positive 

control, produced a 50% inhibition in protein synthesis with a 

concentration of 0.182 nanomolar (nM). In contrast, Cry34Ab1 and 

Cry35Ab1, as well as BSA used as a negative control, showed no 

inhibition of protein synthesis at concentrations up to 2,880 nM. The 

results suggest that the insecticidal activity of Cry34Ab1 and Cry35Ab1 is 

not associated with the inhibition of protein synthesis. 

Classification: Acceptable 

461239-10 

b. Terms and Conditions of the Event DAS-59122-7 Corn Registrations (August 2005 –

 Present)

 

When Event DAS-59122-7 corn was initially registered on August 31, 2005, the Agency issued 

registration notices to both Mycogen Seeds c/o Dow AgroSciences LLC (EPA Reg. No. 68467-5) and 

Pioneer Hi-Bred International, Incorporated (EPA Reg. No. 29964-4) that contained the following 

requirement for further product characterization information: 

 “Provide to the EPA laboratory (Ft. Meade, MD) methodology and/or reagents 

 necessary for validation of a Cry34/35Ab1 analytical method within 6 months 

 of the date of registration.” 

More recently, the Agency has decided to allow this requirement to be satisfied by the Grain Inspection, 

Packers and Stockyards Administration (GIPSA) of the United States Department of Agriculture 

(USDA) performance verification of a qualitative rapid test kit for detecting the presence of the 

biotechnology event in grains and oilseeds (USDA 2004). In the case of Cry34/35Ab1, the Agency has 

confirmed that a test kit has been verified by GIPSA and, therefore, the aforementioned requirement has 

been satisfied for both registrations. 

 

2. Herculex® XTRA Insect Protection Corn (OECD Unique Identifier: DAS-Ø15Ø7-1 x DAS- 

 59122-7) Expressing Cry1F, Cry34Ab1, and Cry35Ab1

a. Data Cited/Submitted for Initial Registrations of Herculex® XTRA Insect Protection Corn

(Prior to October 2005)

Herculex® XTRA Insect Protection Corn was developed through conventional breeding of a corn line 

containing Event DAS-01507-1 (also known as Event TC1507 and Herculex® I), which expresses the 

Cry1F (truncated) and PAT proteins, and a corn line containing Event DAS-59122-7, which expresses 

the Cry34Ab1, Cry35Ab1, and PAT proteins. This product is considered a stacked plant-incorporated 

protectant because it targets both lepidopteran and coleopteran pests and contains two separate active 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

30

ingredients. DAS-01507-1 is briefly summarized in the paragraph that follows, while additional 

information on DAS-59122-7, specifically related to product characterization, can be found in section 

II(A)(1) of this Biopesticides Registration Action Document (BRAD). 

DAS-01507-1 produces the Bacillus thuringiensis var. aizawai Cry1F protein to selectively control 

larvae of European corn borer (Ostrinia nubilalis) and other lepidopteran pests. In addition, DAS01507-1 also produces the PAT protein from Streptomyces hygroscopicus, which confers tolerance to 

glufosinate-ammonium herbicides. On May 18, 2001, the Agency issued Federal Insecticide, Fungicide, 

and Rodenticide Act (FIFRA) section 3 registrations to Mycogen Seeds c/o Dow AgroSciences LLC 

(EPA Reg. No. 68467-2) and Pioneer Hi-Bred International, Incorporated (EPA Reg. No. 29964-3) for 

Herculex® I, expressing Bacillus thuringiensis Cry1F protein and the genetic material necessary (vector 

PHP8999) for its production in corn Event TC1507 (OECD Unique Identifier: DAS-Ø15Ø7-1). The 

product characterization data supporting the registration of Herculex® I, including the submitted study 

titles, conclusions, and their MRID Numbers, can be found in the 2001 Bt Crops Reassessment, August 

2005 Cry1F BRAD, and the July 2010 Cry1Ab and Cry1F BRAD (U.S. EPA 2001b, 2005a, and 2010b). 

The data submitted for Herculex® XTRA Insect Protection Corn, which include DNA analysis of the 

inserts in and protein expression data for the stacked corn product, are summarized in Table 3. 

 

Table 3. Product Characterization Data for Herculex® XTRA Insect Protection Corn (Reviewed 

 in U.S. EPA (2005b)). 

Study Title Summary MRID No.

Characterization of 

Stacked Hybrid of 

Transgenic Corn Lines 

DAS-01507-1 and 

DAS-59122-7 by 

Comparison to the 

Individual Lines 

Southern blot analysis was conducted on restriction enzyme digests of 

DNA from the stacked hybrid of transgenic corn lines DAS-01507-1 and 

DAS-59122-7 as well as the individual lines. Hybridization of Hind III and 

Sac I digests with probes for the cry1F, cry34Ab1, cry35Ab1, and pat

genes gave the expected bands on Southern blots, based on restriction 

enzyme maps of both of the inserts in the individual lines. The results 

indicate that the inserts in the 1507 x 59122 stacked hybrid are equivalent 

to the individual inserts in the inbred lines. 

Classification: Acceptable 

462971-02 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

31

Study Title Summary MRID No.

Agronomic 

Characteristics, 

Quantitative ELISA, 

and Nutrient 

Composition Analysis 

of Hybrid Maize Lines 

Containing the cry1F, 

cry34Ab1, cry35Ab1, 

and pat Genes: U.S. and 

Canada Locations 

Agronomic characteristics, nutrient composition, and protein expression 

levels, for transgenic corn line DAS-01507-1 x DAS-59122-7 grown at five 

locations in the U.S. and Canada, were analyzed and compared with results 

from a non-transgenic control. The presence of the transgenes for the 

Cry1F, Cry34Ab1, Cry35Ab1, and PAT proteins had no notable effect on 

agronomic parameters, such as early and final population, time to silking 

and to pollen shed, and plant and ear height. Cry1F, Cry34Ab1, Cry35Ab1, 

and PAT proteins were detected by ELISA in all plant tissues except that 

PAT was not detected in pollen. On a tissue dry weight basis, mean 

expression levels had the following ranges: Cry34Ab1 – a low of 43 ng/mg 

in grain to a high of 340 ng/mg in leaf tissue at the R4 growth stage; 

Cry35Ab1 – a low of 0.14 ng/mg in pollen to a high of 104 ng/mg in leaf 

tissue at the R4 growth stage; Cry1F – a low of 0.14 ng/mg in pollen to a 

high of 25 ng/mg in leaf tissue at the R4 growth stage; and PAT – a low of 

<LOQ in pollen to a high of 13 ng/mg in leaf tissue at the R4 and R1 

growth stages and whole plant samples from the V9 growth stage. 

Herbicide spraying did not affect protein expression levels. 

Classification: Acceptable 

463438-01 

 b. Terms and Conditions of the Herculex® XTRA Insect Protection Corn Registrations 

 (October 2005 – Present)

When Herculex® XTRA Insect Protection Corn was initially registered on October 27, 2005, the 

Agency issued registration notices to both Mycogen Seeds c/o Dow AgroSciences LLC (EPA Reg. No. 

68467-6) and Pioneer Hi-Bred International, Incorporated (EPA Reg. No. 29964-5) that contained the 

following requirement: 

 “Submit all data required to support the individual plant-incorporated protectants 

 in Event TC1507 (Herculex I) and Event DAS-59122-7 (Herculex Rootworm) 

 corn....” 

All requirements for additional product characterization information for Events TC1507 (see U.S. EPA 

(2010b)) and DAS-59122-7 (see section II(A)(1)(b) of this BRAD) have been satisfied for both 

registrations. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

32

3. 1507 x 59122 x MON 810 (OECD Unique Identifier: DAS-Ø15Ø7-1 x DAS-59122-7 x 

 MON-ØØ81Ø-6) Expressing Cry1F, Cry34Ab1, Cry35Ab1, and Cry1Ab and 59122 x 

 MON 810 (OECD Unique Identifier: DAS-59122-7 x MON-ØØ81Ø-6) Expressing 

 Cry34Ab1, Cry35Ab1, and Cry1Ab 

 a. Data Cited/Submitted for Initial Registrations of 1507 x 59122 x MON 810 and 

 59122 x MON 810 (Prior to February 2010)

The stacked and pyramided product, 1507 x 59122 x MON 810, and the stacked product, 59122 x MON 

810, are hybrids created by crossing the individuals events, TC1507 (Cry1F), DAS-59122-7 

(Cry34/35Ab1), and MON 810 (Cry1Ab), via traditional breeding methods. Product characterization 

background on DAS-59122-7 and TC1507 was discussed or referenced in sections II(A)(1) and II(A)(2)

of this BRAD, respectively; MON 810 is briefly summarized in the paragraph that follows. 

MON 810 produces Bacillus thuringiensis subsp. kurstaki strain HD-1 Cry1Ab protein to selectively 

control larvae of European corn borer (O. nubilalis) and other lepidopteran pests. On December 20, 

1996, the Agency issued a FIFRA section 3 registration to Monsanto Company for MON 810 (EPA Reg. 

No. 524-489), expressing Bacillus thuringiensis Cry1Ab protein and the genetic material necessary (PVZMCT01) for its production in corn Event MON 810 (OECD Unique Identifier: MON-ØØ81Ø-6). The 

product characterization data supporting the registration of MON 810, including the submitted study 

titles, conclusions, and their MRID Numbers, can be found in both the 2001 Bt Crops Reassessment and 

the July 2010 Cry1Ab and Cry1F BRAD (U.S. EPA 2001b, 2010b). 

The data submitted for 1507 x 59122 x MON 810 and 59122 x MON 810, which include molecular 

characterization data, protein expression analyses, and a synergism study, are summarized in Table 4. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

33

Table 4. Product Characterization Data for 1507 x 59122 x MON 810 and 59122 x MON 810 

(Reviewed in U.S. EPA (2010a)). 

Study Title Summary MRID No.

Molecular 

Characterization of 

Maize Combined Trait 

Product DAS-01507-1 x 

DAS-59122-7 x MON00810-6 Using Southern 

Blot Analysis and 

Event-Specific 

Polymerase Chain 

Reaction (Product 

Characterization) 

Molecular analyses (restriction enzyme digests and Southern blots) were 

performed to compare the integrity of the transgenic inserts in Events 

TC1507, DAS-59122-7, and MON 810 corn with the transgenic DNA 

inserts in the combination plant-incorporated protectant (PIP) 1507 x 

59122 x MON 810 corn product, produced by conventional plant breeding. 

The Southern blot data showed the predicted DNA hybridization patterns 

of the cry1F gene from TC1507 corn, the cry34Ab1 and cry35Ab1 genes 

from DAS-59122-7 corn, and the cry1Ab gene from MON 810 corn. These 

data demonstrated equivalence among events because the transgenic inserts 

were stably integrated and retained when the parental lines are crossed to 

create 1507 x 59122 x MON 810 corn. In addition, event-specific PCR 

methods detected and confirmed the presence of each expected transgenic 

DNA insert in the combination PIP corn event. 

Classification: Acceptable

476778-01 

Additional Addendum 

to Expressed Trait 

Protein Concentration 

of Maize Lines 

Containing Events 

TC1507, DAS-59122-7, 

MON 810, and 

Combination PIPs 1507 

x MON 810, 59122 x 

MON 810, and 1507 x 

59122 x MON 810 Corn 

Products (Protein 

Expression Levels) 

A field study was conducted using quantitative ELISA methods to 

statistically compare the level of expression for the Cry1F, Cry34Ab1, 

Cry35Ab1, Cry1Ab, and PAT proteins expressed in 1507 x 59122 x MON 

810, 1507 x MON 810, and 59122 x MON 810 combination PIP corn 

events to the individual parental events. No statistically significant 

differences were found for Cry1F, Cry34Ab1, Cry35Ab1, and Cry1Ab 

protein expression between 1507 x 59122 x MON 810 and parental corn 

Events 1507, 59122, or MON 810. No statistical differences were observed 

in any plant tissue for Cry1F, PAT, and Cry1Ab protein expression when 

TC1507 x MON 810 was compared to Events 1507 and MON 810 or when 

Event 59122 was compared to Event MON 810. Based on the results, the 

protein concentrations of Cry1F, Cry34Ab1, Cry35Ab1, and Cry1Ab 

expressed in combination PIP Events 1507 x 59122 x MON 810, 1507 x 

MON 810, and 59122 x MON 810 are comparable to the respective protein 

concentrations of their respective single parental events. 

Classification: Acceptable 

Note: This study supersedes MRID Nos. 475109-04 and 478654-01. 

478800-01 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

34

Study Title Summary MRID No.

Laboratory 

Characterization of Key 

Lepidopteran Pest 

Response to Pyramided 

Events (Synergism 

Study) 

A seven-day laboratory sensitive insect bioassay was conducted to 

determine if the combination PIP product, 1507 x 59122 x MON 810, has a 

synergistic effect in comparison to the individual parental events, TC1507 

(expressing Cry1F protein) and MON 810 (expressing Cry1Ab protein), on 

target lepidopteran pests. The pests used in the bioassay were European 

corn borer (ECB, Ostrinia nubilalis), southwestern corn borer (SWCB, 

Diatraea grandiosella), fall armyworm (FAW, Spodoptera frugiperda), 

and corn earworm (CEW, Helicoverpa zea). The observed and expected 

larval mortality in the 1507 x 59122 x MON 810 group were similar and 

mean larval weight of the survivors exposed to 1507 x 59122 x MON 810 

leaf tissue was not significantly different from the single parental events or 

the negative control of non-Bt maize. These results indicate that the Cry1F 

and Cry1Ab proteins act independently and do not have a synergistic or 

antagonistic effect on the target pests, other than an additive effect. 

Quantitative ELISA results also confirmed that the expression of each of 

the proteins in the combination PIP was not affected by the presence of the 

other protein. 

Classification: Acceptable 

476778-02 

 b. Terms and Conditions of the 1507 x 59122 x MON 810 and 59122 x MON 810 Registrations

(February 2010 – Present)

When 1507 x 59122 x MON 810 (EPA Reg. No. 29964-8) and 59122 x MON 810 (EPA Reg. No. 

29964-9) were initially registered on February 24, 2010, the Agency issued registration notices to 

Pioneer Hi-Bred International, Incorporated that contained the following requirements: 

 For 1507 x 59122 x MON 810 – 

 “The data submitted by Pioneer are sufficient to support registration for the 

 combination PIP product...provided that the registrant submits/cites any data 

 required to support the PIP registrations of the individual parental events...as 

 well as the combination PIP product TC1507 (DAS-Ø15Ø7-1) x DAS-59122-7....” 

 For 59122 x MON 810 – 

 “The data submitted by Pioneer are sufficient to support registration for the 

 combination PIP product...provided that the registrant submits/cites any data 

 required to support the PIP registrations of the individual parental events....” 

All requirements for additional product characterization information for individual Events TC1507 (see 

U.S. EPA (2010b)), MON 810 (see U.S. EPA (2010b)), and DAS-59122-7 (see section II(A)(1)(b) of 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

35

this BRAD), as well as for combination PIP product TC1507 x 59122-7 (see section II(A)(2)(b) of this 

BRAD), have been satisfied. 

4. References 

Crickmore N, Zeigler DR, Schnepf E, Van Rie J, Lereclus D, Baum J, Bravo A, Dean DH. 2010. 

Bacillus thuringiensis toxin nomenclature (2010). Available from: 

 http://www.lifesci.sussex.ac.uk/Home/Neil_Crickmore/Bt/. 

Korjagin VA. 2000. Characterization of Escherichia coli Produced and Transgenic Maize Expressed 

 Phosphinothricin Acetyltransferase (PAT) Protein (DAS Study Number 000369). 

 Unpublished study prepared by Dow AgroSciences LLC. 

Masson L, Schwab G, Mazza A, Brousseau R, Potvin L, Schwartz J-L. 2004. A novel Bacillus 

 thuringiensis (PS149B1) containing a Cry34Ab1/Cry35Ab1 binary toxin specific for the 

 western corn rootworm Diabrotica virgifera virgifera LeConte forms ion channels in 

 lipid membranes. Biochemistry 43(38):12349–12357. 

MRID No. 452422-01. Narva K, Duck N, Kahn T. 2000. Product Characterization Data for Bacillus 

 thuringiensis PS149B1 13.6 kDa and 43.8 kDa Insecticidal Crystal Proteins Expressed in 

 Transgenic Maize Plants. Lab Study ID: GH-C 5117. Unpublished study prepared by Dow 

 AgroSciences LLC, 398 pages. 

MRID No. 452422-02. Ernest A. 2000. Characterization of Inserted DNA of Event 5639 

 Transgenic Corn Plants: Interim Report. Lab Project Number: 000300. Unpublished study 

 prepared by Dow AgroSciences LLC, 55 pages. 

MRID No. 452422-03. Herman R, Gilbert J, Patterson V. 2000. Equivalency of Microbial- and 

 Maize Expressed PS149B1 Proteins. Lab Project Number: 000367. Unpublished study 

 prepared by Dow AgroSciences LLC, 85 pages. 

MRID No. 452422-04. Herman R. 2000. Microbial PS149B1 Binary Delta-Endotoxin: Maize-Insect- 

 Pest Susceptibility Study. Lab Project Number: 000366. Unpublished study prepared by Dow 

 AgroSciences LLC, 29 pages. 

MRID No. 452422-13. Zeph L, Taggart J, Schmidt J. 2000. Quantitative ELISA Analysis of 

 PS149B1 Protein Expression Levels in Hybrid and Inbred Lines of Maize Event TC5639: 

 Interim Report. Lab Project Number: PHI99-004. Unpublished study prepared by Pioneer 

 Hi-Bred International, Incorporated, 119 pages. 

MRID No. 453584-01. Herman R. 2000. Thermolability of PS149B1 Binary Delta-Endotoxin. Lab 

 Project Number: 001041. Unpublished study prepared by Dow AgroSciences LLC, 18 pages. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

36

MRID No. 453834-01. Collins R. 2001. Lateral Flow Test Kit Method Validation for the Detection 

 of the PS149B1 14 kDa Protein in Maize Grain. Lab Project Number: GH-C 5212. 

 Unpublished study prepared by Dow AgroSciences LLC, 30 pages. 

MRID No. 455845-01. Herman R. 2002. Heat Lability of Individual Proteins of the PS149B1 Binary 

 ICP. Lab Project Number: 010144. Unpublished study prepared by Dow AgroSciences LLC, 

 15 pages. 

MRID No. 457904-01. Schafer B. 2002. Characterization of Cry34Ab1 and Cry35Ab1 from 

 Recombinant Pseudomonas fluorescens and Transgenic Maize. Lab Project Number: 

 GH-C 5545. Unpublished study prepared by Dow AgroSciences LLC, 17 pages. 

MRID No. 457904-02. Locke M, Nirunsuksiri W. 2002. Characterization of DNA Inserted into 

 Transgenic Corn Events (Cry34Ab1 and Cry35Ab1). Lab Project Number: GH-C 5550. 

 Unpublished study prepared by Dow AgroSciences LLC, 28 pages. 

MRID No. 457906-01. Coats I, Herman R, Narva K. 2002. Product Characterization Data for 

Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 Proteins Expressed in Transgenic Maize 

 Plants (PHP17662). Lab Project Number: PHI-2002-046. Unpublished study prepared by 

 Pioneer Hi-Bred International, Incorporated, 283 pages. 

MRID No. 458086-01. Herman R. 2002. Summary of Heat Lability Studies with 

 Cry34Ab1/Cry35Ab1. Lab Project Number: GH-C 5603. Unpublished study prepared by 

 Dow AgroSciences LLC, 21 pages. 

 

MRID No. 458332-01. Essner R. 2002. Quantitative ELISA Analysis of Cry34Ab1 and Cry35Ab1 

 Proteins Expressed in Maize Plants Transformed with the Vector PHP17662. Lab Project 

 Number: PHI-2002-049. Unpublished study prepared by Pioneer Hi-Bred International, 

 Incorporated, 110 pages. 

MRID No. 458602-01. Hunst P, Herman R. 2002. Slide Presentation Summarizing 

 Cry34Ab1/Cry35Ab1 Heat Inactivation Studies. Lab Project Number: DN0006331. 

 Unpublished study prepared by Dow AgroSciences LLC, 18 pages. 

MRID No. 459428-01. Evans S, Layton R. 2003. Probe MOA Studies to Assess Potential for Protein 

 Synthesis Inhibition by Bacillus thuringiensis PS149B1 Cry34Ab1/Cry35Ab1 Proteins in a 

 Rabbit Reticulocyte Assay: Re-Examination of Lab Notebook Data. Lab Project Number: 

 GH-C 5662. Unpublished study prepared by Dow AgroSciences LLC, 77 pages. 

MRID No. 461239-01. Ojala B. 2003. Independent Laboratory Validation of Pioneer Hi-Bred 

 International, Incorporated ELISA Method for the Quantification of Cry34Ab1 Protein from 

 Transgenic Plants. Project Number: BS03/02. Unpublished study prepared by Biolab 

 Solutions, 46 pages. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

37

MRID No. 461239-02. Ojala B. 2003. Independent Laboratory Validation of Dow AgroSciences 

 Method GRM 03.13, “Determination of Cry35Ab1 Insecticidal Crystal Protein in Maize 

 Tissue by Enzyme-Linked Immunosorbent Assay.” Project Number: BS03/01. Unpublished 

 study prepared by Biolab Solutions, 45 pages. 

MRID No. 461239-03. Narva K, Schnepf H, Nygaard L. 2003. Cry 34/35 Protein Distribution and 

 Familiarity Project Number: GH/C/5702. Unpublished study prepared by Dow AgroSciences 

 LLC, 26 pages. 

MRID No. 461239-04. Essner R. 2003. Agronomic Characteristics, Quantitative ELISA and 

 Nutrient Composition Analysis of Hybrid Maize Lines Containing the cry34Ab1, cry35Ab1 

 and pat Genes: Chile Locations. Project Number: PHI/2002/050. Unpublished study prepared 

 by Pioneer Hi-Bred International, Incorporated and EPL Bio-Analytical Services, 1,971 

 pages. 

MRID No. 461239-05. Herman R. 2003. Biological Equivalency of Cry35Ab1 Insecticidal Crystal 

 Protein in Transgenic Plants and Derived from Transgenic Pseudomonas fluorescens. Project 

 Number: GH/C/5696. Unpublished study prepared by Dow AgroSciences LLC, 17 pages. 

MRID No. 461239-06. Schafer B. 2003. Characterization of Cry34Ab1 and Cry35Ab1 Proteins 

 Derived from Transgenic Maize Event E4497.59.1.22 (DAS-59122-7). Project Number: 

 030033. Unpublished study prepared by Dow AgroSciences LLC, 50 pages. 

MRID No. 461239-07. Schafer B. 2003. Characterization of Phosphinothricin Acetyltransferase 

 (PAT) Derived from Transgenic Maize Event E4497.59.1.22. Project Number: 030027. 

 Unpublished study prepared by Dow AgroSciences LLC, 30 pages. 

MRID No. 461239-08. Locke M, Igo E. 2003. Characterization of DNA Inserted into Transgenic 

 Corn Events DAS-45216-6 and DAS-59122-7. Project Number: PHI/2002/038. Unpublished 

 study prepared by E.I. Dupont de Nemours and Company, 81 pages. 

 

MRID No. 461239-09. Locke M, Dietrich N, Weber N. 2003. Detailed Characterization of DNA 

 Inserted into Transgenic Corn Events DAS-45216-6 and DAS-59122-7. Project Number: 

 PHI/2002/041. Unpublished study prepared by E.I. Dupont de Nemours and Company, 

 62 pages. 

MRID No. 461239-10. Schafer B. 2003. Evaluation of Microbe-Derived Cry34Ab1 and Cry35Ab1 

 Proteins for Protein Synthesis Inhibition Activity. Project Number: 031139. Unpublished 

 study prepared by Dow AgroSciences LLC, 37 pages. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

38

MRID No. 462971-02. Weber N, Pfrogner B. 2004. Characterization of a Stacked Hybrid of 

 Transgenic Corn Lines DAS-01507-1 and DAS-59122-7 by Comparison to the Individual 

 Lines. Project Number: PHI/2003/049. Unpublished study prepared by E.I. Dupont de 

 Nemours and Company, 35 pages. 

MRID No. 463438-01. Buffington J. 2004. Agronomic Characteristics, Quantitative ELISA, and 

 Nutrient Composition Analysis of Hybrid Maize Lines Containing cry1F, cry34Ab1, 

cry35Ab1, and pat Genes: U.S. and Canada Locations: Amended Final Report. Project 

 Number: PHI/2003/017. Unpublished study prepared by Dow AgroSciences LLC, EPL 

 Bio-Analytical Services, and Bennett Agricultural Research and Consulting, 1,114 pages. 

MRID No. 475109-04. Werning M. 2008. Expressed Trait Protein Concentration of Maize Lines 

 Containing Events DAS-01507-1, DAS-59122-7, MON-00810-6, and DAS-01507-1 x DAS- 

 59122-7 x MON-00810-6. Project Numbers: PHI/2008/006, PHI/2008/006/012, and 

 PHI/2008/006/011. Unpublished study prepared by Pioneer Hi-Bred International, 

 Incorporated, 174 pages. 

MRID No. 476778-01. Brink K, Dietrich N. 2009. Molecular Characterization of Maize Combined 

 Trait Product DAS-01507-1 x DAS-59122-7 x MON-00810-6 x MON-00603-6 Using 

 Southern Blot Analysis and Event-Specific Polymerase Chain Reaction. Project Number: 

 PHI/2008/082. Unpublished study prepared by E.I. Dupont de Nemours and Company, 

 42 pages. 

MRID No. 476778-02. Binning R. 2009. Laboratory Characterization of Key Lepidopteran Pest 

 Response to Pyramided Events. Project Number: PHI/2008/101. Unpublished study prepared 

 by Pioneer Hi-Bred International, Incorporated, 16 pages. 

MRID No. 478654-01. Staley J, Rood T, Johnson T. 2009. Addendum to Expressed Trait Protein 

 Concentration of Maize Lines Containing Events DAS-01507-1, DAS-59122-7, MON- 

 00810, and Combined Trait Products DAS-01507-1 x MON-00810, DAS-59122-7 x 

 MON-00810, and DAS-01507-1 x DAS-59122-7 x MON-00810: Final Report. Project 

 Number: PHI/2008/006, PHI/2009/182. Unpublished study prepared by Pioneer Hi-Bred 

 International, Incorporated, 21 pages. 

MRID No. 478800-01. Staley J, Rood T, Johnson T. 2009. Expressed Trait Protein Concentration of 

 Maize Lines Containing Events DAS-01507-1, DAS-59122-7, MON-00810-6, and 

 Combined Trait Products DAS-01507-1 x MON-00810-6, DAS-59122-7 x MON-00810-6, 

 and DAS-01507-1 x DAS-59122-7 x MON-00810-6: Additional Addendum. Project 

 Number: PHI/2009/182. Unpublished study prepared by Pioneer Hi-Bred International, 

 Incorporated, 110 pages. 
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U.S. EPA. 2001a. Review of Product Characterization, Expression Analysis and Acute Oral Toxicity 

 Studies for PS149B1 Binary Insect Control Proteins as Expressed in Maize, a Bacillus 

 thuringiensis-Based Plant-Pesticide, for an Experimental Use Permit. Memorandum from 

 C.A. Wozniak, Ph.D. and J.L. Kough, Ph.D. to M. Mendelsohn dated June 7, 2001. 

U.S. EPA. 2001b. Biopesticides Registration Action Document – Bacillus thuringiensis Plant- 

 Incorporated Protectants. Available from: 

 http://www.epa.gov/oppbppd1/biopesticides/pips/bt_brad.htm. 

U.S. EPA. 2002. Review of Heat Stability for PS149B1 Binary Insect Control Proteins, Cry34 and 

 Cry35, as Expressed in Maize, a Bacillus thuringiensis-Based Plant-Incorporated Protectant, 

 for Approval of a Temporary Food Tolerance. Memorandum from C.A. Wozniak, Ph.D. and 

 J.L. Kough, Ph.D. to M. Mendelsohn dated September 10, 2002. 

U.S. EPA. 2003a. Summary of Heat Lability Studies for PS149B1 Binary Insect Control Proteins, 

 Cry34Ab1 and Cry35Ab1, as Expressed in Maize, a Bacillus thuringiensis-Based Plant- 

 Incorporated Protectant, for Approval of a Temporary Food Tolerance. Memorandum from 

 C.A. Wozniak, Ph.D. and J.L. Kough, Ph.D. to M. Mendelsohn dated March 18, 2003. 

U.S. EPA. 2003b. Review of SDS-PAGE Sensitivity and Lateral Flow Detection Method for 

 PS149B1 Binary Insect Control Proteins as Expressed in Maize, a Bacillus thuringiensis- 

 Based Plant-Incorporated Protectant, for an Experimental Use Permit. Memorandum from 

 C.A. Wozniak, Ph.D. and J.L. Kough, Ph.D. to M. Mendelsohn dated April 3, 2003. 

U.S. EPA. 2003c. Review of Product Characterization Data for PS149B1 Binary Insect Control 

 Proteins, Cry34Ab1 and Cry35Ab1, as Expressed in Maize Following Transformation with 

 Construct PHP17662, a Bacillus thuringiensis-Based Plant-Incorporated Protectant, for an 

 Experimental Use Permit. Memorandum from C.A. Wozniak, Ph.D. and J.L. Kough, Ph.D. to 

 M. Mendelsohn dated May 21, 2003. 

U.S. EPA. 2003d. Review of Product Characterization Data for PS149B1 Binary Insect Control 

 Proteins, Cry34Ab1 and Cry35Ab1, as Expressed in Maize Following Transformation with 

 Construct PHP17662, a Bacillus thuringiensis-Based Plant-Incorporated Protectant, for an 

 Experimental Use Permit. Memorandum from C.A. Wozniak, Ph.D. and J.L. Kough, Ph.D. to 

 M. Mendelsohn dated June 12, 2003. 

U.S. EPA. 2003e. Assessment of Ribosomal Inhibition Protein (RIP) Activity in PS149B1 Binary 

 Insect Control Proteins, Cry34Ab1 and Cry35Ab1, as Expressed in Maize Following 

 Transformation with Construct PHP17662, a Bacillus thuringiensis-Based Plant-Incorporated 

 Protectant, for an Experimental Use Permit. Memorandum from C.A. Wozniak, Ph.D. and 

 J.L. Kough, Ph.D. to M. Mendelsohn dated June 19, 2003. 
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U.S. EPA. 2004. Review of Product Characterization and Expression Analysis for Registration of 

B.t. Cry34/35AB1 Construct PHP17662 Corn. Memorandum from R.L. Edelstein, Ph.D. and 

 J.L. Kough Ph.D. to M. Mendelsohn dated December 6, 2004. 

U.S. EPA. 2005a. Biopesticides Registration Action Document – Bacillus thuringiensis 

Cry1F Corn. Available from: 

http://www.epa.gov/oppbppd1/biopesticides/ingredients/tech_docs/brad_006481.pdf. 

U.S. EPA. 2005b. Review of Product Characterization and Human Health Data for Registration of 

 HerculexTM Xtra Insect Resistant Corn. Memorandum from R.L. Edelstein, Ph.D. and J.L. 

 Kough, Ph.D. to M. Mendelsohn dated September 22, 2005. 

U.S. EPA. 2010a. Review of Human Health and Product Characterization Data for Registration of 

Bacillus thuringiensis (Bt) Cry1F, Cry34Ab1, Cry35Ab1, and Cry1Ab Proteins and the 

 Genetic Material Necessary for Their Production in the Combination Plant-Incorporated 

 Protectant (PIP) Products: 1507 x MON 810 [EPA Reg. No. 29964-T], 59122 x MON 810 

 [EPA Reg. No. 29964-O], and 1507 x 59122 x MON 810 [EPA Reg. No. 29964-I]. 

 Memorandum from A. Waggoner and J.L. Kough, Ph.D. to A. Sibold dated 

 February 19, 2010. 

U.S. EPA. 2010b. Biopesticides Registration Action Document – Bacillus thuringiensis 

Cry1Ab and Cry1F Corn. Available from: http://www.regulations.gov (see “Supporting & 

Related Materials” within Docket Number EPA-HQ-OPP-2010-0607). 

USDA. 2004. Performance verification of qualitative mycotoxin and biotech rapid test kits 

 (Directive 9181.2). Available from: 

http://www.gipsa.usda.gov/GIPSA/documents/GIPSA_Documents/9181-2.pdf. 
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B. Human Health Assessment 

1. Human Health Assessment of Cry34Ab1 and Cry35Ab1 

The detailed Agency human health assessment of Cry34Ab1/Cry35Ab1 corn is found in U.S. EPA 

(2005a and 2005d). Portions of the data used in the human health assessment are reviewed in U.S. EPA 

(2001a, 2002, 2003, and 2004a). A summary of the key findings is provided below. 

 a. Mammalian Toxicity and Allergenicity Assessment

Based upon the human health data provided, there is minimal risk of toxic and/or allergenic effects to 

humans or animals due to exposure to the Cry34Ab1 and Cry35Ab1 proteins. Based on review of the 

data, there is a reasonable certainty of no harm to humans and animals posed by the aggregate exposure 

to residues of these proteins. 

i. Mammalian Toxicity

Acute oral toxicity data have been submitted demonstrating the lack of mammalian toxicity at high 

levels of exposure to the pure Cry34Ab1 and Cry35Ab1 proteins separately and combined. These data 

demonstrate the safety of the products at levels well above maximum possible exposure levels that are 

reasonably anticipated in the crops. Basing this conclusion on acute oral toxicity data without requiring 

further toxicity testing and residue data is similar to the Agency position regarding toxicity and the 

requirement of residue data for the microbial Bacillus thuringiensis products from which these plantincorporated protectants were derived (see 40 CFR §§ 158.2130(d)(1)(i) and 158.2140(d)(7)). For 

microbial products, further toxicity testing and residue data are triggered by significant acute effects in 

studies, such as the mouse oral toxicity study, to verify and quantify the observed effects and clarify the 

source of these effects (Tiers II and III). 

Three acute oral toxicity studies on Cry34Ab1 and Cry35Ab1 in mice were submitted, which indicated 

that these proteins are non-toxic to humans. 

In an oral toxicity study of Cry34Ab1 alone (Master Record Identification Number (MRID No.) 

452422-07; reviewed in U.S. EPA (2005a)), Cry34Ab1 produced from microbial culture was 

administered to five male mice (5,000 milligrams/kilogram (mg/kg) body weight) by oral gavage as a 

20% mixture in a 0.5% aqueous methylcellulose vehicle. All animals survived the two-week study. No 

clinical signs were noted for any animals during the study. An initial weight loss was observed in 3 mice 

at test days 1 and 2, but they gained weight for the remainder of the study. The two other animals gained 

weight throughout the study. No treatment-related gross pathologic changes were observed during the 

study. Under the conditions of this study, the acute oral median lethal dose (LD50) for the test substance 

in male CD-1 mice was greater than 5,000 mg/kg. Since the test substance contained Cry34Ab1 at 54% 

purity, the acute oral LD50 for the pure Cry34Ab1 protein was greater than 2,700 mg/kg. 
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In an oral toxicity study of Cry35Ab1 alone (MRID No. 452422-08; reviewed in U.S. EPA (2005a)), 

Cry35Ab1 produced from microbial culture was administered to five male mice (5,000 mg/kg body 

weight) by oral gavage as a 20% mixture in a 0.5% aqueous methylcellulose vehicle. All animals 

survived the two-week study. No clinical signs were noted for any animal during the study. An initial 

weight loss was observed in 2 mice at test days 1 and 2, but they gained weight for the remainder of the 

study. One animal had fluctuating body weight. The other two animals gained weight throughout the 

study. No treatment-related gross pathologic changes were observed during the study. Under the 

conditions of this study, the acute oral LD50 for the test substance in male CD-1 mice was greater than 

5,000 mg/kg. Since the test substance contained Cry35Ab1 at 37% purity, the acute oral LD50 for the 

pure Cry35Ab1 protein was greater than 1,850 mg/kg.

Finally, in an oral toxicity study of Cry34Ab1 and Cry35Ab1 combined (MRID No. 452422-09; 

reviewed in U.S. EPA (2001a)), a mixture of the microbially produced Cry34Ab1 and Cry35Ab1 

proteins (5,000 milligrams (mg) test material, containing 482 mg pure Cry34Ab1 and 1,520 mg pure 

Cry35Ab1 (corresponding to an equimolar ratio), per kilogram (kg) body weight) was administered by 

oral gavage to 5 female and 5 male mice as a 20% mixture in 0.5% aqueous methylcellulose. All 

animals survived the 2-week study. One female mouse exhibited protruding or bulging eyes on days 6 

and 7, but this resolved thereafter. This observation was not attributed to the treatment as it was an 

isolated observation (i.e., no other animals exhibited this). No other clinical signs were noted for any 

animals during the study. An initial weight loss was observed in 2 mice at test days 1 and 2, but both 

gained weight for the remainder of the study. All other animals gained weight throughout the study. No 

treatment-related gross pathologic changes were noted. Under the conditions of the study, the acute oral 

LD50 of the test material in male and female CD-1 mice was greater than 5,000 mg/kg body weight, 

corresponding to 2,000 mg/kg of an equimolar ratio of the pure proteins. 

 

In addition, a study was submitted where the amino acid sequences of the Cry34Ab1 and Cry35Ab1 

proteins were compared with protein sequences in publicly available databases (GenPept dataset) to 

identify any potential similarities with known toxins (MRID No. 465847-01; reviewed in U.S. EPA 

(2005d)). No similarities were identified that would raise a safety concern. 

 

When proteins are toxic, they are known to act via acute mechanisms and at very low dose levels 

(Sjoblad et al. 1992). Therefore, since no effects were shown to be caused by the plant-incorporated 

protectants, even at relatively high dose levels, the Cry34Ab1 and Cry35Ab1 proteins are not considered 

toxic. Further, amino acid sequence comparisons showed no similarity between the Cry34Ab1 and 

Cry35Ab1 proteins and known toxic proteins available in public protein databases. 

 

ii. Allergenicity Assessment

Since Cry34Ab1 and Cry35Ab1 are proteins, allergenic potential was also considered. Currently, no 

definitive tests for determining the allergenic potential of novel proteins exist. Therefore, EPA uses a 

weight-of-the-evidence approach where the following factors are considered: source of the trait; amino 

acid sequence similarity with known allergens; prevalence in food; and biochemical properties of the 

protein, including in vitro digestibility in simulated gastric fluid (SGF) and glycosylation. Current 
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scientific knowledge suggests that common food allergens tend to be resistant to degradation by acid 

and proteases, may be glycosylated, and can be present at high concentrations in the food. In the past, 

EPA has also considered heat stability in assessing allergenicity potential; however, at a March 1–2, 

2005 meeting, the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory 

Panel (SAP) stated that heat stability based on a bioactivity assay is of minimal to no value in predicting 

the allergenicity potential of novel proteins, and EPA agrees. Therefore, EPA did not consider heat 

stability of these proteins in its weight-of-the-evidence approach. 

Source of the trait. Bacillus thuringiensis is not considered a source of allergenic proteins. 

 

Amino acid sequence. A comparison of amino acid sequences of Cry34Ab1 and Cry35Ab1 with known 

allergens (MRID No. 452422-05; reviewed in U.S. EPA (2001a)) showed no overall sequence 

similarities or homology at the level of 8 contiguous amino acid residues. 

Prevalence in food. Expression level analysis indicated that the proteins are present at relatively low 

levels in corn; on a dry weight basis, Cry34Ab1 is present at a concentration of approximately 50 

nanograms per milligram (ng/mg) in grain from Event 59122-7, and Cry35Ab1 is present at a 

concentration of approximately 1 ng/mg in grain from Event 59122-7 (MRID No. 461239-04; reviewed 

in U.S. EPA (2004b)). Thus, expression of the Cry34Ab1 and Cry35Ab1 proteins in corn kernels has 

been shown to be in the parts per million range. 

Digestibility. Two in vitro digestibility studies (MRID No. 452422-12; reviewed in U.S. EPA (2001a)) 

were conducted to determine the stability of the Cry34Ab1 and Cry35Ab1 proteins in simulated gastric 

fluid (i.e., an acid environment containing pepsin; SGF). In the first in vitro digestibility study, the 

proteins were incubated in SGF (pepsin concentration: 3.2 milligrams per milliliter (mg/mL); pH 1.2; 

37°C) with a pepsin to protein substrate ratio of approximately 20:1, moles to moles (mol/mol) 

(equivalent to 60:1, weight-to-weight (w/w) for Cry34Ab1 and 17:1, w/w for Cry 35Ab1). Samples 

taken at 1, 5, 7, 15, 20, 30, and 60 minutes were analyzed by sodium dodecyl sulfate polyacrylamide gel 

electrophoresis (SDS-PAGE) and western blot. Cry35Ab1 was no longer visible at the five-minute time 

point using both SDS-PAGE stained with Coomassie Brilliant Blue and western blot detection. 

Cry34Ab1 was visible on the stained gel for the 15-minute sample but not in later sample time points. In 

the western blot analysis, Cry34Ab1 was visible in the 20-minute sample but not in later sample time 

points. In conclusion, this first study showed that Cry34Ab1 was digested within 30 minutes, and 

Cry35Ab1 was digested within 5 minutes in SGF under the conditions of the study.

Because Cry34Ab1 appeared to be somewhat resistant to SGF in the study that used the time-todisappearance endpoint (as described in the preceding paragraph), Dow AgroSciences LLC submitted a 

second study on the in vitro digestibility of Cry34Ab1 in SGF using a kinetic approach (MRID No. 

455845-02; reviewed in U.S. EPA (2002)). The digestion was performed under the same conditions as 

the previous study, except that reaction mixtures were shaken during incubation and samples were 

analyzed at 1, 2, 3, 5, 7.5, 10, 15, and 20 minutes. The previous study on pepsin digestibility of 

Cry34Ab1 and Cry35Ab1, as well as other pepsin digestibility studies used in allergenicity assessments, 

focused on the time required for the protein to become undetectable and, therefore, the results are 
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dependent on the detection limit of the analytical method used. In this second study, Dow AgroSciences 

LLC determined the rate of pepsin digestion of Cry34Ab1 by measuring the relative amounts of 

Cry34Ab1 at each of the time points based on SDS-PAGE densitometry estimates. Under the conditions 

of the study, the rate of decay fit a first-order model (with respect to Cry34Ab1 concentration), and Dow 

AgroSciences LLC estimated the DT50 (half-life) and DT90 (time until 90% decay) to be 1.9 minutes and 

6.2 minutes, respectively. In this experiment, Cry34Ab1 was visible on gels and blots in 15-minute timepoint samples but not in 20-minute time-point samples. 

Because the digestibility of Cry34Ab1 was assessed using a different method (i.e., the kinetic approach) 

rather than the typical end-point method that has been used previously, comparison studies, using the 

kinetic approach to assess the digestibility of known allergens and non-allergens, were submitted to 

validate the method and allow comparison of the digestibility of Cry34Ab1 with known allergens and 

non-allergens (Master Record Identification Numbers (MRID Nos.) 461239-20 and 463886-01). In the 

comparison study where the conditions used were the same as those used in the kinetic study on the 

digestibility of Cry34Ab1 (MRID No. 463886-01; reviewed in U.S. EPA (2005a)), two allergens and 

two non-allergens were shown to digest similarly to Cry34Ab1. From these studies and published 

studies, EPA concludes that Cry35Ab1 is rapidly digested, and Cry34Ab1 is digested at a moderate rate 

in SGF; Cry34Ab1 appears to digest slower than previously registered proteins and many other proteins 

that are not considered allergens but faster than most previously tested allergens. 

On March 1–2, 2005, EPA held a FIFRA SAP meeting to address the scientific issues that arose during 

the human health safety assessment of Cry34Ab1 and Cry35Ab1. The SAP report (U.S. EPA 2005b) is 

summarized below and in U.S. EPA (2005c). EPA asked the SAP to comment on EPA’s allergenicity 

assessment of Cry34Ab1. The SAP agreed with EPA’s preliminary assessment that the allergenicity 

potential of Cry34Ab1 is low. However, the Panel based its conclusion, in part, on statements made by 

Dow AgroSciences LLC that Cry34Ab1 and Cry35Ab1 do not aggregate in solution. The Panel was 

concerned that if the proteins were to aggregate, protease binding sites could be masked, and the rate of 

digestion could be slower than was observed for the individual proteins. Therefore, EPA asked Dow 

AgroSciences LLC to submit data supporting the claim that Cry34Ab1 and Cry35Ab1 do not associate 

with one another in solution. 

 

To support the digestibility studies on the individual proteins, Dow AgroSciences LLC submitted a 

study using size exclusion chromatography, which demonstrated that Cry34Ab1 and Cry35Ab1 do not 

associate with one another in solution under acidic conditions (MRID No. 465568-01; reviewed in U.S. 

EPA (2005d)).

 

Glycosylation. Cry34Ab1 and Cry35Ab1 expressed in corn were shown not to be glycosylated (MRID 

No. 461239-06; reviewed in U.S. EPA (2004b)). 

Conclusion. Considering that (1) Cry34Ab1 and Cry35Ab1 originate from a non-allergenic source, (2) 

Cry34Ab1 and Cry35Ab1 have no overall sequence similarities or homology at the level of 8 contiguous 

amino acid residues with known allergens, (3) Cry34Ab1 and Cry35Ab1 will only be present at low 

levels in food, (4) Cry35Ab1 is rapidly digested in SGF, (5) Cry34Ab1 is digested at a moderate rate in 
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SGF, and (6) Cry34Ab1 and Cry35Ab1 are not glycosylated when expressed in maize, EPA has 

concluded that the potential for the Cry34Ab1 and Cry35Ab1 proteins to be food allergens is minimal. 

The FIFRA SAP that met on March 1–2, 2005 agreed with this conclusion regarding the allergenicity 

potential of Cry34Ab1. There were no triggers to raise concern about the allergenicity of Cry35Ab1, so 

the SAP was not asked to comment specifically on Cry35Ab1. As noted above, toxic proteins typically 

act as acute toxins with low dose levels. Therefore, since no effects were shown to be caused by the 

plant-incorporated protectants, even at relatively high dose levels, the Cry34Ab1 and Cry35Ab1 proteins 

are not considered toxic. 

 

SAP Opinion on the Kinetic Approach

In general, the Panel supported using a kinetic approach, rather than the disappearance endpoint, for 

assessing proteins that are not rapidly degraded because using several time points is “inherently more 

accurate than the single point assay.” The Panel pointed out, however, that many of the statements and 

assumptions Dow AgroSciences LLC made about the kinetic model are incorrect. In particular, Dow 

AgroSciences LLC has stated that, as long as first-order conditions are met, first-order rate constants and 

half-lives are unaffected by changes in substrate and enzyme concentration (when enzyme is saturating) 

and, therefore, can be used to predict relative digestion efficiencies for proteins even if the 

concentrations are varied among experiments. The Panel stated that it was “impossible to comment” on 

these statements without knowing the affinity of the substrate for the enzyme and emphasized the need 

for standardized assay conditions. In addition, the Panel report stated the following: 

 

“A poor fit of early time points to Michaelis-Menten kinetics indicates a 

 problem with the model. The Panel questioned the application of single 

 substrate Michaelis-Menten kinetics to the registrant data. The registrant did 

 not adequately address the problems of applying classical Michaelis-Menten 

 kinetics to a situation where [E0] >> [S0]. They incorrectly applied the term 

 Vmax/KM to this scenario.” 

In addition, “the Panel noted that at high enzyme to substrate ratios, the simple quasi-steady-state 

Michaelis-Menten equation cannot be applied.” 

Some Panel members expressed concern about omitting early time points to achieve a good fit to firstorder decay but in general “agreed that modeling of the late first order decay was an 

adequate/conservative approach for a given simulated gastric fluid (SGF) degradation assay...provided 

that a significant fraction of the digestion takes place during this slow phase.” The Panel report did not 

specify what a “significant fraction” is but pointed out that, in the case of Cry34Ab1, one-half of the 

substrate had been consumed by the first time point of one minute. The report stated that “one does not 

know whether or not the reaction follows first order kinetics during the initial 50% of the reaction,” but 

in this case, “this may not be important since one is interested in the time course for total substrate 

hydrolysis.” However, the Panel also pointed out that the late phase “may be hard to define in a practical 

setting and consequently impossible to standardize.” In conclusion, although the Panel pointed out some 
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problems with the kinetic approach, it recommended using the approach for proteins that are not rapidly 

digested. 

 

SAP Opinion on Assay Conditions

The Panel emphasized the need for standardized assay conditions throughout the report and gave some 

useful information on appropriate conditions. The Panel report clearly stated that a fixed amount of 

enzyme activity units should be used in digestion studies, and a standardized protocol should be used to 

determine enzyme activity. 

In addition, the Panel indicated that the pepsin to substrate ratio and the concentrations of pepsin and 

substrate have a pronounced effect on the rate of hydrolysis, implying that both the ratio and 

concentrations should be standardized. 

EPA asked if the concentration of test protein should be fixed on a weight basis (mg/mL) or a mole basis 

(mol/L). There was no consensus from the Panel on this issue: “Some Panel members recommended 

comparison of test proteins on a weight/mL, while others recommended a mole/mL.” 

One Panel member stated that a standardized pH should also be used for digestibility assays and 

indicated that there is no evidence that using more than one pH is necessary for predicting allergenicity. 

The Panel did not indicate one particular pH as being more appropriate than another. 

The Panel report discussed the pros and cons of the different methods that can be used for monitoring 

digestion reactions (i.e., SDS-PAGE with staining, western blot analysis, and high-performance liquid 

chromatography (HPLC)). Typically, applicants use SDS-PAGE with staining and western blot analysis. 

The Panel did not provide any information that would suggest a change to the current methodology. 

When asked about the pros and cons of using one digestion reaction and removing aliquots at various 

time points for monitoring or setting up separate reactions for each of the time points, the Panel 

responded that “there would be no difference...as long as there are no pipetting errors and the reactions 

are homogeneous.” In addition, several Panel members indicated that using a single digestion reaction 

gives a “slightly better ability to control extraneous factors that could affect experimental variability.” 

The report also pointed out that different statistical models would be required, depending on which 

approach is used. 

SAP Opinion on Digestibility Studies in Allergenicity Assessments

When asked what weight in vitro digestibility studies should be given in the overall allergenicity 

assessment compared with other criteria, the majority of the Panel indicated that digestibility is of some 

value but is less important than the source of the protein, sequence homology, or a validated animal 

model. The Panel also stated that “the use of digestibility data also is only of value in the context of a 

total weight of evidence approach.” 
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When asked about setting acceptable/unacceptable limits for digestibility in assessing the safety of a 

protein, the Panel stated that it is “difficult if not impossible given the lack of consistency between 

digestibility and allergenicity.” The Panel also noted that the relative digestibility of proteins depends on 

the assay conditions used, and a database of digestibilities under standard conditions needs to be 

established. 

When asked about the significance of the rate of digestion of protein fragments, the Panel recommended 

determining digestion rates for all fragments of a molecular mass >1500 Daltons (Da) (~10–15 amino 

acids) since a number of allergens have been shown to be peptides. The Panel recommended this size 

range because smaller peptides are not detectable using SDS-PAGE. 

 

SAP Opinion on Cry34Ab1 Allergenicity Assessment

The Panel agreed with EPA’s assessment that the weight-of-the-evidence indicates that Cry34Ab1 is 

unlikely to be a food allergen. The Panel reached this decision based on the following: (1) Cry34Ab1 is 

moderately digested in SGF, and it does not self-aggregate or aggregate with Cry35Ab1 in physiologic 

solutions; (2) Cry34Ab1 originates from a non-allergenic source; (3) Cry34Ab1 has no sequence 

similarity with known allergens “based on data presented on the lack of identity of 8 contiguous amino 

acids or more than 35% identity over 80 amino acids with known inhalant and ingested allergens”; and 

(4) Cry34Ab1 is not glycosylated when expressed in maize. 

The majority of Panel members indicated that heat stability is of minimal to no value in predicting the 

allergenicity potential of Cry34Ab1. The Panel also stated that “there is no convincing evidence that B. 

thuringiensis is an allergen in that it has never conclusively been documented to provoke an allergic 

reaction.” The Panel report also noted that “there are no data indicating that crystal proteins are 

allergens.” 

b. Aggregate Exposures

In examining aggregate exposure, section 408 of the Federal Food, Drug, and Cosmetic Act (FFDCA) 

directs EPA to consider available information concerning exposures from the pesticide residue in food 

and all other non-occupational exposures, including drinking water from ground water or surface water 

and exposure through pesticide use in gardens, lawns, or buildings (residential and other indoor uses). 

The Agency has considered available information on the aggregate exposure levels of consumers (and 

major identifiable subgroups of consumers) to the pesticide chemical residue and to other related 

substances. These considerations include dietary exposure under the tolerance exemption and all other 

tolerances or exemptions in effect for the plant-incorporated protectants’ chemical residue, and exposure 

from non-occupational sources. Exposure via the skin or inhalation is not likely since the plantincorporated protectants are contained within plant cells, which essentially eliminates these exposure 

routes or reduces these exposure routes to negligible. Exposure via residential or lawn use to infants and 

children is also not expected because the use sites for the Cry34Ab1 and Cry35Ab1 proteins are all 

agricultural for control of insects. Oral exposure, at very low levels, may occur from ingestion of 
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processed corn products and, potentially, drinking water. Oral toxicity testing, however, did not show 

any adverse effects. Furthermore, the expression of the Cry34Ab1 and Cry35Ab1 proteins in corn 

kernels has been shown to be in the parts per million range, which makes the expected dietary exposure 

several orders of magnitude lower than the amounts of Cry34Ab1 and Cry35Ab1 proteins shown to have 

no toxicity. Therefore, even if negligible aggregate exposure should occur, the Agency concludes that 

such exposure would result in no harm due to the lack of mammalian toxicity and low potential for 

allergenicity demonstrated for the Cry34Ab1 and Cry35Ab1 proteins. 

c. Cumulative Effects from Substances with a Common Mechanism of Toxicity

Section 408(b)(2)(D)(v) of FFDCA requires that, when considering whether to establish, modify, or 

revoke a tolerance, the Agency consider “available information concerning the cumulative effects of [a 

particular pesticide’s] residues and other substances that have a common mechanism of toxicity.” 

EPA has considered available information on the cumulative effects of such residues and other 

substances that have a common mechanism of toxicity. These considerations included the cumulative 

effects on infants and children of such residues and other substances with a common mechanism of 

toxicity. Because there is no indication of mammalian toxicity resulting from the plant-incorporated 

protectants, the Agency concludes that there are no cumulative effects for the Cry34Ab1 and Cry35Ab1 

proteins. For information regarding EPA’s efforts to determine which chemicals have a common 

mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see EPA’s website at 

http://www.epa.gov/pesticides/cumulative. 

 

 d. Determination of Safety for U.S. Population, Infants, and Children

 i. Toxicity and Allergenicity Conclusions

The data submitted and cited regarding potential health effects for the Cry34Ab1 and Cry35Ab1 proteins 

include the characterization of the expressed Cry34Ab1 and Cry35Ab1 proteins in corn, as well as the 

acute oral toxicity and in vitro digestibility of the proteins. The results of these studies were determined 

applicable to evaluate human risk, and the validity, completeness, and reliability of the available data 

from the studies were considered. 

Adequate information was submitted to show that the Cry34Ab1 and Cry35Ab1 protein test material 

derived from microbial cultures was biochemically and functionally similar to the protein produced by 

the plant-incorporated protectant ingredients in corn. Production of microbially produced protein was 

chosen in order to obtain sufficient material for testing. 

The submitted acute oral toxicity data support the prediction that the Cry34Ab1 and Cry35Ab1 proteins 

would be non-toxic to humans. As mentioned in section II(B)(1)(a)(i) of this Biopesticides Registration 

Action Document (BRAD), when proteins are toxic, they are known to act via acute mechanisms and at 

very low dose levels (Sjoblad et al. 1992). Since no effects were shown to be caused by the Cry34Ab1 

and Cry35Ab1 proteins, even at relatively high dose levels, the Cry34Ab1 and Cry35Ab1 proteins are 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

49

not considered toxic. Basing this conclusion on acute oral toxicity data without requiring further toxicity 

testing and residue data is similar to the Agency position regarding toxicity and the requirement of 

residue data for the microbial Bt products from which these plant-incorporated protectants were derived 

(see 40 CFR §§ 158.2130(d)(1)(i) and 158.2140(d)(7)). For microbial products, further toxicity testing 

and residue data are triggered by significant acute effects in studies, such as the mouse oral toxicity 

study, to verify and quantify the observed effects and clarify the source of these effects (Tiers II and III). 

Cry34Ab1 and Cry35Ab1 protein residue chemistry data were not required for a human health effects 

assessment of the subject plant-incorporated protectant ingredients because of the lack of mammalian 

toxicity. Notwithstanding that, submitted data demonstrated low levels of the Cry34Ab1 and Cry35Ab1 

proteins in corn tissues. 

Since Cry34Ab1 and Cry35Ab1 are proteins, their potential allergenicity is also considered as part of the 

toxicity assessment. Considering that (1) Cry34Ab1 and Cry35Ab1 originate from a non-allergenic 

source, (2) Cry34Ab1 and Cry35Ab1 have no overall sequence similarities or homology at the level of 8 

contiguous amino acid residues with known allergens, (3) Cry34Ab1 and Cry35Ab1 are not 

glycosylated when expressed in maize, (4) Cry34Ab1 and Cry35Ab1 will only be present at low levels 

in food, (5) Cry35Ab1 is rapidly digested in SGF, and (6) Cry34Ab1 is digested at a moderate rate in 

SGF, EPA has concluded that the potential for the Cry34Ab1 and Cry35Ab1 proteins to be food 

allergens is minimal. The FIFRA SAP that met on March 1–2, 2005 agreed with this conclusion 

regarding the allergenicity potential of Cry34Ab1. There were no triggers to raise concern about the 

allergenicity of Cry35Ab1, so the SAP was not asked to comment specifically on Cry35Ab1. 

Neither available information concerning the dietary consumption patterns of consumers (and major 

identifiable subgroups of consumers including infants and children) nor safety factors that are generally 

recognized as appropriate for the use of animal experimentation data were evaluated. The lack of 

mammalian toxicity at high levels of exposure to the Cry34Ab1 and Cry35Ab1 proteins, as well as the 

minimal potential to be a food allergen, demonstrate the safety of the product at levels well above 

possible maximum exposure levels anticipated in the crop. 

The genetic material necessary for the production of the plant-incorporated protectant active ingredients 

are the nucleic acids (deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)) that comprise genetic 

material encoding these proteins and their regulatory regions. The genetic material (DNA and RNA) 

necessary for the production of the Cry34Ab1 and Cry35Ab1 proteins have been exempted under the 

blanket exemption for all nucleic acids (40 CFR § 174.507). 

 

 ii. Infants and Children Risk Conclusions 

FFDCA section 408(b)(2)(C) provides that EPA shall assess the available information about 

consumption patterns among infants and children, special susceptibility of infants and children to 

pesticide chemical residues, and the cumulative effects on infants and children of the residues and other 

substances with a common mechanism of toxicity. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

50

In addition, FFDCA section 408(b)(2)(C) also provides that EPA shall apply an additional tenfold 

margin of safety for infants and children in the case of threshold effects to account for prenatal and 

postnatal toxicity and the completeness of the data base unless EPA determines that a different margin 

of safety will be safe for infants and children. 

In this instance, based on all the available information, the Agency concludes that there is a finding of 

no toxicity for the Cry34Ab1 and Cry35Ab1 proteins and the genetic material necessary for their

production. Thus, there are no threshold effects of concern and, as a result, an additional margin of 

safety for infants and children is not necessary. 

 iii. Overall Safety Conclusion 

There is a reasonable certainty that no harm will result from aggregate exposure to the U.S. population, 

including infants and children, to the Cry34Ab1 and Cry35Ab1 proteins and the genetic material 

necessary for their production. This includes all anticipated dietary exposures and all other exposures for 

which there is reliable information. 

The Agency has arrived at this conclusion because, as discussed thus far in this chapter, no toxicity to 

mammals has been observed, nor has there been any indication of allergenicity potential for the plantincorporated protectants. 

 

 e. Other Considerations 

 i. Analytical Enforcement Methodology

Validated enzyme-linked immunosorbent assays, for the detection and quantification of Cry34Ab1 and 

Cry35Ab1 in corn tissue, have been submitted and found acceptable by the Agency (MRID Nos. 

461239-01 and 461239-02; reviewed in U.S. EPA (2004b)). 

 ii. International Residue Limits

In making its tolerance decisions, EPA seeks to harmonize U.S. tolerances with international standards 

whenever possible, consistent with U.S. food safety standards and agricultural practices. In this context, 

EPA considers the international maximum residue limits (MRLs) established by the Codex Alimentarius 

Commission (Codex), as required by FFDCA section 408(b)(4). The Codex Alimentarius is a joint 

United Nations Food and Agriculture Organization/World Health Organization food standards program, 

and it is recognized as an international food safety standards-setting organization in trade agreements to 

which the United States is a party. EPA may establish a tolerance that is different from a Codex 

maximum residue level (MRL); however, FFDCA section 408(b)(4) requires that EPA explain the 

reasons for departing from the Codex level. 

The Codex has not established a MRL for the Cry34Ab1 and Cry35Ab1 proteins in corn. 

 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

51

 f. Endocrine Disruptors 

As required under FFDCA section 408(p), the Agency has developed the Endocrine Disruptor Screening 

Program (EDSP) to determine whether certain substances (including pesticide active and other 

ingredients) may have an effect in humans or wildlife similar to an effect produced by a “naturally 

occurring estrogen, or other such endocrine effects as the Administrator may designate.” The EDSP 

employs a two-tiered approach to making the statutorily required determinations. Tier 1 consists of a 

battery of 11 screening assays to identify the potential of a chemical substance to interact with the 

estrogen, androgen, or thyroid (E, A, or T) hormonal systems. Chemicals that go through Tier 1 

screening and are found to have the potential to interact with E, A, or T hormonal systems will proceed 

to the next stage of the EDSP where the Agency will determine which, if any, of the Tier 2 tests are 

necessary based on the available data. Tier 2 testing is designed to identify any adverse endocrinerelated effects caused by the substance, and establish a quantitative relationship between the dose and 

the E, A, or T effect. 

Between October 2009 and February 2010, the Agency issued test orders/data call-ins for the first group 

of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. This list of 

chemicals was selected based on the potential for human exposure through pathways such as food and 

water, residential activity, and certain post-application agricultural scenarios. This list should not be 

construed as a list of known or likely endocrine disruptors. 

The Cry34Ab1 and Cry35Ab1 proteins are not among the group of 58 pesticide active ingredients on the 

initial list to be screened under the EDSP. Under FFDCA section 408(p), the Agency must screen all 

pesticide chemicals. Accordingly, the Agency anticipates issuing future EDSP orders/data call-ins for all 

pesticide active ingredients. 

For further information on the status of the EDSP, the policies and procedures, the list of 67 chemicals, 

the test guidelines and the Tier 1 screening battery, please visit our website: http://www.epa.gov/endo/. 

 g. Tolerance Exemption 

Certain data submitted and reviewed for experimental use permits, as well as the FIFRA section 3 

registrations of Event DAS-59122-7 corn, also supported the petition for a tolerance exemption for 

residues of the Bt Cry34Ab1 and Cry35Ab1 proteins. Given the available data and information as 

summarized in Table 1, the Agency established a permanent exemption from the requirement of a 

tolerance for residues of the Bt Cry34Ab1 and Cry35Ab1 proteins and the genetic material necessary for 

their production in corn when used as plant-incorporated protectants in the food and feed commodities 

of corn; corn, field; corn, sweet; and corn, pop under 40 CFR § 174.457 (70 Federal Register (FR) 

55254; September 21, 2005). Subsequently, administrative revisions were made to existing plantincorporated protectant tolerance exemptions (e.g., some tolerance exemptions were moved from 40 

CFR part 180 to 40 CFR part 174). The original Cry34Ab1 and Cry35Ab1 tolerance exemption was 

subject to these revisions as it was redesignated from 40 CFR § 174.457 to 40 CFR § 174.506 and 

changed to the following (72 FR 20431; April 25, 2007): 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

52

 “§ 174.506 Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; 

 exemption from the requirement of a tolerance. 

 Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn 

 are exempted from the requirement of a tolerance when used as plant-incorporated 

 protectants in the food and feed commodities of corn; corn, field; corn, sweet; and 

 corn, pop.” 

Table 1. Human Health Assessment Data for Cry34Ab1 and Cry35Ab1. 

Study Title Summary MRID No.

Comparison of the 

Amino Acid Sequence 

of the Bacillus 

thuringiensis strain 

PS149B1 13.6 kDa and 

43.8 kDa Insecticidal 

Crystal Proteins to 

Known Protein 

Allergensa

Based upon the search requirements that at least 8 contiguous amino acids 

are identical to a known allergenic sequence, PS149B1 13.6-kiloDalton 

(kDa) and 43.8-kDa proteins are unrelated to any known allergens in that 

they do not share any linear epitopes with known protein allergens. 

Classification: Acceptable

452422-05 

PS149B1 14 kDa and 

44 kDa Proteins: Acute 

Oral Toxicity Study in 

CD-1 Micea

All animals survived the two-week study. One female mouse exhibited 

protruding or bulging eyes on days 6 and 7, but this resolved thereafter. 

This observation was not attributed to the treatment as it was an isolated 

observation (i.e., no other animals exhibited this). No other clinical signs 

were noted for any animals during the study. An initial weight loss was 

observed in 2 mice at test days 1 and 2, but both gained weight for the 

remainder of the study. All other animals gained weight throughout the 

study. No gross treatment-related observations were recorded during the 

study as represented by gross pathologic observations. An acute oral LD50

was calculated for this study based upon a dosage of a 1:4.6 ratio mixture 

of PS149B1 proteins at greater than 5,000 mg/kg and greater than 2,000 

mg/kg for an equimolar mixture (1:3) of the pure proteins. 

Classification: Acceptable

452422-09 

 

a

 Reviewed in U.S. EPA (2001a) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

53

Study Title Summary MRID No.

in vitro Digestibility of 

PS149B1 Proteinsb

Pseudomonas fluorescens strains MR1253 and MR1256 were used to 

prepare the 14-kDa and 44-kDa PS149B1 proteins, respectively, as 

inclusion bodies. A simulated gastric fluid was produced to determine the 

lability of these proteins in an acid environment containing pepsin. The 

bovine serum albumin (BSA) positive control was rapidly digested (within 

1 minute) and the b-lactoglobulin remained intact for 60 minutes, as 

expected, the duration of the experiment. The 14-kDa protein was visible 

on the SDS-PAGE gel at the 15-minute sample point but not afterwards. It 

was detected on the western blot, which has greater sensitivity, at the 20-

minute time point but not in later sample points. A band was also noted on 

the western blot at approximately 30 kDa. This band was noted in an 

earlier study and considered the result of protein aggregation. For the 44-

kDa protein western blot, bands were observed at approximately 42 kDa 

and 14 kDa. A single band was observed on the 44-kDa SDS-PAGE at 

approximately 15 to 16 kDa. These bands were only observed at the oneminute time point but not afterwards. It is concluded that both insecticidal 

crystal proteins (ICPs) are susceptible to degradation in the simulated 

gastric environment and differ in their lability to these conditions (i.e., the 

44-kDa protein is more rapidly degraded). 

Classification: Acceptable 

452422-12 

In vitro Simulated 

Gastric Fluid 

Digestibility Study of 

Microbially Derived 

Cry34Ab1 Proteinc

Bovine serum albumin, the positive control protein, was digested rapidly in 

the assay and could not be readily detected after 1 minute in the SGF. In 

contrast, the negative control protein, b-lactoglobulin, was detectable and 

appeared to change little during the assay time frame. When averaged 

across the 3 duplicate gels containing Cry34Ab1, the protein appeared to 

have approached full degradation by 7.5 minutes. Volumes remaining at 

the 10- and 15-minute time points were excluded from the calculations 

since they were below background levels. Using this first-order decay 

model, the DT50 and DT90 for this protein in the SGF were estimated to be 

1.9 and 6.2 minutes, respectively. The Cry34Ab1 protein was rapidly 

degraded in the SGF using this assay and detection methodology. The 

conditions of the assay were biologically appropriate in temperature, pH, 

and chemical makeup of the digestive solution. The first-order decay rate 

kinetics accurately portrayed the digestion of Cry34Ab1. 

Classification: Acceptable 

455845-02 

 

b

 Reviewed in U.S. EPA (2001a) 

c

 Reviewed in U.S. EPA (2002)
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

54

Study Title Summary MRID No.

SDS-PAGE Sensitivity 

Analysis for Cry35Ab1 

in Support of the 

Simulated Gastric Fluid 

Digestion Studyd

 

GelCode Blue staining of the SDS-PAGE gel used to electrophorese 

Cry35Ab1 samples indicated that the amount of protein remaining that was 

visualized by dye binding, 15.6 nanograms (ng), represented 2.6% of the 

total load (0.61 mg) in that lane. Therefore, 97% of the protein was 

digested by the simulated gastric digestion assay (pepsin treatment) at this 

5-minute time point. The GelCode Staining Reagent does, however, have a 

sensitivity limitation, which may or may not allow for detection of 

Cry35Ab1 at levels of 8 ng or less. The sequential sample coelectrophoresed on the gel examined was a 7.8 ng Cry35Ab1 protein/lane, 

which was not detected by visual examination following staining and 

destaining. 

Classification: Supplemental 

457904-08 

Digestion of Allergenic 

and Non-Allergenic 

Proteins in Simulated 

Gastric Fluide

The rate of digestion of allergenic and non-allergenic proteins in SGF was 

compared. Proteins were incubated in SGF (pH 1.2 and 2.0; 

pepsin:substrate ratio approximately 3:1, w/w; reaction not shaken), and 

samples analyzed by SDS-PAGE at various time points. The relative 

amount of protein remaining at each time point was estimated by 

densitometry, and the decay was analyzed using a first-order kinetic model. 

Under the conditions used in the study, the five allergenic proteins 

evaluated or a digestion fragment of the allergenic protein had half-lives in 

SGF of over 16 minutes, while the four non-allergenic proteins or a 

digestion fragment had half-lives of under 14 minutes (and 3 of those 4 had 

half-lives of less than 0.5 minutes). 

Classification: Supplemental

461239-20 

Digestion Efficiency of 

Allergens and NonAllergens in Simulated 

Gastric Fluidf

The digestion of seven allergens and eight non-allergens was assessed in 

SGF using a first-order kinetic model. Half-lives for the proteins tested 

ranged from <30 seconds to >60 minutes. Allergens tended to be more 

stable in SGF than non-allergens, but a strong correlation between 

digestion rate and allergenicity was not observed for this set of proteins. 

The data fit well to a first-order decay model, except for early time points, 

and half-lives calculated using initial substrate concentrations that differed 

by 5-fold were fairly consistent. 

Classification: Acceptable

463886-01 

 

d

 Reviewed in U.S. EPA (2003) 

e

 Reviewed in U.S. EPA (2004a) 

f

 Reviewed in U.S. EPA (2005a)
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

55

Study Title Summary MRID No.

PS149B1 14 kDa 

Protein: Acute Oral 

Toxicity Study in CD-1 

Miceg

PS149B1 14-kDa protein (Cry34Ab1; 54% pure) was evaluated for acute 

oral toxicity. Five male CD-1 mice received 5,000 mg of test material per 

kg body weight by oral gavage as a 20% mixture in a 0.5% aqueous 

methylcellulose vehicle. All animals survived the two-week study. No 

clinical signs were noted for any animals during the study. An initial 

weight loss was observed in 3 mice at test days 1 and 2, but they gained 

weight for the remainder of the study. The two other animals gained weight 

throughout the study. No treatment-related gross pathologic observations 

were observed during the study. Under the conditions of this study, the 

acute oral LD50 for the test substance in male CD-1 mice was greater than 

5,000 mg/kg; since the test substance contained PS149B1 14-kDa protein 

(Cry34Ab1) at 54% purity, the acute LD50 for the pure protein was greater 

than 2,700 mg/kg. 

Classification: Acceptable 

452422-07 

PS149B1 44 kDa 

Protein: Acute Oral 

Toxicity Study in CD-1 

Miceg

PS149B1 44-kDa protein (Cry35Ab1; 37% pure) was evaluated for acute 

oral toxicity. Five male CD-1 mice received 5,000 mg of test material per 

kg body weight by oral gavage as a 20% mixture in a 0.5% aqueous 

methylcellulose vehicle. All animals survived the two-week study. No 

clinical signs were noted for any animals during the study. An initial 

weight loss was observed in 2 mice at test days 1 and 2, but they gained 

weight for the remainder of the study, and one animal had fluctuating body 

weight. The other two animals gained weight throughout the study. No 

treatment-related gross pathologic observations were observed during the 

study. Under the conditions of this study, the acute oral LD50 for the test 

substance in male CD-1 mice was greater than 5,000 mg/kg; since the test 

substance contained PS149B1 44-kDa protein (Cry35Ab1) at 37% purity, 

the acute LD50 for the pure protein was greater than 1,850 mg/kg. 

Classification: Acceptable 

452422-08 

Lack of 

Cry34Ab1/Cry35Ab1 

Co-Association in 

Solutionh

Size exclusion chromatography was used to investigate whether Cry34Ab1 

and Cry35Ab1 associate with one another in solution under acidic 

conditions. Two studies were conducted, one at pH 3.6 and one at pH 2.0. 

In both studies, Cry34Ab1 and Cry35Ab1 eluted as separate peaks, 

indicating that the proteins do not associate with one another in solution 

under these conditions. 

Classification: Acceptable 

465568-01 

 

g

 Reviewed in U.S. EPA (2005a) 

h

 Reviewed in U.S. EPA (2005d) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

56

Study Title Summary MRID No.

Evaluation of the 

Sequence Similarities of 

the Cry34Ab1, 

Cry35Ab1, and PAT 

Proteins with the Public 

Protein Sequence 

Datasetsi

The sequences of the Cry34Ab1, Cry35Ab1, and PAT proteins were 

compared with protein sequences in publicly available databases (GenPept 

dataset) to identify any potential similarities with known toxins. The 

BlastP2.2.6 algorithm was used with a cutoff expectation (E) value of 1.0. 

The results of the Cry34Ab1 search identified 10 proteins, 5 of which are 

Cry proteins from Bt that are closely related or identical to the Cry34Ab1 

protein. The other proteins represent putative microbial collagenases and 

hypothetical proteins from genome-sequencing projects with a low degree 

of similarity to the Cry34Ab1 protein. The Cry35Ab1 search identified 22 

proteins, 7 of which are similar or identical Cry proteins from Bt. Other 

significant similarities were with proteins from a related species, Bacillus 

sphaericus, which has mosquitocidal activity. The PAT search identified 

148 accessions. Only 18 of these represent actual GenPept accessions and 

are either phosphinothricin acetyltransferases or other acetyltransferases. 

The remaining 130 proteins are unidentified and/or hypothetical proteins 

from genome-sequencing data. The Cry34Ab1, Cry35Ab1, and PAT 

proteins do not appear to have similarities with any proteins that would 

raise safety concerns. 

Classification: Acceptable 

465847-01 

2. Human Health Assessment of PAT (Expressed in Event DAS-59122-7 Corn, Herculex® 

 XTRA Insect Protection Corn, 59122 x MON 810, and 1507 x 59122 x MON 810), Cry1F 

 (Expressed in Herculex® XTRA Insect Protection Corn and 1507 x 59122 x MON 810), 

 and Cry1Ab (Expressed in 59122 x MON 810 and 1507 x 59122 x MON 810)

Based on previously completed Agency human health assessments, permanent tolerance exemptions 

have been established for the PAT, Cry1F, and Cry1Ab proteins: 

 “§ 174.522 Phosphinothricin Acetyltransferase (PAT); 

 exemption from the requirement of a tolerance.

 Residues of the Phosphinothricin Acetyltransferase (PAT) enzyme are exempt 

 from the requirement of a tolerance when used as plant-incorporated protectant 

 inert ingredients in all food commodities.” 

 **original under 40 CFR § 180.1151 (62 FR 17717; April 11, 1997) 

 **revised under 40 CFR § 174.522 (72 FR 20431; April 25, 2007) 

 

i

 Reviewed in U.S. EPA (2005d) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

57

 “§ 174.520 Bacillus thuringiensis Cry1F protein in corn; 

 exemption from the requirement of a tolerance. 

 Residues of Bacillus thuringiensis Cry1F protein in corn are exempt from 

 the requirement of a tolerance when used as plant-incorporated protectants 

 in the food and feed commodities of corn; corn, field; corn, sweet; and corn, 

 pop. 

 **original under 40 CFR § 180.1217 (66 FR 30321; June 6, 2001) 

 **revised under 40 CFR § 174.520 (72 FR 20431; April 25, 2007) 

 

 “§ 174.511 Bacillus thuringiensis Cry1Ab protein in all plants; 

 exemption from the requirement of a tolerance. 

 Residues of Bacillus thuringiensis Cry1Ab protein in all plants are exempt 

 from the requirement of a tolerance when used as plant-incorporated 

 protectants in all food commodities.” 

 

 **original under 40 CFR § 180.1173 (61 FR 40340; August 2, 1996) 

 **revised under 40 CFR § 174.511 (72 FR 20431; April 25, 2007) 

The toxicological and allergenicity data supporting the establishment of these tolerance exemptions, as 

well as the associated registrations of MON 810 (expressing Cry1Ab protein) and Herculex® I 

(expressing Cry1F and PAT proteins), can be found in the 2001 Bt Crops Reassessment, the August 

2005 Cry1F BRAD, and/or the July 2010 Cry1Ab and Cry1F BRAD (U.S. EPA 2001b, 2005e, and 

2010b). 

The individual data generated for the Cry1Ab, Cry1F, and PAT proteins (and Cry34Ab1 and Cry35Ab1) 

support their inclusion, as expressed in particular stacked and/or pyramided plant-incorporated 

protectants (i.e., Herculex® XTRA Insect Protection Corn, 59122 x MON 810, and 1507 x 59122 x 

MON 810), into the appropriate tolerance exemptions since the mode of action for the proteins does not 

suggest a synergistic activity in combination for mammalian species. 

Human health assessment data, provided specifically in relation to the Herculex® Insect Protection 

Corn, 59122 x MON 810, and/or 1507 x 59122 x MON 810 registrations, are summarized in Table 2. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

58

Table 2. Human Health Assessment Data for PAT, Cry1F, and Cry1Ab. 

Study Title Summary MRID No.

Herculex® XTRA Insect Protection Corn Data 

Summary Information 

in Support of the 

Section 3 Registration 

of Herculex® Xtra 

Resistant Cornj

Summary information is presented in support of the Section 3 registration 

of Herculex® Xtra Insect Resistant Corn, which contains Cry1F, 

Cry34Ab1, Cry35Ab1, and PAT proteins. The information focuses on the 

individual traits (from Herculex® I and Herculex® RW) that comprise 

Herculex® Xtra and potential synergies of the proteins with respect to 

mammalian and environmental risk. Studies of the individual traits, as well 

as the stacked traits, indicate expected efficacy to certain lepidopteran and 

coleopteran pests in field corn and no synergistic effect from the combined 

proteins. Studies indicate no concerns for safety of humans, non-target 

organisms, or threatened and endangered species. Data waiver requests and 

rationale are presented in this submission. 

Classification: Acceptable 

462971-01 

Equimolar Ratio of 

Cry1F (tr) + Cry35Ab1 

+ Cry34Ab1: Acute 

Oral Toxicity Study in 

CD-1 Micek

The acute oral toxicity of a mixture of microbially produced Cry1F 

(truncated), Cry34Ab1, and Cry35Ab1 proteins was assessed by 

administering an equimolar mixture of the proteins to five female mice and 

five male CD-1 mice. A dose of 525 mg pure Cry1F (truncated)/kg body 

weight (bw), 355 mg pure Cry35Ab1/kg bw, and 113 mg pure 

Cry34Ab1/kg bw was given as a suspension in 0.5% aqueous 

methylcellulose by two fractional gavage doses. All animals survived the 

two-week study and gained weight, no clinical signs were noted, and there 

were no gross pathologic changes observed at necropsy. The oral LD50 was 

greater than 993 mg/kg for the equimolar mixture of the pure Cry proteins. 

Classification: Acceptable

463843-01 

59122 x MON 810 & 1507 x 59122 x MON 810 Data

Evaluation of the 

Amino Acid Sequence 

Similarity of the 

Cry1Ab Protein from 

MON 810 to the NCBI 

Protein Sequence 

Datasets (Toxicity 

Study)l

The 818 amino acid sequence of Event MON 810 corn expressing Cry1Ab 

protein was sequentially searched and compared for protein sequence 

homology to known toxins contained in the National Center for 

Biotechnology Information (NCBI) Protein Sequence datasets. The 

BLASTP search showed no significant amino acid sequence homologies, 

using the Cry1Ab protein sequence as a query, with any proteins known to 

be toxins. Therefore, the Cry1Ab protein does not share any amino acid 

sequence homology with any proteins known to be toxins. 

Classification: Acceptable 

477864-06 

 

j

 Reviewed in U.S. EPA (2005f) 

k

 Reviewed in U.S. EPA (2005f) 

l

 Reviewed in U.S. EPA (2010a) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

59

Study Title Summary MRID No.

Evaluation of the 

Amino Acid Sequence 

Similarity of the Cry1F 

Protein from TC1507 to 

the NCBI Protein 

Sequence Datasets 

(Toxicity Study) m

The 605 amino acid sequence of Event TC1507 corn expressing Cry1F 

protein was sequentially searched for comparisons to known toxins 

contained in the NCBI Protein Sequence datasets. The BLASTP search 

showed no significant amino acid sequence homologies, using the Cry1F 

protein sequence as a query, with any proteins known to be toxins. 

Therefore, the Cry1F protein does not share any amino acid sequence 

homology with any proteins known to be toxins. 

Classification: Acceptable

477864-05 

Evaluation of the 

Amino Acid Sequence 

Similarity of the PAT 

Protein to the NCBI 

Protein Sequence 

Datasets (Toxicity 

Study)m

No significant amino acid sequence homologies were identified, using the 

PAT protein sequence as a query, with any proteins known to be toxins 

contained within the NCBI Protein Sequence datasets. Therefore, the 

updated amino acid homology search verifies no changes in the results and 

conclusions of the previously submitted toxin homology assessment for the 

PAT protein (see MRID No. 465847-01). 

Classification: Acceptable

477864-07 

Evaluation of the 

Amino Acid Sequence 

Similarities of the 

Cry34Ab1 and 

Cry35Ab1 Proteins to 

the NCBI Protein 

Sequence Datasets 

(Toxicity Study)m

No significant amino acid sequence homologies were identified, using the 

Cry34Ab1 and Cry35Ab1 protein sequences as a query, with any proteins 

known to be toxins contained within the NCBI Protein Sequence datasets. 

Therefore, the updated amino acid homology search verifies no changes in 

the results and conclusions of the previously submitted toxin homology 

assessment for the Cry34Ab1 and Cry35Ab1 proteins expressed in Event 

DAS-59122-7 corn (see MRID No. 465847-01). 

Classification: Acceptable

477864-08 

Comparison of the 

Amino Acid Sequence 

Identity Between the 

Cry1F Protein and 

Known Protein 

Allergens (Allergenicity 

Study)m

No identity matches of ~35% over ~80 amino acid residues were observed 

for the Cry1F protein sequence against the protein sequences of known 

allergens. In addition, there were no 8 or greater contiguous identical 

amino acid matches observed with the Cry1F protein sequence. Therefore, 

the updated amino acid homology search verifies no changes in the results 

and conclusions of the previously submitted allergen homology assessment 

for the Cry1F protein expressed in Event TC1507 corn (see MRID No. 

449717-01). 

Classification: Acceptable

477864-01 

 

m Reviewed in U.S. EPA (2010a) 
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60

Study Title Summary MRID No.

Comparison of the 

Amino Acid Sequence 

Identity Between the 

Cry34Ab1 and 

Cry35Ab1 Proteins and 

Known Protein 

Allergens (Allergenicity 

Study) n

No identity matches of ~35% over ~80 amino acid residues were observed 

for the Cry34Ab1 and Cry35Ab1 protein sequences against the protein 

sequences of known allergens. In addition, there were no 8 or greater 

contiguous identical amino acid matches observed with the Cry34Ab1 and 

Cry35Ab1 protein sequences. Therefore, the updated amino acid homology 

search verifies no changes in the results and conclusions of the previously 

submitted allergen homology assessment for the Cry34Ab1 and Cry35Ab1 

proteins expressed in Event DAS-59122-7 corn (see MRID No. 452422-

05). 

Classification: Acceptable

477864-02 

Comparison of the 

Amino Acid Sequence 

Identity Between the 

PAT Protein and 

Known Protein 

Allergens (Allergenicity 

Study)n

No identity matches of ~35% over ~80 amino acid residues were observed 

for PAT protein sequence against the protein sequences of known 

allergens. In addition, there were no 8 or greater contiguous identical 

amino acid matches observed with the PAT protein sequence. Therefore, 

the updated amino acid homology search verifies no changes in the results 

and conclusions of the previously submitted allergen homology assessment 

for the PAT protein (see MRID No. 449717-01). 

Classification: Acceptable

477864-03 

Comparison of the 

Amino Acid Sequence 

Identity Between the 

Cry1Ab Protein from 

Event MON 810 and 

Known Protein 

Allergens (Allergenicity 

Study)n

No identity matches of ~35% over ~80 amino acid residues were observed 

for Cry1Ab protein sequence against the protein sequences of known 

allergens. In addition, there were no 8 or greater contiguous identical 

amino acid matches observed with the Cry1Ab protein sequence. 

Therefore, the updated amino acid homology search verifies no changes in 

the results and conclusions of the previously submitted allergen homology 

assessment for the Cry1Ab protein expressed in Event MON 810 corn (see 

MRID No. 458789-02). 

Classification: Acceptable

477864-04 

3. References 

MRID No. 449717-01. Meyer T. 1999. Comparison of Amino Acid Sequence Similarity of Cry1F 

 and PAT Proteins to Known Allergen Proteins: Final Report. Lab Project Number: PHI99- 

 013. Unpublished study prepared by Trait and Technology Development, 24 pages. 

 

n

 Reviewed in U.S. EPA (2010a) 
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61

MRID No. 452422-05. Stelman S. 2000. Comparison of the Amino Acid Sequence of the Bacillus 

 thuringiensis Strain PS149B1 13.6 kDa and 43.8 kDa Insecticidal Crystal Proteins to Known 

 Protein Allergens. Lab Project Number: GH-C 5140. Unpublished study prepared by Dow 

 AgroSciences LLC, 188 pages. 

MRID No. 452422-07. Brooks K, DeWildt P. 2000. PS149B1 14 kDa Protein: Acute Oral Toxicity 

 Study in CD-1 Mice. Lab Project Number: 001130. Unpublished study prepared by Dow 

 AgroSciences LLC, 39 pages. 

MRID No. 452422-08. Brooks K, DeWildt P. 2000. PS149B1 44 kDa Protein: Acute Oral Toxicity 

 Study in CD-1 Mice. Lab Project Number: 001129. Unpublished study prepared by Dow 

 AgroSciences LLC, 39 pages. 

MRID No. 452422-09. Brooks K, DeWildt P. 2000. PS149B1 14 kDa and 44 kDa Proteins: Acute 

 Oral Toxicity Study in CD-1 Mice. Lab Project Number: 001128. Unpublished study 

 prepared by Dow Chemical Company, 45 pages. 

MRID No. 452422-12. Korjagin V. 2000. In vitro Digestibility of PS149B1 Proteins. Lab Project 

 Number: 000302. Unpublished study prepared by Dow AgroSciences LLC, 37 pages. 

MRID No. 455845-02. Korjagin V, Herman R, Hunst P. 2002. In vitro Simulated Gastric Fluid 

 Digestibility of Microbially Derived Cry34Ab1 Protein. Lab Project Number: 010111. 

 Unpublished study prepared by Dow AgroSciences LLC, 95 pages. 

MRID No. 457904-08. Herman R, Schafer B, Korjagin V. 2002. SDS-Page Sensitivity Analysis for 

 Cry35Ab1 in Support of the Simulated Gastric Fluid Digestion Study. Lab Project Number: 

 GH-C 5513. Unpublished study prepared by Dow AgroSciences LLC, 11 pages. 

MRID No. 458789-02. Heileman R, Silvanovich A, Rice E. 2002. Bioinformatics Evaluation of the 

Cry1Ab Protein Produced in Corn Event MON 810 Utilizing an Allergen Database. Lab 

Project Number: 17452: 01-01-39-44. Unpublished study prepared by The Monsanto 

Company, 47 pages. 

MRID No. 461239-01. Ojala B. 2003. Independent Laboratory Validation Pioneer Hi-Bred 

 International, Incorporated ELISA Method for the Quantification of Cry34Ab1 Protein from 

 Transgenic Plants. Project Number: BS03/02. Unpublished study prepared by Biolab 

 Solutions, 46 pages. 

MRID No. 461239-02. Ojala B. 2003. Independent Laboratory Validation of Dow AgroSciences 

 Method GRM 03.13, “Determination of Cry35Ab1 Insecticidal Crystal Protein in Maize 

 Tissue by Enzyme-Linked Immunosorbent Assay.” Project Number: BS03/01. Unpublished 

 study prepared by Biolab Solutions, 45 pages. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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MRID No. 461239-04. Essner R. 2003. Agronomic Characteristics, Quantitative ELISA and 

 Nutrient Composition Analysis of Hybrid Maize Lines Containing the cry34Ab1, cry35Ab1 

 and pat Genes: Chile Locations. Project Number: PHI/2002/050. Unpublished study prepared 

 by Pioneer Hi-Bred International, Incorporated and EPL Bio-Analytical Services, 1,971 

 pages. 

MRID No. 461239-06. Schafer B. 2003. Characterization of Cry34Ab1 and Cry35Ab1 Proteins 

 Derived from Transgenic Maize Event E4497.59.1.22 (DAS-59122-7). Project Number: 

 030033. Unpublished study prepared by Dow AgroSciences LLC, 50 pages. 

 

MRID No. 461239-20. Herman R. 2003. Digestion of Allergenic and Non-Allergenic Proteins in 

 Simulated Gastric Fluid. Project Number: GH/C/5700. Unpublished study prepared by Dow 

 AgroSciences LLC, 73 pages. 

MRID No. 462971-01. Ernest A, Hunst P. 2004. Summary Information in Support of the Section 3 

 Registration of Herculex® Xtra Insect Resistant Corn. Project Number: GH/C/5736. 

 Unpublished study prepared by Dow AgroSciences LLC, 55 pages. 

MRID No. 463843-01. Wilson D, Brooks K, Dowdney R. 2004. Equimolar Ration of Cry1F (tr) + 

 Cry35Ab1 + Cry34Ab1: Acute Oral Toxicity Study in CD-1 Mice. Project Number: 041011. 

 Unpublished study prepared by The Dow Chemical Company, 31 pages. 

 

MRID No. 463886-01. Herman R, Woolhiser M, Ladics G. 2004. Digestion Efficiency of Allergens 

 and Non-Allergens in Simulated Gastric Fluid: Bacillus thuringiensis Cry34/35Ab1 

 Construct PHP17662. Project Number: GH/C/5761. Unpublished study prepared by Dow 

 AgroSciences LLC, Pioneer Hi-Bred Corn Company Production Department, and Dow 

 Chemical Company, 302 pages. 

MRID No. 465568-01. Herman R, Evans S, Zhuang M. 2005. Lack of Cry34Ab1/Cry35Ab1 Co- 

 Association in Solution. Project Number: GH/C/5805. Unpublished study prepared by Dow 

 AgroSciences LLC, 36 pages. 

MRID No. 465847-01. Cressman R. 2003. Evaluation of the Sequence Similarities of the Cry34Ab1, 

 Cry35Ab1, and PAT Proteins to the Public Protein Sequence Datasets. Project Number: 

 PHI/2003/046. Unpublished study prepared by E.I. du Pont de Nemours and Company, 

 Incorporated, 211 pages. 

MRID No. 477864-01. Krauss A, Cressman R. 2009. Comparison of the Amino Acid Sequence 

 Identity Between the Cry1F Protein and Known Protein Allergens. Project Number: 

 PHI/2008/236. Unpublished study prepared by E.I. du Pont de Nemours and Company, 23 

 pages. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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63

MRID No. 477864-02. Krauss A, Cressman R. 2009. Comparison of the Amino Acid Sequence 

 Identity Between the Cry34Ab1 and Cry35Ab1 Proteins and Known Protein Allergens. 

 Project Number: PHI/2008/237. Unpublished study prepared by E.I. du Pont de Nemours 

 and Company, 35 pages. 

MRID No. 477864-03. Krauss A, Cressman R. 2009. Comparison of the Amino Acid Sequence 

 Identity Between the (Inert Ingredient) Protein and Known Protein Allergens. Project 

 Number: PHI/2008/238. Unpublished study prepared by E.I. du Pont de Nemours 

 and Company, 22 pages. 

MRID No. 477864-04. Krauss A, Cressman R. 2009. Comparison of the Amino Acid Sequence 

 Identity Between the Cry1Ab Protein from Event MON 810 and Known Protein Allergens. 

 Project Number: PHI/2008/239. Unpublished study prepared by E.I. du Pont de Nemours 

 and Company, 24 pages. 

MRID No. 477864-05. Cressman R, Krauss A. 2009. Evaluation of the Amino Acid Sequence 

 Similarity of the Cry1F Protein to the NCBI Protein Sequence Datasets. Project Number: 

 PHI/2008/240. Unpublished study prepared by E.I. du Pont de Nemours and Company, 291 

 pages. 

 

MRID No. 477864-06. Krauss A, Cressman R. 2009. Evaluation of the Amino Acid Sequence 

 Similarity of the Cry1Ab Protein from Event MON 810 to the NCBI Protein Sequence 

 Datasets. Project Number: PHI/2008/241. Unpublished study prepared by E.I. du Pont de 

 Nemours and Company, 354 pages. 

MRID No. 477864-07. Krauss A, Cressman R. 2009. Evaluation of the Amino Acid Sequence 

 Similarity of the (Inert Ingredient) Protein to the NCBI Protein Sequence Datasets. Project 

 Number: PHI/2008/242. Unpublished study prepared by E.I. du Pont de Nemours and 

 Company, 278 pages. 

MRID No. 477864-08. Krauss A, Cressman R. 2009. Evaluation of the Amino Acid Sequence 

 Similarities of the Cry34Ab1 and Cry35Ab1 Proteins to the NCBI Protein Sequence 

 Datasets. Project Number: PHI/2008/243. Unpublished study prepared by E.I. du Pont de 

 Nemours and Company, 43 pages. 

Sjoblad RD, McClintock JT, Engler R. 1992. Toxicological considerations for protein components 

 of biological pesticide products. Regulatory Toxicology and Pharmacology 15(1):3–9. 

 

U.S. EPA. 2001a. Review of Product Characterization, Expression Analysis and Acute Oral Toxicity 

 Studies for PS149B1 Binary Insect Control Proteins as Expressed in Maize, a Bacillus 

 thuringiensis-Based Plant-Pesticide, for an Experimental Use Permit. Memorandum from 

 C.A. Wozniak, Ph.D. and J.L. Kough, Ph.D. to M. Mendelsohn dated June 7, 2001. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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U.S. EPA. 2001b. Biopesticides Registration Action Document – Bacillus thuringiensis Plant- 

 Incorporated Protectants. Available from: 

 http://www.epa.gov/oppbppd1/biopesticides/pips/bt_brad.htm. 

U.S. EPA. 2002. Review of in vitro Digestibility for PS149B1 Binary Insect Control Proteins, 

 Cry34 and Cry35, as Expressed in Maize, a Bacillus thuringiensis-Based Plant-Incorporated 

 Protectant, for Approval of a Temporary Food Tolerance. Memorandum from C.A. Wozniak, 

 Ph.D. and J.L. Kough, Ph.D. to M. Mendelsohn dated November 5, 2002. 

U.S. EPA. 2003. Review of SDS-PAGE Sensitivity and Lateral Flow Detection Method for 

 PS149B1 Binary Insect Control Proteins as Expressed in Maize, a Bacillus thuringiensis- 

 Based Plant-Incorporated Protectant, for an Experimental Use Permit. Memorandum from 

 C.A. Wozniak, Ph.D. and J.L. Kough, Ph.D. to M. Mendelsohn dated April 3, 2003. 

U.S. EPA. 2004a. Review of Digestion of Allergenic and Non-Allergenic Proteins in Simulated 

 Gastric Fluid Analyzed by a Kinetic Approach for Support of Registration of Bt 

 Cry34/35Ab1 Construct PHP17762 Corn. Memorandum from R.L. Edelstein, Ph.D. and 

 J.L. Kough, Ph.D. to M. Mendelsohn dated August 17, 2004. 

U.S. EPA. 2004b. Review of Product Characterization and Expression Analysis for Registration of 

B.t. Cry34/35AB1 Construct PHP17662 Corn. Memorandum from R.L. Edelstein, Ph.D. and 

 J.L. Kough Ph.D. to M. Mendelsohn dated December 6, 2004. 

U.S. EPA. 2005a. Review of Human Health Data for Registration of B.t. Cry 34/35Ab1 Construct 

 PHP17662 Corn and Risk Assessment. Memorandum from R.L. Edelstein, Ph.D. and J.L. 

 Kough, Ph.D. to M. Mendelsohn dated February 4, 2005. 

U.S. EPA. 2005b. SAP Report No. 2005-02. A Set of Scientific Issues Being Considered by the 

 Environmental Protection Agency Regarding: Scientific Issues Associated with the Human 

 Health Assessment of the Cry34Ab1 Protein. Dated April 5, 2005. Available from: 

http://www.epa.gov/scipoly/sap/meetings/2005/march/finalmar2005sapmtg.pdf. 

U.S. EPA. 2005c. Evaluation of FIFRA SAP Meeting Minutes Dated April 5, 2005 from the 

 March 1–2, 2005 Meeting on Scientific Issues Associated with the Human Health 

 Assessment of the Cry34Ab1 Protein. Memorandum from R.L. Edelstein, Ph.D. and J.L. 

 Kough, Ph.D. to M. Mendelsohn dated May 12, 2005. 

U.S. EPA. 2005d. Addendum to Review of Human Health Data for Registration of B.t. Cry 

 34/35Ab1 Construct PHP17662 Corn and Risk Assessment. Memorandum from R.L. 

 Edelstein, Ph.D. and J.L. Kough, Ph.D. to M. Mendelsohn dated July 7, 2005. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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U.S. EPA. 2005e. Biopesticides Registration Action Document – Bacillus thuringiensis 

Cry1F Corn. Available from: 

http://www.epa.gov/oppbppd1/biopesticides/ingredients/tech_docs/brad_006481.pdf. 

U.S. EPA. 2005f. Review of Product Characterization and Human Health Data for Registration of 

 HerculexTM Xtra Insect Resistant Corn. Memorandum from R.L. Edelstein, Ph.D. and J.L. 

 Kough, Ph.D. to M. Mendelsohn dated September 22, 2005. 

U.S. EPA. 2010a. Review of Human Health and Product Characterization Data for Registration of 

Bacillus thuringiensis (Bt) Cry1F, Cry34Ab1, Cry35Ab1, and Cry1Ab Proteins and the 

 Genetic Material Necessary for Their Production in the Combination Plant-Incorporated 

 Protectant (PIP) Products: 1507 x MON 810 [EPA Reg. No. 29964-T], 59122 x MON 810 

 [EPA Reg. No. 29964-O], and 1507 x 59122 x MON 810 [EPA Reg. No. 29964-I]. 

 Memorandum from A. Waggoner and J.L. Kough, Ph.D. to A. Sibold dated 

 February 19, 2010. 

U.S. EPA. 2010b. Biopesticides Registration Action Document – Bacillus thuringiensis 

Cry1Ab and Cry1F Corn. Available from: http://www.regulations.gov (see “Supporting & 

Related Materials” within Docket Number EPA-HQ-OPP-2010-0607). 
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C. Environmental Assessment 

1. Tiered Hazard and Risk Assessment Process 

To minimize data requirements and avoid unnecessary tests, risk assessments are structured such that 

risk is determined first from estimates of hazard under “worst-case” exposure conditions. A lack of 

adverse effects under these conditions would provide enough confidence that there is no risk and no 

further data would be needed. Hence, such screening tests conducted early in an investigation tend to be 

broad in scope, but relatively simple in design, and can be used to demonstrate acceptable risk under 

most conceivable conditions. When screening studies suggest potentially unacceptable risk, additional 

studies are designed to assess risk under more realistic field exposure conditions. These later tests are 

more complex than earlier screening studies. Use of this “tiered” testing framework saves valuable time 

and resources by organizing the studies in a cohesive and coherent manner and eliminating unnecessary 

lines of investigation. Lower tier, high-dose screening studies also allow tighter control over 

experimental variables and exposure conditions, resulting in a greater ability to produce statistically 

reliable results at relatively low cost.a 

Tiered tests are designed to first represent unrealistic worst-case scenarios and ONLY progress to realworld field scenarios if the earlier tiered tests fail to indicate adequate certainty of acceptable risk. 

Screening (Tier I) non-target organism hazard tests are conducted at exposure concentrations several 

times higher than the highest concentrations expected to occur under realistic field exposure scenarios. 

This has allowed an endpoint of 50% mortality to be used as a trigger for additional higher tier testing. 

Less than 50% mortality under these conditions of extreme exposure suggest that population effects are 

likely to be negligible given realistic field exposure scenarios. 

The Environmental Protection Agency (EPA) uses a tiered (Tiers I–IV) testing system to assess the 

toxicity of a plant-incorporated protectant (PIP) to representative non-target organisms that could be 

exposed to the toxin in the field environment. Tier I high-dose studies reflect a screening approach to 

testing designed to maximize any toxic effects of the test substance on the test (non-target) organism. 

The screening tests evaluate single species in a laboratory setting with mortality as the endpoint. Tiers 

II–IV generally encompass definitive hazard level determinations, longer term greenhouse or field 

testing, and are implemented when unacceptable effects are seen at the Tier I screening level. 

Testing methods, which utilize the tiered approach, were last published by EPA as Harmonized Office 

of Prevention, Pesticides, and Toxic Substances (OPPTS) Testing Guidelines (now Harmonized Office 

 

a

 Non-target invertebrate hazard tests often are conducted at exposure concentrations several times higher than the maximum 

concentrations expected to occur under realistic exposure scenarios. This has customarily allowed an endpoint of 50% 

mortality to be used as a trigger for additional higher tier testing. Lower levels of mortality under these conditions of extreme 

exposure suggest that population effects are likely to be negligible given realistic exposure scenarios. Thus, it follows that the 

observed proportion of responding individuals can be compared to a 50% effect to determine if the observed proportion is 

significantly lower than 50%. For example, using a binomial approach, a sample size of 30 individuals is sufficient to allow a 

treatment effect of 30% to be differentiated from a 50% effect with 95% confidence using a one-sided Z test. A one-sided test 

is appropriate because only effects of less than 50% indicate that further experiments are not needed to evaluate risk. 
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of Chemical Safety and Pollution Prevention (OCSPP) Testing Guidelines), Series 850 and 885 (EPA 

712-C-96-280, February 1996).b These guidelines apply to microbes and microbial toxins when used as 

pesticides, including those that are naturally occurring and those that are strain improved either by 

natural selection or by deliberate genetic manipulation. Therefore, plant-incorporated protectants (PIPs) 

containing microbial toxins are also covered by these testing guidelines. 

The Tier I screening maximum hazard dose (MHD) approach to environmental hazard assessment is 

based on some factor (whenever possible >10) times the maximum amount of active ingredient expected 

to be available to terrestrial and aquatic non-target organisms in the environment, or the Estimated 

Environmental Concentration (EEC).c Tier I tests serve to identify potential hazards and are conducted 

in the laboratory at high dose levels, which increase the statistical power to test the hypotheses. Elevated 

test doses, therefore, add certainty to the assessment, and such tests can be well standardized. The 

Guidelines call for initial screening testing of a single group or several groups of test animals at the 

maximum hazard dose level. The Guidelines call for testing of one treatment group of at least thirty 

animals or three groups of ten test animals at the screening test concentration. The Guidelines further 

state that the duration of all Tier I tests should be approximately 30 days. Some test species, notably 

non-target insects, may be difficult to culture and the suggested test duration has been adjusted 

accordingly. Control and treated insects should be observed for at least 30 days, or in cases where an 

insect species cannot be cultured for 30 days, until negative control mortality rises above 20%. 

Failing the Tier I (10x EEC) screening at the MHD does not necessarily indicate the presence of an 

unacceptable risk in the field, but it triggers the need for additional testing.d A less than 50% mortality 

effect at the MHD is taken to indicate minimal risk. Greater than 50% mortality, however, does not 

necessarily indicate the existence of unacceptable risk in the field, but it does trigger the need to collect 

additional dose-response information and a refinement of the exposure estimation before deciding if the 

risk is acceptable or unacceptable. Where potential hazards are detected in Tier I testing (i.e., mortality 

is greater than 50%), additional information at lower test doses is required, which can serve to confirm 

whether any effect might still be detected at more realistic field (1x EEC) concentrations and routes of 

exposure.e 

 

b

 General OCSPP Harmonized Testing Guidelines available from: http://www.epa.gov/ocspp/pubs/frs/home/guidelin.htm. 

Series 850 Testing Guidelines available from: 

http://www.epa.gov/ocspp/pubs/frs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/Drafts/index.

html. 

Series 885 Testing Guidelines available from: 

http://www.epa.gov/ocspp/pubs/frs/publications/Test_Guidelines/series885.htm. c

 The dose margin can be less than 10x where uncertainty in the system is low or where high concentrations of test material 

are not possible to achieve due to test organism feeding habits or other factors. High-dose testing also may not be necessary 

where many species are tested or tests are very sensitive, although the test concentration used must exceed 1x EEC. 

d

 Note that the 10x EEC MHD testing approach is not equivalent to what is commonly known as “testing at a 10x safety 

factor,” where any adverse effect is considered significant. Tier I screen testing is not “safety factor testing.” In a “10x safety 

factor” test, any adverse effect noted is a “level of concern,” whereas in the EPA environmental risk assessment scenario any 

adverse effect is viewed as a concern only at 1x the field exposure. 

e

 The 1x EEC test dose is based on plant tissue content and is considered the highest dose in a worst-case scenario 

(sometimes referred to as the Highest Estimated Environmental Concentration or HEEC). This 1x EEC is still much greater 
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When screening tests indicate a need for additional data, the OCSPP Harmonized Guidelines call for 

testing at incrementally lower doses in order to establish a definitive LD50 (i.e., dose that will kill 50% of 

the test organisms within a designated period) and to quantify the hazard. In the definitive testing, the 

number of doses and test organisms evaluated must be sufficient to determine an LD50 value and, when 

necessary, the Lowest Observed Adverse Effect Concentration (LOAEC), No Observed Adverse Effect 

Level (NOAEL), or reproductive and behavioral effects such as feeding inhibition, weight loss, etc. In 

the final analysis, a risk assessment is made by comparing the LOAEC to the EEC; when the EEC is 

lower than the LOAEC, a no risk conclusion is made. These tests offer greater environmental realism, 

but they may have lower statistical power. Appropriate statistical methods, and appropriate statistical 

power, must be employed to evaluate the data from the definitive tests. Higher levels of replication, test 

species numbers, and/or repetition are needed to enhance statistical power in these circumstances. 

Data that shows less than 50% mortality at the maximum hazard dosage level (i.e., LC50, ED50, or LD50

>10x EEC) is sufficient to evaluate adverse effects, making lower field exposure dose definitive testing 

unnecessary. It is also notable that the recommended >10x EEC maximum hazard dose level is a highly 

conservative factor. The published EPA Level of Concern (LOC) is 50% mortality at 5x EEC (U.S. EPA 

1998).f 

Validation: The tiered hazard assessment approach was developed for EPA by the American Institute of 

Biological Sciences (AIBS) and confirmed in 1996 as an acceptable method of environmental hazard 

assessment by a Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel 

(SAP) on microbial pesticides and microbial toxins. The December 9, 1999 SAP agreed that the tiered 

approach was suitable for use with PIPs; however, this panel recommended that, for PIPs with insecticidal 

properties, additional testing of beneficial invertebrates closely related to target species and/or likely to be 

present in genetically modified (GM) crop fields should be conducted. Testing of Bacillus thuringiensis 

(Bt) Cry proteins on species not closely related to the target insect pest was not recommended, although it 

is still performed to fulfill the published EPA non-target species data requirements. In October 2000, 

another SAP also recommended that field testing should be used to evaluate population-level effects on 

non-target organisms. The August 2002 SAP, and some public comments, generally agreed with this 

approach, with the additional recommendation that indicator organisms should be selected on the basis of 

potential for field exposure to the subject protein (U.S. EPA 2000, 2001a, 2002, and 2004b). 

Chronic studies: Since delayed adverse effects and/or accumulation of toxins through the food chain are 

not expected to result from exposure to proteins, protein toxins are not routinely tested for chronic 

effects on non-target organisms. But, the 30-day test duration requirement does amount to subchronic 

 than any amount which any given non-target organism may be ingesting in the field because most non-target organisms do 

not ingest plant tissue. 

f

 The established peer and EPA Science Board reviewed guidance on screening test levels of concern is 50% mortality at 5x 

environmental concentration for terrestrial and 10x for aquatic species. The appropriate endpoints in high-dose 

limit/screening testing are based on mortality of the treated, as compared to the untreated (control) non-target organisms. A 

single group of 30 test animals may be tested at the maximum hazard dose. 
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testing when performed at field exposure test doses. Proteins do not bioaccumulate. The biological 

nature of proteins makes them readily susceptible to metabolic, microbial, and abiotic degradation once 

they are either ingested or excreted into the environment. Although there are reports that some proteins 

(Cry proteins) bind to soil particles, it has also been shown that these proteins are degraded rapidly by 

soil microbial flora upon elution from soil particles. 

Conclusion: The tiered approach to test guidelines ensures, to the greatest extent possible, that the 

Agency requires the minimum amount of data needed to make scientifically sound regulatory decisions. 

EPA believes that maximum hazard dose Tier I screening testing presents a reasonable approach for 

evaluating hazards related to the use of biological pesticides and for identifying negative results with a 

high degree of confidence. The Agency expects that Tier I testing for short-term hazard assessment will 

be sufficient for most studies submitted in support of PIP registrations. If long-range adverse effects 

must be ascertained, however, then higher tier, longer term field testing will be required. As noted 

above, the October 2000 SAP and the National Academy of Sciences (NAS 2000) recommended testing 

non-target organisms directly in the field. This approach, with an emphasis on testing invertebrates 

found in corn fields, was also recommended by the August 2002 SAP and was supported by several 

public comments. Based on these recommendations and due to the lack of baseline data on the potential 

for long-term environmental effects from the cultivation of PIP-producing plants, the Agency has 

required long-term field studies on invertebrate populations/communities and Cry protein accumulation 

in soils as conditions of past PIP registrations. 

Since the commercialization of Bt crops, the number of field studies published in scientific literature, in 

combination with the post-registration field studies submitted to the Agency, has accumulated to a level 

where empirical conclusions can be made. As a result, the issue of long-range effects of cultivation of 

these Cry proteins on the invertebrate community structure in Bt crop fields has since been adequately 

addressed. Specifically, a meta-analysisg of the data collected from 42 field studies indicated that nontarget invertebrates are generally more abundant in Bt cotton and Bt maize fields than in non-transgenic 

fields managed with insecticides (Marvier et al. 2007). In addition, a comprehensive review of shortand long-term field studies on the effects of invertebrate populations in Bt corn and cotton fields 

indicated that no unreasonable adverse effects are taking place as a result of wide-scale Bt crop 

cultivation (Sanvido et al. 2007). Another review of field tests published to date concluded that the 

large-scale studies in commercial Bt cotton have not revealed any unexpected non-target effects other 

than subtle shifts in the arthropod community caused by the effective control of the target pests (Romeis 

et al. 2006). Slight reductions in some invertebrate predator populations are an inevitable result of all 

pest management practices, which result in reductions in the abundance of the pests as prey. 

Overall, the Agency is in agreement with the conclusions of these studies and, collectively, these results 

provide extensive data to support that Bt crops have not caused long-term environmental effects, on a 

population level, to organisms not targeted by Bt proteins. Based on these considerations, regulatory 

 

g This research was funded by EPA grant CR-832147-01. The Bt crop non-target effects database can be found on the 

National Center for Ecological Analysis and Synthesis (NCEAS) Web Site: http://delphi.nceas.ucsb.edu/btcrops/.
Bacillus thuringiensis Cry34/35Ab1 Corn 

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testing of the specialist predators and parasitoids of target pests may eventually be considered 

unnecessary. 

2. Event DAS-59122-7 Corn (Organization for Economic Cooperation and Development 

 (OECD) Unique Identifier: DAS-59122-7) Expressing Cry34Ab1 and Cry35Ab1 

a. Data Cited/Submitted for Initial Registrations of Event DAS-59122-7 Corn (Prior to

 August 2005) 

 i. Background

In 2003, Mycogen Seeds c/o Dow AgroSciences LLC and Pioneer Hi-Bred International, Incorporated 

requested registrations for Bacillus thuringiensis Cry34/35Ab1 binary protein and the genetic material 

necessary for its production in all corn lines and varieties. This protein controls the corn rootworm 

(CRW, Diabrotica spp.), a primary pest of corn in the United States. Corn rootworm larvae feed on corn 

roots, resulting in lodging and a reduction in a plant’s ability to absorb water and nutrients from soil. In 

areas where the CRW is a pest (e.g., Corn Belt), significant financial losses are realized from decreased 

corn yields and increased expenditures on chemical pest control agents, including organophosphate, 

carbamate, and pyrethroid insecticides. 

EPA conducted an environmental hazard assessment of the Cry34/35Ab1-producing corn lines. The 

general topics covered include gene flow to related wild plants, development of weediness, effects on 

wildlife, and fate of Cry34/35Ab1 protein in the environment. The assessment is based on data 

submitted to the Agency during the development of the corn lines; additional data submitted for 

registration; FIFRA SAP recommendations; consultations with scientific experts; and previous public 

comments on plant-incorporated protectant regulation. 

 ii. Non-Target Wildlife Hazard Assessment

Two separate SAP reports (October 2000 and August 2002) recommended that non-target testing should 

focus on species exposed to the crop being registered. Following SAP recommendations, the Agency 

determined that non-target organisms with the greatest exposure potential to protein in transgenic corn 

fields are beneficial insects, which feed on corn pollen and nectar, and soil invertebrates, particularly 

coleopteran species. Therefore, maximum hazard dose toxicity testing on representative beneficials from 

several taxa was performed. The toxicity of the Cry34/35Ab1 protein has been evaluated on several 

species of invertebrates, including larval honey bees, a parasitic hymenoptera, green lacewings, lady 

beetles, collembola, and earthworms. Reproductive and developmental observations were also made on 

collembola, honey bee, and lady beetle larva. 

The non-target organisms tested are chosen as representative indicators of the major groups of wildlife 

and on the potential for field exposure as deduced from data on Cry34/35Ab1 protein expression in the 

plant. Although Bt Cry proteins are very specific in their activity to only certain insect species, for 

Cry34/35Ab1 protein in corn, the Agency has examined the toxicity to birds, fish, honey bees, and 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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certain other beneficial insects even though the October 2000 SAP recommended against testing of nontarget species not related to those susceptible to the specific activity of Bt Cry proteins. In order to 

comply with the Agency’s published data requirements for registration of microbial toxins (40 CFR § 

158.2150), data submissions or waiver justifications were submitted to address these requirements. 

Collembola and earthworm studies were also conducted and voluntarily submitted to the Agency by the 

applicants to ascertain effects of Cry34/35Ab1 on beneficial decomposer species because prolonged 

exposure to Cry34/35Ab1 protein in soil was a possibility. Honey bee effects on brood were also 

required as exposure of honey bee larvae to the Cry34/35Ab1 protein in pollen is expected. 

The form of the test substances used in the studies for this assessment are plant material such as leaves, 

roots, pollen, or purified, bacterially produced Cry34/35Ab1 protein incorporated into the test species 

diet. The October 2000 SAP provided guidance to the Agency that, while actual plant material is the 

preferred test material, bacterially derived protein is also a valid test substance, particularly in testing 

where the test animals do not consume corn plant tissue and where large amounts of Cry protein are 

needed for maximum hazard dose testing. Consistent with the OCSPP Harmonized Testing Guidelines, 

the adult insect studies were generally of 30 days duration or until the negative control mortality reached 

20%. Larval studies were carried out through pupation and adult emergence. 

The results for each study on environmental effects for Cry34/35Ab1 are summarized in Table 1. 

Additionally, the results are presented in a more descriptive format in subsequent sections of this 

Environmental Assessment chapter. Complete reviews of each study can be found in the individual Data 

Evaluation Reports. 

Table 1. Environmental Effects Data for Event DAS-59122-7 Corn (Reviewed in U.S. EPA 

 (2005c) Unless Otherwise Noted). 

Guideline 

Number Study Results

MRID 

Number

885.4050 Avian Dietary 

Testing 

There were no treatment-related deaths or clinical signs observed in 

broilers fed a diet containing 59% (starter ration) or 63% 

(grower/finisher ration) Cry34/35 Bt corn for 42 days. Corn 

containing the test protein supported rapid growth of broiler chickens 

and was similar in performance to non-transgenic varieties. No 

adverse effects on avian wildlife are expected from consumption of 

Cry34/35Ab1 corn. 

Classification: Acceptable 

461239-11 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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Guideline 

Number Study Results

MRID 

Number

885.4150 Wild Mammal 

Testing 

Mammalian wildlife exposure to Cry34/35Ab1 protein is considered 

likely; however, the Cry34/35Ab1 toxicity data, as described in the 

Human Health Assessment (see section II(B)(1) of this Biopesticides 

Registration Action Document (BRAD)), indicate that there is no 

significant toxicity to rodents from testing at the maximum hazard 

dose. Therefore, no hazard to mammalian wildlife is anticipated, and 

data on wild mammal testing are not required. 

N/A 

850.1075 Freshwater 

Fish Testingh

There were no treatment-related deaths or clinical signs observed in 

rainbow trout fed 100 milligrams (mg) PS149B1 insecticidal crystal 

(IC) binary protein/kilogram (kg) diet for 8 days. Based on these 

observations, the 8-day LD50 for rainbow trout was >100 mg 

PS149B1 IC protein. No freshwater fish hazard is expected from 

commercial cultivation of Cry34/35Ab1 corn. 

Classification: Supplemental

457904-03 

850.1010 Aquatic 

Invertebrate 

Acute 

Toxicity Test 

(Daphnia 

magna)

h

A static-renewal, 48-hour limit test was performed on Daphnia 

magna. The test material was purified PS149B1 binary protein at a 

target concentration of 100 mg protein/Liter (L) water. No adverse 

effects were noted for the acute limit test. No hazards to daphnia are 

expected from incidental exposure to Cry34/35Ab1-containing corn 

pollen. 

Classification: Supplemental 

*Note for 2010: There is an update to this summary. See section 

II(C)(2)(b) (“Terms and Conditions of the Event DAS-59122-7 Corn 

Registrations (August 2005 – Present)”) of this BRAD. 

457904-04 

885.4280 Estuarine and 

Marine 

Animal 

Testing 

The estuarine and marine animal studies are not required for this 

product because Cry34/35Ab1 is not intended for direct application 

into the estuarine or marine environment and there is very low to no 

potential for exposure to Cry34/35Ab1 protein from field corn. 

N/A 

885.4300 Non-Target 

Plant Studies 

The active ingredient is an insect toxin (Bt endotoxin) that is nontoxic to aquatic and terrestrial plants. Consequently, non-target plant 

studies have been waived for this product. 

N/A 

885.4380 Honey Bee 

Larva Testingi

The median lethal concentration (LC50) for honey bee larvae and 

adult bee emergence was found to be >5.6 micrograms (μg) 

Cry34/35Ab1 protein (100x the concentration in pollen). Also, no 

behavioral or morphologic abnormalities were seen in bees exposed 

to 2 mg/larva Cry34/35Ab1 corn pollen. Therefore, no hazard to 

honey bee larvae and adult bee emergence is anticipated. 

Classification: Acceptable

453407-01 

 

h

 Reviewed in U.S. EPA (2005a) 

i

 Reviewed in U.S. EPA (2004a) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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Guideline 

Number Study Results

MRID 

Number

885.4340 Parasitic 

Hymenoptera 

Larva Testing 

The LC50 for parasitic Hymenoptera was determined to be >280 parts 

per million (ppm) Cry34/35Ab1 protein. No hazard to parasitic 

Hymenoptera is expected. Testing of a species more common to corn 

fields is recommended. 

Classification: Acceptable 

457904-05 

885.4340 Dietary 

Toxicity to 

Green 

Lacewing 

Larvae 

The LC50 for green lacewing larvae was determined to be >280 ppm 

Cry34/35Ab1 protein (10x field exposure). No hazard to green 

lacewing is expected. It is questionable whether the test species 

ingests the test material in feeding trails. Consequently, another 

species (e.g., minute pirate bug or predatory carabid) with greater 

likelihood of exposure should be tested. 

Classification: Acceptable 

457904-07 

885.4340 Lady Beetle 

Larval 

Feeding Study 

(Coleomegilla 

maculata) 

Significant growth inhibition (80% growth reduction in 7-day study) 

was observed in Coleomegilla maculata larvae feeding on 

Cry34Ab1/Cry35Ab1 diet, compared to larvae feeding on control 

diets. However, since toxic effects were not seen at the field dose 

level when Bt corn pollen- or Bt corn plant-fed aphids were used as 

diet, there is reasonable certainty that Cry34/35Ab1 corn will not 

adversely affect C. maculata. 

Classification: 

Acceptable (MRID Nos. 452422-10 and 452422-11) 

Supplemental (MRID No. 461239-12) because the study was 

terminated prior to pupation. 

452422-10j

452422-11j

461239-12 

885.4340 Collembola 

Chronic 

Dietary 

Toxicity 

Studyk

The LC50 for collembola was found to be >12.7 mg PS149B1 active 

ingredient/kg (10x field exposure). No adverse survival or 

reproductive effects were noted. No hazard to beneficial soilinhabiting decomposers is expected. 

Classification: Acceptable 

457904-06 

850.6200 Earthworm 

Toxicity 

Studyl

The LC50 for earthworm was found to be >76 mg Cry34/35Ab1 

protein/kg dry soil (20x field exposure). No hazard to earthworms is 

expected. 

Classification: Supplemental 

453602-01 

 

j

 Reviewed in U.S. EPA (2001b) 

k

 Reviewed in U.S. EPA (2005b) 

l

 Reviewed in U.S. EPA (2004a) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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Guideline 

Number Study Results

MRID 

Number

N/A Insecticidal 

Activity 

Spectrum 

Studym

The relative sensitivity of the test insects in the feeding bioassays 

suggests that larvae of coleopteran species are far more sensitive to 

the 14-kiloDalton (kDa) and 44-kDa proteins of PS149B1 than the 

lepidopteran or homopteran larval insects evaluated. Adult western 

corn rootworm (WCRW) were not sensitive to the delta-endotoxins, 

however. Rootworms (northern corn rootworm (NCRW), WCRW, 

and southern corn rootworm (SCRW)) were the most susceptible to 

the PS149B1 proteins. European corn borer (ECB) and corn 

earworm (CEW) demonstrated some inhibition of growth at higher 

concentrations of the test substance than the rootworm larvae. Black 

cutworm (BCW) was the least sensitive of the lepidopteran species 

tested. No activity was seen against the corn leaf aphid (CLA), a 

homopteran. Relative susceptibilities of the insect species to 

PS149B1, based upon the more sensitive measure of 50% growth 

inhibition (GI50), were as follows: (most susceptible) WCRW, 

NCRW, SCRW > ECB, CEW >> WCRW adult, CLA, BCW (least 

susceptible). 

Classification: Acceptable

 452422-04 

N/A Non-Target 

Organism 

Field Scale 

Risk 

Assessment 

Field monitoring results from two corn-growing seasons confirmed a 

lack of adverse effects on non-target invertebrates when exposed to 

Cry34/35Ab1 protein. These studies are supplemental to Tier I 

maximum hazard dose testing and are of inadequate statistical power 

for long-term effects determination. 

Classification: Supplemental 

461239-14 

885.5200 Soil Fate The GI50 value for SCRW fed a representative soil containing 

Cry34/35Ab1 protein was 3.2 days. This finding suggests that soilincorporated binary insecticidal protein degrades over time. 

Classification: Supplemental 

452422-14 

N/A Endangered 

Species 

Impact 

Assessment 

Pioneer Hi-Bred International, Incorporated conducted a hazard 

assessment, exposure assessment, and risk characterization to 

demonstrate that Cry34/35Ab1 does not pose risk to endangered 

coleoptera. The Agency’s independent assessment is in agreement 

with these conclusions. 

Classification: Acceptable 

461239-17 

 

m Reviewed in U.S. EPA (2001c) 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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Guideline 

Number Study Results

MRID 

Number

N/A Non-Target 

Invertebrate 

Ecological 

Risk 

Assessment 

Submitted data indicate that Cry34/35Ab1 corn will not pose 

unreasonable adverse effects to corn field flora and fauna and that 

minimal short-term accumulation of Cry34/35Ab1 protein in 

agricultural soil is expected. Further, no adverse effect to endangered 

and threatened species listed by the U.S. Fish and Wildlife Service is 

expected from the proposed Cry34/35Ab1 CRW resistant corn 

registration. 

Classification: Acceptable 

461239-13 

I. Non-Target Wildlife Study Summaries 

 a. Mammalian Wildlife

Mammalian wildlife exposure to Cry34/35Ab1 protein is considered likely; however, the mammalian 

toxicology information gathered to date on Bt Cry proteins does not show a hazard to wild or 

domesticated mammals. The Cry34/35Ab1 toxicity data, as described in the Human Health Assessment 

(see section II(B)(1) of this BRAD), indicate that there is no significant toxicity to rodents from acute 

oral testing at the maximum hazard dose. Therefore, no hazard to mammalian wildlife is anticipated, and 

data on wild mammal testing is not required. 

 b. Avian Species

Published data and studies on file at EPA show that consumption of Bt corn has no measurable 

deleterious effects on avian species. Nonetheless, the following broiler study was submitted to the 

Agency in support of the Cry34/35Ab1 corn registrations. 

 i. Broiler Study (Master Record Identification Number (MRID No.) 461239-11) 

Day-old commercial broiler chickens (Cobb x Cobb) were fed diets containing either transgenic corn 

line Event TC15344 (Cry34Ab1 or Cry35Ab1), a non-transgenic isoline corn (near isoline of Event 

TC15344), or commercial corn from one of two sources (A or B) for 42 days. A starter ration containing 

approximately 59% wet weight corn was fed ad libitum during days 1–20 (Phase I), and a 

grower/finisher ration containing approximately 63% wet weight corn was provided ad libitum during 

days 21–42 (Phase II) of the test period. No biologically significant differences in live weight, carcass 

weight, or feed intake efficiency were seen among treatment groups. These data suggest that the hybrid 

maize line containing Event TC15344 was nutritionally equivalent to the non-transgenic isoline and 

commercial maize sources and that long-term exposure to Cry34/35Ab1 corn is not expected to pose a 

hazard to avian wildlife. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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 c. Aquatic Species 

There is no evidence for sensitivity of aquatic (including endangered) species to anti-coleopteran Cry 

proteins. Aquatic species toxicity studies with coleopteran-active Cry proteins have not revealed hazard 

for fish or invertebrates exposed to either corn pollen or to bacterially expressed Cry protein. 

Furthermore, aquatic exposure from Bt crops is extremely small. 

 i. Freshwater Fish (MRID No. 457904-03) 

The Harmonized Testing Guidelines requirement for a static-renewal freshwater fish toxicity study is 

usually waived based on low to nonexistent exposure to Cry protein produced in corn. Exposure from 

corn pollen, if it does take place, will be of a very short duration and quantity and is not expected to 

have any detectable effect on freshwater fish. Nonetheless, an eight-day limit study was performed and 

submitted for review. This study is scientifically sound but was not performed according to OCSPP 

microbial testing guidelines. 

This limit test was conducted at a target concentration of 100 mg PS149B1 IC binary protein/kg diet, fed 

at 10% approximate fish wet body weight per day for 8 days, in a static-renewal system with water and 

test chambers replaced every 24 hours after feeding. A control group was fed unamended diet only. A 

set of 30 fish (3 replicates, n = 10) were tested for each of the control (diet only) and treatment (diet with 

added PS149B1 IC binary protein) groups. Fish were observed for mortality and sublethal effects every 

24 hours during the 8-day test period. Feed consumption ranged from 70–90% (as reported) during the 

20-minute feeding period. No fish mortality or sublethal effects were reported in either the treatment or 

control groups. Based on these observations, the 8-day LD50 for rainbow trout was >100 mg PS149B1 

IC protein/kg diet fed at 10% approximate fish wet body weight/day. No statistical test was performed 

because it was a single dose (limit) test. Biological loading exceeded guideline parameters of 0.5 grams 

(g) fish/L. 

In view of the lack of demonstrated toxicity to rainbow trout and minimal aquatic exposure, no 

freshwater fish hazard is expected from commercial cultivation of Cry34/35Ab1 corn. 

 ii. Freshwater Aquatic Invertebrates (MRID No. 457904-04) 

This study was conducted according to procedures specified in Series 72 of EPA’s Registration 

Guidelines, Pesticide Assessment Guidelines, FIFRA Subdivision E, Hazard Evaluation for acute 

toxicity testing of pesticidal substances to freshwater aquatic invertebrates. 

This static-renewal limit test was performed on Daphnia magna, a freshwater invertebrate. The test 

material consisted of purified Bacillus thuringiensis PS149B1 crystal binary protein added to water at a 

target concentration of 100 mg PS149B1 insecticidal crystal protein (ICP)/L. The study was 

procedurally sound, and no treatment mortality or behavior changes were reported between the dosed 

and control replicates during the 48-hour exposure period. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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The October 2000 and August 2002 SAP reports recommended that non-target testing be focused on 

species exposed to the crop being registered (i.e., beneficial insects found in corn fields). Nevertheless, 

acute aquatic invertebrate species testing was performed, and no substantial aquatic exposure to 

Cry34/35Ab1 protein contained within corn plant tissue is expected. Therefore, no hazard from the 

registered uses of Cry34/35Ab1-containing corn is anticipated. 

*Note for 2010: There is an update to this summary. See section II(C)(2)(b) (“Terms and Conditions of 

the Event DAS-59122-7 Corn Registrations (August 2005 – Present)”) of this BRAD. 

 

iii. Estuarine and Marine Animals

The estuarine and marine animal study was not required for this product because of no or very low 

potential for exposure to the Cry34/35Ab1 protein in these environments. 

d. Terrestrial and Aquatic Plants

Plant toxicity studies were waived for this product because the active ingredient is an insect toxin (Bt

endotoxin), and we are unaware of any demonstrated toxicity to plants. 

 

 e. Non-Target Insect Testing

i. Effects on Honey Bee Larvae (MRID No. 453407-01)

An acceptable study was conducted based on OCSPP Harmonized Test Guideline 885.4380 (Honey Bee 

Testing, Tier I). This study was conducted in accordance with Good Laboratory Practice Standards (40 

CFR Part 160) with certain exceptions that did not affect the integrity of the test. 

Testing was conducted with three- to five-day-old honey bee (Apis mellifera) larvae. Individual larvae 

were dosed with one of the following treatments: 2 mg pollen collected from non-genetically modified 

maize; 2 mg (0.056 μg PS149B1 ICP) pollen collected from corn plants expressing Bt strain PS149B1 

ICP; 5.6 μg bacterially produced PS149B1 binary ICP (100x protein concentration present in 2 mg 

PS149B1 pollen); 3.2 μg 14-kDa protein; 2.4 μg 44-kDa protein; 20 μg potassium arsenate (positive 

control); or untreated cell (negative control). Larval survival was evaluated 6 and 12 days after 

treatment, and adult emergence was evaluated 26 days after treatment. There were no statistical 

differences (p = 0.05) in larval mortality between those fed PS149B1 pollen, unmodified pollen, or 

bacterially produced PS149B1 binary ICP. Based on results presented in this study, it can be concluded 

that honey bee development and survival are not affected by exposure to the Cry34/35Ab1 corn pollen. 

There was 92.5% mortality among larvae treated with potassium arsenate, the positive control, which 

indicates that bees were adequately exposed to the treatments. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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 ii. Parasitic Hymenoptera Testing (MRID No. 457904-05) 

The study was conducted in accordance with Good Laboratory Practice Standards (40 CFR Part 160) 

with certain exceptions that did not affect the integrity of the test. This study was conducted based on 

OCSPP Harmonized Test Guideline 885.4340 (Non-Target Insect Testing, Tier I). 

A dietary toxicity study was conducted to evaluate the effect that Bt strain PS149B1 binary protein 

(purity equal to 37% 44-kDa protein and 54% 14-kDa protein) has on parasitic Hymenoptera (Nasonia 

vitripennis). The wasp test diet consisted of sugar water mixed with Cry protein at a rate of 280 ppm 

(combined total of 120 ppm 44-kDa protein and 160 ppm 14-kDa protein) PS149B1 protein, which is 

approximately equivalent to 10x the maximum protein concentration present in PS149B1 corn pollen. 

Based on this test, the LC50 for adult parasitic Hymenoptera exposed to dietary Cry PS149B1 protein 

was determined to be >280 ppm. It should also be noted that parasitic Hymenoptera do not feed directly 

on corn plant tissues, including pollen; therefore, minimal exposure of parasitic Hymenoptera to Cry 

protein is expected. As a result of these findings, no hazard to N. vitripennis is expected from exposure 

to Cry34/35Ab1 corn. 

The N. vitripennis study was found acceptable by the Agency. However, the August 27, 2002, SAP 

concluded that the parasitic Hymenoptera (N. vitripennis) is not an appropriate test species for 

coleopteran-active Bt corn because the dipteran parasitoid is not found in corn fields. A more 

appropriate parasitoid, that occurs in corn fields (e.g., Tricogramma spp. or Macrocentrus grandii), 

should be considered for future studies. 

 iii. Green Lacewing Larva Testing (MRID No. 457904-07) 

An acceptable study was conducted in accordance with Good Laboratory Practice Standards (40 CFR 

Part 160) with certain exceptions that did not affect the integrity of the test. This study was conducted 

based on OCSPP Harmonized Test Guideline 885.4340 (Non-Target Insect Testing, Tier I). 

Green lacewing larvae were fed PS149B1 insecticidal crystal protein in a moth egg (Sitotroga spp.) and 

water meal diet at a rate of 280 ppm, which is approximately equivalent to 10x the maximum protein 

concentration in plant tissue. There was 28% mortality in the negative control group on day 10. 

Compared to the negative control, at day 10, there was no significant increase in green lacewing larval 

mortality when fed 10x (280 ppm) the maximum PS149B1 protein concentration found in plant tissue. 

The data show that the LC50 for green lacewing larvae exposed to PS149B1 in diet was >280 ppm. 

Based on these results, it is not expected that the green lacewing will be adversely affected when 

exposed to Cry34/35Ab1 corn in the field. 

The August 27, 2002, SAP concluded that green lacewing (Chrysoperla carnea) is not an appropriate 

test species for several reasons. Green lacewing are difficult to test in the laboratory because of a high 

rate of mortality. For example, in the study outlined above (MRID No. 457904-07), the test was 

terminated after 10 days because there was >28% mortality in the negative control. In addition, it is 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

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questionable whether green lacewings ingest the protein on coated moth eggs, since green lacewing have 

piercing-sucking mouthparts and do not consume the external surface of eggs. For these reasons, the 

applicants should conduct a laboratory insect toxicity test on an alternate organism, such as the minute 

pirate bug (Orius insidiosus). This egg predator, which feeds on pollen when prey is scarce, is typically 

found in corn fields. An appropriate evaluation would involve feeding O. insidiosus pollen, a natural 

food source, and purified protein in diet in two separate diet bioassays. The purified protein assay would 

be useful in determining toxicity at the maximum hazard dose, while the pollen assay would provide 

information on the potential effect of an actual exposure scenario. As noted in Table 2, the Agency has 

requested that the applicants submit this study as a condition of registration. 

*Note for 2010: There is an update to this summary. See section II(C)(2)(b) (“Terms and Conditions of 

the Event DAS-59122-7 Corn Registrations (August 2005 – Present)”) of this BRAD. 

 iv. Lady Beetle Testing

The Cry34/35Ab1 protein specifically targets coleopteran (beetle) insects. Consequently, particular 

attention should be paid to the potential effects that Cry34/35Ab1 protein may have on lady beetles, 

which are in the family Coccinellidae. 

 MRID No. 452422-10 – In a pure Bt binary crystal protein adult lady beetle feeding study, no 

mortality or abnormal clinical signs were observed in treatment or control groups on Day 0 at 3/4 

and 1 3/4 hours after test initiation. At test termination (Day 11), there was 22% (33 of 150) 

mortality in the negative control group. Beetles in the control group appeared normal, except for 

five lethargic individuals. The 280 μg active ingredient/milliliter (mL) treatment group resulted 

in 13% (20 of 150) mortality at test termination. All beetles in the treatment group appeared 

normal except for two immobile beetles. There was a lower mortality rate and fewer clinical 

signs of abnormality in the 280μg active ingredient/mL treatment group then the control group. 

Mortality and abnormal behavior was not treatment related. The dietary LC50 value for ladybird 

beetles exposed to PS149B1 ICP was determined to be greater than 280 μg active ingredient/mL, 

which was the highest concentration tested. 

 MRID No. 452422-11 – A tri-trophic interaction study between field corn expressing PS149B1, 

corn leaf aphids (Rhopalosiphum maidis), and lady beetle (C. maculata), in larval and adult 

stages, was also submitted and reviewed. Field corn plants expressing the PS149B1 protein 

Event TC5638 and non-transgenic isolines were planted in the greenhouse and infested with 

naturally occurring aphid populations. Aphid colonies were allowed to establish on each plant 

before being removed and fed to lady beetles. One to three aphids were fed to individual lady 

beetle adults and larvae in 7 mL scintillation vials daily. Mortality and time between molts was 

monitored daily until day 10. No significant difference in adult lady beetle mortality or weight 

was found between lady beetles feeding on PS149B1-intoxicated aphid and aphids that fed on 

non-transgenic corn. Feeding on PS149B1-intoxicated aphids also did not affect the length of 

time between larval molts. 

 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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 MRID No. 461239-12 – Two diet assays were conducted: (1) a Tier I assay in which lady beetle 

larvae (C. maculata DeGeer) were fed purified Cry34/35Ab1 protein mixed with artificial diet, 

and (2) a Tier II assay in which larvae were exposed to a diet consisting of 50% inbred 

Cry34/35Ab1 pollen from Events E4497.45.2.16, E4497.59.1.22 (renamed as DAS-59122-7, 

which is the event being registered), E4497.45.2.14, and E4497.71.1.33 corn pollen and 50% 

ground corn earworm eggs. These assays are described in more detail below.

Tier I Assay – Lady beetle larvae (C. maculata) were fed an artificial diet containing purified 

Cry34/35Ab1 protein at a concentration equal to approximately 10 times the expected 

environmental exposure concentration through pollen. Cry34Ab1 protein was incorporated at 

900 ppm and Cry35Ab1 protein at 1 ppm (ratio based on Cry34 and Cry35 expression in Event 

DAS-59122-7 corn pollen). The purified proteins were suspended in deionized water and mixed 

with commercially available lady beetle diet. Neonate larvae were placed in individual bioassay 

wells and allowed to feed for 7 days. Larvae were then assessed for mortality and weight. 

There was no significant difference in mortality among C. maculata larvae fed for 

seven days on one of two control diets, which did not contain active protein, and the 

treatment containing purified Cry34/35Ab1 toxin. However, significant growth inhibition 

(80% growth reduction) was observed in C. maculata larvae feeding on the Cry34/35Ab1 diet 

compared to larvae feeding on the control diets. 

Tier II Assay – Corn pollen may comprise up to 50% of a lady beetle larva’s diet during 

corn anthesis. Consequently, a study was conducted to evaluate the effect that Event 

Cry34/35Ab1 corn pollen may have on lady beetle larvae. Pollen from four different events, 

which were tested as four different treatments, was fed to lady beetle larvae in a diet 

consisting of 50% Cry34/35Ab1 corn pollen and 50% ground corn earworm eggs. First 

neonate larvae were placed in individual bioassay wells and allowed to feed ad libitum 

throughout the 14-day larval growth period. 

There was no significant difference in mortality, development, or adult weight among 

C. maculata larvae fed a control diet, which did not contain active protein, and 

treatments containing Cry34/35Ab1 pollen. Among the four events tested, protein expression 

for Cry34Ab1 proteins ranged from 116 to 175 nanograms per milligram (ng/mg). Among 

reported events (values were not provided for two of the four events because they were not 

quantifiable or exceeded the upper limit of detection), Cry35Ab1 protein expression levels 

ranged from 75.5 to 83.5 ng/mg. For the registered event (DAS-59122-7), Cry34Ab1 protein 

expression was 117 ng/mg; Cry35Ab1 expression was not determined because one or more 

of the entries were not quantifiable (additional information on Cry34Ab1 and Cry35Ab1 

protein expression levels may be found in section II(A)(1)(a) of this BRAD). 

Conclusions – Submitted data show that Cry34/35Ab1 protein is toxic to C. maculata at 

dose levels that exceed field exposure (Tier I Assay). However, since toxic effects were not 

seen at the field dose level (Tier II Assay) when C. maculata larvae were fed natural prey and 
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pollen, there is reasonable certainty that Cry34/35Ab1 corn will not adversely affect C. 

maculata. 

 Since the Cry34/35Ab1 protein is toxic to Coleopteran species, evaluations of other 

 appropriate non-target beetle species should be submitted as a component of this risk 

 assessment. The 2002 SAP suggested that Carabids (ground beetles) would be suitable for 

 PIP Tier I testing because beetles found within this family play important ecological and 

 economic roles within agroecosystems, including corn fields. As noted in Table 2, the 

 Agency is requesting that the applicants submit this study as a condition of registration. 

 v. Collembola Feeding Study (MRID No. 457904-06) 

This study was conducted in accordance with Good Laboratory Practice Standards (40 CFR Part 160) 

with certain exceptions that did not affect the integrity of the test. This study was conducted based on 

OCSPP Harmonized Test Guideline 885.4340 (Non-Target Insect Testing, Tier I). 

Juvenile collembola (Folsomia candida) were fed diets consisting of purified PS149B1 protein (purity = 

54% 14-kDa protein and 37% 44-kDa protein) mixed with dry granulated Brewer’s yeast at a single 

treatment level of 12.7 mg PS149B1 active ingredient/kg. Fresh diet was provided to test organisms 

every third day. On days 0 and 28, mortality and observations of sublethal effects on surviving 

collembola were recorded. 

Results of this study show no adverse effects on survival and reproduction of collembola exposed to 

PS149B1 insecticidal crystal protein at 10x concentrations found in transgenic corn plants. It is noted 

that the primary route of collembola exposure to Cry34/35Ab1 protein in the field is from decaying root 

tissue, which is expressed in corn roots at a range of 3–66 micrograms per gram (μg/g) and is 

significantly lower than the treatment level used in this test. 

This study adequately addresses potential concerns for Cry34/35Ab1 protein to collembola (F. candida), 

a representative of beneficial soil insect species. The results of this study demonstrate that Cry34/35Ab1 

protein found in transgenic corn poses no hazard to soil-inhabiting collembola species, and by inference, 

to other beneficial non-coleopteran soil insects. It is noted that the October 2000 Scientific Advisory 

Panel stated that it is unnecessary to conduct non-target testing on invertebrate orders that are not known 

to be affected by the Cry protein in question. 

 vi. Earthworm Toxicity Testing 

Earthworm feeding studies submitted to the Agency demonstrate that Cry proteins are not toxic to 

earthworms at the worst-case environmental concentration. Although some public comments have 

questioned whether earthworm test organisms actually ingested the soil incorporated Bt Cry proteins, 

recently published data show that earthworms do ingest and excrete soil-incorporated Bt Cry proteins. 
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 MRID No. 453602-01 – This study complied with Good Laboratory Practice Standards (40 CFR 

Part 160) and OECD Principles of Good Laboratory Practice with certain exceptions that did not 

affect the integrity of the test. The testing was conducted based on OCSPP Harmonized Test 

Guideline 850.6200 (Earthworm Subchronic Toxicity Test) and OECD Guideline 207. This 

study meets current testing requirements for assessing risks to earthworms from plantincorporated protectants derived from Bt. 

 The 14-day LC50 for earthworms exposed to PS149B1 ICP in an artificial soil substrate was 

determined to be greater than 76 mg active ingredient/kg dry soil (the highest concentration 

tested), or greater than 20 times the expected field concentration. Earthworm mortality and 

changes in average body weights were not statistically different (p >0.05) among the controls 

and protein-amended soils. The LC50 value for earthworms exposed to chloroacetamide, the 

positive control, was approximately 19.4 mg active ingredient/kg dry soil. This finding was 

consistent with historical results, and further confirmed the adequacy and consistency of the 

protocol used in the definitive test. The submitted data suggest that earthworms will not be 

adversely affected by Cry34/35Ab1 corn plants. 

 vii. Insecticidal Activity Spectrum Study (MRID No. 452422-04)

The relative sensitivity of the test insects in the feeding bioassays suggested that larvae of coleopteran 

species are far more sensitive to the 14-kDa and 44-kDa proteins of PS149B1 than the lepidopteran or 

homopteran larval insects evaluated. Adult WCRW were not sensitive to the delta-endotoxins, however. 

Rootworms (NCRW, WCRW and SCRW) were the most susceptible to the PS149B1 proteins. European 

corn borer and CEW demonstrated some inhibition of growth at higher concentrations of the test 

substance than the rootworm larvae. Black cutworm was the least sensitive of the lepidopteran species 

tested. No activity was seen against the CLA, a homopteran. Relative susceptibilities of the insect 

species to PS149B1, based upon the more sensitive measure of GI50, were as follows: (most susceptible) 

WCRW, NCRW, SCRW > ECB, CEW >> WCRW adult, CLA, BCW (least susceptible). 

 viii. Field Evaluation of Cry34/35Ab1 Corn Exposure on Non-Target 

 Invertebrates (MRID No. 461239-14) 

This Tier IV field experiment was submitted as a supplement to the Tier I maximum hazard dose 

findings presented above. 

Methods: 

The field study was conducted over two growing seasons (2001–2002) at two locations in the central 

Corn Belt (York, Nebraska and Johnston, Iowa). The experimental design was a randomized complete 

block design with two replicates for each of five treatments. Treatments were the following: (1) 

Cry34/35Ab1 maize hybrid TC5639; (2) Cry34/35Ab1 maize hybrid TC15344; (3) non-transgenic 

maize hybrid with a planting time application of tefluthrin (Force® 3G); (4) non-transgenic maize 

hybrid sprayed with an application of bifenthrin (Capture® 2EC) at the V10 and R2 corn growth stages 

to control first and second generation CRW adults; and (5) non-transgenic maize hybrid with no corn 
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rootworm control measures taken. Treatment plots covered approximately 2,800 square feet (70 feet x 

40 feet) and were separated by 18 feet of non-transgenic corn. 

Arthropod abundance was evaluated in soil, on the soil surface, and at the crop canopy level. Methods 

used were the following: (1) visual observations; (2) soil sampling with Berlese-Tullgren funnels for 

invertebrate extraction; (3) soil surface collection using pitfall traps; and (4) canopy level sampling 

using yellow sticky traps. Samples were taken at specified intervals throughout the season, and four 

samples were collected within each plot for each collection method at each sampling interval. 

Although data were collected on individual invertebrate families, some families were grouped for 

statistical analyses. At the community level, groupings were based on a family’s abundance in corn 

fields, as well as their function within the agricultural ecosystem. Representatives from several 

functional groups (decomposers, herbivores, predators, parasitoids, and generalist feeders) served as 

indicator species. 

Two analyses were applied. Principal response curves (Van den Brink and Ter Braak 1999) were used to 

investigate and describe treatment effects at the community level, while analysis of variance (ANOVA) 

was performed for each key indicator species and taxa group to detect invertebrate abundance among 

treatments. 

Results:

Neither Cry34/35Ab1 event showed signs of adverse effects on non-target arthropods at the community 

level or in key taxa. The two primary effects observed were an overall abundance decrease at the 50% 

pollen shed sampling date in the foliar insecticide-treated plots compared to the untreated control plots, 

and an increase in collembola abundance at the R2 and R5 sampling stages of the foliar insecticidetreated plots compared to the untreated control plots. It is noted that the two Cry34/35Ab1 events 

presented in this study are not planned for commercial release; however, they represent equal or greater 

Cry34/35Ab1 expression levels when compared to commercial event DAS-59122-7. 

Conclusions:

According to submitted data, Cry34/35Ab1 corn does not adversely impact the abundance of non-target 

invertebrates found in corn fields. The utility of these data, however, is limited because the plot size (70 

feet × 40 feet) was too small, and the experiment included only two replicates at each of two locations. 

In addition, only four samples, for each collection method, were taken from each plot. The August 2002 

SAP concluded that field experiments must be appropriately designed (larger fields, more replicates, 

more samples) to provide a measure of ecological impacts and, further, that a two-year field study would 

not be sufficient to determine if Cry34/35Ab1 corn will have long-term impact on non-target 

invertebrates. However, since the endpoint for field census studies has not been identified, it is difficult 

to determine the appropriate field size, number of replicates, and number of samples needed per plot. 

The data provided in this report suggest that corn events containing the Cry34/35Ab1 protein did not 

adversely affect non-target arthropods. Supplemental studies, employing larger plot sizes, more 

replicates, and more samples per plot, are recommended for further verification of a long range no 
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adverse effect finding. In response to these concerns, as requested by the Agency in Table 2, the 

applicants are preparing additional field census data that will be submitted to the Agency as a condition 

of registration. 

Although the experimental design of the field assays needs improvement, the submitted field census data 

are useful for short-term hazard assessment and as supplementary information that supports the nohazard trend seen in the maximum hazard dose single species laboratory testing described above. It is an 

accepted practice in the Office of Pesticide Programs to use the trends seen in several supplemental 

studies for hazard assessment when a perfect study is not available. 

*Note for 2010: There is an update to this summary. See section II(C)(2)(b) (“Terms and Conditions of 

the Event DAS-59122-7 Corn Registrations (August 2005 – Present)”) of this BRAD. 

II. Soil Fate (MRID No. 452422-14)

Soil organisms may be exposed to Cry34/35Ab1 protein through contact with corn plant roots (by direct 

feeding), corn plant root exudates, incorporation of aboveground plant tissues into soil following 

harvest, or by soil-deposited pollen. Some evidence suggests that acidic soils (pH 5.6), and those which 

are high in clays and humic acids, are more likely to bind Cry protein, and thus decrease the rate of 

protein degradation by soil microorganisms. It is noted, however, that the pH factor should not 

contribute to protein binding in corn fields, since maize is generally grown on neutral soils (above pH 

5.6). Despite evidence that soils high in clay and humic acids may bind Cry proteins, and thus interfere 

with the microbial degradation processes, the weight-of-evidence suggests that Cry proteins do not 

accumulate in soil to arthropod-toxic levels. Nonetheless, the Agency requires soil fate evaluations for 

each new insect-protected crop. 

This study was conducted in accordance with Good Laboratory Practice Standards (40 CFR Part 160). 

Methods: 

An insect bioassay was conducted to measure the rate of purified PS149B1 delta-endotoxin degradation 

in a representative silt loam field soil. The southern corn rootworm (SCRW, Diabrotica 

undecimpunctata subsp. howardi) was selected as the test species for this bioassay due to its 

susceptibility to PS149B1 insecticidal proteins. An aqueous mixture of the test material, composed of 

14-kDa and 44-kDa binary insecticidal proteins, was pipetted onto 1 gram (dry weight) soil at a 

concentration of 5 mg per protein per gram of soil. The soil-protein mixture was transferred to 50 mL 

perforated vials (to allow gas exchange) and incubated at approximately ~25 ̊C for 0, 1, 3, 7, 14, or 28 

days. Four vials were prepared for each incubation period. Aliquots (50 microliters (μL)) of these 

dilutions were applied to the surface of small wells (1.5 square centimeters in diameter) containing 500 

μL of artificial insect diet. Soil-agar and agar-only negative controls were also included in bioassay 

trays. Following treatment application, single neonate rootworm larvae were introduced into each well 

and housed for six days at ~27 ̊C. To reach the artificial diet, larvae had to eat through the soil-protein 

surface layer and thus consume the insecticidal proteins. Fourteen to 16 larvae were tested at each 
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dilution level, for a total of 94–96 larvae per incubation interval. Larvae mortality and weights were 

collected for all treatments.

Results: 

Larval mortality was negligible and did not correlate with insecticidal protein content. Consequently, 

protein degradation at each incubation interval was defined as the amount of insecticidal protein 

required to reduce larval growth by 50% (GI50). GI50s were calculated from treatment averages for each 

soil-protein incubation interval, along with their 95% upper and lower confidence limits. Results 

indicate that larval growth inhibition was inversely correlated with soil-protein incubation periods, 

suggesting that protein degradation increased with time. Regression of the GI50s with time (0 to 7 days) 

showed a degradation half-life of 3.2 days for the insecticidal protein. The 14- and 28-day GI50s did not 

fit the first-order decay model and, consequently, were excluded from half-life calculations. 

Conclusions: 

Based on these results, it may be concluded that purified PS149B1 insecticidal proteins degrade rapidly 

in silt loam soil; however, persistence and accumulation at low levels is not addressed. Silt loam soil is 

just one of many soil classes used for corn production in the United States. A more useful study would 

evaluate protein degradation/accumulation in a range of soil types, including those with high clay and 

humic acid content, due to their known binding affinity for proteins. 

In addition, this study utilized field soil spiked with purified insecticidal protein. This approach is useful 

because dose responses can be easily quantified. However, the degradation and accumulation of Cry 

proteins found within decaying plant tissue may behave differently than proteins in artificially spiked 

soil. Thus, the relevance of these study results is unclear other than to show that degradation in soil does 

take place. 

To account for the above concerns, it is recommended that additional studies be conducted to evaluate 

insecticidal protein degradation, accumulation, and persistence in a variety of soil types, including those 

high in clay and humic acids into which all non-harvested corn plant material is incorporated. Sampling 

should be conducted at the end of three years in a field sown with continuous Cry34/35Ab1 corn. Soil 

should be monitored for a minimum of one growing season after harvest and continued until the 

Cry34/35Ab1 protein can no longer be detected. As noted in Table 2, the Agency has requested that the 

applicants submit these studies as a condition of registration. 

*Note for 2010: There is an update to this summary. See section II(C)(2)(b) (“Terms and Conditions of 

the Event DAS-59122-7 Corn Registrations (August 2005 – Present)”) of this BRAD. 

III. Effects on Soil Microorganisms

Numerous published studies indicate that exposure to Cry protein produced in Bt PIP crop plants does 

not adversely affect soil microorganisms (Sanvido et al. 2007; Oliveira et al. 2008). In addition, Bt toxin 

released from root exudates and biomass of Bt corn has no apparent effect on earthworms, nematodes, 

protozoa, bacteria, and fungi in soil (Saxena and Stotzky 2001). Other research findings conclude no Bt-
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related risks have evolved from the decomposition of Bt-corn leaves for the meso- and macrofauna soil 

community (Hönemann et al. 2008). Although a minimal transient increase and shift in microbial 

populations may result from the presence of transgenic plant tissue in soil, no adverse effects have been 

attributed to the Cry protein. 

In addition, there are several ongoing U.S. Department of Agriculture and EPA Office of Research and 

Development funded research projects evaluating the effects of Bt crops on soil microbial flora. If 

adverse effects are seen from this or any other research, the Agency will take appropriate action to 

mitigate potential risks. 

With regard to the impact of genetically engineered crops on soil, it is important to note that agricultural 

practices themselves cause large changes in soil and soil microbial composition. Furthermore, factors 

such as variations in seasons and weather, plant growth stage, and plant varieties, independent of being 

genetically engineered, are also responsible for significant shifts in soil microbial communities. To date, 

most studies with genetically engineered crops have shown minor or no effects on soil microbes beyond 

the variation caused by the factors listed above. 

IV. Horizontal Transfer of Transgenes from Bt Crops to Soil Organisms

EPA has evaluated the potential for horizontal gene transfer (HGT) from Bt crops to soil organisms and 

has considered possible risk implications if such a transfer were to occur. Genes that have been 

engineered into Bt crops are mostly found in, or have their origin in, soil-inhabiting bacteria. Soil is also 

the habitat of anthrax, tetanus, and botulinum toxin-producing bacteria. Transfer of these genes and/or 

toxins to other microorganisms or plants has not been detected. Furthermore, several experiments 

(published in scientific journals), that were conducted to assess the likelihood of HGT, have been unable 

to detect gene transfer under typical environmental conditions. Horizontal gene transfer to soil 

organisms has only been detected with very promiscuous microbes under laboratory conditions designed 

to favor transfer. 

As a result of these findings, which suggest that HGT is at most an artificial event, and the fact that the 

Bt toxins engineered into Cry34/35Ab1 corn are derived from soil-inhabiting bacteria, EPA has 

concluded that there is a low probability of risk from HGT of transgenes found in Cry34/35Ab1-

producing corn. 

V. Gene Flow and Weediness Potential

The movement of transgenes from the host plant into weeds has been a significant concern for the 

Agency due to the possibility of novel exposures to the pesticidal substance. The Agency has determined 

that there is no significant risk of gene capture and expression of Cry34/35Ab1 protein by wild or weedy 

relatives of corn in the U.S., its possessions, and/or its territories. In addition, the Animal and Plant 

Health Inspection Service (APHIS) of the United States Department of Agriculture (USDA) has made 

this same determination under its statutory authority under the Plant Pest Act. 
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Under FIFRA, the Agency has reviewed the potential for gene capture and expression of Bt endotoxins 

by wild or weedy relatives of corn, cotton, and potatoes in the U.S., its possessions, and/or its territories. 

Bt plant-incorporated protectants that have been registered to date have been expressed in agronomic 

plant species that, for the most part, do not have a reasonable possibility of passing their traits to wild 

native plants. Feral species related to these crops, as found within the United States, cannot be pollinated 

by these crops (corn, potato, and cotton) due to differences in chromosome number, phenology (i.e., 

periodicity or timing of events within an organism’s life cycle as related to climate, e.g., flowering time) 

and habitat. The only exception, however, is the possibility of gene transfer from Bt cotton to wild or 

feral cotton relatives in Hawaii, Florida, and the Caribbean. 

The Scientific Advisory Panel meeting held on October 18–20, 2000, further discussed the matter of 

gene flow and offered some issues for consideration in this matter. The panel agreed that the potential 

for gene transfer between corn (maize) and any receptive plants within the U.S., its possessions, and/or 

its territories was of limited probability and nearly risk free. 

Concern over the potential for species related to maize (Zea mays ssp. mays), such as Tripsacum species 

and the teosintes, as potential recipients of gene flow from genetically modified Zea mays indicated a 

need for review of what is known related to gene flow potential of Z. mays. Some Zea species, such as 

the teosintes, are known to be interfertile with maize and are discussed as potential recipients of pollendirected gene flow from maize. This issue is of particular concern based upon the increased planting of 

genetically modified maize. Therefore, the Agency conducted a reevaluation in early 2000, the results of 

which are reported here. 

 a. Zea mays ssp. mays - Maize - General Biology 

Zea mays is a wind-pollinated, monoecious, annual species with imperfect flowers. This means that 

spatially separate tassels (male flowers) and silks (female flowers) are found on the same plant, a feature 

that limits inbreeding. A large variety of types are known to exist (e.g., dent, flint, flour, pop, sweet) and 

have been selected for specific seed characteristics through standard breeding techniques. Maize 

cultivars and landraces are known to be diploid (2n = 20) and interfertile to a large degree. Nonetheless, 

some evidence for genetic incompatibility exists within the species (e.g., popcorn x dent crosses; 

Mexican maize landraces x Chalco teosinte). Zea mays has been domesticated for its current use by 

selection of key agronomic characters, such as a non-shattering rachis, grain yield, and resistance to 

pests. The origin of corn is thought to be in Mexico or Central America, based largely on archaeological 

evidence of early cob-like maize in indigenous cultures approximately 7,200 years ago. 

A recent study has indicated that cross-pollination of commercial maize cultivars at 100 feet downwind 

from the source of genetically modified maize was 1%, and this proportion declined exponentially to 

0.1% at 130 feet and further declined to 0.03% at 160 feet. At 1,000 feet, the farthest distance measured, 

no cross-pollination was detected (Jemison and Vayda 2000). For production of Foundation Seed, a 

distance of 660 feet has been generally required to mitigate outcrossing between different genotypes. 

The relatively large size of corn pollen and its short viability period under most conditions reduce long 

distance transfer for purposes of outcrossing (Schoper, personal communication,1999). Under conditions 
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of high temperature or low humidity, corn pollen may only survive for a matter of minutes. Under more 

favorable conditions in the field or with controlled handling in the laboratory, pollen life may be 

extended to several hours. 

 b. Tripsacum species - Gama Grass - General Biology

Close relatives of corn or maize are found in the genus Tripsacum. Sixteen species of Tripsacum are 

known worldwide and generally recognized by taxonomists and agrostologists; most of the 16 different 

Tripsacum species recognized are native to Mexico, Central America, and South America, but three 

occur within the U.S. Hitchcock (1971) reports the presence of three species of Tripsacum in the 

continental United States: Tripsacum dactyloides, Tripsacum floridanum, and Tripsacum lanceolatum. 

Of these, T. dactyloides, Eastern Gama Grass, is the only species of widespread occurrence and of any 

agricultural importance. It is commonly grown as a forage grass and has been the subject of some 

agronomic improvement (i.e., selection and classical breeding). T. floridanum is known from southern 

Florida, and T. lanceolatum is present in the Mule Mountains of Arizona and possibly southern New 

Mexico. 

For the species occurring in the United States, T. floridanum has a diploid chromosome number of 2n = 

36 and is native to Southern Florida; T. dactyloides includes 2n = 36 forms, which are native to the 

central and western U.S., and 2n = 72 forms, which extend along the Eastern seaboard and along the 

Gulf Coast from Florida to Texas but which have also been found in Illinois and Kansas; these latter 

forms may represent tetraploids (x = 9 or 18)(Lambert, personal communication, 1999); and T.

lanceolatum (2n = 72), which occurs in the southwestern U.S. Tripsacum differs from corn in many 

respects, including chromosome number (T. dactyloides n = 18; Z. mays n = 10). Many species of 

Tripsacum can cross with Zea, or at least some accessions of each species can cross, but only with 

difficulty and the resulting hybrids are primarily male and female sterile (Duvick, personal 

communication, 1999; Galinat 1988; Wilkes 1967). Tripsacum/maize hybrids have not been observed in 

the field but have been accomplished in the laboratory using special techniques under highly controlled 

conditions. 

Eastern Gama Grass is considered by some to be an ancestor of Z. mays or cultivated maize 

(Mangelsdorf 1947), while others dispute this (Galinat 1983; Iltis 1983; Beadle 1980), based largely on 

the disparity in chromosome number between the two species (maize n = 10; Gama Grass x = 9 or 18, 

with diploid, triploid, and tetraploid races existing; 2n = 36 or 72), as well as radically different 

phenotypic appearance. Albeit with some difficulty, hybrids between the two species have been made 

(Mangelsdorf and Reeves 1939; DeWald, personal communication,1999). In most cases, these progeny 

have been sterile or viable only by culturing with in vitro “embryo rescue” techniques. 

Even though some Tripsacum species occur in areas where maize is cultivated, gene introgression from 

maize under natural conditions is highly unlikely, if not impossible (Beadle 1980). Hybrids of 

Tripsacum species with Z. mays are difficult to obtain outside of the controlled conditions of laboratory 

and greenhouse. Seed obtained from such crosses are often sterile or progeny have greatly reduced 

fertility. Approximately 10–20% of maize-Tripsacum hybrids will set seed when backcrossed to maize, 
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and none are able to withstand even the mildest winters. The only known case of a naturally occurring 

Zea - Tripsacum hybrid is a species native to Guatemala known as Tripsacum andersonii. It is 100% 

male and nearly 99% female sterile and is thought to have arisen from gene flow to teosinte, but the 

lineage is uncertain (Doebley, personal communication, 2000). Z. mays is not known to harbor 

properties that indicate it has weedy potential and, other than occasional volunteer plants in the previous 

season’s corn field, maize is not considered as a weed in the U.S. 

In a telephone conversation with Dr. Chester “Chet” DeWald (Agricultural Research Service of the 

USDA; Woodward, Oklahoma), a geneticist working on improvement of grasses, he stated that 

relatively few accessions of T. dactyloides will cross with maize, and the majority of progeny are not 

fertile or viable even in those that do. In controlled crosses, if the female parent is maize, there is a 

greater likelihood of obtaining viable seed. When these hybrids have been backcrossed to maize in 

attempts to introgress Tripsacum genes for quality enhancement or disease resistance, the Tripsacum

chromosomes are typically lost in successive generations. In many instances where hybridization has 

been directed between these two species, the resultant genome is lacking in most or all of the 

chromosomal complements of one of the parent species in subsequent generations. 

Only recently has Dr. DeWald (or anyone else) succeeded in obtaining a true Tripsacum cytoplasm with 

a maize nuclear background. This was done by using gama grass as the female parent and maize as the 

male or pollen donor. Numerous accessions were tested and crosses made before this came to fruition. 

The Tripsacum-derived mitochondrial chondrome and chloroplast plastome in these hybrids contribute 

to the seed qualities of the plants, but the nuclear genome appears to be totally maize in origin (DeWald 

et al. 1999). 

Dr. DeWald concluded that the possibility of maize contributing genetic material to Eastern Gama Grass 

through random pollen flow in agricultural or natural situations is extremely remote based upon his 

experience trying to create hybrids under the best of conditions. He also felt that no other known grass 

species present in the continental U.S. would interbreed with commercial maize populations (i.e., be 

recipients of pollen-directed gene flow). This is in agreement with Holm et al. (1979), who determined 

that none of the sexually compatible relatives of corn in the U.S. are considered serious, principal, or 

common weeds in the U.S. 

 c. Zea species - Teosintes - General Biology

Teosintes—specifically Zea mays ssp. mexicana (Schrader) Iltis, Zea mays ssp. parviglumis Iltis and 

Doebley, Zea mays ssp. huehuetenangensis (Iltis and Doebley) Doebley, Zea luxurians (Durieu and 

Ascherson) Bird, Zea perennis (Hitchc.) Reeves and Mangelsdorf, and Zea diploperennis Iltis, Doebley 

and Guzman—have co-existed and co-evolved in close proximity to maize in the Americas over 

thousands of years; however, maize and teosinte maintain distinct genetic constitutions despite sporadic 

introgression (Doebley 1990). 

The teosintes retain a reduced cob-like fruit/inflorescence that shatters more than cultivated maize but 

still restricts the movement of seeds as compared to more widely dispersed weedy species. Hence, the 
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dispersal of large numbers of seeds, as is typical of weeds, is not characteristic of teosintes or maize. In 

their native habitat, some teosintes have been observed to be spread by animals feeding on the plants. 

Teosintes and teosinte-maize hybrids do not survive even mild winters and could not propagate in the 

U.S. Corn Belt. Additionally, some types have strict day length requirements that preclude flowering 

within a normal season (i.e., they would be induced to flower in November or December) and, hence, 

seed production under our temperate climate (Beadle 1980; Iltis, personal communication, 2000; 

Wilkes, personal communication, 2000; Wilkes 1967). 

Since both teosinte and Tripsacum are included in botanical gardens in the U.S., the possibility exists 

(although unlikely) that exchange of genes could occur between corn and its wild relatives. The Agency 

is not aware, however, of any such case being reported in the United States. Gene exchange between 

cultivated corn and transformed corn would be similar to what naturally occurs at the present time 

within cultivated corn hybrids and landraces. Plant architecture and reproductive capacity of the 

intercrossed plants will be similar to normal corn, and the chance that a weedy type of corn will result 

from gene flow with cultivated corn is extremely remote. 

Like corn, Z. mays ssp. mexicana (annual teosinte) and Z. diploperennis (diploid perennial teosinte) have 

10 pairs of chromosomes, are wind pollinated, and tend to outcross but are highly variable species that 

are often genetically compatible and interfertile with corn, especially when maize acts as the female 

parent. Z. perennis (perennial teosinte) has 20 pairs of chromosomes and forms less stable hybrids with 

maize (Edwards et al. 1996; Magoja and Pischedda 1994). Corn and compatible species of teosinte are 

capable of hybridization when in proximity to each other. In Mexico and Guatemala, teosintes exist as 

weeds around the margins of corn fields. The F1 hybrids have been found to vary in their fertility and 

vigor. Those that are fertile are capable of backcrossing to corn. A few isolated populations of annual 

and perennial teosinte were said to exist in Florida and Texas, respectively (USDA APHIS 1997). The 

Florida populations were presumably an escape from previous use of Z. mays ssp. mexicana as a forage 

grass, but local botanists have not documented any natural populations of this species for approximately 

twenty-five years (Bradley, personal communication, 2000; Hall, personal communication, 2000; 

Wunderlin, personal communication, 2000). 

Consultation with botanists and agronomists familiar with Texas flora suggested that no teosinte 

populations exist in the state (Benz, personal communication, 2000; Read, personal communication, 

2000; Orzell, personal communication, 2000; Wilson, personal communication, 2000). Further, given 

the day length characteristics of Z. diploperennis, it is highly unlikely a sustaining population would 

result from introduction of this species. Z. mays ssp. mexicana, Z. mays ssp. parviglumis, Z. luxurians, 

and Z. diploperennis may cross with maize to produce fertile hybrids in many instances (Wilkes 1967). 

None of these teosinte species have, however, been shown to be aggressive weeds in their native or 

introduced habitats (Schoper, personal communication, 1999). Except for special plantings as noted 

above, teosinte is not present in the U.S. or its territories. Its natural distribution is limited to Mexico, 

Honduras, Nicaragua, El Salvador, and Guatemala. 

Given the cultural and biological relationships of various teosinte species and cultivated maize over the 

previous two millennia, it would appear that significant gene exchange has occurred (based upon 
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morphological characters) between these two groups of plants, and that no weedy types have 

successfully evolved as a result. More recent cytogenetic, biochemical, and molecular analyses have 

indicated that the degree of gene exchange is far less than previously thought (Doebley 1984; Doebley et 

al. 1987; Kato 1997a; Kato 1997b; Smith et al. 1985). Partial and complete gametophytic 

incompatibility has been documented among cultivated maize, landraces, and teosinte (Kermicle 1997). 

The former is demonstrated by differential pollen growth and a skewed recovery of alleles linked to 

incompatibility genes. Complete incompatibility mechanisms serve to isolate a species or subspecies and 

are evidenced as pollen exclusion or non-functioning of pollen types on certain genotypes. Attempts to 

cross six collections of Z. mays ssp. mexicana with U.S. maize cultivars (W22, W23) yielded no or few 

seeds in five of the six groups (Kermicle and Allen 1990). 

Based on the ability of maize to hybridize with some teosintes, the suggestion of previous genetic 

exchange amongst these species over centuries, and their general growth habits, any introgression of 

genes into wild teosinte from Z. mays is not considered a significant agricultural or environmental risk. 

The growth habits of teosintes are such that the potential for serious weedy propagation and 

development is not biologically plausible in the United States. 

 d. Conclusion

The potential for pollen-directed gene flow from maize to Eastern Gama Grass is extremely remote. This 

is evidenced by the difficulty with which T. dactyloides x Z. mays hybrids are produced in structured 

breeding programs. Additionally, the genus does not represent any species considered as serious or 

pernicious weeds in the United States or its territories. Any introgression of genes into this species as a 

result of cross fertilization with genetically modified maize is not expected to result in a species that is 

weedy or difficult to control. In many instances where hybridization has been directed between these 

two species, the resultant genome is lacking in most or all of the maize chromosomal complement in 

subsequent generations. 

Many of the Zea species loosely referred to as “teosintes” will produce viable offspring when crossed 

with Z. mays ssp. mays. None of these plants are known to harbor weedy characteristics and none of the 

native teosinte species, subspecies, or races are considered aggressive weeds in their native or 

introduced habitats. In fact, many are on the brink of extinction where they are indigenous and will be 

lost without human intervention (i.e., conservation measures). Further, none of the landraces or 

cultivated lines of Z. mays are considered to have weedy potential and are generally considered 

incapable of survival in the wild as a result of breeding practices (i.e., selection) during domestication of 

the crop. 

 iii. Impacts on Endangered Species (MRID No. 461239-17)

The primary route of exposure to Cry34/35Ab1 protein in corn is through ingestion of corn tissue. There 

are no reports of threatened or endangered species feeding on corn plants; therefore, such species would 

not be exposed to corn tissue containing the Cry protein. Since Cry34/35Ab1 corn pollen has shown no 

toxicity at the estimated environmental concentration rates to mammals, birds, plants, aquatic species, 
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insects, and other invertebrate species tested, a “may affect” situation for endangered land and aquatic 

species is not anticipated. In addition, EPA does not expect that any threatened or endangered plant 

species will be affected by outcrossing to wild relatives or by competition with such entities. Hybrid 

corn does not exist in the wild, nor are there wild plants that can interbreed with corn in the United 

States. 

Because of the selectivity of Cry34/35Ab1 protein for coleopteran species, endangered species concerns 

are mainly restricted to the order Coleoptera. Examination of an overlay map showing the county-level 

distribution of the 16 endangered/threatened coleopteran species (as currently listed by the U.S. Fish and 

Wildlife Service) relative to corn production counties in the United States clearly indicated that any 

potential concern regarding range overlap with corn production was mainly restricted to the American 

burying beetle (Nicrophorus americanus). The American burying beetle is the largest carrion beetle in 

North America and is only found today in limited areas in Rhode Island and the portions of the Great 

Plains into Arkansas and Georgia. Adults are nocturnal and feed on carrion and sometimes prey on other 

arthropods. Larvae feed exclusively on buried carrion provided by their parents. The American burying 

beetle’s habitat is variable and often includes deciduous forest, grassland, and agricultural areas. 

Considering that both larvae and adult insects feed exclusively on carrion with some limited adult 

predation, even if American burying beetles did occur in proximity to Bt corn fields, there would be 

little chance of exposure to Bt protein due to their feeding habits. After careful review of the available 

data, EPA determined that exposure of American burying beetle to harmful levels of Cry34/35Ab1 corn 

tissue is not expected. Likewise, a review of the preferred habitats of other coleopteran species, listed as 

endangered by the U.S. Fish and Wildlife Service, indicated that no exposure to harmful levels of 

Cry34/35Ab1 protein would take place. The main reasons for the lack of exposure are geographical and 

habitat limitations. These other species are located in non-corn production areas and/or their habitat does 

not encompass agricultural areas. 

Likewise, other endangered/threatened insect species in the orders Diptera, Hemiptera, Lepidoptera, 

Odonata, and Orthoptera are found in dune, meadow/prairie, or open forest habitats and are not closely 

associated with row crop production often times due to the specificity of the habitat of their host plants. 

The reviewed toxicological data show the relative insensitivity of a range of insects from nonColeopteran orders to the Cry34/35Ab1 protein, indicating that the Cry34/35Ab1 corn hybrids will not 

likely cause detrimental effects to the non-Coleopteran insects on the endangered/threatened species list. 

Likewise, several insect species listed are aquatic species and are unlikely to come in contact with 

Cry34/35Ab1 corn. Many of the endangered and threatened beetles occur in cave or aquatic habitats. 

Since movement of Cry34/35Ab1 in soil and into water bodies is expected to be negligible, pollen drift 

was considered the primary source of potential hazard to endangered aquatic Coleoptera. According to 

estimates based on published studies, if 100% of the pollen grains leaving a corn field were deposited in 

a 1 hectare pond with 2 meters depth and located ≥1 meter from the edge of the corn field, <0.0001 μg 

Cry34/35Ab1/mL of water would be expected. This is a few orders below the toxic level to any insect. 
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Conclusions: 

The reviewed non-target data confirm the expectation that Cry34/35Ab1 corn is not likely to jeopardize 

the continued existence of any endangered and/or threatened species listed by the U.S. Fish and Wildlife 

Service, including mammals, birds, or terrestrial and aquatic plants and invertebrate species. Therefore, 

no consultation with the U.S. Fish and Wildlife Service is required under the Endangered Species Act. 

 iv. Environmental Assessment Summary (MRID No. 461239-13)

The Agency is using a maximum hazard dose tiered system for biopesticide non-target wildlife hazard 

assessment. When no adverse effects are observed at the maximum hazard dose, the Agency concludes 

that there are no unreasonable adverse effects from the use of the pesticide. From all of the required and 

voluntarily developed indicator and host range species test data on Cry34/35Ab1 corn, the Agency 

concludes that the levels of Cry34/35Ab1 protein in corn will not pose unreasonable adverse effects to 

corn field flora and fauna. Available data also indicate that there should be minimal short-term 

accumulation of Cry34/35Ab1 protein in agricultural soil. In addition, no adverse effect on endangered 

and threatened species, as listed by the U.S. Fish and Wildlife Service, is expected from the proposed 

Cry34/35Ab1 CRW resistant corn registration. 

At present, the Agency is aware of no identified significant adverse effects of Cry34/35Ab1 protein on 

the abundance of non-target beneficial organisms in any population in the field, whether they are pest 

parasites, pest predators, or pollinators. Field testing and field census data submitted to the Agency show 

minimal to undetectable changes in beneficial insect abundance or diversity. To date, available field test 

data show that, compared to crops treated with conventional chemical pesticides, the transgenic crops 

have no detrimental effect on the abundance of non-target insect populations. 

The Agency believes that cultivation of Cry34/35Ab1 corn may result in fewer adverse impacts to nontarget organisms than result from the use of chemical pesticides. Under normal circumstances, 

Cry34/35Ab1 corn requires substantially fewer applications of chemical pesticides. This should result in 

fewer adverse impacts to non-target organisms because application of non-specific conventional 

chemical pesticides is known to have an adverse effect on non-target beneficial organisms found living 

in the complex environment of an agricultural field. Many of these beneficial organisms are important 

integrated pest management controls for secondary pests, such as aphids and leafhoppers. The overall 

result of Cry34/35Ab1 corn cultivation is that the number of chemical insecticide applications for nontarget pest control is reduced for management of multiple pest problems. 

The movement of transgenes from Cry34/35Ab1 host plants into weeds and other crops has also been 

considered. The Agency has determined that there is no significant risk of gene capture and expression 

of Cry34/35Ab1 protein by wild or weedy relatives of corn in the U.S., its possessions, and/or territories. 

The fate of Cry34/35Ab1 protein in soils and indirect effects on soil biota have also been evaluated. Test 

data show that most of the Cry protein deposited into soil is quickly degraded, although a residual 

amount may persist in biologically active form for a much longer period of time. It is also reported that 

the same degree of Bt Cry protein persistence takes place in soils that have been exposed to repeat Bt

spray applications when compared to soil exposed to growing Bt crops. Limited data do not indicate that 
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Cry proteins have any measurable effect on microbial populations in the soil. Horizontal transfer of 

genes from transgenic plants to soil bacteria has not been demonstrated. Published studies of Bt Cry 

protein in soil show no effect on bacteria, actinomyces, fungi, protozoa, algae, nematodes, springtails, or 

earthworms. In addition, new plants planted in Bt Cry protein-containing soil do not take up the Bt

protein. 

Conclusion:

At the present time and for the purposes of a time-limited registration, this risk assessment finds no 

hazard to the environment from cultivation of corn expressing the Cry34/35Ab1 protein. 

 v. Supplemental Studies Needed for Long-Term Cry34/35Ab1 Non-Target Hazard

 Assessment

The Agency has sufficient information to believe that there is no risk from the proposed uses of 

Cry34/35Ab1 corn to non-target wildlife, aquatic, and soil organisms. Nonetheless, in response to the 

August 2002 SAP recommendations, the Agency is requesting supplementary studies that will evaluate 

more appropriate non-target invertebrates (e.g., those found in corn fields) and facilitate identification of 

potential adverse effects that may result from long-term use of Cry34/35Ab1 corn. The Agency does not 

believe that these data requirements were reasonably foreseeable by Mycogen Seeds c/o Dow 

AgroSciences LLC and Pioneer Hi-Bred International, Incorporated at the time of their respective 

applications. 

Table 2. Supplemental Data Requirements.

Testing Category Type of Data

Non-target insect more 

appropriate for corn fields 

Conduct a maximum hazard dose laboratory toxicity test with Orius insidiosus

(minute pirate bug). 

Non-target insect more 

appropriate for corn fields 

Conduct a maximum hazard dose laboratory toxicity test with a carabid (ground 

beetle). 

Ecosystem effects Additional long-range field studies should be conducted based on recommendations 

from the August 2002 SAP (as presented in summary form in the conclusions 

section of the MRID No. 461239-14 review). 

Soil fate studies Additional long-range soil degradation field studies should be conducted to include 

the parameters outlined by the August 2002 SAP (as presented in summary form in 

the conclusions section of the MRID No. 452422-14 review). 

*Note for 2010: There is an update to this summary. See section II(C)(2)(b) (“Terms and Conditions of 

the Event DAS-59122-7 Corn Registrations (August 2005 – Present)”) of this BRAD. 

b. Terms and Conditions of the Event DAS-59122-7 Corn Registrations (August 2005 –

 Present)
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When Event DAS-59122-7 corn was first registered on August 31, 2005, the Agency issued registration 

notices to both Mycogen Seeds c/o Dow AgroSciences LLC (EPA Reg. No. 68467-5) and Pioneer HiBred International, Incorporated (EPA Reg. No. 29964-4) that, given the conclusions set forth in the 

initial environmental risk assessment (see section II(C)(2)(a) of this BRAD), contained the following 

three requirements for further environmental effects data: 

 “Submit field degradation studies evaluating accumulation and persistence of 

 Cry34/35Ab1 in several different soils in various strata. Representative fields must 

 have been planted with Cry34/35Ab1 corn and include both conventional tillage and 

 no-till samples and be harvested under typical agronomic conditions. Sampling must 

 continue until the limit of detection is reached. Studies should include soils with high 

 levels of a variety of clays. Both ELISA and insect bioassays need to be conducted and 

 compared to determine if Cry34/35Ab1 is accumulating or persisting in soil samples... 

 A final report regarding data from fields that have had three continuous years of 

 cultivation of Event DAS-59122-7 corn is due by January 31, 2010.” 

 “Submit laboratory toxicity tests with Orius insidiosus (minute pirate bug) [and] 

 carabid (ground beetle) within 24 months of the date of registration....” 

 “Additional 3 year full-scale field or semi-field studies for evaluation of Cry34/35Ab1 

 Event DAS-59122-7 corn exposure on non-target invertebrates must be conducted. 

 Full-scale field experiments must be appropriately designed to provide a measure of 

 ecological impacts (larger fields, more replicates, more samples per plot based on 

 recommendations of the August 2002 SAP). The previously submitted two-year field 

 study is not sufficient to determine if Cry34/35Ab1 corn will have long term impact 

 on non-target invertebrates...A final report is due September 30, 2009.” 

For both registrations, the abovementioned requirements for additional environmental effects data have 

been satisfied by submission of appropriate studies; summaries of the studies are presented in Table 3. 

Current environmental effects data, to include those conditional data referenced in Table 3, and EPA 

reviews of Cry34/35Ab1 protein support the Agency’s original determination that adverse effects will 

not occur to non-target organisms. Due to a demonstrated lack of toxicity and/or exposure, no effects 

from Cry34/35Ab1 protein are anticipated for any non-target species, including federally listed 

threatened and endangered (“listed”) lepidopteran and coleopteran species and their designated critical 

habitats. The Agency is therefore upholding its determination that the registered uses of Cry34/35Ab1 

will have “No Effect,” direct or indirect, on endangered or threatened terrestrial or aquatic species as 

listed by the U.S. Fish and Wildlife Service and the National Marine Fisheries Service. 

Despite the conclusions made in the previous paragraph, the Agency is aware of a recently published 

laboratory study showing reduced growth in shredding caddis flies exposed to anti-lepidopteran Cry1A 

protein corn litter (Rosi-Marshall et al. 2007). In light of the findings of this particular study, additional 

aquatic invertebrate data are required. The submitted D. magna study (MRID No. 457904-04) is now 
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considered unacceptable because it is an 850 Series OCSPP Guideline study. The 48-hour duration of 

this study is not sufficient to detect mortality due to Bt proteins. It takes more than 48 hours for the 

target pests to succumb to the Cry proteins; therefore, 48 hours is also not expected to show mortality or 

reproductive effects on D. magna. A 7- to 14-day D. magna study, as per the 885 Series OCSPP 

Guidelines, needs to be performed for Cry34/35Ab1. Alternatively, a dietary study of the effects on an 

aquatic invertebrate, representing the functional group of a leaf shredder in headwater streams, can be 

performed and submitted in lieu of the D. magna study. The Agency will consider this study, which 

must be submitted by a certain date and deemed acceptable, to be a new data requirement within any 

revised terms and conditions drafted for the Event-DAS-59122-7 corn registration extensions. 

Table 3. Environmental Effects Data Submitted in Response to Conditions of Registration for 

 Event DAS-59122-7 Corn 

Study Title Summary MRID No.

Three-Year Field 

Monitoring of 

Cry34/35Ab1 and 

Cry1F x Cry34/35Ab1 

Maize Hybrids for NonTarget Arthropod 

Effectsn

A multi-year field study evaluated the impact of Event DAS-59122-7 

maize (expressing Cry34Ab1 and Cry35Ab1 proteins) and its respective 

stacked maize hybrid, DAS-01507-1 x DAS-59122-7 (expressing Cry1F 

and Cry34/35Ab1 proteins), on non-target arthropods after continuous 

cropping at three locations in the Corn Belt (Iowa, Nebraska, and Indiana). 

Community-level analyses and key indicator species data were collected 

using visual observations, sticky traps, pitfall traps, and litter bag traps. 

Results showed similar dynamics on non-target arthropod populations 

between non-Bt isogenic maize hybrid fields and the Bt transgenic PIP corn 

events, DAS-59122-7 and DAS-59122-7 x TC1507. Therefore, there is 

negligible potential for long-term adverse effects on non-target arthropods 

on the community level and key taxon abundance after continuous 

cultivation of both Herculex® RW and Herculex® XTRA Bt corn events. 

Classification: Acceptable 

478703-01 

Soil Accumulation of 

Cry34Ab1 and 

Cry35Ab1 Proteins after 

Three Years of 

Cropping with DAS59122-7 Cornn

After 3 years of continuous cropping with DAS-59122-7 corn, the enzymelinked immunosorbent assay (ELISA) analyses showed no detectable 

residues of Cry34Ab1 and Cry35Ab1 proteins in soil (bulk and 

rhizosphere) extracted from 3 different field sites (Illinois, Minnesota, and 

North Carolina) containing a range of soil properties. In addition, no 

biological activity was observed in insect bioassays of southern corn 

rootworm (Diabrotica undecimpunctata howardi) neonates after exposure 

to rhizosphere soil samples. Therefore, there is negligible potential for 

Cry34Ab1 and Cry35Ab1 proteins to persist or accumulate in agricultural 

soils in various soil matrices across cropping cycles of DAS-59122-7 corn. 

Classification: Acceptable

479595-01 

 

n

 Reviewed in U.S. EPA (2010c) 
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Study Title Summary MRID No.

Summary Report of 

Carabid Beetle 

Laboratory Toxicity 

Study Using Cry34Ab1 

and Cry35Ab1o

In a laboratory bioassay, ground beetle (Poecilus cupreus) larvae were fed 

blowfly (Calliphora vomitoria) pupae containing target concentrations of a 

combination of 1,000 nanograms (ng) Cry34Ab1 + 333.3 ng Cry35Ab1/mg 

of pupa. A negative control group of larvae was fed pupae treated with 

deionized water, and a positive control group was fed pupae treated with 

teflubenzuron. Survival of the ground beetle larvae was monitored 

throughout pupation and adult emergence. There was no statistically 

significant difference in pre-imaginal mortality between the negative 

control and Cry34Ab1 + Cry35Ab1 groups (15% and 8%, respectively), 

while mortality in the positive control group was 83%. Mean development 

time and mean adult weight of the negative control and Cry34Ab1 + 

Cry35Ab1 groups were comparable. This study shows that when carabid 

beetle larvae are fed diet containing Cry34/35Ab1 protein, no negative 

adverse effect is observed. Therefore, at field concentrations, it is unlikely 

that Cry34/35Ab1 will have negative adverse effects on carabid beetles. 

Classification: Acceptable

467141-01 

Evaluation of Potential 

Dietary Effects of 

Cry34/35Ab1 Protein 

on Insidious Flower 

Bugs, Orius insidiosus o

Four separate 10- to 14-day tests were conducted from December 2005 to 

July 2007 to evaluate the dietary effects of combined Cry34Ab1 and 

Cry35Ab1 proteins on survival and development of insidious flower bug 

(O. insidious) nymphs. Each test included a group given a combination of 

750 ng Cry34Ab1 + 85 ng Cry35Ab1/mg of diet (bee pollen), a positive 

control group given potassium arsenate (8 ng active ingredient/mg of diet 

volume by weight), and an assay control group given purified reagent 

grade water mixed with diet. In addition, one test included a group given 

750 ng of heat-treated Cry34Ab1 + 85 ng of heat-treated Cry35Ab1/mg of 

diet. The control group mortality in each test exceeded the allowable rate 

specified in the test protocol of less than 20% control mortality. However, 

the survival of the test species in the control groups and test groups was 

similar in each test. It is concluded that, at field concentrations, it is 

unlikely that Cry34/35Ab1 will have negative adverse effects on the 

insidious flower bug. 

Classification: Supplemental

474367-01 

 

o

 Reviewed in U.S. EPA (2010b) 
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3. Herculex® XTRA Insect Protection Corn (OECD Unique Identifier: DAS-Ø15Ø7-1 x DAS- 

 59122-7) Expressing Cry1F, Cry34Ab1, and Cry35Ab1

a. Data Cited/Submitted for Initial Registrations of Herculex® XTRA Insect Protection Corn 

(Prior to October 2005)

i. Background

In 2004, Mycogen Seeds c/o Dow AgroSciences LLC and Pioneer Hi-Bred International, Incorporated 

requested full and unrestricted FIFRA section 3 registrations for commercialization of Herculex® 

XTRA Insect Protection Corn, a stacked product containing the following registered active ingredients: 

Cry1F (EPA Reg. No. 68467-2 and EPA Reg. No. 29964-3; Herculex® I) and Cry34/35Ab1 (EPA Reg. 

No. 68467-5 and EPA Reg. No. 29964-4; Event DAS-59122-7 corn or Herculex® RW). Herculex® 

XTRA was developed by crossing inbred lines of Cry1F lepidopteran-active and Cry34/35Ab1 

coleopteran-active corn to produce hybrid maize line 1507 x 59122. Southern blot analyses 

demonstrated that the insertions in the Herculex® XTRA hybrid are equivalent to those of the 

Herculex® I and Herculex® RW lines and indicated that the stacked hybrid was a successful cross of 

the two inbred lines, 1507 and 59122 (MRID No. 462971-02; reviewed in U.S. EPA (2005f)). In 

addition to the insecticidal genes, the phosphinothricin acetyltransferase gene, which encodes PAT 

protein, is also present in the stacked trait corn plants. The inclusion of the pat gene provides tolerance 

to glufosinate-ammonium herbicides. 

The insecticidal proteins expressed in single-trait Events DAS-01507-1 (Herculex® I) and DAS-59122-

7 (Herculex® RW) have been previously evaluated for adverse impacts on non-target organisms and 

have been shown to pose negligible risk. Thus, the evaluation of Herculex® XTRA is simplified, 

requiring only demonstration of no synergy in the biological activity of the combined traits from 

Herculex® I and Herculex® RW. 

 ii. Non-Target Wildlife Hazard Assessment

An environmental risk assessment was conducted to characterize the risk of adverse impacts of the traits 

expressed in Herculex® XTRA on non-target organisms, particularly invertebrates found in or near 

agro-ecosystems. Concerns over possible effects on endangered and threatened species, especially 

butterfly (Lepidoptera) and beetle (Coleoptera) species were also addressed. 

Expression of the Cry1F, Cry34Ab1, and Cry35Ab1 proteins in Herculex® XTRA was determined in 

various tissue types at various stages of development utilizing ELISA kits specific for each protein 

(MRID No. 463438-01; reviewed in U.S. EPA (2005f)). These data indicate that protein levels are 

comparable between the Herculex® I, Herculex® RW, and Herculex® XTRA hybrids. Therefore, the 

environmental effects data submitted and reviewed in support of the Herculex® I and Herculex® RW 

registrations, including studies submitted as conditions of registration, may be bridged to support the 

Herculex® XTRA product registrations. The environmental risk assessments for the insecticidal proteins 

(Cry1F and Cry34/Cry35Ab1) expressed in the single-trait events have been evaluated for adverse 
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impacts on non-target organisms and have been shown to pose negligible risk (see U.S. EPA 2001d, 

2005d, and 2010d for Cry1F; see section II(C)(2) of this BRAD for Cry34/35Ab1). 

Of unique concern to the environmental risk assessment of stacked PIPs, is the potential for synergistic 

effects that may result from the insertion of multiple active ingredients into a single crop plant. 

Therefore, the conceptual model for evaluation of the stacked Herculex® XTRA hybrid is focused on 

the demonstration of no synergy in the biological activity of the two traits, Herculex® I and Herculex® 

RW. To address this issue and in support of the Herculex® XTRA registrations, four new studies were 

submitted: three comparing the effects of the single and stacked proteins in the sensitive target insect 

pests and two non-target insect species and one evaluating the effects of the stacked proteins on broiler 

chickens. These studies were reviewed in U.S. EPA (2005f) and are summarized in the sections that 

follow. 

I. Non-Target Wildlife Study Summaries 

 a. Potential Synergistic Interaction Between the Cry1F and Cry34/35Ab1 Proteins 

(MRID No. 463438-06)

Laboratory bioassays were conducted to determine if combining the Cry1F and Cry34/35Ab1 proteins 

increased their activity against southern corn rootworm or European corn borer larvae. No synergism or 

antagonism between Cry1F and Cry34/35Ab1 was seen in the tests. Therefore, the absence of additive 

or synergistic effects in sensitive organisms makes it extremely unlikely that the Cry1F x Cry34/35Ab1 

proteins produced in Herculex® XTRA will have any adverse effect on non-target organisms different 

from what was seen in individual Cry protein testing. 

 b. Lady Beetle Study (MRID No. 463438-07)

In a 12-day laboratory feeding study, ladybird beetle (C. maculata) larvae were provided a prepared test 

diet consisting of 50% Cry1F x Cry34/35Ab1 maize pollen and 50% ground corn earworm eggs until 

adult emergence. Larvae fed the treated diet for 12 days did not show any developmental delays 

compared to those fed the control diet. There was no statistically significant difference in larval 

mortality between the treated and control groups (7% and 0%, respectively). The average weight of 

adults in the treated and control groups was comparable. These results demonstrated no additional 

adverse effect to C. maculata, at the expected field exposure dosage, from the mixture in Herculex® 

XTRA over that observed with the Cry1F and Cry34/35Ab1 proteins alone. 

Since the Cry34/35Ab1 protein toxicity is specific to coleopteran species, evaluations of other 

appropriate non-target beetle species should be submitted in support of Cry34/35Ab1-containing corn 

lines. Studies submitted in support of Herculex® RW may be bridged to support the Herculex® XTRA 

registrations. 
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c. Monarch Butterfly Testing (MRID No. 463438-08)

In a 4-day laboratory feeding study, first-instar monarch butterfly (Danaus plexippus) larvae were 

exposed to transgenic (Cry1F x Cry34/35Ab1 stack) or non-transgenic pollen at densities of 50, 100, 

200, 400, 800, or 1600 pollen grains/square centimeter on milkweed leaves. After 96 hours, the larvae 

were transferred to clean milkweed leaves for an additional 120 hours. Exposure to the transgenic pollen 

did not significantly reduce larval survival, weight gain, developmental life stage, or leaf consumption 

during the 216-hour observation period. These data indicate that subchronic effects were not seen when 

D. plexippus was exposed to the Cry1F and Cry34/35Ab1 proteins at the recommended field dosage for 

4 days. Therefore, no hazard to monarch butterflies is expected from incidental exposure to Herculex® 

XTRA corn pollen. 

d. Avian Study (MRID No. 463438-03)

Broiler chickens were fed diets containing transgenic maize grain (containing Cry1F x Cry34/35Ab1 

and PAT proteins), a non-transgenic near-isoline maize grain, or non-transgenic commercial reference 

maize grains. Feeding began on the day of hatch and continued for 42 days. There were no statistically 

significant differences in broiler mortality, body weight, body weight gain, feed efficiency, or 

carcass/carcass part yields for any of the diets. These results indicate that hybrid maize line 1507 x 

59122 (Cry1F x Cry34/35Ab1) was nutritionally equivalent to the near-isoline and commercially 

available non-transgenic hybrids and, like with the corn events producing the individual Cry proteins, 

there were no adverse effects noted on the growth and development of broiler chickens. Therefore, longterm exposure to Herculex® XTRA is not expected to pose a hazard to avian wildlife. 

e. Other Non-Targets Organism Risk Assessments

Waiver rationales were also submitted for the additional non-target studies normally required for 

environmental risk assessments: Avian Oral (OCSPP Harmonized Guideline 885.4050); Avian Injection 

(now Avian Inhalation) (OCSPP Harmonized Guideline 885.4100); Freshwater Fish (OCSPP 

Harmonized Guideline 885.4200); Freshwater Invertebrate (OCSPP Harmonized Guideline 885.4240); 

Estuarine and Marine Animal (OCSPP Harmonized Guideline 885.4280); Non-Target Plant (OCSPP 

Harmonized Guideline 885.4300); Non-Target Insect (OCSPP Harmonized Guideline 885.4340); and 

Honey Bee (OCSPP Harmonized Guideline 885.4380). A poultry broiler study was submitted, so a 

standard avian oral study is not required. The rationale for the waiver from avian injection and 

freshwater fish is that the active ingredient is not an infectious agent and is expressed at very low levels 

in plants. The rationale for the waiver from estuarine and marine animal studies is that the active 

ingredient is not an infectious agent, is expressed at very low levels in plants, and there is very low to no 

potential for exposure to the protein from field corn. The rationale for waivers from freshwater 

invertebrate, non-target insect, and honey bee studies is that appropriate studies were completed for the 

single-trait products (Cry34/35Ab1 and Cry1F). The rationale for the waiver from non-target plant 

studies is that the active ingredient is an insect toxin (Bt endotoxin) that is non-toxic to aquatic and 

terrestrial plants. Lastly, toxicity data submitted for the Human Health Assessment (see section II(B)(2)
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of this BRAD) indicate that there is no significant toxicity to rodents from testing at the maximum 

hazard dose and, therefore, no hazard to mammalian wildlife is anticipated. 

Additional support for a complete environmental risk assessment is gained from an overview of the 

assessments done for the individual Cry1F (Herculex® I) and Cry34/35Ab1 (Herculex® RW) 

registrations. A brief summary of the Cry1F environmental risk assessment is provided in the section 

that follows, while the comprehensive environmental risk assessment for Cry34/35Ab1 can be found in 

section II(C)(2) of this BRAD. 

f. Herculex® I (Lepidopteran-Active Cry1F Protein) Environmental Risk Assessment

EPA has conducted an extensive review of effects of the Cry1F protein present in Herculex® I to nontarget organisms in an environmental risk assessment as part of the registration process (U.S. EPA 

2001d, 2005d, and 2010d). EPA reviewed studies conducted on representative non-target species with 

Cry1F protein and performed risk or impact assessments on plants, wild mammals, birds, fish, aquatic 

invertebrates, estuarine and marine animals, earthworms, terrestrial non-target insects (including honey 

bee adults and larvae, parasitic wasps, green lacewings, lady beetles, springtails (collembola 

toxicity/reproduction), and monarch butterflies), field invertebrate abundance studies, soil 

degradation/persistence studies, and endangered species with special emphasis on the Karner blue 

butterfly. In addition, weediness and gene flow assessments (via pollen and Cry protein 

deoxyribonucleic acid (DNA) uptake by plants and soil microorganisms) were also performed. 

The Agency concluded that, considering all available information, the weight-of-evidence indicates no 

unreasonable adverse effects of Cry1F proteins in corn to non-target wildlife, plants, or beneficial 

invertebrates. 

 iii. Endangered Species Considerations

The reviewed non-target data confirm the expectation that Cry1F x Cry34/35Ab1 corn is not likely to 

jeopardize the continued existence of any endangered and/or threatened species listed by the U.S. Fish 

and Wildlife Service, including mammals, birds, or terrestrial and aquatic plants and invertebrate 

species. Herculex® XTRA is not likely to adversely affect Karner blue butterflies because exposure to 

harmful levels of Cry1F corn pollen is not expected (U.S. EPA 2001d, 2005d, and 2010d). Likewise, a 

review of the preferred habitats of other lepidopteran species listed as endangered by the U.S. Fish and 

Wildlife Service, including the endangered Mitchell satyr butterfly, indicates that no exposure to 

harmful levels of Cry1F protein-containing pollen will take place. Furthermore, there is also no overlap 

of endangered beetle species habitat with corn production. Therefore, EPA believes that this action will 

have “No Effect” on listed species. This finding was triggered by the reviewed Cry protein toxicity and 

exposure data on terrestrial and aquatic species. As a result, no endangered species labeling is required 

for the registration of Herculex® XTRA corn. 
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iv. Environmental Assessment Summary

From all of the required and voluntarily developed indicator and host range species test data on Cry1F, 

Cry34/35Ab1, and Cry1F x Cry34/35Ab1 corn, the Agency concludes that the levels of Cry1F x 

Cry34/35Ab1 protein in Herculex® XTRA corn will not pose unreasonable adverse effects to corn field 

flora and fauna. Available data also indicate that there should be minimal short-term accumulation of 

Cry1F x Cry34/35Ab1 protein in agricultural soil. No evidence of synergy between the lepidopteranactive and coleopteran-active insecticidal proteins expressed by Herculex® XTRA corn was found in 

laboratory studies of target and non-target insects evaluated for these registrations. 

Endangered/threatened species assessments conducted in support of individual trait (Herculex® I and 

Herculex® RW) registrations were sufficient to demonstrate a “No Effect” finding for the stacked 

product. In conclusion, Herculex® XTRA is projected to control certain lepidopteran and coleopteran 

pests in field corn without concerns of risk to non-target organisms. 

Conclusion:

At the present time and for the purposes of a time-limited registration, this risk assessment finds no 

hazard to the environment from cultivation of corn expressing the Cry1F and Cry34/35Ab1 proteins. 

v. Supplemental Studies Needed for Long-Term Cry1F x Cry34/35Ab1 Non-Target Hazard 

Assessment

The Agency has sufficient information to believe that there is no evidence of risk from the proposed 

uses of Herculex® XTRA corn to non-target wildlife, aquatic, and soil organisms. However, after 

consultation with the Scientific Advisory Panel in August 2002, and based upon several public 

comments, the Agency is requesting more data. The supplementary studies would provide additional 

weight to support the Agency’s conclusions. The Agency does not believe that these data requirements 

were reasonably foreseeable by Mycogen Seeds c/o Dow AgroSciences LLC and Pioneer Hi-Bred 

International, Incorporated at the time of their respective applications. 

The following data (Table 4) may be required to ascertain any possible adverse environmental effects 

from long-term use of Herculex® XTRA corn. 

Table 4. Supplemental Data Requirements. 

Testing Category Type of Data

Toxicity data on non-target insects 

more appropriate for corn fields, 

ecosystem effects, and soil 

persistence determination 

Laboratory toxicity testing with Orius insidiosus (minute pirate bug) and a carabid 

(ground beetle) may be required, as well as long range effects on invertebrate 

populations in the field and soil persistence studies with Cry1F x Cry34/35Ab1 corn 

as per the parameters outlined by the August 2002 FIFRA SAP. In the event that 

Cry34/35Ab1 (Herculex® RW) studies sufficiently demonstrate a lack of long range 

adverse effects, no additional data with Herculex® XTRA will be required. 
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*Note for 2010: There is an update to this summary. See section II(C)(3)(b) (“Terms and Conditions of 

the Herculex® XTRA Insect Protection Corn Registrations (October 2005 – Present)”) of this BRAD. 

b. Terms and Conditions of the Herculex® XTRA Insect Protection Corn Registrations 

 (October 2005 – Present)

When Herculex® XTRA Insect Protection Corn was initially registered on October 27, 2005, the 

Agency issued registration notices to both Mycogen Seeds c/o Dow AgroSciences LLC (EPA Reg. No. 

68467-6) and Pioneer Hi-Bred International, Incorporated (EPA Reg. No. 29964-5) that contained the 

following requirement in relation to further environmental effects data: 

 “Submit all data required to support the individual plant-incorporated protectants 

 in Event TC1507 (Herculex I) and Event DAS-59122-7 (Herculex Rootworm) 

 corn...In the event that the Agency concludes Cry34/35Ab1 (Herculex 

 Rootworm) studies do not sufficiently demonstrate a lack of long range adverse 

 effects, additional data with Herculex Xtra must be submitted. This data may 

 include a) laboratory toxicity testing with Orius insidiosus (minute pirate bug), 

 b) laboratory toxicity testing with a carabid (ground beetle), c) long range 

 effects testing on invertebrate populations in the field, and d) long range soil 

 persistence testing.” 

All requirements for additional environmental effects data for Events TC1507 (see U.S. EPA (2010d)) 

and DAS-59122-7 (see section II(C)(2)(b) of this BRAD), as set forth in the October 27, 2005 

Herculex® XTRA Insect Protection Corn registration notices, have been satisfied for both registrations. 

Moreover, after evaluating the conditional data submitted to support the registrations of Event DAS59122-7 corn, the Agency has concluded that these data do not demonstrate the potential for long-range 

adverse effects to the environment as a result of the cultivation of Cry34/35Ab1 corn. It should be noted 

that Mycogen Seeds c/o Dow AgroSciences LLC and Pioneer Hi-Bred International, Incorporated, 

although not specifically requested by the Agency, did include Herculex® XTRA Insect Protection Corn 

in the three-year non-target arthropod field study (MRID No. 478703-01; reviewed in U.S. EPA 

2010(b)). 

4. 1507 x 59122 x MON 810 (OECD Unique Identifier: DAS-Ø15Ø7-1 x DAS-59122-7 x 

 MON-ØØ81Ø-6) Expressing Cry1F, Cry34Ab1, Cry35Ab1, and Cry1Ab and 59122 x 

 MON 810 (OECD Unique Identifier: DAS-59122-7 x MON-ØØ81Ø-6) Expressing 

 Cry34Ab1, Cry35Ab1, and Cry1Ab 

 a. Data Cited/Submitted for Initial Registrations of 1507 x 59122 x MON 810 and 

 59122 x MON 810 (Prior to February 2010)

The stacked and pyramided product, 1507 x 59122 x MON 810, and the stacked product, 59122 x MON 

810, are hybrids created by crossing the individuals events, TC1507 (Cry1F), DAS-59122-7 
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(Cry34/35Ab1), and MON 810 (Cry1Ab), via traditional breeding methods. Although background 

information on individual Events DAS-59122-7, TC1507, and MON 810 is provided throughout this 

BRAD, the most specific information on each of these events is discussed or referenced in the Product 

Characterization chapter (see sections II(A)(1)–II(A)(3) of this BRAD). 

To support their registration applications for 1507 x 59122 x MON 810 and 59122 x MON 810, Pioneer 

Hi-Bred International, Incorporated submitted molecular characterization data, protein expression 

analyses, and a synergism study. Collectively, these data (as summarized in the paragraphs that follow) 

justified bridging the existing findings and conclusions from the environmental assessments conducted 

for the single PIP events (TC1507, DAS-59122-7, and MON 810) to the combination PIP products 

(1507 x 59122 x MON 810 and 59122 x MON 810) (MRID Nos. 476778-01, 476778-02, and 478800-

01; reviewed in U.S. EPA (2010a)). 

 

The molecular characterization of Bt Cry1F, Cry34Ab1, Cry35Ab1, and/or Cry1Ab insect control 

proteins and the genetic material necessary for their production in 59122 x MON 810 and 1507 x 59122 

x MON 810 combination PIP corn products demonstrated the stability and integrity of the intended 

transgenic DNA inserts of Cry1F protein expressed in TC1507, Cry34Ab1 and Cry35Ab1 proteins 

expressed in DAS-59122-7, and/or Cry1Ab protein expressed in MON 810 corn events, when combined 

through traditional plant breeding. Protein expression analyses also demonstrated similar levels of 

Cry1F, Cry34Ab1, Cry35Ab1, and/or Cry1Ab protein concentrations of each respective parental event 

when compared to 59122 x MON 810 and 1507 x 59122 x MON 810 combination PIP corn events. 

Laboratory assays, using sensitive target pest species, found no antagonistic or synergistic effects among 

the Cry proteins expressed in each combination PIP product. This determination demonstrates functional 

equivalence among the single parental events and the combination PIP products, and the results and 

conclusions of the non-target organism studies (conducted for each single parental event) can be bridged 

(see U.S. EPA 2001d, 2005d, and 2010d for Cry1F; see section II(C)(2) of this BRAD for Cry34/35Ab1; 

and see U.S. EPA 2001d and 2010d for Cry1Ab). Therefore, no unreasonable adverse effects on nontarget organisms and the environment are expected from 59122 x MON 810 and 1507 x 59122 x MON 

810. 

 b. Terms and Conditions of the 1507 x 59122 x MON 810 and 59122 x MON 810 Registrations 

(February 2010 – Present)

When 1507 x 59122 x MON 810 (EPA Reg. No. 29964-8) and 59122 x MON 810 (EPA Reg. No. 

29964-9) were initially registered on February 24, 2010, the Agency issued registration notices to 

Pioneer Hi-Bred International, Incorporated that contained the following requirements: 

 For 1507 x 59122 x MON 810 – 

 “The data submitted by Pioneer are sufficient to support registration for the 

 combination PIP product...provided that the registrant submits/cites any data 

 required to support the PIP registrations of the individual parental events...as 
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 well as the combination PIP product TC1507 (DAS-Ø15Ø7-1) x DAS-59122-7....” 

 For 59122 x MON 810 – 

 “The data submitted by Pioneer are sufficient to support registration for the 

 combination PIP product...provided that the registrant submits/cites any data 

 required to support the PIP registrations of the individual parental events....” 

All requirements for additional environmental effects data for individual Events TC1507 (see U.S. EPA 

(2010d)), MON 810 (see U.S. EPA (2010d)), and DAS-59122-7 (see section II(C)(2)(b) of this BRAD), 

as well as for combination PIP product TC1507 x 59122-7 (see section II(C)(3)(b) of this BRAD), as set 

forth in the February 24, 2010 1507 x 59122 x MON 810 and 59122 x MON 810 registration notices, 

have been satisfied. 

5. References

Andow DA, Hilbeck A. 2004. Science-based risk assessment for nontarget effects of transgenic crops. 

Bioscience 54(7):637–649. 

 

Andow DA, Zwahlen C. 2006. Assessing environmental risks of transgenic plants. Ecology Letters

9:196–214. 

Beachy RN, Federoff NV, Goldberg RB, McHughen A. 2008. The burden of proof: a response to RosiMarshall et al. Proceedings of the National Academy of Sciences of the United States of America, 

pp. 0711431105. Available from: http://www.ask-force.org/web/Bt/Beachy-Rosi-MarshallBurden-2008.pdf. 

Beadle G. 1980. The ancestry of corn. Sci. American 242:112–119. 

Benz B. 2000. Personal communication. Botanist, Professor, Department of Biology, Texas Wesleyan 

University, Fort Worth, Texas. 

Bradley K. 2000. Personal communication. Botanist, Institute for Regional Conservation, Miami, 

Florida. 

De Schrijver A, Devos Y, Van den Bulcke M, Cadot P, De Loose M, Reheul D, Sneyers M. 2007. Risk 

assessment of GM stacked events obtained from crosses between GM events. Trends in Food 

Science & Technology 18:101–109. 

 

DeWald C. 1999. Personal communication. Plant Breeder and Geneticist, United States Department of 

Agriculture (USDA) – Agricultural Research Service (ARS), Woodward, Oklahoma 

(580-256-7449). 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

106

DeWald CL, Sims PL, Li Y, Sokolov V. 1999. A novel cytoplasm for maize. Maize Genetics 

Conference Abstracts 41:114. 

Doebley JF. 1984. Maize introgression into teosinte - A reappraisal. Ann. Missouri Bot. Gard. 

71:1100–1113. 

Doebley JF. 1990. Molecular evidence for gene flow among Zea species. BioScience 40:443–448. 

Doebley JF. 2000. Personal communication. Geneticist/Visiting Professor, Department of Genetics, 

University of Wisconsin, Madison, Wisconsin (608-265-5803). 

Doebley JF, Goodman MM, Stuber CW. 1987. Patterns of isozyme variation between maize and 

Mexican annual teosinte. Econ. Bot. 41(2):234–246. 

Duan JJ, Marvier M, Huesing J, Dively G, Huang ZY. 2008. A meta-analysis of effects of Bt crops on 

honey bees (Hymenoptera: Apidae). PLoS ONE 3(1):e1415. 

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0001415. 

Duvick S. 1999. Personal communication. Geneticist, Department of Plant Genetics, Iowa State 

University, Ames, Iowa (515-294-9375). 

Edwards JW, Allen JO, Coors JG. 1996. Teosinte cytoplasmic genomes: I. Performance of maize 

inbreds with teosinte cytoplasms. Crop Sci. 36:1088–1091. 

Galinat WC. 1983. The origin of maize as shown by key morphological traits of its ancestor teosinte. 

Maydica 28:121–138. 

Galinat WC. 1988. The Origin of Corn, pp. 1–31. In: Corn and corn improvement, Third Edition. 

Sprague GF, Dudley JW (Eds.). American Society of Agronomy, Crop Science Society of 

America, and Soil Science Society of America, Madison, Wisconsin. 

Hall D. 2000. Personal communication. Forensic Botanist and Environmental Consultant, Gainesville, 

Florida (352-375-1370). 

Hilbeck A, Andow DA, Arpaia S, Birch ANE, Fontes EMG, Lövei GL, Sujii ER, Wheatley RE, 

Underwood E. 2006. Methodology to support non-target and biodiversity risk assessment. In: 

Environmental risk assessment of genetically modified organisms: Vol. 2. Methodologies for 

assessing Bt cotton in Brazil, pp. 108–132, Hilbeck A, Andow D, Fontes EMG (Eds.), CABI, 

Wallingford, Oxfordshire. 

Hitchcock AS. 1971. In: Manual of the grasses of the United States. Dover Publications, Mineola, 

 New York. ISBN 0486227170 and 0486227189. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

107

Holm L, Pancho JV, Herberger JP, Plucknett DL. 1979. In: A geographical atlas of world weeds. John 

Wiley and Sons, New York, New York. pp. 391. ISBN 0471043931. 

Hönemann L, Zurbrügg C, Nentwig W. 2008. Effects of Bt-corn decomposition on the composition of 

the soil meso- and macrofauna. Applied Soil Ecology 40:203–209. 

Iltis HH. 1983. From teosinte to maize: The catastrophic sexual transmutation. Science 222:886–894. 

Iltis H. 2000. Personal communication. Professor Emeritus of Botany, University of Wisconsin, 

Madison, Wisconsin (608-262-7247). 

Jemison J, Vayda M. 2000. University of Maine at Orono, Pollen transport from genetically engineered 

corn to forage corn hybrids: A case study. Abstract presented to the Maine Agricultural Trade 

Show, January 2000. 

Kato-Y TA. 1997a. Review of Introgression between maize and teosinte. In: Gene flow among maize 

landraces, improved maize varieties, and teosinte: Implications for transgenic maize, 

pp. 44–53, Serratos JA, Wilcox MC, Castillo-Gonzalez F (Eds.), Mexico, D.F., CIMMYT. 

Kato-Y TA. 1997b. Plenary session: Analysis of workshop reports and discussions. Group I report. In: 

Gene flow among maize landraces, improved maize varieties, and teosinte: Implications for 

transgenic maize, pp. 94–103, Serratos JA, Wilcox MC, Castillo-Gonzalez F (Eds.), Mexico, 

D.F., CIMMYT. 

Kermicle JL. 1997. Cross incompatibility within the genus Zea. In: Gene flow among maize landraces, 

improved maize varieties, and teosinte: Implications for transgenic maize, pp. 40–43, Serratos 

JA, Wilcox MC, Castillo-Gonzalez F (Eds.), Mexico, D.F., CIMMYT. 

Kermicle JL, Allen JO. 1990. Cross-incompatibility between maize and teosinte. Maydica 35:399–408. 

Lambert J. 1999. Personal communication. Plant Breeder and Geneticist, Department of Crop Sciences, 

University of Illinois, Champaign-Urbana, IL (217-333-9642). 

Lawo NC, Romeis J. 2008. Assessing the utilization of a carbohydrate food source and the impact of 

insecticidal proteins on larvae of the green lacewing, Chrysoperla carnea. Biological Control

44:389–398. 

Magoja JL, Pischedda G. 1994. Maize x Teosinte hybridization. Biotechnology in Agriculture and 

Forestry 25:84–101. In: Maize, (Ed.) Y.P.S. Bajaj, Springer-Verlag, Berlin, Heidelberg. 

Mangelsdorf PC. 1947. The origin and evolution of maize. In: Advances in genetics, (Ed.) M. Demerec, 

1:161–207, Academic Press, New York. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

108

Mangelsdorf PC, Reeves RG. 1939. The origin of Indian corn and its relatives, Texas Agricultural 

Experiment Station Bulletin 574 (monograph):80–81, 89–109. 

Marvier M, McCreedy C, Regetz J, Kareiva P. 2007. A meta-analysis of effects of Bt cotton and 

maize on nontarget invertebrates. Science 316:1475–1477. 

MRID No. 452422-04. Herman R. 2000. Microbial PS149B1 Binary Delta-Endotoxin: Maize-Insect- 

 Pest Susceptibility Study. Lab Project Number: 000366. Unpublished study prepared by Dow 

 AgroSciences LLC, 29 pages. 

MRID No. 452422-10. Bryan R, Porch J, Krueger H. 2000. PS149B1 Insecticidal Crystal Protein: A 

Dietary Toxicity Study with the Lady Bird Beetle – Final Report. Lab Project Number: 379-103. 

Unpublished study prepared by Wildlife International, Limited, 18 pages. 

MRID No. 452422-11. Higgins L. 2000. The Tri-Trophic Interaction Between PS149B1 

Transformed Maize, Corn Leaf Aphid and Ladybird Beetle. Lab Project Number: PHI-2000- 

022. Unpublished study prepared by Trait and Technology Development, 145 pages. 

MRID No. 452422-14. Herman R, Collins R, Young D. 2000. Degradation of Microbial Binary 

PS149B1 Delta-Endotoxin in a Representative Soil from the Mid-Western USA MaizeGrowing Region. Lab Project Number: 000365. Unpublished study prepared by Dow 

AgroSciences LLC, 26 pages. 

MRID No. 453407-01. Maggi V. 2001. Microbial PS149B1 Binary Insecticidal Crystal Protein, 

Pollen Expressing PS149B1 Binary Insecticidal Crystal Protein, and Individual PS149B1 14 kDa 

and 44 kDa Insecticidal Crystal Proteins: Evaluation of Dietary Exposure on Honeybee 

Development. Lab Project Number: CAR 149-00. Unpublished study prepared by California 

Agricultural Research, Incorporated, 58 pages. 

MRID No. 453602-01. Bryan R, Porch J, Krueger H. 2000. PS149B1 Binary Insecticidal Crystal 

Protein: Acute Toxicity to the Earthworm in an Artificial Substrate – Final Report. Lab 

Project Number: 379-104. Unpublished study prepared by Wildlife International, Limited, 22 

pages. 

MRID No. 457904-03. Marino T, Yaroch A. 2002. PS149B1 Binary Insecticidal Crystal Protein: An 

8-Day Dietary Toxicity Study with the Rainbow Trout, Oncorhynchus mykiss, Walbaum. Lab 

Project Number: 011193. Unpublished study prepared by The Dow Chemical Company, 31 

pages. 

MRID No. 457904-04. Marino T, Yaroch A. 2001. PS149B1 Binary Insecticidal Crystal Protein: An 

Acute Toxicity Study with the Daphnid, Daphnia magna Straus. Lab Project Number: 011137. 

Unpublished study prepared by The Dow Chemical Company, 28 pages. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

109

MRID No. 457904-05. Porch J, Krueger H. 2001. PS149B1 Binary Insecticidal Crystal Protein: Dietary 

Toxicity to Parasitic Hymenoptera (Nasonia vitripennis) – Final Report. Lab Project Number: 

379-115. Unpublished study prepared by Wildlife International, Limited, 27 pages. 

MRID No. 457904-06. Teixeira D. 2001. Assessment of Chronic Toxicity of Diet Containing Bacillus 

thuringiensis PS149B1 Insecticidal Crystal Protein to Collembola (Folsomia candida). Lab 

Project Number: 12550.6142: 011106. Unpublished study prepared by Springborn Laboratories, 

Incorporated, 35 pages. 

MRID No. 457904-07. Sindermann A, Porch J, Krueger H. 2001. PS149B1 Insecticidal Crystal Protein: 

Dietary Toxicity to Green Lacewing Larvae (Chrysoperla carnea) – Final Report. Lab Project 

Number: 379-116A: 011104. Unpublished study prepared by Wildlife International, Limited, 30 

pages. 

MRID No. 461239-11. Smith B, McNaughton J, Hinds M. 2003. Nutritional Equivalency Study of 

Maize Containing Cry34Ab1 and Cry35Ab1: Poultry Feeding Study. Project Number: 

2001/OPT/48/BB, PHI/2001/043. Unpublished study prepared by Woodson-Tenent Lab, 

Incorporated, Exygen Research, and Pioneer Hi-Bred International, Incorporated, 33 pages. 

MRID No. 461239-12. Higgins L. 2003. The Effect of Cry34Ab1/Cry35Ab1 Proteins on the 

Development and Mortality of the Ladybird Beetle, Coleomegilla maculata DeGeer. Project 

Number: PHI/2003/045. Unpublished study prepared by Pioneer Hi-Bred International, 

Incorporated, 97 pages. 

MRID No. 461239-13. Poletikia N. 2003. Non-Target Invertebrate Ecological Risk Assessment for Field 

Corn Expressing Cry34Ab1 and Cry35Ab1 Insecticidal Crystal Proteins in Event DAS-59122-7. 

Project Number: GH/C/5681. Unpublished study prepared by Dow AgroSciences LLC, 98 pages. 

MRID No. 461239-14. Higgins L, Wright D. 2003. Evaluation of the Impact of Corn Rootworm Control 

Strategies on Non-Target Arthropods. Project Number: PHI/2001/020. Unpublished study 

prepared by Pioneer Hi-Bred International, Incorporated, 85 pages. 

MRID No. 461239-17. Higgins L. 2003. Evaluation of Endangered/Threatened Insect Species Relative 

to the Use of Cry34Ab1/Cry35Ab1 Corn Rootworm-Resistant Maize Hybrids. Project Number: 

PHI/2003/25. Unpublished study prepared by Pioneer Hi-Bred International, Incorporated, 407 

pages. 

MRID No. 462971-02. Weber N, Pfrogner B. 2004. Characterization of a Stacked Hybrid of 

 Transgenic Corn Lines DAS-01507-1 and DAS-59122-7 by Comparison to the Individual 

 Lines. Project Number: PHI/2003/049. Unpublished study prepared by E.I. Dupont de 

 Nemours and Company, 35 pages. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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110

MRID No. 463438-01. Buffington J. 2004. Agronomic Characteristics, Quantitative ELISA, and 

 Nutrient Composition Analysis of Hybrid Maize Lines Containing cry1F, cry34Ab1, 

cry35Ab1, and pat Genes: U.S. and Canada Locations: Amended Final Report. Project 

 Number: PHI/2003/017. Unpublished study prepared by Dow AgroSciences LLC, EPL 

 Bio-Analytical Services, and Bennett Agricultural Research and Consulting, 1,114 pages. 

MRID No. 463438-03. Delaney B, Smith B. 2004. Nutritional Equivalency Study of Stacked Hybrid of 

Transgenic Maize Line 1507 (Event DAS-01507-1) and 59122 (Event DAS-59122-7): Poultry 

Feeding Study. Project Number: 2003/OPT/56/BB, PHI/2003/047. Unpublished study prepared 

by Solution BioSciences, Incorporated, Woodson-Tenent Laboratories, Incorporated, and 

Pioneer Hi-Bred Corn Company Production Department, 214 pages. 

MRID No. 463438-06. Herman R, Storer N. 2004. Investigation of Potential Interaction Between Cry1F 

and the Binary Cry34Ab1/Cry35Ab1 Proteins. Project Number: GH/C/5748. Unpublished study 

prepared by Dow AgroSciences LLC, 12 pages. 

MRID No. 463438-07. Higgins L. 2004. The Effect of Maize Pollen Expressing the Cry1F and 

Cry34Ab1/Cry35Ab1 Proteins on the Development and Mortality of the Ladybird Beetle 

(Coleomegilla maculata DeGeer): Final Report. Project Number: PHI/2004/001. Unpublished 

study prepared by Pioneer Hi-Bred Corn Company Production Department, 74 pages. 

MRID No. 463438-08. Staley J. 2004. Laboratory Bioassay Assessment of Corn Pollen Protein, 

(Cry34/Cry35 and Cry1F, Stacked Transgenes), and Their Effect on the Larvae of the Monarch 

Butterfly. Project Number: PHI/2004/032. Unpublished study prepared by Pioneer Hi-Bred Corn 

Company Production Department, 26 pages. 

MRID No. 467141-01. Comstock B. 2005. Summary Report of a Carabid Beetle Laboratory Toxicity 

Study Using Cry34Ab1 and Cry35Ab1 Including Copies of References. Project Number: 

PHI/2005/092, PIO/04/1. Unpublished study prepared by Mambo-Tox Limited, Pioneer Hi-Bred 

International, Incorporated, and Biologische Bundesanstalt fuer Land- and Forstwirtschaft, 197 

pages. 

MRID No. 474367-01. Patnaude M. 2008. Evaluation of Potential Dietary Effects of Cry34/35Ab1 

Protein on Insidious Flower Bugs, Orius insidiosus (Hemiptera: Anthocoridae). Project Number: 

13855/6105, PHI/2004/099, 092705/OPPTS/PIONEER. Unpublished study prepared by 

Springborn Smithers Laboratories, 41 pages. 

MRID No. 476778-01. Brink K, Dietrich N. 2009. Molecular Characterization of Maize Combined 

 Trait Product DAS-01507-1 x DAS-59122-7 x MON-00810-6 x MON-00603-6 Using 

 Southern Blot Analysis and Event-Specific Polymerase Chain Reaction. Project Number: 

 PHI/2008/082. Unpublished study prepared by E.I. Dupont de Nemours and Company, 

 42 pages. 
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MRID No. 476778-02. Binning R. 2009. Laboratory Characterization of Key Lepidopteran Pest 

 Response to Pyramided Events. Project Number: PHI/2008/101. Unpublished study prepared 

 by Pioneer Hi-Bred International, Incorporated, 16 pages. 

MRID No. 478703-01. Higgins L, Storer N, Pascual M. 2009. Three-Year Field Monitoring of 

Cry34/35Ab1 and Cry1F x Cry34/35Ab1 Maize Hybrids for Nontarget Arthropod Effects. 

Project Number: PHI/2009/160. Unpublished study prepared by Pioneer Hi-Bred Corn Company 

Production Department, Dow AgroSciences LLC, and Pioneer Hi-Bred International, 

Incorporated, 48 pages. 

MRID No. 478800-01. Staley J, Rood T, Johnson T. 2009. Expressed Trait Protein Concentration of 

 Maize Lines Containing Events DAS-01507-1, DAS-59122-7, MON-00810-6, and 

 Combined Trait Products DAS-01507-1 x MON-00810-6, DAS-59122-7 x MON-00810-6, 

 and DAS-01507-1 x DAS-59122-7 x MON-00810-6: Additional Addendum. Project 

 Number: PHI/2009/182. Unpublished study prepared by Pioneer Hi-Bred International, 

 Incorporated, 110 pages. 

MRID No. 479595-01. Dunville C, Sosa M, Herman R. 2010. Soil Accumulations of Cry34Ab1 and 

Cry35Ab1 Proteins after Three Years of Cropping with DAS-59122-7 Corn. Project Number: 

060016. Unpublished study prepared by Dow AgroSciences LLC, 43 pages. 

Muir WM, Howard RD. 2001. Fitness components and ecological risk of transgenic release: a model 

using Japanese medaka (Oryzias latipes). The American Naturalist 158:1–16. 

National Academy of Sciences (NAS). 2000. Environmental Effects of Transgenic Plants: The Scope 

and Adequacy of Regulation is available from the National Academies Press, 500 Fifth Street 

NW, Lockbox 285, Washington, D.C. 20055; (888) 624-8373 or (202) 334-3313 (in the 

Washington D.C. metropolitan area); http://www.nap.edu/. 

Oliveira AP, Pampulha ME, Bennett JP. 2008. A two-year field study with transgenic Bacillus 

 thuringiensis maize: Effects on soil microorganisms. Science of the Total Environment 405:351–

357. 

Orzell S. 2000. Personal communication. Botanist/Ecologist, United States Air Force, Avon Park Air 

Force Range, Florida, 2000. 

Parrott W. 2008. Study of Bt impact on caddisflies overstates its conclusions: response to Rosi-Marshall 

et al. Proceedings of the National Academy of Sciences of the United States of America, pp. E10. 

Available from: http://www.ask-force.org/web/Bt/Parrott-Rosi-Marshall-2008.pdf. 

Read J. 2000. Personal communication. Professor, Texas Agricultural Experiment Station, Dallas, Texas 

(972-231-5362). 
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Romeis J, Meissle M, Bigler F. 2006. Transgenic crops expressing Bacillus thuringiensis toxins and 

 biological control. Nature Biotechnology 24:63–71. 

Rosi-Marshall EJ, Tank JL, Royer TV, Whiles MR, Evans-White M, Chambers C, Griffiths NA, 

 Pokelsek J, Stephen ML. 2007. Toxins in transgenic crop byproducts may affect headwater 

 stream ecosystems. Proceedings of the National Academy of Sciences of the United States of 

 America 104(41):16204–16208. 

Rosi-Marshall EJ, Tank JL, Royer TV, Whiles MR. 2008. Reply to Beachy et al. and Parrott: study 

 indicates Bt corn may affect caddisflies. Proceedings of the National Academy of Sciences of the 

 United States of America, 105, 7, pp. E11–E11. Available from: 

http://www.ask-force.org/web/Bt/Rosi-Marschall-Bt-Aquatic-reply-2008.pdf. 

Sanvido O, Romeis J, Bigler F. 2007. Ecological impacts of genetically modified crops: ten years of 

field research and commercial cultivation. Advances in Biochemical Engineering and 

Biotechnology 107:235–278. 

Saxena D, Stotzky G. 2001. Bacillus thuringiensis (Bt) toxin released from root exudates and biomass of 

Bt corn has no apparent effect on earthworms, nematodes, protozoa, bacteria, and fungi in soil. 

Soil Biology and Biochemistry 33:1225–1230. 

Schoper J. 1999. Personal communication. Geneticist, Pioneer Hi-Bred International, Johnston, Iowa 

 (515-270-3544). 

Smith JSC, Goodman MM, Stuber CW. 1985. Relationships between maize and teosinte of Mexico and 

Guatemala: Numerical analysis of allozyme data. Econ. Bot. 39:12–24. 

U.S. EPA. 1998. “Guidelines for Ecological Risk Assessment.” EPA 630/R-95-002F. Washington, 

D.C., USA. [Federal Register, May 14, 1998. 63(93): 26846–26924.] 

U.S. EPA. 2000. SAP Report No. 99-06. Sets of Scientific Issues Being Considered by the 

Environmental Protection Agency Regarding: Section I – Characterization and Non-Target 

Organism Data Requirements for Protein Plant-Pesticides. Dated February 4, 2000. Available 

from: http://www.epa.gov/scipoly/sap/meetings/1999/december/report.pdf. 

U.S. EPA. 2001a. SAP Report No. 2000-07. Sets of Scientific Issues Being Considered by the 

Environmental Protection Agency Regarding: Bt Plant-Pesticides Risk and Benefit Assessments. 

Dated March 12, 2001. Available from: 

http://www.epa.gov/scipoly/sap/meetings/2000/october/octoberfinal.pdf. 
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U.S. EPA. 2001b. Ecological Risk Assessment for Mycogen Seeds c/o Dow AgroSciences and Pioneer 

Hi-Bred International Applications for Experimental Use Permits for Bacillus thuringiensis

PS149B1 Insecticidal Crystal Protein as Expressed in Maize for Control of Western Corn 

Rootworm and Northern Corn Rootworm. Memorandum from R. Rose and Z. Vaituzis, Ph.D. to 

M. Mendelsohn dated May 15, 2001. 

U.S. EPA. 2001c. Review of Product Characterization, Expression Analysis and Acute Oral Toxicity 

Studies for PS149B1 Binary Insect Control Proteins as Expressed in Maize, a Bacillus 

thuringiensis-Based Plant-Pesticide, for an Experimental Use Permit. Memorandum from C.A. 

Wozniak, Ph.D. and J.L. Kough, Ph.D. to M. Mendelsohn dated June 7, 2001. 

U.S. EPA. 2001d. Biopesticides Registration Action Document – Bacillus thuringiensis Plant- 

 Incorporated Protectants. Available from: 

 http://www.epa.gov/oppbppd1/biopesticides/pips/bt_brad.htm. 

U.S. EPA. 2002. SAP Meeting Minutes No. 2002-05. A Set of Scientific Issues Being Considered by the 

Environmental Protection Agency Regarding: Corn Rootworm Plant-Incorporated Protectant 

Non-Target Insect and Insect Resistance Management Issues. Dated November 6, 2002. 

Available from: http://www.epa.gov/scipoly/sap/meetings/2002/august/august2002final.pdf. 

U.S. EPA. 2004a. Reviews of Honeybee Dietary and Earthworm Acute Toxicity Studies for Bacillus 

thuringiensis Cry34Ab1 and Cry35Ab1 Proteins and the Genetic Material Necessary for 

Their Production in Corn. Memorandum from H. Hill and Z. Vaituzis, Ph.D. to M. 

Mendelsohn dated March 30, 2004. 

 

U.S. EPA. 2004b. SAP Report No.2004-05. Product Characterization, Human Health Risk, 

Ecological Risk, and Insect Resistance Management for Bacillus thuringiensis (Bt) Cotton 

Products. Dated August 19, 2004. Available from: 

http://www.epa.gov/scipoly/sap/meetings/2004/june/final1a.pdf. 

U.S. EPA. 2005a. Review of PS149B1 Binary Insecticidal Crystal Protein TGAI Non-Target Studies. 

Memorandum from J. Gagliardi, Ph.D. and Z. Vaituzis, Ph.D. to M. Mendelsohn dated May 5, 

2005. 

U.S. EPA. 2005b. Assessment of Chronic Toxicity of Diet Containing Bacillus thuringiensis PS149B1 

Insecticidal Crystal Protein to Collembola (Folsomia candida). Memorandum from Z. Vaituzis, 

Ph.D. to T. Milofsky and D. Szuhay dated May 18, 2005. 

 

U.S. EPA. 2005c. Environmental Risk Assessment for Cry34/35Ab1 Bacillus thuringiensis Binary 

 Protein and the Genetic Material Necessary for Its Production in Corn. Memorandum from T. 

 Milofsky and Z. Vaituzis, Ph.D. to M. Mendelsohn dated July 19, 2005. 
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U.S. EPA. 2005d. Biopesticides Registration Action Document – Bacillus thuringiensis 

Cry1F Corn. Available from: 

http://www.epa.gov/oppbppd1/biopesticides/ingredients/tech_docs/brad_006481.pdf. 

U.S. EPA. 2005e. Environmental Effects Assessment of HerculexTM Xtra Stacked Cry34/35Ab1 x 

Cry1F Proteins and the Genetic Material Necessary for Their Production in Corn. Memorandum 

from T. Milofsky and Z. Vaituzis, Ph.D. to M. Mendelsohn dated September 15, 2005. 

U.S. EPA. 2005f. Review of Product Characterization and Human Health Data for Registration of 

 HerculexTM Xtra Insect Resistant Corn. Memorandum from R.L. Edelstein, Ph.D. and J.L. 

 Kough, Ph.D. to M. Mendelsohn dated September 22, 2005. 

U.S. EPA. 2010a. Review of Human Health and Product Characterization Data for Registration of 

Bacillus thuringiensis (Bt) Cry1F, Cry34Ab1, Cry35Ab1, and Cry1Ab Proteins and the 

 Genetic Material Necessary for Their Production in the Combination Plant-Incorporated 

 Protectant (PIP) Products: 1507 x MON 810 [EPA Reg. No. 29964-T], 59122 x MON 810 

 [EPA Reg. No. 29964-O], and 1507 x 59122 x MON 810 [EPA Reg. No. 29964-I]. 

 Memorandum from A. Waggoner and J.L. Kough, Ph.D. to A. Sibold dated 

 February 19, 2010. 

U.S. EPA. 2010b. Review of Carabid (MRID No. 467141-01) and Orius (MRID No. 474367-01) Insect 

Studies Submitted as a Condition of Registration for Mycogen Seeds/Dow AgroSciences and 

Pioneer Hi-Bred International Cry34Ab1 and Cry35Ab1 Protein in Corn (HerculexTM EPA Reg. 

No. 68467-5). Memorandum from Z. Vaituzis, Ph.D. to M. Mendelsohn dated July 8, 2010. 

U.S. EPA. 2010c. Review of Multi-Year Field Studies on Non-Target Arthropod Populations and Soil 

Persistence for PIP Corn Events: TC1507 [Herculex ITM, EPA Reg. 68467-2, 29964-3], DAS59122-7 [Herculex RWTM, EPA Reg. 68467-5, 29964-4], and Its Associated Stacked DAS59122-7 x TC1507 Hybrid [Herculex XTRATM, EPA Reg. 68467-6, 29964-5], Expressing Bt

Cry1F, Cry34Ab1/Cry35Ab1, and Cry1F x Cry34Ab1/Cry35Ab1, Respectively. Memorandum 

from A. Waggoner and Z. Vaituzis, Ph.D. to M. Mendelsohn dated July 12, 2010. 

U.S. EPA. 2010d. Biopesticides Registration Action Document – Bacillus thuringiensis 

Cry1Ab and Cry1F Corn. Available from: http://www.regulations.gov (see “Supporting & 

Related Materials” within Docket Number EPA-HQ-OPP-2010-0607). 

USDA APHIS. 1997. USDA/APHIS Petition 97-265-01 for Determination of Nonregulated Status for Bt

Cry9C Insect Resistant and Glufosinate Tolerant Corn Transformation Event CBH- 351: 

Environmental Assessment. USDA, APHIS, Riverdale, Maryland. 

Van den Brink P, Ter Braak CJF. 1999. Principal Response Curves: Analysis of Time-Dependent 

 Multivariate Responses of Biological Community to Stress. Environmental Toxicology and 

 Chemistry 18:138–148. 
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Wilkes GH. 1967. Teosinte: The closest relative of maize. Bussey Institute, Harvard University, 

Cambridge, MA. 

Wilkes GH. 2000. Personal communication. Professor of Plant Genetics, University of Massachusetts, 

Amherst, Massachusetts (617-287-6662). 

Wilson H. 2000. Personal communication. Professor of Biology, Texas A&M University, College 

Station, Texas (409-845-3354). 

Wolfenbarger LL, Naranjo SE, Lundgren JG, Bitzer RJ, Watrud LS. 2008. Bt effects on functional 

 guilds of non-target arthropods: a meta-analysis. PLoS ONE 3(5):e2118. 

http://dx.doi.org/10.1371/journal.pone.0002118. 

Wunderlin R. 2000. Personal communication. Professor of Botany, Institute for Systematic Botany, 

University of South Florida, Tampa, Florida (813-974-2359). 
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D. Insect Resistance Management (IRM) 

1. Supporting Information for Development of the Cry34/35 Event DAS-59122-7 Corn Durability 

 Plan (2005 Registration) 

 a. Pest Biology

A clear understanding of pest biology is essential to the development of a sound IRM plan. Cry34/35 

Bacillus thuringiensis (Bt) corn was developed to control three target pest species: western corn 

rootworm (Diabrotica virgifera virgifera LeConte, WCRW), northern corn rootworm (Diabrotica 

barberi Smith and Lawrence, NCRW) and Mexican corn rootworm (Diabrotica virgifera zeae Krysan 

and Smith, MCRW). Key factors believed to influence corn rootworm (CRW) adaptation to Cry34/35 

corn include distribution, univoltinism, adult dispersal among fields, adult dispersal within fields, larval 

dispersal across rows, larval mortality due to density-dependent processes, insecticide use, egg 

mortality, fecundity, and adult and larval population density. Some of these factors are discussed below. 

Distribution 

WCRW is the most prevalent target pest in the United States and throughout most of the Corn Belt1

. 

NCRW, also found throughout the Corn Belt, is considered the second most prevalent rootworm pest in 

the United States and is the primary target pest of the north-central region2. MCRW, the third target 

pest, is limited to Texas, is considered a relatively minor pest in the United States, and is generally 

excluded from discussion in the data package. Southern corn rootworm (SCRW), also a minor pest of 

corn in the U.S., is not identified as a target pest of Cry34/35-protected corn. 

Life Cycle 

The traditional life cycle of CRW is as follows: adult female rootworms deposit eggs in corn fields 

during late summer; eggs overwinter and hatch in late-spring, generally between late May and mid-June; 

larvae feed on corn roots for three to four weeks, during which time they complete three instar stages 

(most significant damage to corn plants caused during this period); the third instar transforms into a 

pupa, which develops for one to two weeks; pupae mature to become adult beetles, which emerge from 

the soil in mid-July to feed on corn foliage, pollen, and silks; adults remain active for 10 to 12 weeks, 

during which time they feed, mate, and deposit eggs. 

Recently, deviations from the traditional life-cycle have emerged. A biotype of WCRW is depositing 

eggs in soybean fields, while a NCRW biotype has broken from the traditional univoltine life cycle by 

utilizing an extended diapause. In affected regions, these adaptations diminish the pest control benefits 

 

1

 WCRW is the primary rootworm pest in Colorado, Kansas, Nebraska, Ohio, Indiana, Illinois, Iowa, Missouri, and 

Michigan. 

2

 NCRW is the primary rootworm pest in Wisconsin, Minnesota, South Dakota, and northern Iowa.
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associated with corn-soybean/corn-alternate crop rotations, a management practice that has long been 

recognized as the most effective means of controlling CRW.

Dispersal/Movement 

Much remains to be learned about CRW larval and adult dispersal patterns; however, some preliminary 

research has been completed. In their study of larval movement between corn rows, Hibbard et al. 

(2003) reported that 0.75% and 6% of larvae moved across rows. Larval movement was largely 

dependent on the density of plants within a row, food availability, soil porosity, and level of soil 

compaction. 

In their discussion of adult dispersal factors (reference to model discussion), the applicants referenced 

Nowatzki et al.’s research (Nowatzki et al. 2003), which described a study of male and female WCRW 

dispersal in a commodity grain field. Results of this research indicate that males moved at least 184 

meters (m) in 4 days, or 45 m per day, while females took around 14 days to move the same distance, 

traveling up to 13 m per day. 

The applicants also referenced Hill and Mayo’s (1980) research on interfield dispersal, which shows that 

NCRW was three times more prevalent than WCRW in first-year corn, yet that NCRW populations were 

half of WCRW in second-year corn. Lance et al. (1988) later reported that NCRW adults are more likely 

than WCRW to disperse from mature corn and, further, that NCRW has a tendency to disperse from 

corn to feed on flowers and pollen of other plants (Naranjo 1994). 

Biopesticides and Pollution Prevention Division (BPPD)’s Analysis of Pest Biology

Sufficient information has been provided on the pest biology of western corn rootworm, northern corn 

rootworm, and Mexican corn rootworm to develop an IRM strategy. Because there are still information 

gaps, additional information on WCRW, NCRW, and MCRW biology and ecology could improve 

understanding of resistance risks and lead to improvements in the IRM strategies. Specific areas to be 

examined include the following: dispersal behavior (categorized by sex and developmental stage); 

reproductive biology, including mating habits and frequency, ovipositional patterns, role of densitydependent mortality, use of non-corn hosts, and fecundity; level of Cry34/35 expression in corn roots 

relative to developmental stage of CRW pests; determination of whether IRM strategies designed for 

WCRW and NCRW are appropriate for MCRW; and the effect that new rotation-resistant WCRW and 

NCRW biotypes may have on the development of appropriate IRM strategies. These research efforts are 

recommended to be continued and bolstered. New information published since the trait durability plan 

was submitted to the Environmental Protection Agency (EPA) regarding CRW larval dispersal in the 

field and use of non-maize host as unstructured refuge should be considered, as appropriate, in the 

model (Hibbard et al., 2003; Hibbard et al., 2004; Moeser and Hibbard 2005; Oyediran et al. 2004; 

Clark and Hibbard 2004). 
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 b. Mode of Action and Cross-Resistance

Cry34Ab1 (14-kiloDalton (kDa)) and Cry35Ab1 (44-kDa) proteins are both required for high activity 

against WCRW larvae (Ellis et al. 2002). The mode of action appears to be similar to other Bt proteins. 

Experimental feeding studies conducted by Moellenbeck et al. (2001) with WCRW neonates and later 

(2nd and 3rd) instar indicated that these proteins bind to midgut receptors, followed by membrane 

disruption. As a result, high levels of resistance to Cry34/35Ab1 will likely result from loss of binding 

or loss of activity following bindings, as reported for other Cry proteins (Ferré and Van Rie 2002). 

Amino acid sequence comparisons did not show any significant similarity between the 14- and 44-kDa 

proteins (Cry34Ab1 and Cry35Ab1, respectively) and other registered Bt plant-incorporated protectants, 

including the Cry3 family (Ellis et al. 2002). These proteins also share no sequence homology with the 

Bt vegetative insecticidal proteins (VIPs). Because of this lack of sequence homology with known Bt

plant-incorporated protectants (PIPs) and VIPs, Storer and Lefko (2003, Master Record Identification 

Number (MRID No.) 461239-18) assume that high levels of cross-resistance development is unlikely 

with any other rootworm-targeted Bt proteins. Field trials conducted in areas where methyl-parathion 

resistance is present and absent showed no associated difference in adult emergence (Storer et al. 2003, 

MRID No. 461239-15). Similarly, field trials in areas where rotational-adapted populations (behavioral 

resistance) of NCRW and WCRW are present and absent showed no associated differences in adult 

emergence (Storer et al. 2003, MRID No. 461239-15). Agricultural systems in which Cry34/35 corn is 

deployed will likely reduce the selection pressure for resistance to alternative corn rootworm control 

tactics, including other PIPs. Simulation models have shown that the use of Cry34/35 corn can reverse 

selection for rotation resistance in WCRW (Storer 2003b, MRID No. 461239-19). 

The 14-kDa protein (Cry34Ab1) alone shows some insecticidal activity against southern corn rootworm 

(Diabrotica undecimpunctata howardi Barber), but was enhanced by the 44-kDa protein (Cry35Ab1), 

indicating that both proteins are necessary for maximal insecticidal activity (Herman et al. 2002). A 

recent study by Masson et al. (2004) provided evidence that Cry34Ab1/Cry35Ab1 causes pore 

formation in the midgut, which results in membrane permeability. This study provides evidence that the 

mode of action is similar to that previously identified for other B. thuringiensis and Bacillus sphaericus

toxins. 

Receptor binding sites for Cry34Ab1 and Cry35Ab1 have not been identified and characterized. Ellis et 

al. (2002) indicate that there is little sequence homology between the Cry34Ab1 and Cry35Ab1 proteins 

and other registered Cry proteins and VIPs. Lack of sequence similarity would suggest that high levels 

of cross-resistance conferred by Cry34Ab1 and Cry35Ab1 would be unlikely. There is some 

evolutionary relatedness between the larger Cry35Ab1 protein (44-kDa) and the 42-kDa and 51-kDa 

dipteran-active toxins from B. sphaericus (Baumann et al. 1988). However, since B. sphaericus

biopesticide products act against dipterans rather than coleopterans, cross-resistance with these toxins 

should not be an issue. Field trials (Storer et al. 2003, MRID No. 461239-15) suggest that there is little 

possibility of cross-resistance between Cry34Ab1/Cry35Ab1 and any other rootworm-control tool. The 

use of Cry34Ab1/Cry35Ab1 corn will likely reduce the selection pressure for resistance to other corn 

rootworm control tactics, including other PIPs. Simulation models predict that use of 
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Cry34Ab1/Cry35Ab1 corn can reverse selection for rotation resistance in WCRW (Storer 2003b, MRID 

No. 461239-19). 

BPPD’s Analysis of Mode of Action and Cross-Resistance 

To confirm that high levels of Cry34Ab1 or Cry35Ab1 cross-resistance with other Bt proteins is 

unlikely, it is recommended that research efforts should focus on determining the likelihood of crossresistance. Midgut binding receptors for Cry34Ab1 and Cry35Ab1 are recommended to be identified 

and characterized. Resistant colonies might be used to study the cross-resistance potential. Models could 

be run with scenarios that include the possibility for cross-resistance to see how the selection for 

resistance is impacted. Resistance may evolve through a detoxification or binding modification 

mechanism, for example, and/or through a behavioral modification mechanism. Multiple mechanisms 

should be considered as one evaluates the cross-resistance potential. This information would provide 

further evidence that cross-resistance is unlikely. 

There is also a potential “repellent” behavior that should be further investigated. It is required that 

additional research efforts focus on characterizing and understanding the implications of this mode of 

action on selection for WCRW and NCRW resistance. 

 

 c. Genetics and Mechanisms of Resistance

The resistance mechanism of the greatest concern is that which could occur through a single gene 

mutation (i.e., monogenic) through loss of effective receptor binding. In nearly all known Bt resistance 

cases that have conferred high levels of resistance, this is the single most common mechanism (Ferré 

and Van Rie 2002). Other forms of resistance, such as metabolic resistance or increased midgut protease 

activity, do not confer high levels of resistance because multiple mutations in individual insects would 

be required to have high fitness on the transgenic plants. The IRM plan is based on the worst-case 

assumption that resistance will be monogenic, with two alleles, one conferring resistance (r-allele) and 

the other conferring susceptibility (S-allele). In addition, there is another worst-case assumption that 

homozygous resistant insects will be completely resistant to Cry34Ab1/Cry35Ab1 corn. 

Tabashnik et al. (2003) reports that most resistance (laboratory-selection) to Cry proteins is incomplete 

meaning that less than 100% of target pests survive on a Bt crop. Incomplete resistance will evolve more 

slowly than complete resistance since the relative fitness of the r-allele compared with the S-alleles will 

be lower. The IRM plan for Cry34Ab1/Cry35Ab1 corn has made the worst-case assumption that 

resistance will be complete and that homozygous resistant individuals would have the same fitness on 

transgenic and non-transgenic plants (i.e., complete resistance). 

The fitness costs of rootworm resistance to Cry34Ab1/Cry35Ab1 are unknown. Resistance to other Bt

proteins has generally been shown to have high fitness costs (Ferré and Van Rie 2002). Despite this 

evidence, the IRM plan assumes the worst-case assumption that there will be no loss of fitness 

associated with resistance. 
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Receptor modifications are the most likely cause of resistance. Resistance will be incompletely to 

completely recessive, and heterozygotes will retain partially functioning Cry protein receptors. 

Resistance associated with receptor modifications usually results in low resistance ratios for 

heterozygotes. IRM plans developed for lepidopteran-protected Bt corn products have assumed that 

heterozygous insects will be 25-fold resistant to the associated Cry proteins, an assumption that was 

deemed sufficiently conservative for PIPs (U.S. EPA 1998 and 2001a). The IRM plan for 

Cry34Ab1/Cry35Ab1 corn assumes that heterozygous insects will be 25-fold resistant to 

Cry34Ab1/Cry35Ab1. This assumption enables the estimation of the functional dominance of the ralleles and, therefore, heterozygote survival used in the Storer model (Storer 2003b, MRID No. 461239-

19). Based on the dose information, the functional dominance is predicted to be around 0.08 in WCRW 

and between 0.15 and 0.37 in NCRW (Storer 2003b, MRID No. 461239-19). 

 

Given the limited availability of information on the genetics of resistance to Cry34/35, the IRM plan 

utilizes “worst-case” assumptions of resistance potential in the modeling simulations of target pest 

adaption to Cry34Ab1/Cry35Ab1 corn (Storer 2003b, MRID No. 461239-19). These assumptions 

include the following: (1) all resistance to Cry34Ab1/Cry35Ab1 is monogenic; (2) all resistance is 

complete; (3) resistance does not confer a fitness cost; and (4) heterozygotes will be 25-fold resistant to 

Cry34Ab1/Cry35Ab1. BPPD agrees with this approach. 

BPPD’s Analysis of Genetics and Mechanism of Resistance 

When resistance does occur, little is known about how that resistance would affect rootworm fitness. 

Most studies of target pest resistance to Bt products and Cry proteins have shown that resistance is 

unstable, most likely due to fitness costs associated with resistance genes or with other closely linked 

loci (Ferré and Van Rie 2002). These findings suggest that the affected midgut receptors may perform 

alternate functions. Despite insights provided by these preliminary investigations, the trait durability 

plan acknowledges that “the fitness costs of rootworm resistance to Cry34/35Ab1 are currently 

unknown” and that further research on fitness costs is needed. 

Given that functional dominance and/or recessiveness of resistance to Cry34/35 is presently unknown 

and will remain unknown until field resistance occurs, resistant (homozygous or heterozygous) colonies 

would be useful to study functional dominance. It is recommended that the applicants establish 

Cry34/35 resistant CRW laboratory colonies to study possible mechanisms, genetics, and inheritance of 

resistance. While useful information is likely from the study of resistant colonies, it is important to note 

that conclusions made from laboratory studies may not necessarily be extended to situations in the field. 

However, even without this confirmatory information, the IRM durability plan is sufficiently 

conservative and assumes the worst case that there will be no fitness costs associated with resistance. 

Laboratory assays submitted by the applicants also suggest a “repellent” behavior. While larvae feeding 

on control plants tended to feed in one location, CRW larvae failed to become established on Cry34/35-

protected corn roots. It follows that inconsistent feeding patterns could contribute to poor larval 

development and decreased fitness. A combination of both behavioral and binding modification 

resistance mechanisms would also slow the rate of resistance evolution. It is recommended that the 
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applicants further study the “repellent” or behavioral mode of action and its implications in the selection 

of resistance. 

 d. Dose

 

The term “high dose” is not well characterized for the CRW complex, and the previous dose definition 

developed for lepidopteran pests (“a level of toxin 25 times greater than is needed to kill all susceptible 

insects”) may not apply to CRW species. Dose evaluation for CRW-targeted PIPs is also complicated by 

the fact that (1) CRW larvae and adults both feed on corn tissues and each life stage must be evaluated 

separately for dose; (2) CRW larvae feed underground, making direct observations of mortality difficult; 

and (3) CRW are notoriously difficult to rear in the laboratory. 

In terms of adult susceptibility and dose, Dow AgroSciences LLC/Pioneer Hi-Bred International, 

Incorporated (Dow/Pioneer) conducted adult feeding studies with WCRW and Cry34/35 corn tissue. 

These studies indicated that adult WCRW feeding (solely) on Cry34/35Ab1 aboveground corn tissue 

does not reduce adult fitness as characterized by longevity, fecundity, or egg viability. Therefore, dose 

considerations for Cry34/35 corn can be relegated to the larval life stage. 

To investigate larval dose, Dow/Pioneer conducted a series of single-season field trials that measured 

adult emergence while correcting for density-dependent mortality to provide an indirect estimate of 

larval mortality. These trials indicated that WCRW larval mortality ranged between 99.82% and 

99.98%, while NCRW larval mortality ranged between 92.77% and 99.14%. Laboratory feeding studies 

were also conducted with neonate, as well as 2nd and 3rd instar, WCRW and NCRW. The lab studies 

documented evidence of repellent or avoidance behavior but did not provide estimates of mortality or 

dose measures. 

The mortality estimates obtained from the field indicate that it is likely that Cry34/35 corn expresses 

slightly less than a high dose for CRW (perhaps a “borderline” high dose) when evaluated relative to the 

previously used “25x” high dose definition. These data for dose were directly applied to CRW models to 

evaluate the durability of the IRM plan. 

BPPD’s Analysis of Dose 

The studies (both larval and adult dose) are acceptable for the purposes of registration and the 

development of an IRM plan for Cry34/35 corn. Nonetheless, there are still significant uncertainties 

regarding the CRW dose expressed in Cry34/35 corn. At best, the results are an educated estimate of the 

true effects of Cry34/35 corn on CRW. The exact toxicity (i.e., mode of action) of the Cry34/35 proteins 

to CRW is unclear: the field studies indicated high levels of mortality, while the laboratory studies 

suggested less toxic mechanisms such as growth inhibition or feeding deterrence. Given these 

uncertainties, it is recommended that Dow/Pioneer continue to research the dose issue, including the 

concept of dose for CRW, specific assays to evaluate dose for rootworm-protected corn hybrids, and the 

role of density dependence in dose determinations. 
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 e. Refuge (General Considerations)

Unstructured refuge

Several non-maize grassy weeds are known to support CRW species. Earlier work characterizing nonmaize hosts of WCRW and NCRW (Branson and Ortman 1970; Branson and Ortman 1971; Siegfried 

and Mullin 1990) has been augmented by the work of Oyediran et al. (2004) and Clark and Hibbard 

(2004) on prairie and forage grasses, and weedy species. The results of these new studies indicate that 

WCRW can readily develop to adulthood by feeding on non-maize hosts and, in the case of pubescent 

wheatgrass, the number of reared adults was not significantly different from that produced on maize 

(Oyediran et al. 2004). 

When alternate hosts are present in close proximity to Cry34/35 corn fields, it is assumed that some 

percentage of target pests develop on alternate plant hosts. As a result, alternate hosts may be considered 

unstructured refuge for target pests. Although much remains to be learned about the role of alternate 

hosts as refuge, the Storer CRW model (Storer 2003a; Storer 2003b, MRID No. 461239-19) makes the 

assumption that 0.5% of larvae attacking Cry34/35 maize have developed on non-maize hosts. 

Technology adoption is expected to be incomplete (and will likely never reach 100%). Therefore, not all 

fields will be planted to Cry34/35 corn, and these will serve as essentially unstructured refuge. This will 

reduce the selection pressure and provide susceptible adults that can mate with any resistant survivors 

from Cry34/35 corn fields. It is important to note, however, that the trait durability plan proposed by 

Dow/Pioneer does not rely on this source of unstructured refuge. 

Alternative hosts, such as common grassy weeds, should not be considered as refuge for CRW-protected 

transgenic corn until more information is available regarding those plants’ ability to produce susceptible 

CRW individuals. Potential areas of investigation could include: 

• Expanded listing of potential alternate hosts, including identification of most promising hosts 

(e.g., most attractive to target pests, most prevalent near Cry34/35 production regions, etc.); 

• CRW movement between maize and non-maize plants at different points in target pest life 

cycle; 

• Impact that movement between Cry34/35 maize and non-maize plants could have on 

resistance/susceptibility of target pests to Cry proteins. 

Even though 100% adoption of Cry34/35 corn is unlikely, unstructured refuge consisting of corn fields 

not planted in Cry34/35 corn is not sufficiently reliable in all production areas. 
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Structured refuge

A structured refuge of non-Cry34/35 corn will function to delay monogenic3 resistance evolution by (1) 

reducing population-wide selection pressure for resistance and (2) providing a source of non-selected 

(SS genotype) adults to mate with any partially or fully-resistant (genotypes rr or rS) adults that may 

survive in the Cry34/35 corn fields. The higher the dose, the more effective the refuge, and thus a 

smaller refuge is required for a given durability. 

Refuge location is important, especially for higher dose traits. Susceptible insects must be produced in 

sufficiently close proximity so that any resistant survivors in the Bt fields are likely to mate with 

susceptible insects rather than amongst themselves. CRW biology potentially favors this inter-mating. 

Males emerge 3–5 days before females, and they actively disperse to seek females. Females, by contrast, 

tend to mate while they are teneral and cannot fly and, therefore, are in close proximity to their 

emergence site. Although CRW long-range dispersal remains poorly understood, a preliminary 

investigation of WCRW movement in a commodity grain field showed that male and female adults 

moved 45 m and 13 m per day, respectively (Nowatzki et al. 2003). Another study, which imposed high 

target pest infestation rates on experimental fields, documented between-row CRW larval movement of 

0.76 m in susceptible corn and between-plant larval movement equal to “three plants down the row,” or 

approximately 0.54 centimeter (cm)(Hibbard et al. 2003, 2004). This degree of larval dispersal is density 

dependent (increasing movement with increasing density) and is associated with significant host plant 

damage (less food results in greater movement). These studies support the assumption that CRW larvae 

and adults are poorly mobile. Because long-distance movement by WCRW and NCRW prior to mating 

is still poorly understood, refuge areas should be close to or within the Cry34/35 corn fields to be most 

effective. 

Another important factor in refuge management is the use of insecticides in Cry34/35 fields and 

accompanying refuge to control CRW and non-CRW pests. An effective refuge must produce an 

abundance of susceptible CRW adults that are available to breed with resistant adults from the Cry34/35 

field. To encourage technology adoption and refuge deployment, it is important for growers to have the 

option of treating the refuge (protecting it against rootworm larval feeding), but this must be balanced 

against maintaining the refuge as a source of large numbers of susceptible Cry34/35 insects. Pest 

management should be carefully considered. Consequently, insecticide applications that function to kill 

refuge-produced adult CRW must also be applied to the Cry34/35 field to nullify any negative impact on 

the value of the refuge. 

Adulticide treatments can be very effective at reducing CRW adult numbers if applied at the right time 

(i.e., appearance of gravid females) and thus management through adult control should be discouraged 

in the refuge 

 

3

 Monogenic resistance is assumed given what is presently known about the genetics of resistance. 
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Use of seed and granular insecticide treatments to control CRW larvae could be allowed on refuge acres, 

even if not applied to the Cry34/35 field, since these treatments are shown to be non-high dose controls 

(Meinke et al. 1998). Data have been collected that support the premise that banded insecticides and 

seed treatments will allow considerable survival of rootworms to adult (Sutter et al. 1991; Cormier and 

Martel 1997). There is ongoing research as to the impact of clothianidin and Cruiser® seed treatments 

on rootworm fitness, but preliminary data suggest that there is a minimal impact of CRW exposed to 

these seed treatments. 

Crop rotation will have a high impact on larval survival. If a refuge is planted on rotated ground, it will 

encourage adaptation to Cry34/35 unless the Cry34/35 corn is also planted on rotated ground. 

A structured refuge is necessary to reduce the population-wide selection pressure for resistance and 

providing a source of non-selected (SS genotype) adults to mate with any partially or fully resistant 

(genotypes rr or rS) adults that may survive in the Cry34/35 corn fields. Four basic aspects should be 

examined: refuge size, refuge deployment, refuge management, and grower feasibility. The higher the 

dose, the smaller the refuge needed. Because of the uncertainties associated with CRW long-range 

dispersal, the refuge should be placed adjacent to or within the same field as Cry34/35 corn. Refuge 

management should consider the roles of chemical insecticides, crop rotation, and other practices in the 

context of an integrated pest management program. For a detailed discussion of structured refuge 

specific for Cry34/35 corn, see the “Analysis of Dow/Pioneer’s Proposed Cry34/35 Event 59122-7 Corn 

Durability Plan (2005 Assessment)” section later in this chapter. 

 f. Computer Simulation Models

Simulation models were used to predict the impact of various factors on the rate of adaptation to 

Cry34/35 (Event DAS-59122-7) corn by western corn rootworm and northern corn rootworm. In 

designing the Cry34/35 durability plan, Dow and Pioneer used simulation models. Simulation modeling, 

leading to the development of the proposed trait durability plan, is summarized and documented in 

Storer (2003b). The product durability plan based on the simulated modeling is discussed in Storer and 

Lefko (2003). These materials and published CRW resistance management models (Onstad et al. 2001; 

Storer 2003a) were also considered. 

Overview of the Storer CRW model 

The CRW model used in the submission (Storer 2003b, MRID No. 461239-19) is described in detail in 

Storer (2003a). A brief overview is presented in this section. The model is stochastic. Mortality, 

dispersal, development, and crop development are probabilistic. The model describes an agricultural 

ecosystem in a spatially explicit manner, with 25-hectare (ha) square fields arranged in a grid of size 10 

x 10 or 12 x 12 fields. The fields can be planted in either corn or soybean. Corn fields can be planted to 

conventional or rootworm-resistant corn. Also, corn fields can be subdivided into blocks or strips so that 

a rootworm-resistant field can have an internal refuge of conventional corn. External refuge fields can 

also be simulated, including adjacent refuge fields or randomly distributed refuge fields. The model can 

simulate continuous corn cultivation, such as practiced in the western Corn Belt, or crop rotation with 
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soybean, as practiced in much of the central and eastern Corn Belt. The model can examine the rate of 

adaptation of two types of rootworm-protected corn planted simultaneously as a mosaic in the 

environment. The following processes were modeled: crop development; larval development, survival, 

and movement; adult emergence, development, and survival; mating and oviposition; and adult 

dispersal. 

Input Parameters 

Dow has determined that Cry34/35 corn expresses a dose that kills at least 99.75% of susceptible 

WCRW larvae (using the lower end of the range of field studies to estimate dose; see previous 

discussion in section II(D)(1)(d) of this Biopesticides Registration Action Document (BRAD)). For 

NCRW, there was greater uncertainty in the intensity of density-dependent mortality, and two 

conservative estimates of dose were derived: 95.0% and 99.0% (midpoint of the range of the lower dose 

estimate and higher dose estimate, respectively; see previous discussion in section II(D)(1)(d) of this 

BRAD). The expected mortality of the heterozygotes was calculated by assuming that the dose-response 

curves were parallel and that heterozygotes are 25 times more tolerant of the proteins than are 

homozygous susceptibles (Storer 2003a). Although it is not possible to calculate a dose-mortality 

relationship from a limited set of data points, the relationships for both WCRW and NCRW species are 

consistent with a default assumption of a slope of 1.0. Based on the dose estimates, assumptions of doseresponse slopes, and the assumption that heterozygotes are 25x resistant, the functional dominance of 

resistance for WCRW is estimated as 0.08 and, for NCRW, between 0.34 and 0.15. Previous research 

submitted by Dow (Storer and Lang 2003, MRID 461239-16) showed that Cry34/35 corn has no effect 

on adults that feed on it, so the dose against adults was 0 for all genotypes. 

The default model parameters and sensitivity analysis of the parameters for the runs with wild-type 

WCRW are summarized in the Dow modeling submission (Storer 2003b, MRID No. 461239-19). 

Additional discussion is provided on the following parameters. 

1. Larval movement. A default value of 2.5% of larvae moving one row was used. Hibbard et al. 

(2003) showed that between 0.75% and 6% of larvae moved across rows. This represents a relatively 

high-end estimate of the number of larvae that cross rows. Homozygous susceptible (SS) larvae that 

crossed from transgenic to refuge were assumed to suffer 100% mortality after feeding on transgenic 

plants, while those crossing in reverse were assumed to suffer 90% mortality. Partially adapted 

heterozygotes (rS) were assumed to suffer 50% of the mortality after crossing from transgenic to 

refuge plants, while those crossing in reverse were assume to suffer 30% of the mortality. Adapted 

homozygous resistant larvae did not suffer any mortality. Field data showing the level of survival of 

SS and rS larvae when crossing between transgenic Cry34/35 and refuge rows when collected can be 

incorporated into the model. 

2. Adult in-field movement. Dow cited to a study by Nowatzki et al. (2003) that described male and 

female WCRW intrafield dispersal using rubidium as a marker. Based on this study, females were 

shown to move about one third the distances of males in irrigated corn fields. By the time females 

reached the same distance as males, they were assumed to be mated. On average, females mated 
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within 2 rows of their emergence row. For block refuge scenarios, the destination of dispersing 

adults is always the other block (i.e., transgenic to refuge or vice-versa). For strip refuge scenarios, 

the probability that those leaving each strip end up in the opposite kind of strip (i.e., transgenic strip 

to refuge strip or vice-versa) is equal to the proportion of the field that is in the opposite kind of 

strip. 

3. Soybean biotype WCRW biology parameters. The soybean-biotype WCRW lays eggs in crops 

other than corn. Only the dispersal parameters differ from that of the wild-type WCRW (see Table 1 

in Storer (2003b)). Investigations on durability of Cry34/35 corn in areas where soybean-adapted 

populations are prevalent were initialized with an allele frequency of 0.5. 

4. Wild-type NCRW biology parameters. The parameter values for NCRW are assumed to be the 

same as for wild-type WCRW, except for adult survival, daily fecundity, adult between-field 

dispersal, pre-oviposition period, and density dependence. The survival probability decreases from 

0.99 at the first day of adult emergence, rather than from 0.999 for WCRW. A value of 16 eggs per 

female per day is used to ensure the population was sustainable. The longevity of NCRW is shorter 

than WCRW, the fecundity is lower, and the equilibrium population is around 6-fold lower. 

Between-field dispersal is three times higher for NCRW than for WCRW. The pre-oviposition 

period of 10 to 14 days was the same for both NCRW and WCRW. Less information is available 

regarding density-dependent mortality in NCRW than in WCRW, and the WCRW parameter for 

density-dependent survival was modified. 

Model Output 

The model output is the predicted rate of resistance evolution expressed relative to a benchmark rate. 

The same benchmark used in Storer (2003a) was used in the model submission (Storer 2003b, MRID 

No. 461239-19). The benchmark rate is for runs with: 

 A product that kills 100% of the susceptible rootworm larvae, 90% of larvae heterozygous for 

resistance, and 0% of resistant larvae; 

 A product planted on 100% of the acreage with the exception of the refuge; 

 20% refuge in external fields whose location is randomized each year; 

 Default values for all model parameters as described in Storer (2003a). 

The relative rate of adaptation (RRA) is calculated by the following equation: RRA = (1/Y ln qγ/q0)/ 

0.327; where, the qγ equals the r-allele frequency after Y years and 0.327 is the adaptation rate (yr-1) for 

the baseline run (Storer 2003a). The relative rate of adaptation is calculated when the r-allele frequency 

first exceeds 0.075, when the rootworm egg population in the autumn falls below 20,000 per field, or 

after 10 years, whichever is soonest. The relative rate of adaptation for the benchmark setting is 1.0. A 

relative rate of 2.0 implies resistance would evolve twice as fast as the benchmark, while a relative rate 
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of 0.5 implies resistance would evolve twice as slowly. From the equation described above, a relative 

rate of adaptation of 1 implies that the modeled r-allele frequency would increase 100-fold (e.g., from 

0.001 to 0.1) in approximately 14 model years. 

Runs or Scenarios Conducted 

Several scenarios were modeled to understand how various refuge options may affect the rate at which 

WCRW and NCRW adapt to Cry34/35 corn. One set of simulations was designed to investigate the 

effects of refuge size, refuge placement, and refuge strip width on WCRW adaptation. Other model runs 

were designed to look at the durability obtained with Cry34/35 against WCRW compared with a lower 

dose event. Another set of simulations was designed to examine the effects of incomplete adoption of 

the technology, incomplete deployment of the refuge, and a competitive mosaic with an alternate 

rootworm plant-incorporated (PIP) expressed at a lower dose. Simulations also included, adaptation in a 

crop-rotation system, where 50% of the WCRW population is rotation resistant (soybean biotype). 

Adaptation by NCRW was compared with wild-type and extended diapause biotype. Each run was 

conducted at two refuge sizes (10% and 20%) repeated for a total of five runs at each setting to 

investigate the effects of stochasticity. 

Analysis of Variance 

Output from the runs was subjected to analysis of variance for a completely randomized factorial design 

to identify the parameters that had a significant effect on RRA. All factors were treated as fixed. Means 

separation was conducted using Tukey’s method to identify significant differences among refuge 

placement options. 

Sensitivity Analysis 

Conservative estimates of the mean values of biological and genetic parameters in the models were used 

for the simulations, based on empirical data. The uncertainty in these values, as they affect the 

confidence of product durability, was studied using a Monte Carlo analysis (the WCRW model was run 

2,000 times). Twenty-one parameters were analyzed and a 10% in-field refuge was used. The relative 

importance of each of the parameters was analyzed through rank correlation between parameter value 

and adaptation rate (Storer 2003b, MRID No. 461239-19). The parameters with the largest effects on the 

relative rate of adaptation were the functional dominance of the r-allele (explaining 58.5% of the 

variation) and the dose (explaining 33.5% of the variation). The next most important parameters were 

the fitness cost of resistance (3.1% of the variation), winter survival (2.9%), and fecundity (1.1%). 

Winter survival and fecundity were correlated. All other parameters accounted for less than 1% of the 

variation. 
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Model Results

Western Corn Rootworm

1. How does dose affect durability?

An in-field block refuge design was used, and the position of the refuge within the field was not held 

constant from year to year. Refuge sizes were 10% and 20%. The simulations predict that higher doses 

result in longer durability (i.e., lower relative rate of adaptation), and refuge size was most important at 

higher doses. 

2. How does refuge size affect durability of Cry34/35 corn?

With a 20% refuge, the mean RRA of the moderate dose (one that kills 90% of susceptibles with a 

functional dominance of 0.5) line was 3.17 (standard error = 0.01), while for the Cry34/35 Event DAS59122-7 line, the mean RRA was 0.64 (standard error = 0.002). These results indicate that the adaptation 

would take five times longer for the Cry34/35 corn than for a moderate dose rootworm corn. With a 

10% refuge, the mean RRA for Cry34/35 Event DAS-59122-7 was 1.24 (standard error = 0.009) or 

approximately half the durability as predicted with the 20% refuge. This means that a 4% refuge used 

with Cry34/35 Event DAS-59122-7 corn lines would have the same predicted durability as a 20% refuge 

used with a moderate dose event corn line. 

3. How does refuge placement affect durability?

The effect of different refuge designs, using the conservative dose estimate of 99.75% (WCRW) for the 

Cry34/35 corn line, was simulated. The following deployment strategies were compared: in-field single 

block with an adjacent field and a random pattern of Cry34/35 and refuge fields. A 20% refuge was used 

because this allowed the model to place every Cry34/35 field directly adjacent to one refuge field. The 

model predicts that the RRA was lower (approximately half the relative rate of adaptation) for all three 

scenarios where the refuge was in the same location each year (i.e., a fixed refuge) than for refuge 

locations randomized each year. As discussed in Storer (2003a), the fixed refuge allows a higher 

population of susceptible insects from year to year. For randomized locations, the RRA was higher the 

greater the distance between the refuge and the Cry34/35 fields, but the differences among these three 

scenarios was relatively small. 

4. How does refuge strip width affect durability?

The effect of different strip widths for the refuge on the durability of Cry34/35 was simulated. These 

simulations assume that the strips are not in the same place each year, so that the distribution of hatching 

eggs across the field is independent of the position of the refuge and the Cry34/35 strips. The survival 

estimates were based on the assumption that the heterozygous individuals the move between the refuge 

and the Cry34/35 plants have a higher probability of surviving than either the heterozygous individuals 

that remain on the Cry34/35 plants or homozygous susceptible individuals that move between the refuge 

and Cry34/35 plants. The overall conclusion is that strip width is not likely to greatly affect predictions 

of durability with either a 10% or 20% refuge. That is, there is very little difference in the relative rate of 

adaptation between a two-row strip and a ten-row strip, although there are some minor benefits. The 

model predicts that blocks are more durable than strips. This is because there are more interfaces 
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between Cry34/35 and refuge strips, allowing greater larval movement and thus greater survival 

differential between SS and rS genotypes, and the adults that disperse from Cry34/35 strips are more 

likely to end up in other Cry34/35 strips rather than refuge strips because there are more Cry34/35 strips 

relative to the number of refuge strips. Based on these simulations, as strip width increases, the 

durability will increase up to the point of a single block, but the effect will be small due to the practical 

range of planting wider strips. 

5. How does crop rotation affect durability?

Farmers may use Cry34/35 corn (or other CRW-protected Bt corn) to help manage rotation-resistant 

WCRW (soybean biotype) or NCRW (extended diapause biotype). The model was used to investigate 

the possible effects crop rotation (i.e., corn-soybean rotations vs. corn-corn) may have on durability of 

Cry34/35 corn under two refuge deployment structures: in-field block and external fixed block. Both a 

10% and 20% refuge were considered. Based on the model predictions, crop rotation reduced the 

relative rate of adaptation for both in-field and external refuge options. There was a significant 

interaction between refuge size and rotation in the in-field refuge scenarios. For external refuges, there 

was a main effect of crop rotation, but no interaction with refuge size. 

6. How does rotation-resistant WCRW affect durability?

In certain parts of the eastern range of the WCRW (i.e., Illinois, Indiana, part of Michigan), WCRW has 

adapted to crop rotation by laying eggs in fields that are not planted in corn, most notably in soybean 

fields (“soybean biotype”). The soybean biotype lays its eggs in soybean fields and they hatch when it is 

rotated to corn. The model was used to examine the effect of this behavior on durability of Cry34/35 

corn. Three refuge scenarios were run: fixed external refuge (continuous corn), with Cry34/35 corn 

rotated with soybean; in-field refuge, with all fields in corn-soybean rotation; and in-field refuge, with 

all fields planted to continuous corn. All scenarios were run with both 10% and 20% refuge size. 

Rotation resistance is assumed to be controlled by a single gene. Based on the modeling simulations, 

rotation resistance did not significantly affect the durability of any refuge scheme. That is, the soybean 

biotype adapted to Cry34/35 at the same rate as wild-type WCRW. However, there were differences in 

effects on the rate of relative adaptation caused by different deployment schemes. The external, fixed 

refuge served as a refuge for both Cry34/35 susceptibility and rotation susceptibility and, therefore, 

reduced the incidence of rotation resistance. These results suggest that Cry34/35 corn has the potential to 

decrease the incidence of WCRW rotation resistance if used in rotation with soybean while an external 

refuge is planted to continuous non-rootworm protected corn. 

7. How do refuge implementation rates and technology adoption rates affect durability?

Adoption of Cry34/35 corn will not be 100% in all locations from the time of commercialization and 

will vary from area to area. The rate of technology adoption is affected by grower attitudes, market 

acceptance, perceived need for the technology, and effectiveness of the technology. The model was used 

to investigate the impact of Cry34/35 corn adoption and refuge implementation on Cry34/35 corn 

durability. A grid of 12 x 12 fields planted to continuous corn was divided into 16 farms, each consisting 

of 3 x 3 fields with each farm designated as either an adopter or non-adopter of Cry34/35 corn. Adopting 

farms were further designated by those either deploying the required refuge block within each field or 

not deploying a refuge at all (i.e., 100% Cry34/35 corn). Adoption rates were between 25% and 100% 
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and refuge deployments were between 50% and 100%. Based on the modeling simulations, rootworm 

adaptation rate is least when adoption is lowest (i.e., 25%). When adoption was 25%, refuge 

implementation had no effect on the overall r-allele frequencies. Refuge size (whether 10% or 20%) had 

a significant effect on the relative rate of adaptation only when there was 100% adoption of the 

technology. At 50% and 75% levels of technology adoption, refuge implementation had virtually no 

impact on the relative rate of adaptation. 

Modeling simulations indicated that the spatial patterns of population size and r-allele frequencies are 

the inverse of one another. The overall r-allele frequency was dominated by populations in the farms 

with the refuge and non-adopting farms. Sufficient dispersal of the adults from these farms to those 

without a refuge would prevent the r-allele frequencies from becoming locally elevated. 

8. How does a mosaic with an alternative rootworm PIP affect durability against WCRW?

Dow modeled the effect of a spatial mosaic of two rootworm PIP products on durability. It is expected 

that multiple rootworm PIP products will be grown as a spatial mosaic across the landscape. Currently, 

there are two registered rootworm PIPs, YieldGard® Rootworm Corn (expresses the Cry3Bb1 protein, 

Event MON 863, EPA Reg. No. 524-528) and YieldGard® Plus Corn (expresses both the Cry3Bb1 and 

Cry1Ab proteins, EPA Reg. No. 524-545). The 2002 Scientific Advisory Panel (SAP) concluded that 

MON 863 expressed a moderate dose to control rootworm (U.S. EPA 2002). For the simulations, MON 

863 was assumed to kill 90% of the insects susceptible to it, and the functional dominance was assumed 

to be 0.5. It was assumed there is no cross-resistance between Cry3Bb1 and Cry34/35 proteins. 

Simulations were run with 0, 25, 50, 75, and 100% of the rootworm-protected corn expressing Cry34/35, 

and corresponding 100, 75, 50, 25, and 0% expressing Cry3Bb1. All corn fields had an in-field refuge. 

EPA has required that both YieldGard® Rootworm Corn and YieldGard® Plus Corn have a 20% 

structured refuge (U.S. EPA 2007a, 2010d). For Cry34/35 corn, the refuge size was assumed to be 10%. 

The modeling simulations indicate that the relative rate of adaptation for Cry34/35 corn was lower at 

comparable market share levels than Cry3Bb1 corn. For example, at equal deployment of 50% market 

share for Cry3Bb1 corn and 50% market share for Cry34/35 corn, the model predicts that adaptation to 

Cry34/35 would take four times longer (RRA = 0.33, standard error = 0.005) than at 100% Cry34/45 

market share (RRA = 1.25, standard error = 0.016). There is a more dramatic reduction in the rate of 

adaptation to Cry34/35 corn as its market share increases than the rate of adaptation to Cry3Bb1 corn as 

its market share increases. This is because the Cry34/35 fields produce very few Cry3Bb1-susceptible 

insects. However, these simulations suggest that in a competitive spatial mosaic, both products would 

benefit in terms of durability from the presence of the other. 

Northern Corn Rootworm

1. How is the durability prediction altered for Northern Corn Rootworm?

The model was run to compare differences in predictions of durability between NCRW and WCRW. A 

range of doses and refuge sizes were run. The output was compared with WCRW. Dose and refuge size 

significantly affected the relative rate of adaptation. The predicted values for NCRW showed a very 

similar relationship to dose and refuge as for WCRW, although for any given dose and refuge size, the 
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relative rate of adaptation for NCRW is lower than that for WCRW. It is thought that a lower estimate 

for dose of Cry34/35 corn would be 95% and a higher estimate for dose of Cry34/35 corn would be 

around 99% for control of NCRW. Based on the simulations, a 20% refuge had lower comparable 

relative rate of adaptation values than a 10% refuge at both the lower and higher estimates of dose. For 

example, at the lower dose estimate, the 20% refuge increased durability by about 50% compared with 

the 10% refuge, while for the higher dose estimate, the 20% refuge increased durability two-fold 

compared with the 10% refuge. 

2. How do crop rotation and rotation-resistant NCRW affect durability? 

The model was run to examine how crop rotation and rotation-resistant NCRW affected durability of 

Cry34/35 corn. The model predicted that crop rotation had the biggest advantage when practiced only on 

the Cry34/35 corn fields and when the refuge fields were planted in the same location each year. Just as 

for WCRW, there are two modes of action operating in the rotated Cry34/35 corn fields: the direct effect 

of Cry34/35 and the effect on the progeny of insects laying their eggs in corn fields that could not 

survive since they hatched in soybean fields. 

Rotation-resistant NCRW spend two winters as eggs in the soil; therefore, they act as a temporal refuge 

from selection for refuge. The model predicted that for in-field refuge options, rotation resistance 

approximately doubled the durability of Cry34/35 corn when the corn/soybean rotation was maintained 

and increased the durability 60% to 80% when corn was grown continuously. On the other hand, if the 

refuge was external in fixed locations, while Cry34/35 corn was rotated with soybean, the rotation 

resistance accelerated resistance evolution to Cry34/35. This is in contrast to the relative rates of 

adaptation predicted in WCRW. The NCRW rotation-resistant genotype was only exposed to Cry34/35 

every second year, while the wild type was exposed every year. Each year, Cry34/35 corn would kill 

half of the proportion of rotation-resistant biotype as compared to the wild type and, thus, the frequency 

of the rotation-resistant biotype was increased from its initial value of 0.5. The rate of increase is 

affected by how Cry34/35 corn and the refuge were deployed. When the refuge was planted in the same 

location each year (continuous corn) and the Cry34/35 corn was rotated with soybean, the rate of 

increase was lowest. 

Storer Modeling Summary

Using the lower end of the range of field studies to estimate dose, Cry34/35 Event DAS-59122-7 corn 

expresses a dose that kills at least 99.75% of susceptible WCRW larvae. The model predicts that the 

durability is likely to be adequate with a 10% refuge, planted in-field or in an adjacent field. Durability 

is extended even further when there is market competition with other transgenic and non-transgenic 

rootworm management options. Cry34/35 corn has the potential to decrease the incidence of WCRW 

rotation resistance if used in rotation with soybean while an external refuge is planted to continuous nonrootworm protected corn. Both the Onstad et al. (2001) model and the Storer model (Storer 2003a; 

Storer 2003b, MRID No. 461239-19) predict that a 10% refuge would provide acceptable durability 

against WCRW resistance. 
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In contrast, Cry34/35 Event DAS-59122-7 expresses a dose (midpoint of the range of the lower dose 

estimate and higher dose estimate, respectively) that kills at least 95 to 99% of susceptible NCRW 

larvae. The model predicts that the durability of a 20% refuge for wild-type NCRW at the higher dose 

estimate results in comparable durability of a 10% refuge for wild-type WCRW, and less durability at 

the lower dose estimate. Rotation resistance through extended diapause results in more than 50% longer 

durability. 

Onstad and Guse WCRW model

Dow also discussed the WCRW simulation model of Onstad and his colleagues (Onstad et al. 2001). 

The Onstad et al. (2001) model of WCRW adaptation differs from the Storer model in that it is 

deterministic and non-spatial (the Storer models are stochastic and spatial). Two refuge structures were 

considered: external blocks and in-field strips. It is assumed that the block refuge is fixed (same location 

annually for maintaining large, non-selected populations) and the strip refuge moves (planted randomly 

each year). The difference between fixed and moving refuge drives the model. The most important 

parameter in the Onstad et al. (2001) model affecting durability of a rootworm-protected PIP was the 

functional dominance of the resistance allele (expressed as “allele expression”). 

If the allele was fully recessive, resistance did not occur in this model within 99 years. If the allele was 

fully dominant, resistance always occurred within 2–5 years for refuge sizes between 5% and 30%. For 

incompletely recessive alleles, the time to resistance depended on both dose and refuge size. For the 

95%, 90%, and 80% doses, the functional dominance was calculated to be 0.5. The model predicted that 

the time to resistance in these runs was 3 to 9 model years with a 20% refuge, depending on whether the 

refuge was fixed (block) or moved from year to year (row strips). For a dose of 99.9% (i.e., a “practical 

high dose”), the functional dominance was calculated to be 0.009. In this instance, the time to resistance 

with the moving 20% refuge (strips) was 29 model years and with a moving 10% refuge was 22 model 

years. At the theoretical high dose, 100%, the functional dominance was 0, and resistance did not evolve 

within 99 model years with a 20% moving refuge and evolved in 52 model years with a 5% moving 

refuge. For a fixed 5% refuge, resistance did not evolve within 99 model years at 99.9% or 100% dose. 

Using a low-end estimate, Cry34/35 Event DAS-59122-7 corn expresses a dose of at least 99.75% 

against WCRW, which is similar to Onstad et al.’s (2001) designation of a “practical high dose.” At this 

dose, the model predicts that a 5% refuge would give more than four times the durability of a 80%, 90%, 

or 95% dose PIP with a 20% refuge. A 10% refuge would give more than 20 model years of durability if 

the refuge is moved around each year (strips), and greater than 99 model years of durability if the refuge 

is fixed (blocks). 

BPPD’s Analysis of Proposed Computer Models 

BPPD agrees with Dow and Pioneer’s assessment of CRW adaptation using the Storer simulation 

models (Storer 2003a; Storer 2003b, MRID No. 461239-19) and Onstad et al.’s (2001) simulation 

model. Using the lower end of the range of field studies to estimate dose, Cry34/35 Event DAS-59122-7 

corn expresses a dose that kills at least 99.75% of susceptible WCRW larvae. The Storer simulation 
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model (Storer 2003b, MRID No. 461239-19) predicts that the durability is likely to be adequate with a 

10% refuge, planted in-field or in an adjacent field. Durability is extended even further when there is 

market competition with other transgenic and non-transgenic rootworm management options. Cry34/35 

corn has the potential to decrease the incidence of WCRW rotation resistance if used in rotation with 

soybean while an external refuge is planted to continuous non-rootworm protected corn. Both the 

Onstad et al. (2001) model and the Storer models (Storer 2003a; Storer 2003b, MRID No. 461239-19) 

predict that a 10% refuge would provide acceptable durability against WCRW resistance. 

In contrast, Cry34/35 Event DAS-59122-7 expresses a dose (midpoint of the range of the lower dose 

estimate and higher dose estimate, respectively) that kills at least 95% to 99% of susceptible NCRW 

larvae. The Storer model (Storer 2003b, MRID No. 461239-19) predicts that the durability of a 20% 

refuge for wild-type NCRW at the higher dose estimate results in comparable durability of a 10% refuge 

for wild-type WCRW, and less durability at the lower dose estimate. Rotation resistance through 

extended diapause results in more than 50% longer durability. 

 

 g. Technology Adoption

Product durability is affected by market penetration. Modeling efforts (Storer 2003b, MRID No. 

461239-19) make the conservative assumption of complete adoption (i.e., all corn acres are planted in 

Cry34Ab1/35Ab1 corn) because the applicants do not wish the durability of the product to depend upon 

the presence of competing products (Storer and Lefko 2003, MRID No. 461239-18). The applicants 

stated, however, that actual adoption is likely to be significantly less than 100% and governed by 

multiple parameters (availability of alternate controls, economic and market factors, etc.)(Storer and 

Lefko 2003, MRID No. 461239-18). Implementation of a variety of controls, the most likely scenario, 

discourages over-reliance on a single control method and, consequently, helps to delay resistance 

development to control options (Gray 2001; Ostlie 2001; Carrière et al. 2004). 

The assumption of 100% adoption, while not likely, is a reasonable one on which to base a conservative 

IRM plan to manage the Cry34Ab1/Cry35Ab1 corn durability. 

2. Analysis of Dow/Pioneer’s Proposed Cry34/35 Event 59122-7 Corn Durability Plan (2005 

 Assessment) 

Dow and Pioneer proposed a Cry34/35 Event 59122-7 corn durability plan that has the following 

elements: (1) structured refuge, (2) resistance monitoring, (3) remedial action plan, and (4) compliance 

and education. Simulation models were used to assist in evaluating and comparing structured refuge 

options (discussed previously). Using the model predictions, Dow and Pioneer were able to propose 

specific refuge guidelines. Given the uncertainties in understanding the dose, genetics and mechanism(s) 

of resistance, functional dominance, pest biology and ecology, and level of adoption of the technology, 

Dow and Pioneer have proposed a conservative insect resistance management (durability) plan. The 

proposed plan is “acceptable,” with one exception—that of the size of the in-field strips (see discussion 

below). Additional data are needed to support independent treatment of the refuge for other pests, other 

than corn rootworm when corn rootworm may be present, but not targeted and its impact on corn 
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rootworm resistance management. Additional research should be conducted to further evaluate the 

sustainability of the proposed durability plan and confirm the assumptions made in the simulation 

models. Each aspect of Dow and Pioneer’s proposed durability plan will be discussed below. 

 a. Structured Refuge

The guidelines for structured refuge address the following: refuge size, refuge deployment (proximity of 

the refuge to the Cry34/35 corn fields), and refuge management (acceptable chemical management of 

target pests in the transgenic fields and refuge and agronomic management). In developing the refuge 

guidelines, Dow and Pioneer stated that a goal was to ensure that the structured refuge would remain 

productive for the grower, while serving as an effective reservoir of susceptible target pests. The 

applicants’ plan is designed around NCRW for which there is greater uncertainty surrounding the 

estimation of the Cry34/35 dose and, thus, the extent of functional dominance of resistance alleles. 

Based on the modeling simulations by Storer (2003b), this plan would then be more conservative for 

WCRW. Since WCRW is related to MCRW (Clark et al. 2001), the plan should also be applicable to 

and conservative for MCRW. Additionally, the simulations by Storer (2003b) indicated that rotation 

resistance in the WCRW soybean biotype did not affect durability of Cry34/35 corn, while rotation 

resistance in NCRW populations (extended diapause) increased the durability of Cry34/35 corn. These 

simulations indicated the trait durability plan could reverse the spread of the soybean biotype WCRW. 

Several assumptions make this plan conservative. The Monte Carlo simulations (see the earlier 

simulation models section) indicate that the choice of default parameter settings lie within the 5-percent 

worse-case settings. The assumptions of the genetics of resistance are conservative because it is unlikely 

that there will be incomplete recessiveness of the resistance allele, rather the more realistic expectation 

is for complete or near-complete functional recessiveness. Finally, the trait durability plan is based on 

the unrealistic expectation that 100% of the corn in a given area will be planted to Cry34/35 corn. 

Storer’s simulations (Storer 2003b, MRID No. 461239-19) indicate that the plan would be effective at 

managing region-wide resistance evolution if only 75% of farms correctly implement the refuge. 

Dow and Pioneer’s Proposed Structured Refuge Guidelines 

1. Refuge size. The use of Cry34/35 corn from Event DAS-59122-7 would require an accompanying 

20% refuge. The refuge size is governed by the greater uncertainties in the dose determination of 

NCRW to Cry34/35. Based on the modeling simulations for WCRW and NCRW (Storer 2003b, MRID 

No. 461239-19), the refuge size is considered to be conservative for WCRW (and MCRW). 

2. Refuge location. Given the uncertainties regarding rootworm long-range dispersal, the rootworm 

refuge would be required to be planted within or adjacent (e.g., across the road) to the Cry34/35 corn 

field. 

3. Refuge management options. The rootworm refuge must be managed in such a way that there is little 

or no yield loss to rootworms, but it is sufficiently productive of susceptible rootworm adults. Dow and 

Pioneer propose the following refuge management guidelines. 
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 The in-field refuge options may be planted as a single block or as a series of strips measuring at 

least two crop rows wide. (BPPD does not agree with this portion of the proposed plan as 

discussed later; at least four crop rows wide should be required.) Modeling (Storer 2003b, MRID 

No. 461239-19) showed that the strip width had a very small effect on durability. Single-row 

strips could be too narrow and allow too much larval movement across rows to sufficiently 

maintain low functional recessiveness. 

 Seed mixtures of Cry34/35 and refuge corn are not permitted. Larval movement within rows 

would compromise the value of the effective dose of the Cry34/35 corn and allow enhanced 

heterozygote survival. 

 If the refuge is planted on rotated ground, then Cry34/35 corn must also be planted on rotated 

ground. Refuge on rotated ground is likely to produce few individuals. Therefore, adult 

production would need to be mirrored in the Cry34/35 corn field to nullify the effect on 

resistance evolution. 

 If the refuge is planted in continuous corn, the Cry34/35 field may be planted on either 

continuous or rotated land (option encouraged where WCRW rotation-resistant biotype may be 

present). The Storer simulations (Storer 2003b, MRID No. 461239-19) predicted that planting 

the refuge on continuous corn ground and rotating the Cry34/35 corn with a second crop can lead 

to a reduction in the prevalence of rotation-resistant WCRW. 

 Banded application of soil insecticide is permitted in the refuge. As discussed previously, there 

are several studies that have shown that this control option permits very high survival of 

rootworm and, therefore, will not affect refuge performance but will protect the yield in the 

refuge making this option attractive to growers. Simulations by Storer (2003a and 2003b) were 

based on the assumption that the refuge will be managed by soil-insecticides in banded 

applications when egg populations warrant protection. 

 Seed treatment is permitted in the refuge, either at a high rate for rootworm protection or at a low 

rate for controlling secondary soil pests. As discussed previously, insecticide seed treatments 

have been shown to have little impact on the number or timing of adult emergence and, 

therefore, are acceptable for use in a Cry34/35 corn structured refuge. 

 If aerial insecticides are applied to the refuge for control of CRW adults, the same treatment 

must also be applied to Cry34/35 corn. It is important that aerial applications be properly timed 

and that egg population reductions are not reduced more in the refuge than the Cry34/35 corn 

fields. Application of adult-targeted aerial insecticides, applied at the same time to Cry34/35 

corn areas and the refuge, will nullify any negative effects on the value of the refuge. 
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 The refuge and Cry34/35 corn may be treated with independent insecticide applications that 

comply with local integrated pest management guidelines, to control pests other than adult 

rootworms. Foliar sprays targeted at other pests, other than rootworm adults, will have a much 

lower effect on the rootworm egg populations. The timing of the applications is also important to 

avoid any significant impact on future adult emergence. (BPPD does not agree with this portion 

of the proposed plan at this time. Additional data are needed to address independent treatment of 

the refuge for other pests (not corn rootworm) and its impact on corn rootworm resistance 

management.) 

 The rootworm refuge can be planted to any corn hybrid that does not express PIPs for rootworm 

control (e.g., lepidopteran-protected Bt corn, herbicide-tolerant corn, or conventional corn). 

 The refuge and Cry34/35 corn should be sown on the same date, or with the shortest window 

possible between planting dates, to ensure that corn root development is similar among varieties. 

 Based on simulations by Storer (2003a and 2003b) and Onstad et al. (2001), it may be best for 

growers to plant the rootworm refuge in the same location each year, as it allows the rootworm 

population to remain high and the durability of the trait is extended. This refuge can be protected 

with banded application of soil insecticides or with seed treatments. This option may be 

preferable to growers who wish to only think of their refuge design once and for growers who 

grow continuous corn. However, for those growers who need to employ crop rotation, a fixed 

refuge would be impractical. 

BPPD’s Analysis of Dow and Pioneer’s Proposed Structured Refuge Guidelines 

Given the uncertainties in understanding the dose, genetics and mechanism(s) of resistance, functional 

dominance, pest biology and ecology, and level of adoption of the technology, Dow and Pioneer have 

proposed a conservative insect resistance management (trait durability) plan for Cry34/35 corn. The trait 

durability plan, while based on the best available scientific information regarding rootworm biology and 

ecology, has also strongly considered grower feasibility and practicality. If the grower does not 

implement the structured refuge and manage it correctly, then the value of the trait durability plan is 

minimal. The refuge guidelines are designed around NCRW to which there is greater uncertainty 

surrounding the estimation of the Cry34/35 dose and, thus, the extent of functional dominance of 

resistance alleles. Based on the modeling simulations by Storer (2003a and 2003b), this plan would be 

more conservative for WCRW. Since WCRW is related to MCRW, the plan should also be applicable to 

and conservative for MCRW. Based on BPPD’s analysis, the proposed plan is acceptable with two 

modifications: one to the proposed size of the in-field strips and the other to the agronomic treatment of 

the refuge. 

1) BPPD disagrees with Dow and Pioneer’s recommendation that the in-field strip width be ≥2 row 

strips. 

Recent larval movement data, published by Hibbard et al. (2003), showed that between 0.75% and 6% 
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of larvae moved across rows. This represents a relatively high-end estimate of the number of larvae that 

could cross rows. This means that much narrower in-field strips should be sufficient to provide adequate 

protection from sublethal selection caused by CRW larval movement across rows and maintain low 

functional recessiveness. Any increase in sublethal selection would be offset by a greater probability that 

potentially resistant adults emerging from the Bt corn rows would mate with susceptible adults from the 

refuge row. Simulations by Storer (2003b) incorporated the Hibbard et al. (2003) larval movement data 

to compare how strip width can affect the durability. These simulations predicted that narrower in-field 

strips, between 2 and 10 rows, did not affect trait durability. Single-row strips could be too narrow and 

allow too much larval movement across rows to sufficiently maintain low functional recessiveness. 

While the Storer simulations (Storer 2003b, MRID No. 461239-19) indicate that trait durability is 

virtually unaffected by strip width, in-field strips of ≥4 rows would provide some marginal, additional 

protection (see Figure 4 of MRID No. 461239-19) and also provide the advantage of being more 

compatible with the current in-field strip width requirement, ≥4 row strips (≥6 row strips preferred) for 

lepidopteran-protected Bt corn hybrids. In-field strips of ≥4 rows would also be practical and flexible for 

the grower, just as a ≥2 row strips. Because Cry34/35 will likely be stacked with Cry1F, for example, a 

recommendation of ≥4 row strips will provide the grower a more easily understandable and consistent 

message regarding the width of in-field strips and reduce confusion associated with in-field row strips 

for lepidopteran-protected Bt corn hybrids, rootworm-protected Bt corn hybrids, and those Bt corn 

hybrids that have both traits. Overall, BPPD believes that a requirement of ≥4 row in-field strips will 

simplify refuge deployment and potentially increase compliance with refuge requirements. 

Note: Herculex® RW (Cry34/35 corn) was registered with an in-field strip width refuge requirement of 

at least 4 rows. 

2) BPPD disagrees with Dow and Pioneer’s recommendation for independent treatment of the refuge for 

other pests (not corn rootworm).

Properly timed aerial sprays are very effective at reducing the corn rootworm egg population in the field, 

and it is important that the refuge productivity is not reduced more than the Cry34/35Ab1 corn field 

productivity. Sprays targeted at adults in the current year’s refuge may significantly reduce the number 

of adults available for mating with Cry34/35-resistant survivors in Cry34/35 corn fields. Sprays targeted 

at adults in the area to be used as refuge the next year may significantly reduce the number of adults 

emerging from that area the following year, reducing refuge effectiveness. BPPD agrees with Dow and 

Pioneer’s conclusion that insecticide applications that function to kill refuge-produced adult CRW must 

also be applied to the Cry34/35 corn field to nullify any negative impact on the value of the refuge. 

Foliar sprays targeted at pests other than rootworm adults are thought to have a much lower effect on the 

rootworm egg populations. If the sprays are applied before peak adult emergence, then residual activity 

may be too low to have a significant impact on future adult emergence. Similarly, if the sprays are 

applied after peak egg-laying, they are likely to have a reduced impact on egg numbers. Therefore, if the 

treatment windows for other pests do not overlap with the critical period in which corn rootworms 

would be treated, growers could be permitted to use aerial sprays on any fields (refuge or not) if they are 

needed for management of other pests besides adult corn rootworm. Dow and Pioneer proposed 
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allowing independent treatment of the refuge and Bt fields if pests other than corn rootworm are 

targeted. While this would prevent unnecessary spraying of the Bt corn fields, additional data are needed 

to determine if the treatment windows for other insect pests, e.g., European corn borer (2nd generation), 

Southwestern corn borer, spider mites and corn rootworm overlap and what impact treatment for other 

pests would have on the effectiveness of the corn rootworm refuge. At this time, pests other than adult 

corn rootworms can only be treated with CRW-labeled insecticide on the refuge acres without treating 

the Cry34/35 acres if treatment occurs when corn rootworms are not present. Pests on the Cry34/35 

acres can be treated as needed without having to treat the refuge. 

BPPD agrees with Dow and Pioneer that the use of seed and granular insecticide treatments to control 

CRW larvae should be allowed on refuge acres, even if not applied to the Cry34/35 corn field, since 

these treatments are shown to be non-high dose controls (Meinke et al. 1998). Data have been collected 

that support the premise that banded insecticides and seed treatments will allow considerable survival of 

rootworms to adult (Sutter et al. 1991; Cormier and Martel 1997). There is ongoing research that 

suggests that clothianidin and Cruiser® seed treatments have a minimal impact on CRW fitness. 

Crop rotation will have a high impact on larval survival, e.g., corn-soybean rotations. If a refuge is 

planted on rotated ground, it will encourage adaptation to Cry34/35 unless the Cry34/35 corn is also 

planted on rotated ground. This is because susceptible corn rootworm production is lower on rotated 

ground (i.e., soybean is not a host of corn rootworms). BPPD agrees with Dow and Pioneer that if the 

refuge is planted on rotated ground, then Cry34/35 corn must also be planted on rotated ground. 

Based on simulation models (Storer 2003a; Onstad et al. 2001), it may be best for growers to plant the 

rootworm refuge in the same location each year, as it allows the rootworm population to remain high 

and the durability of the rootworm-protection trait to be extended. This refuge can be protected with 

banded application of soil insecticides or with seed treatments. For those growers who need to employ 

crop rotation, a fixed refuge would be impractical. 

Based on BPPD’s analysis, a 20% structured non-lepidopteran Bt corn refuge planted adjacent to, or as 

≥4 row strips within the Cry34/35 corn field (rather than ≥2 row strips), is sufficiently conservative to 

mitigate CRW resistance to the Cry34Ab1 and Cry35Ab1 proteins expressed in Event DAS-59122-7 

corn hybrids. BPPD agrees with all of Dow and Pioneer’s proposed agronomic management 

recommendations except for one. Additional data are needed to address independent treatment of the 

refuge for other pests (not corn rootworm) and its impact on corn rootworm resistance management. 

Additional research on corn rootworm pest biology and ecology, genetics and mechanisms of resistance, 

functional dominance, fitness costs, cross-resistance potential, dose, and mode of action will also be 

useful to evaluate the proposed durability plan and confirm the assumptions made in the simulation 

models. 

Note: Herculex® RW (Cry34/35 corn) was registered with the following insecticide use restrictions to 

address the concerns regarding refuge treatment discussed above: 
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 If aerial insecticides are applied to the refuge for control of CRW adults, the same treatment 

must also be applied in the same time-frame to Cry34/35 corn. 

 Pests other than adult corn rootworms can only be treated with CRW-labeled insecticide on the 

refuge acres without treating the Cry34/35 acres if treatment occurs when adult corn rootworms 

are not present. Pests on the Cry34/35 acres can be treated as needed without having to treat the 

refuge. 

 Application of soil insecticide is permitted in the refuge. 

 Seed treatment is permitted in the refuge, either for rootworm protection or for controlling 

secondary soil pests. 

 b. Resistance Monitoring

The need for proactive resistance detection and monitoring is critical to the survival of Bt technology. 

Consequently, the Agency mandates that a resistance monitoring plan must be implemented for all 

registered Bt corn products. Resistance can evolve regionally or as a local increase in resistance (r-) 

allele frequency. The resistance monitoring plan designed for Cry34/35, an adaptation of the 

Agricultural Biotechnology Stewardship Technical Committee (ABSTC) program developed for 

lepidopteran-protected corn, will attempt to detect either local or regional resistance early enough to 

initiate effective remedial action (see below). Resistance monitoring will be implemented through a twopronged approach, field reports of unexpected damage and population testing and sampling. 

Field Reports of Unexpected Damage

Field monitoring is intended to detect localized resistance. The applicants are working to accumulate a 

data set of Cry34/35 field efficacy under a wide range of pest pressures, soil types, and environmental 

conditions. This information will be used to develop efficacy guidelines that applicants will use to 

determine whether the level of rootworm damage in their fields is considered “normal” or outside the 

range of normal. 

Once field guidelines have been set, reports of unexpected CRW damage will be evaluated to determine 

if crop damage is due to failure of Cry34/35 or to some alternative factor. Specifically, the applicant will 

confirm that plants under question were expressing Cry34/35Ab1 proteins, that the Cry34Ab1 and 

Cry35Ab1 proteins were expressed at expected levels in corn plant roots, and that damage was caused 

by target CRW pests. If, after having completed the confirmatory procedures described above, the 

damage report still points to Cry34/35 failure, the case will be considered “suspected resistance” and 

remedial action will be implemented. Eggs or adults will also be collected for the “Population Testing 

and Sampling” program. 
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Population Testing and Sampling

Population sampling and testing will be used to identify area-wide increases in r-allele frequency before 

widespread field failure occurs. R-allele detection programs will employ dose-response and 

discriminating dose bioassays to detect non-recessive and fully recessive r-alleles in the homozygous 

state (ABSTC 2003). 

CRW species are challenging to rear in the laboratory. Of the identified target pest species, scientists 

have had the most success rearing WCRW and have had little success with NCRW. Consequently, 

monitoring through population sampling will focus on WCRW and include NCRW populations when 

available. 

A bioassay that “accurately and reliably” determines dose-response relationships for WCRW is being 

used by a third-party laboratory to establish baseline sensitivity. Efforts to establish baseline sensitivity 

will continue through the early years of commercial Cry34/35 corn deployment, before significant 

selection pressure is placed on rootworm populations. Dow and Pioneer are also working to develop a 

“high-throughput diagnostic screen,” which uses Cry34/35 seedlings to determine discriminating dose. 

The applicants state that this screen will be able to identify potential field-resistant insects, may be able 

to detect heterozygotes for r-alleles, and will provide estimates of phenotype and genotype frequencies. 

European and southwestern corn borer are multivoltine insects that produce one to three generations per 

year. Monitoring programs developed for these pest species evaluate every second or third generation 

for resistance. In contrast, rootworm species are univoltine, meaning that they produce a single 

generation of insects per year. Since corn borer is evaluated every second or third generation (two or 

three generations produced per year), the applicants argue that a similar level of monitoring intensity 

would be achieved by testing four or five CRW populations per year. 

Rootworm populations will be collected from targeted areas where resistance is most likely to develop. 

Market penetration of Cry34/35 is considered the most important factor in determining the risk for 

resistance. Consequently, county sales data will be used to identify areas with the greatest Cry34/35 

adoption rates. 

BPPD’s Analysis of the Proposed Resistance Monitoring Plan

BPPD agrees with Dow and Pioneer’s approach to resistance monitoring. Detecting shifts in the 

frequency of resistance genes (i.e., susceptibility changes) through resistance monitoring can be an 

aggressive method for detecting the onset of resistance prior to widespread crop failure. As such, the 

utilization of sensitive and effective resistance monitoring techniques is critical to the success of an IRM 

plan. 

Dow and Pioneer state that a third-party laboratory is using a bioassay that “accurately and reliably” 

determines dose-response relationships for WCRW to establish baseline sensitivity. While BPPD agrees 

that a sensitive and reliable bioassay should be developed, these efforts are currently under development. 
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Once this work is completed, the applicants need to develop guidelines as to what level of root damage 

will be expected under various conditions, and what level of rootworm control is normally achieved. 

Applicants will investigate grower reports of reduced product performance to determine whether 

damage is unexpected. However, without guidelines as to what is “acceptable” rootworm damage, then 

it will not be possible to determine what the “unexpected” rootworm damage is. Once these guidelines 

are established, it will be possible to define what is “suspected resistance” as described under the 

“Remedial Action Plans” to mitigate the spread of putative resistant populations. Because of the 

importance of these guidelines, it should be required that the applicants develop interim rootworm 

damage guidelines by 2008 and final guidelines by 2010 and submit these to the Agency for review. 

Dow and Pioneer also mention that they are working to develop a “high-throughput diagnostic screen,” 

which uses Cry34/35 seedlings to determine discriminating dose. The premise is that this screen will be 

able to identify potential field-resistant insects and provide estimates of phenotype and genotype 

frequencies. The applicants state that the screen should also be able to detect heterozygotes for r-alleles. 

While this type of screen would be highly valuable, the submission does not provide enough information 

about this diagnostic test. It is required that the applicants provide BPPD with a detailed explanation and 

validation (steps for) of the “high-throughput diagnostic screen” if it is to be considered an acceptable 

addition to present monitoring strategies. 

Finally, it is recommended that Cry34/35 corn be given the following resistance monitoring 

requirements: 

1. The applicants should monitor for resistance and/or trends in increased tolerance for corn 

rootworm. Sampling should be focused in those areas in which there is the highest risk of 

resistance development. The applicants should submit to EPA an appropriate sampling protocol 

as part of its monitoring plan. 

2. The applicants should provide EPA a description of its resistance monitoring plan by January 31, 

2006. The description would include the following: sampling (number of locations and samples 

per locations), sampling methodology, bioassay methodology, standardization procedures 

(including quality assurance/quality control provisions), detection technique and sensitivity, and 

the statistical analysis of the probability of detecting resistance. A final resistance monitoring 

plan is required by January 31, 2008. 

3. The applicants should develop an appropriate discriminating or diagnostic dose assay by January 

31, 2008. 

4. The applicants should follow-up on grower, extension specialist, or consultant reports of 

unexpected damage or control failures for corn rootworm. 

5. The applicants should provide EPA with an annual resistance monitoring report. 

Note: A discussion of the ongoing resistance monitoring program for Cry34/35, including the conditions 

listed above and results from the annual testing, is contained in the “Conditionally Required Data for 

Cry34/35 Corn (2010 Update)” section of this chapter. 
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 c. Remedial Action

The remedial action plan is designed as a tiered approach for mitigating WCRW, NCRW, and MCRW 

resistance development to the Cry34/35Ab1 proteins. The following program summary describes, in 

order of events, the steps that will be taken to implement a remedial action plan if resistance to target 

pests is confirmed. 

1. Definition of Suspected Resistance: Resistance will be suspected if investigations of unexpected 

damage reports show that: 

a. Implicated corn plant roots were expressing Cry34/35Ab1 proteins at the expected levels; 

b. Alternative causes of damage or lodging, such as non-target pest insect species, weather, 

physical damage, larval movement from alternate hosts, planting errors, and other reasonable 

causes for the observations, have been ruled out; 

c. The level of damage exceeds guidelines for expected damage. 

If resistance is “suspected,” the applicants will instruct affected growers to use alternate pest control 

measures such as adulticide treatment, crop rotation the following year, or soil or seed insecticides the 

following year. These measures are intended to reduce the possibility of potentially resistant insects 

contributing to the following year’s pest population. 

2. Confirmation of Resistance: Resistance will be confirmed if all of the following criteria are met by 

progeny from the target pest species sampled from the area of “suspected resistance”: 

a. The proportion of larvae that can feed and survive on Cry34/35 roots from neonate to adult is 

significantly higher than the baseline proportion (currently being established); 

b. The median lethal concentration (LC50) of the test population exceeds the upper limit of the 95% 

confidence interval for the LC50 of a standard unselected population and/or survival in the 

diagnostic assay is significantly greater than that of a standard unselected population, as 

established by the ongoing baseline monitoring program; 

c. The ability to survive is heritable; 

d. Cry34/35 plant assays determine that damage caused by surviving insects would exceed 

economic thresholds; 

e. The identified frequency of field resistance could lead to widespread product failure if 

subsequent collections in the affected field area(s) demonstrated similar bioassay results. 

3. Response to Confirmed Resistance: When resistance is “confirmed,” the following steps will be 

taken: 

a. EPA will receive notification within 30 days of confirming resistance; 

b. Affected customers and extension agents will be notified about confirmed resistance; 

c. Affected customers and extension agents will be encouraged to employ alternative CRW control 

measures; 
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d. Sale and distribution of Cry34/35 corn in the affected area will cease immediately; 

e. A long-term resistance management action plan will be devised according to the characteristics 

of the resistance event and local agronomic needs. 

BPPD’s Analysis of Proposed Remedial Action Plan

BPPD agrees with the general framework for the Remedial Action Plan; however, because the “baseline 

sensitivity” has not been calibrated, this plan cannot be implemented. The submission states that 

mitigation measures will be initiated when unexpected levels of CRW damage occur. However, 

confirmation of insect resistance cannot be done until levels of baseline sensitivity are determined (see 

previous discussion on “Resistance Monitoring”). Consequently, it should be required that baseline 

sensitivity be established within two years of product commercialization. Unexpected damage guidelines 

and confirmation of target pest resistance (using baseline sensitivity information) will be used to initiate 

a remedial action plan when needed. 

Note: Baseline susceptibility data through the 2008 growing season are discussed in the “Conditionally 

Required Data for Cry34/35 Corn (2010 Update)” section of this chapter. However, a credible diagnostic 

assay may need to be developed for resistance confirmation (e.g., Sublethal Seedling Assay; Nowatzki 

et al. 2008) so that a functional remedial action plan can be enacted. 

 d. Compliance

Compliance programs are important in that they encourage growers to comply with IRM requirements, 

while providing mechanisms by which registrants can be held accountable for noncompliant growers. 

The compliance program presented in this submission mirrors those developed for existing Bt corn 

registrations. Program components include the following: grower and sales force education/training 

programs that include workshops and educational pamphlets/brochures; contractual technology 

agreements that require grower adherence to IRM requirements; public relation activities, including 

media interviews, press releases, and conferences; and an annual affirmation program, which includes 

use of seed bag tags and tag language. 

Grower Education

The applicants state that “grower education is the single most important element of any strategy for 

promoting compliance with the IRM requirements.” The grower education program described in this 

submission is similar to that developed for other registered insect-protected corn products, so growers 

are familiar with the proposed concepts. 

BPPD’s Analysis of Grower Education and Compliance Assurance Program

Grower education and compliance are critical to the success of the trait durability plan. The applicants’ 

grower education plans are acceptable. However, the applicants have not presented any additional 

information as to their compliance assurance program analogous to what has previously been required 
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for all Bt corn PIP products. It is recommended that a compliance assurance program be required and 

submitted to the Agency that is in concert with existing Bt corn PIP products. Computer simulations by 

Storer (2003b) have shown that the level of refuge deployment needed for the trait durability plan to be 

fully effective depends on the level of technology adoption (see previous discussion under “Computer 

Simulation Models”). The proposed trait durability plan is based on 100% adoption, a very conservative 

assumption. However, as a worst-case scenario, refuge implementation by 75% of farmers would be 

needed for the proposed plan to be fully effective. At lower levels of adoption such as 75%, only refuge 

implementation by 50% of farmers would be effective in managing region-wide resistance. To ensure 

refuge implementation is high, a compliance assurance program should be required. 

Note: A discussion of the ongoing compliance program for Cry34/35 corn is contained in the 

“Conditionally Required Data for Cry34/35 Corn (2010 Update)” section of this chapter. 

 e. Annual Reports

It is required that the applicants provide BPPD with the following annual reports: resistance monitoring, 

compliance assurance program, and sales data at the state level (county level data to be available if 

requested). Data from the resistance monitoring and compliance reports are discussed in the next 

section. 

3. Conditionally Required Data for Cry34/35 Corn (2010 Update) 

As part of the terms and conditions of the Herculex® RW (Cry34/35 corn) registrations, the registrants 

were required to submit programs for resistance monitoring and refuge compliance. In addition, the 

registrants were required to submit annual reports summarizing the data collected under these 

requirements. The following elements of resistance monitoring and compliance were required: 

 Resistance Monitoring 

o Description of the steps to be taken to establish corn rootworm baseline sensitivity and 

damage guidelines (due January 31, 2006); 

o Submission of plan. Description of the program including baseline sensitivity, sampling 

(number of locations and samples per locations), sampling methodology, bioassay 

methodology, standardization procedures, detection technique, sensitivity, and the 

statistical analysis of the probability of detecting resistance, and an interim description of 

rootworm damage guidelines (due January 31, 2008); 

o Submission of rootworm damage guidelines (for unexpected pest damage) (due January 

31, 2010); 

o Development of diagnostic dose assay/high throughput screen (due January 31, 2008); 

o Annual report of the insect resistance monitoring program. Results of monitoring and 

investigations of damage reports (due August 31st each year, beginning in 2008). 
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 Compliance 

o Written description of Compliance Assurance Program (due January 31, 2006); 

o Grower agreements. Proposed system to assure growers sign grower agreements and 

affirmation system to assure annual affirmation by growers of their IRM obligations (due 

January 31, 2006); 

o Annual report on Compliance Assurance Program (CAP) activities and results. Thirdparty grower survey, on-farm visitation program, phased-compliance report, tips and 

complaints, and grower education programs (due January 31st each year, beginning in 

2007); 

o Grower education program for Cry34/35 corn. Subsequent changes to the grower 

education program must be included in the annual compliance assurance program report 

(due January 31, 2007). 

Dow and Pioneer have submitted all of the required reports as mandated under the terms of registration. 

A discussion of the reports and data for the resistance monitoring and compliance programs for 

Cry34/35 corn follows in the next sections. 

 a. Resistance Monitoring

Monitoring Plan for Cry34/35 Corn (2008) 

A preliminary resistance monitoring program was submitted to EPA in 2006 (reviewed in U.S. EPA 

2006a). This submission described work to establish baseline susceptibility data for Cry34/35, develop a 

diagnostic bioassay (sublethal seedling assay), and develop unexpected pest damage guidelines. 

Dow provided a revised monitoring plan in 2008 (MRID No. 473342-01), which is based on the 

framework of the ABSTC document titled “Updated Monitoring Plan for Bt Corn.” Specifically, Dow 

addressed the following elements of monitoring: initial baseline sensitivity, sampling plan, bioassay 

methodologies and analyses, probability of detecting resistance, and an interim description of process 

for developing rootworm damage guidelines. 

Monitoring for CRW resistance to the Bt crystal protein Cry34/35Ab1 relies on two approaches: 

population screening (random sampling, F1 screen with diet bioassays, and possible Sublethal Seedling 

Assay) and field observations of product performance by growers, consultants, and extension agents. To 

understand the biological relevance of any future variation in target pest response to Cry34/35Ab1 and 

whether changes in susceptibility are due to selection to the protein, the population variation in 

sensitivity needs to be understood. 

Sampling for CRW resistance will focus on WCRW (one of three Diabrotica target pests in the US) 

because this species represents the worst-case scenario (wide geographic distribution, greater 

abundance, and hence more likely to evolve resistance to Bt protein first) and is coordinated by the IRM 

technical subcommittee of ABSTC. Collection efforts will focus on regions where WCRW pest pressure 
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is greatest, and CRW-protected Bt corn adoption is greatest. Such areas of focus are Illinois, Iowa, and 

Nebraska; however, Indiana, Missouri, Wisconsin, Minnesota, and Kansas are also potential candidates 

for sampling collections. ABSTC’s core sampling area is divided into three regions: Region 1 consists of 

eastern Illinois and Indiana (rotation-resistant variant); Region 2 consists of western Illinois, Iowa, and 

Missouri (wild-type variant); and Region 3 consists of Nebraska and Kansas (organophosphate-resistant 

variant). Sampling locations will change on a yearly basis, and sampling intensity will reflect adoption 

of CRW-protected Bt corn. ABSTC will obtain coordinates of sampling locations so that re-sampling in 

subsequent years can occur when needed. Fifteen or 16 population subsamples from different counties 

across the sampling region will be collected, and colonies reared and maintained in the lab. Each 

collection should consist of 2,000 adult beetles to ensure a minimum of 5,000 eggs from at least eight of 

the total samples collected. 

The diet bioassay tool is available to monitor for changes in WCRW susceptibility to Cry34/35Ab1 and 

the Sublethal Seedling Assay (SSA) (Nowatzki et al. 2008) may be available as well. It is Dow’s 

intention to eventually select for use a single method once the advantages and validity of each approach 

have been verified. A final description of how the SSA can be used in resistance monitoring should be 

available in 2010. 

BPPD’s Analysis of Cry34/35 Resistance Monitoring Plan 

BPPD has reviewed Dow’s revised monitoring plan for DAS-59122-7 and has found it adequate for 

Cry34/35 (see review in U.S.EPA 2009c). BPPD recommends that Dow/Pioneer consider the use of the 

Sublethal Seedling Assay (Nowatzki et al. 2008) for detecting shifts in susceptibility rather than the diet 

bioassay approach (EC50/LC50 data). Nowatzki et al. (2008) were able to show that the SSA was more 

sensitive in detecting shifts in susceptibility than the bioassay because it used the increased sensitivity of 

a sublethal measure. 

BPPD also recommends that Dow/Pioneer address monitoring for resistance with northern corn 

rootworm. Baseline susceptibility data have been developed in the past by the Siegfried lab at the 

University of Nebraska, which now can serve as a reference. Past difficulties with rearing of NCRW and 

arguments of limited geographic distribution should not be the driving factors for failure to monitor for 

resistance in this corn pest. 

Unexpected Pest Damage Guidelines (2010)

The few follow-ups to unexpected pest damage reports showed that most crop damage was due to 

weather-related causes rather than trait failure. The “interim unexpected pest damage guidelines” 

(submitted in 2008) encompassed the variability seen in registrant-generated field trial data from 2005–

2007. The Iowa State 0–3 Node Injury Scale (NIS) was used to assess root damage and assign ratings. 

To create worst-case guidelines, only results from locations where the average damage to the untreated 

isoline control exceeded a rating of 1.0 were used. Since environmental and ecological factors affect 

both trait performance and manifestation of rootworm damage and can cause outliers from the expected 
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distribution, the interim guidelines for unexpected pest damage call for assessment of reports of root 

damage to be considered on a case-by-case basis. 

Final unexpected pest damage guidelines were submitted in 2010 (MRID No. 480455-01). Dow reported 

that corn rootworm damage on Cry34/35-protected Bt corn was a function of the non-high dose effects 

of the crystal toxin and environmental conditions. Because of the multitude of factors playing a potential 

role in root-feeding damage, stalk and root lodging, Dow stated that it was impossible to derive a 

threshold damage level (i.e., NIS score) that would qualify as “unexpected” for all possible scenarios. 

The following are factors that affect the root damage levels: 

● Rootworm population pressure ● Soil chemical environment 

● Rootworm egg distribution across fields ● Soil fertility 

● Field history (previous crop) ● Winter conditions (e.g., temperature, 

● Soil conditions in the previous year snow cover, freeze-thaw cycles) 

 (affecting egg distribution) ● Weather events before and during the 

● Soil structure and type period of rootworm feeding (storms, 

● Use of insecticides drought, etc.) 

● Use of fertilizers ● Presence of CRW pathogens and 

● Presence of grassy weeds as alternate predators 

 larval plant hosts ● Density-dependent CRW larval 

● Presence of off-type plants not expressing competition for feeding sites 

 the toxin ● Phenotypic variation in expression of 

● Presence of volunteer corn the proteins 

● Soil moisture at rootworm egg hatch ● Temporal and spatial pattern of 

● Timing of rootworm egg hatch Cry34/35 concentration in roots 

 and corn root growth 

● Duration of rootworm egg hatch ● Rootworm ability to find suitable host 

● Size of root mass at the time of rootworm tissue 

 feeding ● Chronic effects of Cry34/35 on larvae 

● Re-growth of corn roots following feeding ● Environmental impacts on corn growth 

● Root damage due to other agents and development 

 other than corn rootworm 

● CRW species mix 

Both Dow and Pioneer have conducted field trials with their corn rootworm products expressing DAS59122-7 and have found that, under extreme conditions and in the absence of resistance, Cry34/35 may 

not provide economic protection in part due to its non-high dose nature. 

Dow and Pioneer have therefore set up their own protocol for investigating reports of unexpected CRW 

damage on DAS-59122-7 corn. A field visit will occur as soon as reasonably possible following a 

grower complaint. Lodging, stunting, and other symptoms will be investigated through the entire 

affected area on DAS-59122-7 expressing Bt and non-Bt corn plants, and the cause of damage will be 

determined (CRW or other pest damage, adverse weather, or other factors). If causes other than CRW or 
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planting error do not explain the damage, then plants will be sampled from the affected field and root 

injury scored and plant samples will be tested to verify the presence of the trait. If the trait was 

expressed in the injured plants, then Dow proposed to collect more root samples from the affected 

field(s) to identify whether inadvertent seed mixing occurred. If the trait was expressed in these 

additional samples and non-expressing plants were not present in significant numbers, then Dow would 

escalate the incident for further investigation. 

Further investigation involves collecting adult CRW and root tissue for expression analysis. If the 

expression analysis verified the expected expression level in roots and other factors did not explain the 

damage levels observed, then the collected CRW samples would be submitted to a third-party laboratory 

for bioassay analysis, which would determine whether the population samples are less sensitive to 

Cry34/35 than normal. 

Dow expects this process to last up to a year. However, when damage reports come in too late to collect 

adults, then the investigation would start in the next growing season. The field and surrounding area 

would be assessed and, if damage cannot be explained by any other factors, then adults would be 

collected for rearing and consequent bioassay purposes. 

Dow proposes that resistance would be confirmed if two years of unexplained damage and significantly 

lower than normal sensitivity to Cry34/35 are observed in offspring of collected adults. Dow’s response 

to confirmed resistance was outlined in the registration letters and triggers the long-term resistance 

management remedial action plan according to the characteristics of the Bt trait and local agronomic 

needs. 

BPPD’s Analysis of Unexpected Damage Guidelines 

Dow proposed that a damage threshold was no longer feasible to use as an indicator for potential CRW 

field resistance because other non-toxin related factors could act together in such a manner as to mimic 

field resistance. BPPD does not concur with Dow’s proposition nor with their arguments to completely 

abandon the “damage threshold level” as an indicator for CRW field resistance and proposes a revised 

approach instead (see review in U.S. EPA 2010c). At the time, the 2002 SAP proposed a Node Injury 

Score threshold level of 0.5 for Cry3Bb1 as an indicator of “damage across the economic threshold 

level.” BPPD notes that this value cannot be transferred to other single toxins, or even pyramided toxins, 

and that each report of unexpected CRW damage needs to be dealt with on an individual basis. The 

“damage threshold level” as expressed by node injury scores is an important tool for alerting the 

stakeholder community and EPA that some unusual event in Bt corn has occurred; however, this tool 

should not be used alone and out of context. The following points should be considered when following 

up with a reported incident of unexpected pest damage: 

1) The inherent dose of the toxin to control CRW (high dose vs. non-high dose control); 

2) Prior use and crop history in the Bt field where excessive damage was observed; 

3) Damage on non-Bt plants in the same field or immediately adjacent to the Bt plants; 
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4) Insect pressure during that corn-growing season (low vs. moderate vs. high); and 

5) Weather pattern during the corn-growing season and possible effects on Bt protein expression and 

 pest population dynamics. 

When greater node injuries are observed on the refuge corn than on the Bt corn, then this could be an 

indication that damage is not due to resistance but some other factors. Likewise, if Bt plants have less 

damage than refuge plants that were treated with insecticides, then the cause of damage is less likely due 

to resistance. However, if damage levels on Bt plants exceed the level observed on non-Bt plants, then 

field resistance could be a concern. A NIS damage threshold level of 1.0 may be suitable for single 

toxin, non-high dose CRW products such as DAS-59122-7. When CRW pressure is exceedingly high, 

however, then both Bt and refuge corn will incur greater damage. Under these circumstances, a threshold 

level of 1.5 may be appropriate to use by the registrants. 

BPPD concluded that Dow/Pioneer’s response strategy for dealing with unexpected damage reports in 

DAS-59122-7 corn is protracted and could be improved (U.S. EPA 2010c). For example, Dow/Pioneer 

stated that they would first survey the area with unexpectedly high CRW damage, then collect root 

tissues and conduct tissue tests to verify appropriate Bt expression. If the Bt toxin was expressed, 

Dow/Pioneer proposed to collect more tissue samples to rule out planting error, and then after they 

failed ruling out CRW resistance, would they begin collecting adults. With this sequence of steps, BPPD 

notes that Dow/Pioneer will lose valuable time to obtain adult CRW collections. BPPD recommends that 

Dow/Pioneer collect adult CRW immediately after first being alerted to unusually high root damage to 

DAS-59122-7 corn. These adults can be held until all the other proposed causative agents have been 

ruled out. The benefit to BPPD’s approach is that if field resistance is the cause of product failure and 

the unexpected damage reports, then Dow/Pioneer would already have a population sample available 

and could start the rearing process, bioassays, and have results to report possibly within one year rather 

than Dow/Pioneer’s worst-case scenario of two years. 

When CRW adults are collected in response to an unexpected damage report, BPPD recommends that 

samples originate from the Bt field of concern and the adjacent refuge corn. However, studies by 

Naranjo (1990) and Coats et al. (1986) suggest that a significant fraction of the female WCRW 

population engages in longer distance and pre-ovipositional dispersal. Hence, collections of putative 

resistant individuals should also be obtained past the 1⁄2 mile radius from the affected field. 

Resistance Monitoring Results (Through 2008) 

In 2008 (report detailed in MRID No. 479008-01), nine populations of western corn rootworm were 

collected across the Corn Belt where the species was most abundant and where all three biotypes 

occurred (see below). At each collection site, 2,000 individuals were collected in one day and 

maintained for oviposition purposes by Custom Bio-Products in Maxwell, Iowa—an independent 

laboratory conducting bioassays for Dow since 2006. 
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ABSTC Region 1, rotation-resistant variant 

 McLean County, Illinois 

 Piatt County, Indiana 

 Henry County, Illinois 

ABSTC Region 2, wild-type variant 

 Scott County, Iowa 

 Palo Alto County, Iowa 

 Clinton County, Iowa 

ABSTC Region 3, organophosphate-resistant variant 

 York County, Nebraska 

 Polk County, Nebraska 

 Seward County, Nebraska 

Concentration response bioassays were conducted using neonates from each of the nine collected 2008 

populations; the same protocol was followed as for the baseline susceptibility studies described in 

Dow’s report to the Agency (MRID No. 473342-01). The protein used in the assays consisted of 

microbially produced, partially purified powders mixed in a ratio of 3:1 by active ingredient weight 

(Cry34 to Cry35). Concentrations tested included 0, 0.56, 1.67, 5.0, 15.0, and 45.0 micrograms per 

square centimeter (μg/cm2). Growth inhibition (EC50) and mortality (LC50) were measured from 

neonates of the collected insects and compared to the established baseline susceptibility. In addition, the 

variation in sensitivity was measured using a ratio of the greatest to lowest LC50 and ratio of greatest to 

lowest EC50 and compared to prior results. 

Data from 2008 were reported in MRID No. 479008-01 (reviewed in U.S. EPA 2010c). Estimated EC50

and LC50 values for the nine geographically distinct 2008 WCRW populations ranged from 2.0 μg/cm2

to 7.9 μg/cm2 and 6.2 μg/cm2 to 15.4 μg/cm2, respectively. For EC99 and LC90 measures, the estimates 

ranged from 83.8 μg/cm2 to 596.6 μg/cm2 (EC99) and 58.4 μg/cm2 to 613.6 μg/cm2 (LC90). The 2008 

results are summarized in Table 1 below, along with data from susceptibility assays in previous seasons 

(2004–2008). Dow concluded that the sensitivity of WCRW, as measured by the ratio of highest to 

lowest LC50 and EC50, was similar to those in previous years (see Figure 1). 
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Table 1. Cumulative WCRW Cry34/35 Susceptibility Data (2004–2008). 

Year EC50 (μg/cm2

) EC99 (μg/cm2) LC50 (μg/cm2) LC90 (μg/cm2)

2004–2005 0.8–1.1 2.0–2.4

2006 0.8–2.3 21.0–56.6 1.2–7.3 9.2–78.1 

2007 1.0–3.7 51.9–213.6 3.0–11.5 23.9–463.5 

2008 2.0–7.9 83.8–596.6 6.2–15.4 58.4–613.6

 BPPD generated table from data submitted by Dow. 

Figure 1. Variation in response to Cry34/35 (as measured by the ratio of high:low LC50 and EC50) 

 among WCRW field populations collected between 2004 and 2008 (Dow figure 

 extracted from MRID No. 479008-01). 

Overall, there has been a trend of decreasing susceptibility in WCRW to Cry34/35. All measured and 

extrapolated mean EC and LC values were higher in 2008 than in previous years (see ranges for EC99

and LC90 values in Table 1). From 2006 to 2008, the range of mean EC99 and LC90 values obtained in 

bioassay tests or from extrapolations increased from 21.0–56.6 μg/cm2 to 83.8–596.6 μg/cm2 and 9.2–

78.1 μg/cm2 to 58.4–613.6 μg/cm2, respectively. However, the statistical relevance of these increases is 

not clear from the submitted data. 

As an additional point of analysis, two counties that were previously sampled in 2006 and 2007 were 

also sampled in 2008, and a more direct data comparison could be made for these two locations (see 

Table 2). U.S. EPA (2010c) focused on EC data, since these showed less variation than LC data. When 

the mean EC50 and EC99 values were compared across three consecutive years in Henry and Scott 
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County (Illinois), it was apparent that the extrapolated EC99 values had increased. The mean EC99 values 

for Henry and Scott County ranged from 21.0 μg/cm2 to 388.3 μg/cm2 and 48.7 μg/cm2 to 95.8 μg/cm2, 

respectively. BPPD concluded that susceptibility to DAS-59122-7 may have decreased in this 

geographic region (Henry County and Scott County, Illinois) and recommended that additional sampling 

occur in these counties during future corn-growing seasons to assess whether these susceptibility trends 

continue. 

Table 2. Cry34/35 Susceptibility Data for WCRW populations in Two Illinois Counties 

 (2006–2008) (BPPD generated table from data submitted by Dow/Pioneer). 

Location/Year EC50 (μg/cm2

) EC99 (μg/cm2)

Henry Co (2006) 1.3 21.0 

Henry Co (2007) 2.1 213.6 

Henry Co (2008) 4.0 388.3 

Scott Co (2006) 0.8 48.7 

Scott Co (2007) 1.8 63.2 

Scott Co (2008) 2.9 95.8 

 b. Compliance

Dow/Pioneer’s compliance reports, including grower agreements, grower affirmation procedures, and 

CAP, were reviewed in U.S. EPA (2006b). The compliance program for DAS-59122-7 (Cry34/35 corn) 

is aligned with that developed by ABSTC (in consultation with the EPA) for corn-borer protected Bt

corn products. Specific elements of the program and additional reports with annual survey data are 

discussed below. 

DAS-59122-7 Compliance Assurance Program 

As a term of the Herculex RW (DAS-59122-7; Cry34/35Ab1) registration, Dow and Pioneer were 

required to develop and submit to EPA a CAP to ensure grower adherence to IRM requirements. The 

terms of registration mandated a number of components for the compliance program including: 

 Grower Agreements: Contractual arrangement between the registrant and grower to obligate 

adherence to IRM requirements. 

 Annual IRM Survey: A survey (conducted anonymously by an independent research firm) 

intended to provide a statistically representative sample of growers from various corn-growing 

regions in the U.S. Results from the survey should assess levels of grower compliance with 

refuges, as well as grower motivations, attitudes, and reasons for non-compliance. 
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 On-Farm Assessments: The registrant is required to develop an on-site assessment program in 

which trained personnel from each company make visits to farms growing Bt corn. During these 

visits, compliance with refuge requirements is assessed and growers not in compliance are 

identified for corrective action under the Phased Compliance Approach. 

 Tips and Complaints: The registrant must establish a means for the reporting and investigation of 

incidences of refuge non-compliance. 

 Phased Compliance Approach (PCA): A consistent set of procedures (for all Bt corn registrants) 

to be employed to address non-compliance among growers and seed dealers. 

 

ABSTC, a consortium of Bt corn registrants, previously developed and submitted a CAP for 

lepidopteran Bt corn PIPs in 2002. Subsequently, ABSTC submitted revised versions of the CAP in 

2004 and 2005 in response to EPA reviews of annual growing season reports (see discussion in U.S. 

EPA 2010e). Herculex® RW (and other registered products with Cry34/35) have been included as part 

of this existing program, though data are tabulated separately for lepidopteran, rootworm, and stacked 

(lepidopteran + rootworm) Bt corn PIPs. EPA reviews of compliance data for rootworm-protected PIPs 

(some of which predates the registration of Herculex® RW) can be found in U.S. EPA (2004, 2007b, 

and 2009a). 

Annual Grower Surveys 

As a condition of each individual Bt corn registration, the registrant must perform an annual third-party 

survey of a statistically representative sample of Bt corn growers. The grower survey functions to 

measure compliance adherence to refuge size and distance requirements at a regional level and to 

identify educational opportunities to increase grower compliance with IRM requirements. More than 

500 growers from four separate regions are anonymously surveyed annually. The methodology for 

conducting the grower survey has remained virtually unchanged since it was first conducted by 

Marketing Horizons, Incorporated in 2000 for the lepidopteran Bt corn registrations. Starting in 2007, 

however, due to an increasing complexity of growers’ Bt corn planting practices and a need to 

standardize the grower survey across insect-protected traits, Marketing Horizons, Incorporated utilized 

an internet-based survey approach. 

Surveys for the corn rootworm PIPs encompass all growers planting rootworm-protected traits 

(Cry3Bb1, mCry3A, and Cry34/35Ab1). Cumulative results of the surveys are summarized in Table 3 

below. Results from the stacked (lepidopteran + rootworm) Bt corn surveys are tabulated separately 

(Table 4) and also include all registered rootworm PIP traits. 
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Table 3. Summary of Telephone (2005–2006) and Online (2007–2008) Survey Results for 

 Rootworm-Protected Bt Corn Growers. 

Survey Question 

20051

% 

Respondents 

20062

% 

Respondents 

2007 

% 

Respondents 

2008 

% 

Respondents 

Adherence to Refuge3 Size 93 89 80 74 

Adherence to Distance 

Requirements3 87 82 79 63 

Awareness of IRM 

Requirements 97 93 97 96 

Unaided Recall of Refuge Size 51 57 63 72 

Unaided Recall of Refuge 

Distance 58 55 33 34 

1 Includes YieldGard® RW and YieldGard® Plus corn growers

2 Includes YieldGard® RW, YieldGard® Plus, Herculex® RW, and Herculex® XTRA corn growers 

3 Weighted averages across all four regions surveyed

Table 4. Summary of Telephone and Online Survey Results for Stacked Bt Corn Growers 

 (2006–2008). 

Survey Question 

2006 

% 

Respondents 

2007 

% 

Respondents 

2008 

% Respondents 

Adherence to Refuge Size1 78 70 724

Adherence to Distance 

Requirements1 92 66 663

Awareness of IRM Requirements 95 96 97 

Unaided Recall of Refuge Size 59 62 and 552 81 

Unaided Recall of Refuge Distance 

CRW 48 39 36 

Unaided Recall of Refuge Distance 

European Corn Borer (ECB) 32 77 86 

1 Weighted average across all four regions surveyed 2 First number listed is for ECB and the second number for CRW refuge compliance. 3

 On a per field basis, adherence was 76%. 

4

 On a per field basis, adherence was 73%. 

Overall compliance (per grower) with refuge requirements for both single-trait and stacked rootwormprotected PIPs has declined from 2005 to 2008. Grower adherence to the necessary refuge size fell to 
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below 75% in 2008 for single-trait and stacked rootworm PIPs. Compliance with refuge proximity was 

lower; in 2008, ≤66% of rootworm PIP growers deployed refuges within the required distance to the Bt

field. The percent of growers who were able to recall the correct refuge distance requirements (unaided) 

for rootworm PIPs drastically declined to below 40% in 2008. Refuge distance requirements for 

rootworm-protected Bt corn products may be more challenging for growers because the refuge must be 

deployed either within or immediately adjacent to the Bt field. Stacked products present additional 

challenges due to the need to plan either two refuges (for lepidoptera and rootworm) or a combined 

refuge for both pest complexes. Grower awareness of the distance requirements has been poor and likely 

explains much of the reported non-compliance. 

On-Farm Assessments 

The on-farm assessment program is the portion of the CAP that identifies individual non-compliant 

growers (regardless of farm size) for remedial IRM education, follow-up reassessments, and other 

activities as part of the PCA. It can also serve as a tool to enhance the registrant’s understanding of the 

obstacles growers face in implementing IRM requirements. The mandatory on-farm assessment program 

was fully implemented for the first time in 2003 (for lepidopteran registrations) and has typically 

encompassed more than 2,000 growers per season (for all types of Bt corn). On-farm assessments for 

rootworm-protected PIPs (including Cry34/35 products) began in 2006. 

Data from the on-farm assessments (2006 through 2008) of rootworm-protected Bt corn PIPs are 

summarized in Table 5 below. These on-farm assessments encompass all growers planting rootwormprotected PIPs, including varieties expressing the Cry3Bb1, mCry3A, and Cry34/35Ab1 toxins. Results 

for the on-farm assessments of stacked (lepidopteran + rootworm) PIPs are detailed in Table 6. The 

assessments do not have the statistical power associated with the consistently stratified and randomized 

telephone/on-line surveys and are not used to measure representative rates of non-compliance. In 2007 

and 2008, no information was provided regarding specific non-compliance with refuge size and 

distance. This information should be provided in future reports to be consistent with previously collected 

data and to illustrate how growers are out of compliance (U.S. EPA 2009a). 
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Table 5. Cumulative Results for the On-Farm Assessments of Coleopteran-Protected Bt Corn 

 Growers (2006–2008)1. 

2006 2007 2008 

Growers Assessed 395 247 134 

Refuge Distance 

Deviations2 13 N/A N/A 

Refuge Size Deviations 7 N/A N/A 

Significant Deviations 11 (2.8%) 16 (6.5%) 12 (9.0%) 

Insignificant Deviations 10 (4.0%) 8 (3.2%) 7 (5.2%) 

Compliant Growers 374 (94.7%) 223 (90.3%) 115 (85.8%) 

Non-Compliant 

Growers 21 (5.3%) 24 (9.7%) 19 (14.2%) 

1

Table adapted from page 12 of MRID No. 470444-01. 

2

 Some growers had compliance deviations other than refuge size or distance; thus, the total of refuge distance and size deviations does not 

 equal the number of non-compliant growers. 

Table 6. Cumulative Results of the On-Farm Assessments of Stacked Bt Corn 

 (Rootworm + Corn Borer) Growers (2006–2008)1. 

2006 2007 2008 

Growers Assessed 600 1,069 1,799 

Refuge Distance 

Deviations 512 N/A N/A 

Refuge Size Deviations 8 N/A N/A 

Significant Deviations 45 (7.5%) 77 (7.2%) 863

Insignificant Deviations 16 33 (3.1%) 363

Compliant Growers 539 (89.8%) 959 (89.7%) 1546 (85.9%) 

Non-Compliant 

Growers 61 (10.2%) 110 (10.3%) 253 (14.1%) 

1 Table adapted from page 12 of MRID No. 470444-01. 

2

 Some growers had compliance deviations other than refuge size or distance; thus, the total of refuge distance and size deviations does not 

 equal the number of non-compliant growers. 

3

 The numbers of deviations do not add up to the 253 non-compliant cases reported. 

Tips and Complaints 

As required by the terms of registration, Bt corn registrants must have a “tips and complaints” system as 

a mechanism for individuals (e.g., growers, sales representatives, etc.) to report alleged instances of IRM 

non-compliance. The number of tips and complaints (summarized for all Bt corn registrations, including 

lepidopteran and rootworm varieties) received through 2008 is summarized in Table 7 below. Each of 

these growers identified through the tips and complaints mechanism were visited as part of the on-farm 
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assessment program. However, it is not possible to determine whether any of the non-compliant 

growers, identified via the tips and complaints route, were subject to the Phased Compliance Approach. 

Table 7. Anonymous Tips and Complaints about Non-Compliance with IRM Requirements 

 (Data from ABSTC Annual Reports 2003 through 2008). 

Year Number of Tips and 

Complaints 

2003 0 

2004 0 

2005 5 

2006 3 

2007 14 

2008 5 

Phased Compliance Approach 

ABSTC’s CAP for lepidopteran and rootworm-protected PIPs includes a standard set of procedures 

(shown in Table 8), known as the Phased Compliance Approach (PCA), which is to be used by 

registrants when responding to instances of grower non-compliance with the IRM requirements. The 

PCA also established a tiered approach for non-compliance with “significant” deviations and “other” 

deviations. For a 20% CRW refuge requirement (Corn Belt), a significant size deviation is defined as a 

Bt grower planting less than 15% non-Bt corn refuge. This definition is also applicable to “combined” 

refuges planted for both lepidoptera and CRW for stacked Bt corn PIPs. On the other hand, a significant 

deviation based on refuge proximity has not been clearly defined for CRW refuges and, as of the 2008 

CAP report, it is unclear what standards are being used by ABSTC. For lepidopteran Bt corn, a 

significant deviation is triggered if fewer than 2/3 of the Bt corn fields are planted within 1⁄2 mile of a 

non-Bt corn refuge. However, this definition is not compatible with CRW refuge because the distance 

requirement mandates that refuges be placed adjacent to or within the Bt corn field. A reasonable 

extension of the lepidopteran definition for CRW could be “less than 2/3 of the non-Bt refuge is 

deployed adjacent to or within the Bt field” and “fewer than two-thirds (2/3) of the in-field strips are at 

least four rows wide” (U.S. EPA 2006b). This formula would also be applicable to combined refuges for 

stacked PIPs. 
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Table 8. Phased Compliance Approach (PCA) – Standards for Bt Corn Refuge Non-Compliance 

 (Submitted with the ABSTC 2002 CAP). 

Mandatory Responses Additional Responses

Significant Deviations  IRM education 

 Warning letter 

 Compliance assistance contact 

prior to planting 

 Compliance assessment 

contact for the following 

growing season 

 Deny access to the Bt corn 

product for any significant 

deviation two years in a row 

Other Deviations  IRM education 

 Letter and/or compliance 

assistance contact prior to 

planting 

 Compliance assessment 

contact in the following 

growing season 

 Invoice monitoring 

 Technical assistance 

 Grower IRM training 

 Reaffirmation of IRM 

obligations 

 Deny access to the Bt corn 

product for other deviations that 

are repeated over a period of 

years 

Under the PCA, sales are to be suspended to individual growers for one year after two years of 

significant deviations. Following the one-year suspension, growers will need to be requalified to 

purchase seeds. Grower identified as non-compliant (significant or other deviations) are required to 

receive a “compliance assessment contact” the following year under the PCA. Non-compliant growers 

are typically identified through the on-farm assessment program (see previous discussion in the “OnFarm Assessments” section). Table 9 summarizes the numbers of non-compliant growers reassessed 

under the PCA, and the growers still found to be out of compliance. As of the 2008 growing season, one 

grower was denied access to Bt corn technology due to a refusal to be reassessed in the following season 

after significant non-compliance. Compliance data, including results of on-farm assessments and PCA 

activities, are detailed in U.S. EPA (2007b and 2009a). 
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Table 9. Reassessment of Rootworm-Protected and Stacked Bt Corn Growers Under the Phased 

 Compliance Approach (Taken from ABSTC Annual CAP Reports)1. 

Year Reassessments 2 Significant Deviations 3 Loss of Access to 

Technology 

2006 62 0 1 4 

2007 82 0 0 

2008 134 0 0 

1

 The data in this table includes both growers planting single-trait rootworm PIPs and stacked (lepidopteran + rootworm) 

 PIPs. The data in the table has been summed for both groups. 

2

 Reassessments of growers identified with deviations (significant and other) to refuge requirements the previous growing 

 season. 

3

 Significant deviations recorded the following season. Two successive years of significant deviations results in loss of access 

 to Bt corn technology. 4

 One grower refused to be reassessed in 2006 and was denied access to Bt corn 

4. Stacked Bt Corn PIPs Containing Cry34/35 

Several “stacked” Bt corn PIPs have been registered that contain Cry34/35. Stacked products express 

two or more toxins targeted at separate pest complexes. Cry34/35 (rootworm control) has been paired 

with lepidopteran-active proteins for control of European corn borer and other pests. The stacked 

Cry34/35 products (registered as of 2010) are described below. A separate product has been registered 

with a “pyramid” (two or more toxins targeted at the same pest complex) of Cry34/35 and Cry3Bb1 for 

rootworm control. This product (SmartStaxTM) is discussed in a separate Fact Sheet (U.S. EPA 2009b). 

Another product containing a seed blend mix of Cry34/35 corn (Optimum® AcreMaxTM 1) has also 

been registered and is discussed in a separate Biopesticides Registration Action Document (U.S. EPA 

2010b and 2010f). 

 a. Herculex® Xtra (DAS 59122-7 x TC1507)

Herculex Xtra (EPA Reg. Nos. 68467-6 and 29964-5) is a stacked product that is the result of a 

conventional breeding cross between Herculex® I (Event DAS 01507-1; EPA Reg. Nos. 68467-2 and 

29964-3) and Herculex® Rootworm (Event DAS-59122-7; EPA Reg. Nos. 68467-5, 29964-4). 

Herculex® I (first registered in 2001) expresses the Cry1F Bt toxin and is targeted against stalk-boring 

lepidopteran pests, while Herculex® Rootworm corn (registered August 31, 2005) expresses the 

Cry34Ab1/35Ab1 binary toxin for control of CRW. The complete list of targeted pests is as follows: 

European corn borer (ECB, Ostrinia nubilalis), southwestern corn borer (SWCB, Diatraea 

grandiosella), corn earworm (CEW, Helicoverpa zea), fall armyworm (FAW, Spodoptera frugiperda), 

black cutworm (BCW, Agrotis ipsilon), western bean cutworm (WBCW, Richia albicosta), western corn 

rootworm (WCRW, Diabrotica virgifera virgifera), northern corn rootworm (NCRW, Diabrotica 

barberi), and Mexican corn rootworm (MCRW, Diabrotica virgifera zeae). 
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When evaluating a stacked PIP created from previously registered single-trait PIPs, the dose profiles for 

each of the toxins in the stack will have been previously established for the isolines. Therefore, the dose 

of the stacked PIP can be verified relatively easily through confirmatory studies. Two sets of data are 

typically analyzed: (1) plant expression data to verify that the toxin expression in the stacked product is 

at least as high as in the single-gene isolines; and (2) efficacy data to confirm that the level of control 

against the target pests in the stacked product is at least as high as the isolines. Dow/Pioneer submitted 

efficacy studies (Master Record Identification Numbers (MRID Nos.) 463438-04 and 463438-05) that 

were designed largely to confirm efficacy in the newly created stacked product, Herculex® Xtra. The 

data revealed that Herculex® Xtra offered comparable levels of protection against ECB, FAW, and 

WCRW as the single-gene hybrids (Herculex® I and Herculex® Rootworm) used to create the stacked 

product. Other labeled pests (e.g., BCW, SWCB, and NCRW) were not evaluated in these studies. 

However, since previously submitted data have demonstrated efficacy against all the labeled pests in the 

single-gene hybrids (Herculex® I and Herculex® Rootworm), it is expected that Herculex® Xtra will 

offer comparable protection. The results are also supported by toxin expression data (MRID No. 

463438-04), which showed that the stacked hybrid expresses both Cry1F and Cry34/35 at comparable 

(or higher levels) than the single-gene hybrids (U.S. EPA 2005c). 

IRM must be addressed for lepidopteran and corn rootworm by deploying either separate 20% non-Bt

corn refuges (for each pest complex) or a combined 20% refuge that addresses both pest complexes. A 

combination refuge must address the proximity restrictions for CRW (i.e., the refuge must be placed 

adjacent to or within the Bt field and in-field strips must be at least 4 rows wide). 

Other aspects of the IRM program for Herculex® Xtra (resistance monitoring, remedial action, and 

compliance) were incorporated into the existing programs for the single-toxin PIPs (Cry34/35 and 

Cry1F). The IRM program for Cry34/35 is discussed in sections II(D)(2) and II(D)(3) of this BRAD; 

Cry1F is discussed in the August 2005 Cry1F BRAD and the July 2010 Cry1Ab and Cry1F BRAD (U.S. 

EPA 2005b and 2010d). 

 b. 59122 x MON 810 and 1507 x 59122 x MON 810 

Both 59122 x MON 810 (EPA Reg. No. 29964-9) and 1507 x 59122 x MON 810 (EPA Reg. No. 29964-

8) are stacked products registered by Pioneer for control of rootworm and corn borer pests. The first, 

59122 x MON 810, expresses Cry34/35 and Cry1Ab, while 1507 x 59122 x MON 810 expresses Cry1F, 

Cry34/35, and Cry1Ab. Like other stacked Bt corn PIPs, these two products were supported by efficacy 

and expression data to confirm the dose profile against the major target pests. 

Protein expression data were generated for each of the stacked products (59122 x MON 810 and 1507 x 

59122 x MON 810) and the single-toxin constituent PIPs (MRID No. 475109-04). Studies were 

conducted in greenhouses, and plant tissues were analyzed by enzyme-linked immunosorbent assay 

(ELISA) for protein expression. Pioneer sampled leaf, stalk, root, whole plant, and grain tissues for the 

analyses (pollen tissue was also collected but was often below the limit of detection). Corn tissues were 

sampled during the R1 corn growth stage, except for grain which was taken from the R6 stage. The 

results from the ELISA assays showed that Cry1F, Cry1Ab, Cry34Ab1, and Cry35Ab1 protein were 
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expressed at comparable levels in the stacked products to the single-toxin constituent products. 

Expression was consistent throughout all tissues—only small differences in protein levels, which were 

not statistically significant, were noted between the stacked and single-toxin products. 

Pioneer conducted field studies to investigate the efficacy of their stacked products against ECB, 

SWCB, FAW, and CRW. The company asserted that testing was not necessary for other labeled pests 

(i.e., secondary lepidopteran corn pests) given that the constituent PIPs (1507, 59122, and MON 810) 

have well established efficacy profiles. These studies were described in MRID No. 476778-03. The 

submitted field efficacy data were sufficient to demonstrate that the Bt toxins in the three proposed 

stacked products have comparable dose expression profiles as their single-trait constituent products 

(U.S. EPA 2010a). Both MON 810 (Cry1Ab) and 1507 (Cry1F) have been considered “high dose” for 

ECB and likely SWCB but not for CEW. With CRW, 59122 (Cry34/35) is known not to have high dose 

expression. Given the confirmatory protein expression and efficacy studies, the stacked products can 

also be considered high dose for ECB and SWCB and non-high dose for CEW and CRW. 

Similar to other stacked products, refuge must be addressed by planting separate (corn borer and 

rootworm) 20% refuges or a combination 20% refuge for both pests. Other aspects of the IRM program 

(resistance monitoring, remedial action, and compliance) are largely the same as the existing programs 

for the single-toxin PIPs (Cry34/35, Cry1Ab, and Cry1F). The IRM program for Cry34/35 is discussed 

in sections II(D)(2) and II(D)(3) of this BRAD; Cry1Ab and Cry1F are discussed in the 2001 Bt Crops 

Reassessment, August 2005 Cry1F BRAD, and/or the July 2010 Cry1Ab and Cry1F BRAD (U.S. EPA 

2001b, 2005b, and 2010e). 

c. Refuges for Stacked Bt Corn Products

Table 10 below describes the refuge requirements for stacked Bt corn PIPs targeting lepidopteran (e.g., 

ECB) and rootworm pests. Growers must either plant two separate refuges for each pest complex or a 

combined refuge that addresses both insect groups. 
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Table 10. Comparison of Lepidopteran (e.g., TC 1507, MON 810) and Rootworm (e.g., 

 DAS-59122-7) IRM Requirements for Stacked Bt Corn PIPs (e.g., Herculex® Xtra) 

Requirements (Separate 

Lepidopteran Refuge)

 (Separate Rootworm 

Refuge)

 (Combined Refuge) 

Refuge Size  20%  20%  20% 

Refuge 

Placement

 1⁄2 mile Adjacent or within field Adjacent or within field 

Refuge 

Configuration

Block, in-field strips (

4 rows), or edges 

Block or strips ( 4 rows) Block or strips ( 4 rows) 

Refuge 

Management

Any corn rotation 

meeting placement and 

configuration 

requirements 

Insecticides can be used 

in refuge to control 

ECB/SWCB when 

above economic 

thresholds. 

Microbial Bt insecticides 

are not allowed. 

Same corn rotation as the 

rootworm-protected Bt

fields (e.g., first year corn 

or corn followed by corn) 

Conventional insecticides 

or seed treatments can be 

used in refuge to control 

CRW larvae and other soil 

pests. If the refuge is 

treated with a foliar 

insecticide labeled for 

CRW control when CRW 

adults are present, then the 

Bt fields also must be 

treated. 

(Not applicable) 

Same corn rotation as the 

Bt fields (e.g., first year 

corn or corn followed by 

corn) 

Conventional insecticides 

or seed treatments can be 

used in refuge to control 

CRW larvae and other soil 

pests. If the refuge is 

treated with a foliar 

insecticide labeled for 

CRW control when CRW 

adults are present, then the 

Bt fields also must be 

treated. 

Microbial Bt insecticides 

are not allowed. 

Refuge Corn 

Types

Conventional (Non-Bt) Conventional (Non-Bt) 

Corn borer-protected Bt

corn (a corn borer refuge 

planted 1⁄2 mile also will 

be required) 

Herbicide-tolerant corn 

(Non-Bt) 

Conventional (Non-Bt) 

Corn borer-protected Bt

corn (an additional refuge 

for corn borer will be 

required) 

Herbicide-tolerant corn 

(Non-Bt) 
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5. IRM Terms and Conditions of Registration (2005) 

The following are the IRM terms and conditions of the 2005 Herculex® RW registrations. Dow and 

Pioneer’s responses to the conditionally required data (and timelines) are discussed in section II(D)(3) of 

this BRAD. 

The Insect Resistance Management Program has the following elements: 

a) Requirements relating to creation of a non-(corn rootworm-protected PIP) corn refuge in 

conjunction with the planting of any acreage of commercial Cry34/35Ab1 Bt corn; 

b) Requirements for the registrants to prepare and require Cry34/35Ab1 Bt corn users to sign 

“grower agreements,” which impose binding contractual obligations on the grower to comply with 

the refuge requirements; 

c) Requirements for the registrants to develop, implement, and report to EPA on programs to 

educate growers about IRM requirements; 

d) Requirements for the registrants to develop, implement, and report to EPA on programs to 

evaluate and promote growers’ compliance with IRM requirements (the Cry34/35Ab1 Compliance 

Assurance Program (CAP) must integrate with the Cry1 Compliance Assurance Programs); 

e) Requirements for the registrants to develop, implement, and report to EPA on monitoring 

programs to evaluate whether there are statistically significant and biologically relevant changes in 

target insect susceptibility to Cry34/35Ab1 proteins in the target insects; 

f) Requirements for the registrants to develop, and if triggered, to implement a “remedial action 

plan,” which would contain measures the registrants would take in the event that any insect 

resistance was detected, as well as to report on activity under the plan to EPA; 

g) Submit annual reports on units sold by state (units sold by county level will be made available 

to the Agency upon request), IRM grower agreements results, compliance assurance program, 

including the education program, and resistance monitoring on or before January 31st each year 

beginning in 2007. 

 

Refuge Requirements 

Grower agreements (also known as stewardship agreements) will specify that growers must adhere to 

the refuge requirements as described in the grower guide/product use guide and/or in supplements to the 

grower guide/product use guide. 

1. Refuge size. The use of Cry34/35 corn from Event DAS-59122-7 requires an accompanying 20% 

refuge. 
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2. Refuge location. The rootworm refuge is required to be planted within or adjacent (e.g., across the 

road) to the Cry34/35 corn field. 

3. Refuge management options. The rootworm refuge may be managed in such a way that there is little 

or no yield loss to rootworms but must be managed in a way that it is sufficiently productive of 

susceptible rootworm adults. The in-field refuge options may be planted as a single block or as a series 

of strips measuring at least four (4) crop rows wide. 

 Seed mixtures of Cry34/35 and refuge corn are not permitted. 

 If the refuge is planted on rotated ground, then Cry34/35 corn must also be planted on rotated 

ground. 

 If the refuge is planted in continuous corn, the Cry34/35 field may be planted on either 

continuous or rotated land (option encouraged where WCRW rotation-resistant biotype may be 

present). 

 Application of soil insecticide is permitted in the refuge. 

 Seed treatment is permitted in the refuge, either for rootworm protection or for controlling 

secondary soil pests. 

 If aerial insecticides are applied to the refuge for control of CRW adults, the same treatment 

must also be applied in the same timeframe to Cry34/35 corn. 

Pests other than adult corn rootworms can only be treated with CRW-labeled insecticide on the 

refuge acres without treating the Cry34/35 acres if treatment occurs when adult corn rootworms 

are not present. Pests on the Cry34/35 acres can be treated as needed without having to treat the 

refuge. 

 The rootworm refuge can be planted to any corn hybrid that does not express PIPs for rootworm 

control (e.g., lepidopteran-protected Bt corn, herbicide-tolerant corn, or conventional corn). 

 The refuge and Cry34/35 corn should be sown on the same date, or with the shortest window 

possible between planting dates, to ensure that corn root development is similar among varieties. 

 Growers are encouraged to plant the rootworm refuge in the same location each year, as it allows 

the rootworm population to remain high and the durability of the trait is extended. This option 

may be preferable to growers who wish to only think of their refuge design once and for growers 

who grow continuous corn. However, for those growers who need to employ crop rotation, a 

fixed refuge would be impractical. 
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Grower Agreements

1. Persons purchasing the Bt corn product must sign a grower agreement. The term “grower agreement” 

refers to any grower purchase contract, license agreement, or similar legal document. 

2. The grower agreement and/or specific stewardship documents referenced in the grower agreement 

must clearly set forth the terms of the current IRM program. By signing the grower agreement, a grower 

must be contractually bound to comply with the requirements of the IRM program. 

3. The registrant must develop a system (equivalent to what is already approved for Cry1F Bt corn), 

which is reasonably likely to assure that persons purchasing the Bt corn product will affirm annually that 

they are contractually bound to comply with the requirements of the IRM program. The proposed system 

will be submitted to EPA by January 31, 2006. 

 

4. The registrant must use grower agreements and submit to EPA by January 31, 2006 a copy of that 

agreement and any specific stewardship documents referenced in the grower agreement. If either 

registrant wishes to change any part of the grower agreement or any specific stewardship documents 

referenced in the grower agreement that would affect either the content of the IRM program or the legal 

enforceability of the provisions of the agreement relating to the IRM program, thirty days prior to 

implementing a proposed change, the registrant must submit to EPA the text of such changes to ensure 

that it is consistent with the terms and conditions of the registration 

 

5. The registrant must establish a system (equivalent to what is already approved for Cry1F Bt Corn), 

which is reasonably likely to assure that persons purchasing the Bt corn product sign grower 

agreement(s), and must provide by January 31, 2006 a written description of that system. 

6. The registrant shall maintain records of all Bt corn grower agreements for a period of three years from 

December 31st of the year in which the agreement was signed. 

7. Beginning on January 31, 2007 and annually thereafter, the registrant shall provide EPA with a report 

showing the number of units of its Cry34/35Ab1 corn seeds sold or shipped and not returned, and the 

number of such units that were sold to persons who have signed grower agreements. The report shall 

cover the timeframe of the twelve-month period covering the prior August through July. 

8. The registrant must allow a review of the grower agreements and grower agreement records by EPA 

or by a State pesticide regulatory agency if the State agency can demonstrate that confidential business 

information, including names, personal information, and grower license number, will be protected. 

IRM Education and IRM Compliance Monitoring Programs

1. The registrants must implement a comprehensive, ongoing IRM education program designed to 

convey to Bt Cry34/35Ab1 corn users the importance of complying with the IRM program. The program 
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shall include information encouraging Bt Cry34/35Ab1 corn users to pursue optional elements of the 

IRM program relating to refuge configuration and proximity to Bt Cry34/35Ab1 corn fields. The 

education program shall involve the use of multiple media, e.g., face-to-face meetings, mailing written 

materials, EPA reviewed language on IRM requirements on the bag or bag tag, and electronic 

communications such as by Internet, radio, or television commercials. Copies of the materials will be 

provided to EPA for its records for the first year of commercialization (2006 growing season) by 

January 31, 2007. The program shall involve at least one written communication annually to each Bt

Cry34/35Ab1 corn user separate from the grower technical guide. The communication shall inform the 

user of the current IRM requirements. The registrants shall coordinate their education programs with 

educational efforts of other registrants and other organizations, such as the National Corn Grower 

Association and state extension programs. 

2. Annually, the registrant shall revise, and expand as necessary, its education program to take into 

account the information collected through the compliance survey required under paragraph 6 and from 

other sources. The changes shall address aspects of grower compliance that are not sufficiently high. 

3. Beginning January 31, 2008 and annually thereafter, the registrant must provide EPA any substantive 

changes to its grower education activities as part of the overall IRM compliance assurance program 

report. The required features of the compliance assurance program are described in paragraphs 4–15 

below. 

4. The registrant must design and implement an ongoing IRM compliance assurance program designed 

to evaluate the extent to which growers purchasing its Cry34/35Ab1 Bt corn product are complying with 

the IRM program and that takes such actions as are reasonably needed to assure that growers who have 

not complied with the program either do so in the future or lose their access to the Cry34/35Ab1 Bt corn 

product. The registrant shall coordinate with other Bt corn registrants in designing and implementing its 

compliance assurance program and integrate the Cry34/35Ab1 CAP with the Cry1 Compliance 

Assurance Programs. The registrant must prepare and submit by January 31, 2006 a written description 

of their compliance assurance program including a summary of the program implemented in the 2006 

growing season. Other required features of the program are described in paragraphs 5–15 below. 

5. The registrant must establish and publicize a “phased compliance approach,” i.e., a guidance 

document that indicates how the registrant will address instances of non-compliance with the terms of 

the IRM program and general criteria for choosing among options for responding to any non-compliant 

growers. The options shall include withdrawal of the right to purchase Cry34/35Ab1 Bt corn for an 

individual grower or for all growers in a specific region. An individual grower found to be significantly 

out of compliance two years in a row would be denied sales of the product the next year. Similarly, seed 

dealers who are not fulfilling their obligations to inform/educate growers of their IRM obligations will 

lose their opportunity to sell Cry34/35Ab1 Bt corn. 

6. The IRM compliance assurance program shall include an annual survey conducted by an independent 

third party of a statistically representative sample of Cry34/35Ab1 Bt corn growers who plant the vast 

majority of all corn in the U.S. and in areas in which the selection intensity is greatest. The survey shall 
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consider only those growers who plant 200 or more acres of corn in the Corn Belt and who plant 100 or 

more acres of corn in corn-cotton areas. The survey shall measure the degree of compliance with the 

IRM program by growers in different regions of the country and consider the potential impact of nonresponse. The sample size and geographical resolution may be adjusted annually, based upon input from 

the independent marketing research firm and academic scientists, to allow analysis of compliance 

behavior within regions or between regions. The sample size must provide a reasonable sensitivity for 

comparing results across the U.S. 

7. The survey shall be designed to provide an understanding of any difficulties growers encounter in 

implementing IRM requirements. An analysis of the survey results must include the reasons, extent, and 

potential biological significance of any implementation deviations. 

8. The survey shall be designed to obtain grower feedback on the usefulness of specific educational tools 

and initiatives. 

9. The registrant shall provide a written summary of the results of the prior year’s survey (together with 

a description of the regions, the methodology used, and the supporting data) to EPA by January 31st of 

each year, beginning with 2007. The registrant shall confer with EPA on the design and content of the 

survey prior to its implementation. 

10. Annually, the registrant shall revise, and expand as necessary, its compliance assurance program to 

take into account the information collected through the compliance survey required under paragraphs 6 

through 8 and from other sources. The changes shall address aspects of grower compliance that are not 

sufficiently high. The registrant must confer with the Agency prior to adopting any significant changes. 

11. The registrant shall conduct an annual on-farm assessment program. The registrant shall train its 

representatives who make on-farm visits with Cry34/35Ab1 Bt corn growers to perform assessments of 

compliance with IRM requirements. There is no minimum corn acreage size for this program. Therefore, 

growers will be selected for this program from across all farm sizes. In the event that any of these visits 

result in the identification of a grower who is not in compliance with the IRM program, the registrant 

shall take appropriate action, consistent with the “phased compliance approach,” to promote compliance. 

12. The registrant shall carry out a program for investigating legitimate “tips and complaints” that its 

growers are not in compliance with the IRM program. Whenever an investigation results in the 

identification of a grower who is not in compliance with the IRM program, the registrant shall take 

appropriate action, consistent with the “phased compliance approach.” 

13. If a grower, who purchases Cry34/35Ab1 Bt corn for planting, was specifically identified as not 

being in compliance during the previous year, the registrant shall visit with the grower and evaluate 

whether that the grower is in compliance with the IRM program for the current year. 

14. Beginning January 31, 2007 and annually thereafter, the registrants shall provide a report to EPA 

summarizing the activities carried out under their compliance assurance program for the prior year, 
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including changes to the grower education program, and the plans for the compliance assurance program 

during the current year. The report will include information regarding grower interactions (including, 

but not limited to, third-party grower survey, on-farm visitation program, verified tips and complaints, 

education programs (e.g., grower meetings and letters), the extent of non-compliance, corrective 

measures to address the non-compliance (phased-compliance program), and any follow-up actions 

taken). 

15. The registrant and the seed corn dealers for the registrant must allow a review of the compliance 

records by EPA or by a State pesticide regulatory agency if the State agency can demonstrate that 

confidential business information, including the names, personal information, and grower license 

number of the growers, will be protected. 

Insect Resistance Monitoring 

The Agency is imposing the following conditions for this product: 

The registrants must monitor for Cry34Ab1/35Ab1 resistance and/or trends in increased tolerance for 

corn rootworm. Sampling should be focused in those areas in which there is the highest risk of resistance 

development. 

1. The registrants must provide EPA its resistance monitoring plan for approval. A preliminary plan 

must be submitted to the Agency by January 31, 2006, consisting of a description of the steps to be 

taken to establish corn rootworm baseline sensitivity and damage guidelines. A detailed resistance 

monitoring plan must be submitted to the Agency for review by January 31, 2008. This plan must 

include the following: baseline sensitivity data, sampling (number of locations, samples per locations), 

sampling methodology and life-stage sampled, bioassay methodology, standardization procedures 

(including quality assurance and quality control provisions), detection technique and sensitivity, the 

statistical analysis of the probability of detecting resistance, and an interim description of rootworm 

damage guidelines. 

2. The registrants must develop and validate an appropriate discriminating or diagnostic dose assay by 

January 31, 2010. Further, the registrants must provide BPPD with a detailed explanation and validation 

(steps for) of the “high-throughput diagnostic screen” if it is to be considered an acceptable diagnostic 

dose assay. 

3. The registrants must finalize rootworm damage guidelines and submit these to BPPD by January 31, 

2010. 

4. The registrants must follow-up on grower, extension specialist, or consultant reports of unexpected 

damage or control failures for corn rootworm. 

5. The registrants must provide EPA with an annual resistance monitoring report by January 31st of each 

year, beginning with 2008, reporting on populations collected the previous year. 
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Remedial Action Plans

The remedial action plan is designed as a tiered approach for mitigating WCRW, NCRW, and MCRW 

resistance development to the Cry34/35Ab1 protein. The following program summary describes, in 

order of events, the steps that must be taken to implement a remedial action plan if resistance to target 

pests is confirmed. However, the levels of “expected” damage cannot be identified until baseline 

sensitivity is determined. EPA requires that the registrants establish the baseline sensitivity by January 

31, 2008, so that expected levels of crop damage and target pest resistance can be established, and a 

remedial action plan initiated when needed. 

1. Definition of Suspected Resistance: Resistance will be suspected if investigations of unexpected 

damage reports show that: 

a. Implicated corn plant roots were expressing Cry34/35Ab1 proteins at the expected levels; 

b. The seed used was not mixed with non-Cry34/35Ab1 seed; 

c. Alternative causes of damage or lodging, such as non-target pest insect species, weather, 

physical damage, larval movement from alternate hosts, planting errors, and other reasonable 

causes for the observations, have been ruled out; 

d. The level of damage exceeds guidelines for expected damage. 

If resistance is “suspected,” the registrants will instruct affected growers to use alternate pest control 

measures, such as adulticide treatment, crop rotation the following year, or use of soil or seed 

insecticides the following year. These measures are intended to reduce the possibility of potentially 

resistant insects contributing to the following year’s pest population. 

2. Confirmation of Resistance: Resistance will be confirmed if all of the following criteria are met by 

progeny from the target pest species sampled from the area of “suspected resistance”: 

a. The proportion of larvae that can feed and survive on Cry34/35Ab1 roots from neonate to adult 

is significantly higher than the baseline proportion (currently being established); 

b. The LC50 of the test population exceeds the upper limit of the 95% confidence interval for the 

LC50 of a standard unselected population, and/or survival in the diagnostic assay is significantly 

greater than that of a standard unselected population, as established by the ongoing baseline 

monitoring program; 

c. The ability to survive is heritable; 

d. Cry34/35Ab1 plant assays determine that damage caused by surviving insects would exceed 

economic thresholds; 

e. If subsequent collections in the affected field area demonstrate similar bioassay results. 

3. Response to Confirmed Resistance: When resistance is “confirmed,” the following steps will be 

taken: 

a. EPA will receive notification within 30 days of confirming resistance; 

b. Affected customers and extension agents will be notified about confirmed resistance; 
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c. Affected customers and extension agents will be encouraged to employ alternative CRW control 

measures; 

d. Sale and distribution of Cry34/35Ab1 corn in the affected area will cease immediately; 

e. A long-term resistance management action plan will be devised according to the characteristics 

of the resistance event and local agronomic needs. 

Annual Reports

The registrants must provide annual reports to EPA on its Cry34/35Ab1 PIP expressed in corn based on 

the following table. 

 Report Description Due Date 

Annual Sales Units sold by state (county information is available 

upon request by the Agency) 

January 31st each year, 

beginning in 2007 

Grower Agreement Number of units of Bt corn seeds shipped or sold and 

not returned, and the number of such units that were 

sold to persons who have signed grower agreements 

January 31st each year, 

beginning in 2007 

Grower Education (Part of the 

Compliance Assurance 

Program Report, Except for 

the 2006 Growing Season) 

Education program for the 2006 growing season. 

Subsequent changes to the grower education 

program must be included in the annual compliance 

assurance program report. 

January 31, 2007. 

Annual changes: 

January 31st each year, 

beginning in 2008 as part of the 

Compliance Assurance Program 

Report 

Proposed Compliance Plan Written description of Compliance Assurance 

Program 

January 31, 2006 

Compliance Assurance 

Program 

Compliance Assurance Program Activities and 

Results: third-party grower survey, on-farm 

visitation program, phased-compliance report, tips 

and complaints, and grower education programs 

January 31st each year, starting 

in 2007 

Insect Resistance Monitoring 

Plan 

Description of the steps to be taken to establish corn 

rootworm baseline sensitivity and damage guidelines 

January 31, 2006 

Insect Resistance Monitoring 

Plan 

Submission of plan: Description of the program, 

including baseline sensitivity, sampling (number of 

locations and samples per locations), sampling 

methodology, bioassay methodology, 

standardization procedures, detection technique, 

sensitivity, and the statistical analysis of the 

probability of detecting resistance, and an interim 

description of rootworm damage guidelines 

January 31, 2008 
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 Report Description Due Date 

Insect Resistance Monitoring Submission of rootworm damage guidelines January 31, 2010 

Insect Resistance Monitoring Development of diagnostic dose assay/high 

throughput screen 

January 31, 2008 

Insect Resistance Monitoring Annual report of the insect resistance monitoring 

program. Results of monitoring and investigations of 

damage reports 

August 31st each year beginning 

in 2008 

Additional reports are due as described in the following table: 

Report Description Due Date

IRM Grower Agreements Proposed system to assure growers sign grower 

agreements 

January 31, 2006 

IRM Affirmation Plan System to assure annual affirmation by growers of 

their IRM obligations 

January 31, 2006 

Changes to Grower 

Agreement and/or IRM 

Documents 

Current grower agreement(s) and any specific 

stewardship documents 

At least 30 days before any 

changes related to IRM are 

expected to be imposed. 

Grower Agreement Submission of grower agreement and any specific 

stewardship documents referenced in the grower 

agreement 

January 31, 2006 

6. References 

Agricultural Biotechnology Stewardship Technical Committee (ABSTC). 2003. “Updated Monitoring 

 Plan for Bt Corn.” Unpublished report of the Agricultural Biotechnology Stewardship Technical 

 Committee to the U.S. Environmental Protection Agency, January 31, 2003. 

Baumann L, Broadwell AH, Baumann P. 1988. Sequence analysis of the mosquitocidal toxin genes 

 encoding 51.4- and 41.9-kilodalton proteins from Bacillus sphaericus 2362 and 2297. 

 J. Bacteriol. 170:2045–2050. 

Branson TF, Ortman EE. 1970. The host range of larvae of the western corn rootworm: Further studies. 

 J. Econ. Entomol. 63:800–803. 

Branson TF, Ortman EE. 1971. The host range of larvae of the northern corn rootworm: Further studies. 

 J. Kans. Entomol. Soc. 44:50–52. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

172

Carrière Y, Sisterson MS, Tabashnik BE. 2004. Resistance management for sustainable use of Bacillus 

 thuringiensis crops in integrated pest management. Pp. 65–95 in A.R. Horowitz and I. Ishaaya 

 (editors), Insect Pest Management. Springer-Verlag, Berlin Heidelberg. 

Clark TL, Hibbard BE. 2004. Comparison of non-maize hosts to support western corn rootworm 

 (Coleoptera: Chrysomelidae) larval biology. Environ. Entomol. 33:681–689. 

Clark TL, Meinke LJ, Foster JE. 2001. Molecular phylogeny of Diabrotica beetles (Coleoptera: 

 Chrysomelidae) inferred from analysis of combined mitochondrial and nuclear sequences. 

 Insect Molecular Biology 10:303–314. 

Coats SA, Tollefson JJ, Mutchmore JA. 1986. Study of migratory flight in the western corn rootworm. 

 Environ. Entomol. 15:1–6. 

Cormier D, Martel P. 1997. Effects of soil insecticide treatments on northern corn rootworm, Diabrotica 

 barberi (Coleoptera: Chrysomelidae), populations and on corn yield. Phytoprotection 78:67–73. 

Ellis RT, Stockhoff BA, Stamp L, Schepf HE, Schwab GE, Knuth M, Russell J, Cardineau GA, Narva 

 KE. 2002. Novel Bacillus thuringiensis binary insecticidal crystal proteins active on western 

 corn rootworm, Diabrotica virgifera virgifera LeConte. Appl. and Environ. Micro. 

 68:1137–1145. 

Ferré J, Van Rie J. 2002. Biochemistry and genetics of insect resistance to Bacillus thuringiensis. 

 Annu. Rev. Entomol. 47:501–533. 

Gray ME. 2001. Transgenic insecticidal cultivars for corn rootworms: Meeting the challenges of 

 resistance management. Pp. 36–41 in Proceedings of Illinois Crop Protection Technology 

 Conference, University of Illinois, Urbana-Champaign, Illinois. 

Herman RA, Scherer PN, Young DL, Mihaliak CA, Meade T, Woodsworth AW, Stockholl BA, Nara 

 KE. 2002. Binary insecticidal crystal protein from Bacillus thuringiensis strain PS149B1: Effects 

 of individual protein compounds and mixtures in laboratory bioassays. J. Econ. Entomol. 

 95:635–639. 

Hibbard BE, Durran PN, Ellersieck MR, Ellsbury MM. 2003. Post-establishment movement of western 

 corn rootworm larvae (Coleoptera: Chrysomelidae) in central Missouri corn. J. Econ. Entomol. 

 96(3):599–608. 

Hibbard BE, Higdon ML, Duran DP, Schweikert YM, Ellersieck MR. 2004. Role of egg density on 

 establishment and plant-to-plant movement by western corn rootworm larvae (Coleoptera: 

 Chrysomelidae). J. Econ. Entomol. 97(3):871–882. 

 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

173

Hill RE, Mayo ZB. 1980. Distribution and abundance of corn rootworm species as influenced by 

 topography and crop rotation in eastern Nebraska. Environ. Entomol. 9:122–127. 

Lance DR. 1988. Response of northern and western corn rootworms to semiochemical attractants in 

 corn fields. J. Chem. Ecol. 14:1177–1185. 

Naranjo SE. 1994. Flight orientation of Diabrotica virgifera virgifera and D. barberi (Coleoptera: 

 Chrysomelidae) at habitat interfaces. Ann. Entomol. Soc. Am. 87(3):383–394. 

Naranjo SE. 1990. Comparative flight behavior of Diabrotica virgifera virgifera and Diabrotica barberi 

 in the laboratory. Ent. Experimantalis et Aplicata 87:383–394. 

Nowatzki TM, Niimi B, Warren KJ, Putnam S, Meinke LJ, Gosselin DC, Harvey FE, Hunt TE, 

Siegfried BD. 2003. In-field labeling of western corn rootworm adults (Coleoptera: 

Chrysomelidae) with rubidium. J. Econ. Entomol. 96:1750–1759. 

Nowatzki T, Lefko SA, Binning RR, Thompson SD, Spencer TA, Siegfried BD. 2008. Validation of a 

 novel resistance monitoring technique for corn rootworm (Coleoptera: Chrysomelidae) and 

 Event DAS-59122-7 maize. J. Appl. Entomol. 132:177–188. 

Masson L, Schwab G, Mazza RB, Potvin L, Schwartz J. 2004. A novel Bacillus thuringiensis 

 (PS149B1) containing a Cry34Ab1/Cry35Ab1 binary toxin specific for the western corn 

 rootworm Diabrotica virgifera virgifera LeConte forms ion channels in lipid membranes. 

 Biochemistry 43:12349–12357. 

Meinke LJ, Siegfried BD, Wright RJ, Chandler LD. 1998. Adult susceptibility of western corn 

 rootworm (Coleoptera: Chrysomelidae) populations to selected insecticides. J. Econ. Entomol. 

 91:594–600. 

Moellenbeck DJ, Peters ML, Bing JW, Rouse JR, Higgins LS, Sims L, Nevshemal T, Marshall L, Ellis 

 RT, Bystrak PG, Lang BA, Stewart JL, Kouba K, Sondag V, Gustafson V, Nour K, Xu D, 

 Swenson J, Zheng J, Czapia T, Schwab G, Jayne S, Stockhoff BA, Narva K, Schepf EE, 

 Stelman SJ, Poutre C, Koziel M, Duck N. Insecticidal proteins from Bacillus thuringiensis 

 protect corn from corn rootworms. Nature Biotech. 19:668–672. 

Moeser J, Hibbard BE. 2005. Nouvelle cuisine for the invasive maize pest D. v. virgifera in Europe? 

 A synopsis on the nutritional ecology of larvae and adults in the New and Old World. In Ecology 

 and Management of Western Corn Rootworm (Diabrotica virgifera virgifera LeConte). S. Vidal, 

 U. Kuhlmann, and R. Edwards (eds.), CABI Publishers, Wallingford, United Kingdom (in press). 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

174

MRID No. 463438-04. Bing J, Babcock J. 2004. Comparison of Insect Efficacy and Expression in 

Cry34/35Ab1 Corn Events DAS-59122-7 and DAS-59132-8 Expressed as a Single Trait and a 

Stack with DAS-01507-1. Project Number: GH/C/5738. Unpublished study prepared by Dow 

AgroSciences LLC, 21 pages. 

MRID No. 463438-05. Higgins L. 2004. Field Efficacy of Herculex Xtra (DAS-01507-1 x 

DAS-59122-7) Insect Resistant Corn. Project Number: PHI/2004/065. Unpublished study 

prepared by Pioneer Hi-Bred Corn Company Production Department, 13 pages. 

MRID No. 470444-01. Reding H. 2007. 2006 Insect Resistance Management Compliance Assurance 

Program Report for Corn Borer-Protected BT Corn, Corn Rootworm-Protected BT Corn, and 

Corn Borer/Corn Rootworm-Protected Stacked BT Corn. Project Number: CAP/2006. 

Unpublished study prepared by Agricultural Biotechnology Stewardship Technical Committee, 

14 pages. 

MRID No. 473342-01. Storer N. 2008. Detailed Resistance Monitoring Plan for Cry34/35Ab1 Corn 

Event DAS-59122-7. Project Number: 081006. Unpublished study prepared by Dow 

AgroSciences LLC, 35 pages. 

MRID No. 473396-01. Bailey L. 2008. 2007 Insect Resistance Management Compliance Assurance 

 Program Report for Corn Borer-Protected Bt Corn, Corn Rootworm-Protected Bt Corn, and Corn 

Borer/Corn Rootworm-Protected Stacked Bt Corn. Project Number: CAP/2007. Unpublished 

study prepared by Agricultural Biotechnology Stewardship Technical Committee, 17 pages. 

MRID No. 475109-04. Werning M. 2008. Expressed Trait Protein Concentration of Maize Lines 

Containing Events DAS-01507-1, DAS -59122-7, MON-00810-6, and DAS-01507-1 x 

DAS-59122-7 x MON-00810-6. Project Number: PHI/2008/006, PHI/2008/006/012, 

PHI/2008/006/011. Unpublished study prepared by Pioneer Hi-Bred International, Incorporated, 

174 pages. 

MRID No. 476633-01. Bailey L. 2009. 2008 Insect Resistance Management Compliance Assurance 

Program Report for Corn-Borer Protected Bt Corn, Corn Rootworm-Protected Bt Corn, and Corn 

Borer/Corn Rootworm-Protected Stacked Bt Corn. Project Number: CAP/2008. Unpublished 

study prepared by Agricultural Biotechnology Stewardship Technical Committee, 15 pages. 

MRID No. 476778-03. Alves A, Bailey L, Cressman R. 2009. Field Efficacy, Allergen/Toxin Homology 

and Trait Durability Supplemental Information for 1507 x 59122 x MON810, 1507 x MON810 

and 59122 x MON810. Project Number: PHI/2009/025. Unpublished study prepared by Pioneer 

Hi-Bred International, Incorporated, 40 pages. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

175

MRID No. 479008-01. Storer N, Owens E. 2009. Monitoring Corn Rootworm Susceptibility to 

Cry34/35Ab1 Event DAS-59122-7: 2008 Insect Collections. Project Number: 091147. 

Unpublished study prepared by Dow AgroSciences, LLC and Pioneer Hi-Bred International, 

Incorporated, 29 pages. 

MRID No. 480455-01. Storer N, Owens E. 2010. Investigating Performance of Herculex RW and 

Herculex XTRA under Commercial Use. Project Number: 101564. Unpublished study prepared 

by Dow AgroSciences LLC and Pioneer Hi-Bred International, Incorporated, 14 pages. 

Onstad DW, Guse CA, Spencer JL, Levine E, Gray ME. 2001. Modeling the dynamics of adaptation to 

 transgenic corn by western corn rootworm (Coleoptera: Chrysomelidae). J. Econ. Entomol. 

 94: 529–540. 

Ostlie K. 2001. Crafting crop resistance to corn rootworms. Nature Biotech. 19:624–625. 

Oyediran IO, Hibbard BE, Clark TL. 2004. Prairie grasses as hosts of the western corn rootworm 

 (Coleoptera: Chrysomelidae). Environ. Entomol. 33:740–747. 

Siegfried BD, Mullin CA.1990. Effects of alternative host plants on longevity, oviposition and 

 emergence of western and northern corn rootworm (Coleoptera: Chrysomelidae). Environ. 

 Entomol. 19(3):474–480. 

Storer NP. 2003a. A spatially explicit model simulating western corn rootworm (Coleoptera: 

 Chrysomelidae) adaptation to insect-resistant maize. J. Econ. Entomol. 96:1530–1547. 

Storer NP. 2003b. Simulations of Corn Rootworm Adaptation to Cry34/35-Corn Rootworm Protected 

 Corn in Support of Trait Durability Plans for Event DAS-59122-7. MRID No. 461239-19, 

 Internal Report GH-C 5688, DAS. 

Storer NP, Lang BA. 2003. Effect on Western Corn Rootworm Adults of Feeding on Cry34/35 Maize 

 Tissues and Implications for Product Durability for Event DAS-59122-7. MRID No. 461239-16, 

 Internal Report GH-C 5686, DAS. 

Storer NP, Lefko SA. 2003. Trait Durability Plan for Cry34/35-Corn Rootworm Protected Corn Event 

 DAS-59122-7 Following Commercialization. MRID No. 461239-18, Internal Report GH-C 

 5689, DAS. 

Storer NP, Lefko SA, Babcock JM, Edwards JM, Binning RR. 2003. Investigations into Dose of 

 Cry34Ab1/Cry35Ab1 Rootworm-Resistant Maize Event DAS-59122-7 Against Western and 

 Northern Corn Rootworms in Support of Trait Durability Plan. MRID No. 461239-15, Internal 

 Report GH-C 5687, DAS. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

176

Sutter GR, Branson TF, Fisher JR, Elliot NC. 1991. Effect of insecticides on survival, development, 

 fecundity, and sex ratio in controlled infestations of western corn rootworm (Coleoptera: 

 Chrysomelidae). J. Econ. Entomol. 84:1905–1912. 

Tabashnik BE, Carrière Y, Dennehy TJ, Morin S, Sisterson MS, Roush RT, Shelton AM, Zhao JZ. 

 2003. Insect resistance to transgenic Bt crops: Lessons from the laboratory and field. J. Econ. 

 Entomol. 96:1031–1038. 

U.S. EPA. 1998. SAP Report. Bacillus thuringiensis (Bt) Plant-Pesticides and Resistance 

Management. Dated April 28, 1998. Available from: 

http://www.epa.gov/scipoly/sap/meetings/1998/february/finalfeb.pdf. 

U.S. EPA. 2001a. SAP Report No. 2000-07. Sets of Scientific Issues Being Considered by the 

Environmental Protection Agency Regarding: Bt Plant-Pesticides Risk and Benefit Assessments. 

Dated March 12, 2001. Available from: 

http://www.epa.gov/scipoly/sap/meetings/2000/october/octoberfinal.pdf. 

U.S. EPA. 2001b. Biopesticides Registration Action Document – Bacillus thuringiensis Plant- 

 Incorporated Protectants. Available from: 

 http://www.epa.gov/oppbppd1/biopesticides/pips/bt_brad.htm. 

U.S. EPA. 2002. SAP Meeting Minutes No. 2002-05. A Set of Scientific Issues Being Considered by the 

Environmental Protection Agency Regarding: Corn Rootworm Plant-Incorporated Protectant 

Non-Target Insect and Insect Resistance Management Issues. Dated November 6, 2002. 

Available from: http://www.epa.gov/scipoly/sap/meetings/2002/august/august2002final.pdf. 

U.S. EPA. 2004. Technical Review of Monsanto Co.’s 2003 Grower Education Program, Including 

Proposed Changes for 2004, and IRM CAP for MON 863 Bt Corn (EPA Reg. No. 524-528). 

Memorandum from T. Milofsky to M. Mendelsohn dated June 23, 2004. 

U.S. EPA. 2005a. EPA Review of Dose, Adult Feeding Effects, and Insect Resistance Management 

(Trait Durability) Simulations and Plans for Bt Cry34/35Ab1 Construct PHP17662 (Event DAS59122-7) Corn. Memorandum from S. Matten, Ph.D. to M. Mendelsohn dated July 13, 2005. 

U.S. EPA. 2005b. Biopesticides Registration Action Document – Bacillus thuringiensis 

Cry1F Corn. Available from: 

http://www.epa.gov/oppbppd1/biopesticides/ingredients/tech_docs/brad_006481.pdf. 

U.S. EPA. 2005c. Review of Efficacy Data and Insect Resistance Management (IRM) Plan Submitted 

for Herculex Xtra Corn. Memorandum from A. Reynolds to M. Mendelsohn dated September 

20, 2005. 
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U.S. EPA. 2006a. Review of the Preliminary Resistance Monitoring Plan for Herculex Rootworm Corn 

Submitted by Dow AgroSciences LLC. Memorandum from A. Reynolds to M. Mendelsohn 

dated July 24, 2006. 

U.S. EPA. 2006b. Technical Review of Dow AgroSciences’ Grower Agreements, Grower Affirmation 

Procedures, and Compliance Assurance Program (CAP) as Required as Part of the Terms and 

Conditions of the Herculex Rootworm (EPA Reg. No. 68467-5) and Herculex Xtra (EPA Reg. 

No. 68467-6) Registrations. Memorandum from S. Matten, Ph.D. to M. Mendelsohn dated 

November 27, 2006. 

U.S. EPA. 2007a. Biopesticides Registration Action Document – Bacillus thuringiensis Cry3Bb1 Corn. 

 Available from: 

 http://www.epa.gov/oppbppd1/biopesticides/ingredients/tech_docs/brad_006484.htm. 

U.S. EPA. 2007b. Review of IRM Compliance Assurance Program (CAP) Components Covered in 

ABSTC’s Submission on Behalf of Corn Borer-Protected (EPA Reg. Nos. 524-489, 68467-2, 

67979-1, and 29964-3), Corn Rootworm-Protected (EPA Reg. Nos. 524-528, 68467-5, and 

29964-4), and Stacked (Corn-Borer/Corn Rootworm-Protected) (EPA Reg. Nos. 524-545, 

68467-6, and 29964-5) Bt Corn Registrations. Memorandum from T. Milofsky and 

S. Matten, Ph.D. to M. Mendelsohn dated August 30, 2007. 

U.S. EPA. 2009a. EPA Review of ABSTC’s 2007 and 2008 Corn Insect Resistance Management 

Compliance Assurance Program (EPA Registration Nos. 524-489, 68467-2, 67979-1, 29964-3, 

524-528, 524-551, 68467-5, 67979-5, 29964-4, 524-545, 524-552, 68467-6, 67979-8, and 

29964-5; MRIDs 473396-01 and 476633-01). Memorandum from J. Martinez to M. 

Mendelsohn dated April 15, 2009. 

U.S. EPA. 2009b. Fact Sheet – SmartStaxTM (MON 89034 x TC1507 x MON 88017 x DAS-59122-7). 

 Available from: http://www.epa.gov/oppbppd1/biopesticides/pips/smartstax-factsheet.pdf. 

U.S. EPA. 2009c. Review of Dow’s 2007 Corn Rootworm Monitoring Report and Revised Resistance 

Monitoring Plan for DAS-59122-7. Memorandum from J. Martinez to M. Mendelsohn dated 

October 14, 2009. 

U.S. EPA. 2010a. Review of Insect Resistance Management (IRM) Considerations for Bt Corn Events 

1507 x MON 810, 59122 x MON 810, 1507 x 59122 x MON 810. Memorandum from 

A. Reynolds to A. Sibold dated January 7, 2010. 

U.S. EPA. 2010b. Biopesticides Registration Action Document – Optimum® AcreMaxTM B.t. Corn 

 Seed Blends. Available from: 

 http://www.epa.gov/pesticides/biopesticides/ingredients/tech_docs/brad_006490_oam.pdf. 
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U.S. EPA. 2010c. Review of Dow’s 2008 Corn Rootworm Monitoring Report and Revised Resistance 

Monitoring Plan for DAS-59122-7. Memorandum from J. Martinez to M. Mendelsohn dated 

June 30, 2010. 

U.S. EPA. 2010d. Biopesticides Registration Action Document – Bacillus thuringiensis 

Cry3Bb1 Corn. Available from: http://www.regulations.gov (see “Supporting & 

Related Materials” within Docket Number EPA-HQ-OPP-2010-0607). 

U.S. EPA. 2010e. Biopesticides Registration Action Document – Bacillus thuringiensis 

Cry1Ab and Cry1F Corn. Available from: http://www.regulations.gov (see “Supporting & 

Related Materials” within Docket Number EPA-HQ-OPP-2010-0607). 

U.S. EPA. 2010f. Biopesticides Registration Action Document – Optimum® AcreMaxTM B.t. Corn 

 Seed Blends. Available from: http://www.regulations.gov (see “Supporting & Related Materials” 

 within Docket Number EPA-HQ-OPP-2010-0607). 
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E. Benefits and Public Interest Finding for Initial Registrations of Event DAS-59122-7 Corn 

1. Overview 

The Environmental Protection Agency (EPA) has reviewed the public interest document for Event DAS59122-7 corn (Master Record Identification Numbers (MRID Nos.) 461227-01 and 461239-21; 

reviewed in U.S. EPA (2005)) and concludes that, under section 3(c)(7)(C) of the Federal Insecticide, 

Fungicide, and Rodenticide Act (FIFRA), conditional registration of Event DAS-59122-7 corn is in the 

public interest. Cry34/35Ab1 corn rootworm (CRW)-protected corn hybrids (Event DAS-59122-7 corn) 

will extend the benefits of insecticide use reduction that have been established for the Cry3Bb1 (Event 

MON 863) CRW-protected corn products. Cry34/35Ab1 CRW-protected corn is comparatively less 

risky to human health and the environment than currently registered chemical pesticides. It also provides 

a different mode of action for CRW control, comparable or better efficacy and yield compared to other 

CRW-control products, expanded product choices for growers, and indirect benefits (e.g., energy 

savings resulting from reduced chemical insecticide use). 

2. Public Interest Finding 

The criteria for determining whether registration of a pesticide chemical is in the public interest are set 

forth in a Federal Register Notice dated March 5, 1986 (51 Federal Register (FR) 7628). There is a 

presumption that registration of a pesticide chemical is in the public interest if one of the following 

criteria is met: (1) the use is for a minor crop; (2) the use is a replacement for another pesticide that is of 

continuing concern to the Agency; (3) the use is one for which an emergency exemption under FIFRA 

section 18 has been granted (i.e., the basis for the exemption was lack of a registered alternative 

product); or (4) the use is against a pest of public health significance. Further, EPA may determine that 

such a registration is in the public interest on the basis of the following criteria: (1) there is a need for 

the new chemical that is not being met by currently registered pesticides; (2) the new pesticide is 

comparatively less risky to health or the environment than currently registered pesticides; or (3) the 

benefits (including economic benefits) from the use of the new active ingredient exceed those of 

alternative registered pesticides and other available non-chemical techniques. 

Mycogen Seeds c/o Dow AgroSciences LLC and Pioneer Hi-Bred International, Incorporated (hereafter 

referred to as Dow and Pioneer, respectively) have provided data to support their claim that 

Cry34/35Ab1 CRW-protected corn is in the public interest. EPA’s analysis supports the following 

conclusions: 

1. Cry34/35Ab1-protected corn provides effective control of key rootworm pests of field corn and 

may prove more efficacious than chemical insecticides presently registered for this purpose. 
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2. Economic models suggest that, under conditions of high rootworm pressure, use of 

Cry34/35Ab1-protected corn will provide greater net returns to farmers. Cost benefits include 

reduced expenditures on insecticides, application equipment, and personnel, complemented by 

greater potential corn yields. Under high rootworm pressure, these benefits are expected to 

outweigh the higher cost of seed. 

3. Registration of Cry34/35Ab1-protected corn is expected to result in further reduction of chemical 

insecticide use by growers. This is of special importance since many pesticides registered for 

CRW-control are highly toxic to humans and the environment, while Cry34/35Ab1-expressing 

corn poses no foreseeable human health or environmental risks. 

4. If Cry34/35Ab1 corn is registered, it will be the second CRW-protected Bacillus thuringiensis

(Bt) corn product on the market (the first was Cry3Bb1). The availability of multiple CRWprotected corn products will increase grower choice and price competition, likely resulting in 

lower seed prices for consumers and higher adoption rates. 

5. The Cry34/35Ab1 CRW-protected corn will provide a different mode of action and extend the 

durability of other CRW control measures, including other Bt CRW-protected corn hybrids. 

a. Background

Corn is the most widely cultivated U.S. crop, in terms of acreage planted and net value. In 2004, U.S. 

corn acreage totaled 80.9 million, yielding 11.8 billion bushels. Corn rootworm (CRW, Diabrotica spp.), 

one of the most damaging pests of field corn, can cause yield losses in the range of 8 to 16 percent if left 

uncontrolled. 

Prior to the advent of insect-protected field corn, CRW was controlled through the use of crop rotation 

and insecticides. Although crop rotation is regarded as an effective CRW-control tool (Levine and 

Oloumi-Sadeghi 1991), behavior changes in northern corn rootworm (extended diapause) and western 

corn rootworm (soybean rotation) have reduced the effectiveness of this management option in some 

corn-growing regions. Insecticidal control, a pest management alternative to crop rotation, employs 

chemicals that are highly toxic to fish, birds, and other wildlife species. In addition, resistance to some 

CRW insecticides, such as methyl parathion and carbaryl (Meinke et al. 1998; Scharf et al. 1999; Zhu et 

al. 2001), may result in increased chemical use. 

Since 2003, transgenic CRW-protected Bt corn, a third method of CRW control, has been available to 

farmers. The first Bt field corn product registered for CRW control was Monsanto’s Event MON 863 

(expresses the Cry3Bb1 protein). This review concerns the second CRW-protected Bt corn product 

submitted for registration, Dow’s and Pioneer’s DAS-59122-7, which produces the Cry34Ab1 and 

Cry35Ab1 insecticidal proteins (originally isolated from Bt strain PS149B1). Similar to Event MON 863 

corn hybrids, Event DAS-59122-7 Bt corn is targeted against the western corn rootworm (WCRW,

Diabrotica virgifera virgifera LeConte), northern corn rootworm (NCRW, Diabrotica barberi Smith 

and Lawrence), and Mexican corn rootworm (MCRW, Diabrotica virgifera zeae Krysan and Smith).
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 b. Efficacy

 i. Summary of Submitted Information

In 2003, Dow and Pioneer conducted field trials at multiple locations to evaluate the performance of 

Cry34/35Ab1 CRW-protected corn against coleopteran insect pests. Several efficacy trials were 

designed to compare Cry34/35Ab1 hybrids to their non-Bt isolines across multiple genetic backgrounds 

following exposure to natural and/or artificial CRW infestations. Results suggest that DAS-59122-7 

offers excellent control of WCRW, NCRW, and MCRW. Further details on studies of individual pest 

species are provided below. 

WCRW: Field trials were conducted to evaluate the efficacy of WCRW control by Cry34/35Ab1 

rootworm-protected corn, compared to non-Bt isolines and chemical control measures. Each applicant 

conducted separate efficacy trials, and Pioneer completed two independent evaluations (Dow completed 

one evaluation). All trials were replicated in four locations, using a randomized complete block design 

with three blocks per location. Fields used in these trials had been planted to corn in previous years and 

contained natural infestations of western and northern corn rootworm. In addition, corn plants were 

artificially infested with WCRW eggs (1,000 eggs per plant) at plant growth stage V3. Roots were 

harvested and scored when larvae reached pupation, which was at approximately plant growth stage R1. 

Event DAS-59122-7 corn roots consistently showed less WCRW damage compared to non-Bt isolines 

with no chemical control (Tables 1, 2, and 3). However, results suggest that efficacy of Cry34/35Ab1 

corn is similar, or slightly better, than that of non-Bt isolines treated with chemical insecticides. 

Table 1. Efficacy of Cry34/35Ab1 Rootworm-Protected Corn for Control of WCRW in 2003 

 (1st Pioneer Study). 

Pioneer Experiment #1 

Corn Line York, NE Johnston, IA Janesville, WI Windfall, IN Average

Non-Bt Hybrid 2.461 a

2

 1.06 a 0.59 a 0.12 a 1.22 a 

Force 3G 0.57 b 0.11 b 0.16 b 0.05 a 0.31 b 

DAS-59122-7 0.06 b 0.10 b 0.06 b 0.03 a 0.12 c 1 Iowa State University Node Injury Root Rating Scale (Oleson 1998): 0.00 = no feeding damage, 1.00 = one node eaten 

back to within two inches of stalk, 2.00 = two nodes eaten, and 3 = three or more nodes eaten. 2 Within each column, means that are followed by the same letter are not significantly different. 
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Table 2. Efficacy of Cry34/35Ab1 Rootworm-Protected Corn for Control of WCRW in 2003 

 (2nd Pioneer Study). 

Pioneer Experiment #2 

Corn Line York, NE Johnston, IA Janesville, WI Rochelle, IL Average

Non-Bt Hybrid 0.991 a

2

 0.79 ab 1.96 a 0.78 a 1.03 a 

Force 3G 0.32 bc 0.45 bc 1.20 b 0.11 b 0.44 b 

Counter 15G 0.25 bc 0.04 c 0.52 c 0.13 b 0.19 c 

DAS-59122-7 

(hybrid 1) 0.02 c 0.04 c 0.44 c 0.03 b 0.11 c 

DAS-59122-7 

(hybrid 2) 0.07 c 0.04 c 0.06 c 0.02 b 0.04 c 

DAS-59122-7 

(hybrid 3) 0.02 c 0.17 c 0.30 c 0.04 b 0.11 c 

DAS-59122-7 

(hybrid 4) 0.01 c 0.05 c 0.24 c 0.02 b 0.07 c 

1 Iowa State University Node Injury Root Rating Scale (Oleson 1998): 0.00 = no feeding damage, 1.00 = one node eaten 

 back to within two inches of stalk, 2.00 = two nodes eaten, and 3 = three or more nodes eaten. 2 Within each column, means that are followed by the same letter are not significantly different. 

Table 3. Efficacy of Cry34/35Ab1 Rootworm-Protected Corn for Control of WCRW in 2003 

 (Dow Study).

Dow Experiment #1 

Corn Line Huxley, IA York, NE Arlington, WI Fowler, IN Average

Non-Bt Hybrid 1.94 a2 0.93 a 1.03 a 2.43 a 1.58 a 

Force 3G 0.15 d 0.11 b 0.19 c 0.57 b 0.25 b 

Counter 15G 0.02 d 0.10 b 0.09 c 0.27 b 0.12 b 

DAS-59122-7 0.03 d 0.04 b 0.05 c 0.09 b 0.05 b 1 Iowa State University Node Injury Root Rating Scale (Oleson 1998): 0.00 = no feeding damage, 1.00 = one node eaten 

back to within two inches of stalk, 2.00 = two nodes eaten, and 3 = three or more nodes eaten. 2 Within each column, means that are followed by the same letter are not significantly different. 

NCRW: In 2003, each applicant completed a NCRW trial that compared the efficacy of Cry34/35Ab1 

rootworm-protected corn to a non-Bt isoline. Each trial was conducted in a single location, using a 

randomized complete block design with three replicates. 

Pioneer’s evaluation of NCRW (natural infestations) was conducted in conjunction with their WCRW 

study (artificial infestations) at Janesville, WI. Beetle emergence traps showed that the ratio of naturally 

emerging NCRW and WCRW was 1:1, but quantification of natural population pressure was difficult 

due to the artificial infestation of WCRW (1,000 WCRW/plant). Root ratings (Tables 1 and 2) show that 
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Event DAS-59122-7 is more efficacious against CRW than non-Bt hybrids with no insecticide treatment 

and comparable to non-Bt hybrids treated with conventional insecticides. 

Dow’s NCRW efficacy trial, conducted at Lamberton, MN, utilized a randomized complete block design 

with three replicates. Fields used in this trial had been planted to corn in previous years and contained 

natural infestations of WCRW and NCRW; however, the ratio of WCRW and NCRW was not 

determined. Thus, results indicate product efficacy against an undetermined combination of NCRW and 

WCRW. Roots were harvested and scored when larvae reached pupation, at approximately growth stage 

R1. Results suggest that Event DAS-59122-7 corn had less CRW damage compared to the non-Bt 

hybrids (Table 4). 

Table 4. Efficacy of Cry34/35Ab1 Rootworm-Protected Corn for Control of NCRW and WCRW 

 at Lamberton, MN in 2003 (Dow Study).

Corn Line Average Root Rating (1–6 scale)1

Non-Bt Hybrid 4.38 a2

DAS-59122-7 2.54 b 1 Modified root rating scale: 1 = no visible damage, 2 = slight feeding damage on one or more roots, 3 = 1–5 roots pruned to 

within 1.5 inches of stalk, 4 = one whorl of roots pruned, 5 = two whorls of roots pruned, and 6 = three whorls of roots 

pruned. 2 Means that are followed by the same letter are not significantly different. 

MCRW: Pioneer conducted a field trial to evaluate the efficacy of MCRW control by Event DAS59122-7 corn, compared to a non-Bt isoline and a non-Bt isoline treated with a chemical control. The 

trial was conducted in Sugarek, TX using a randomized complete block design with four replicates. 

Fields used in this trial had been planted to corn in previous years and contained natural infestations of 

MCRW. Results show that Event DAS-59122-7 corn had less MCRW damage compared to non-Bt corn 

with and without chemical treatment (Table 5). 

Table 5. Efficacy of Cry34/35Ab1 Rootworm-Protected Corn for Control of Mexican Corn 

 Rootworm at Sugarek, TX in 2003 (Pioneer Study).

Corn Line Average Root Rating

Non-Bt Hybrid 0.801 a2

Non-Bt Hybrid + Aztec 0.21 a 

DAS-59122-7 0.05 b 1 Iowa State University Node Injury Root Rating Scale (Oleson 1998). 2 Within each column, means that are followed by the same letter are not significantly different. 
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 ii. Biopesticides and Pollution Prevention Division (BPPD) Review

Results indicated that Event DAS-59122-7 corn had less CRW damage when compared to non-Bt corn 

and comparable efficacy to non-Bt corn treated with conventional insecticides. Field plots used for 

WCRW and NCRW efficacy studies contained natural infestations of both pest species and 

discrimination between the species was not determined at all sites. Despite the presence of WCRW and 

NCRW species, efficacy against WCRW is likely to have been adequately measured because WCRW 

densities were boosted through artificial infestations (1,000 eggs per plant). However, efficacy results 

for NCRW evaluations could not be clearly determined. At the Janesville, WI location, NCRW 

populations were dwarfed by artificial WCRW infestations and, at the Lamberton, MN location, the 

ratio of NCRW to WCRW was not determined. Consequently, one may conclude that low root ratings 

associated with CRW-protected corn suggests that NCRW was controlled at some undetermined level. 

Mexican corn rootworm efficacy was measured at one location, Sugarek, TX, under natural infestation 

pressure. Results indicate that Event DAS-59122-7 corn was more efficacious against MCRW than nonBt hybrids with and without chemical insecticide treatment. Additional efficacy data, collected from 

multiple locations and years, would be necessary to determine whether lower root ratings were due to 

high product efficacy, low initial pest populations, or a combination of both.

 c. Yield and Agronomic Performance

 i. Summary of Submitted Information

Several yield and agronomic performance studies were completed by the applicants. Each evaluation is 

described below. 

In 2003, Pioneer conducted a yield trial (in conjunction with the first WCRW efficacy trial described 

above) to evaluate the benefit of Event DAS-59122-7 hybrids in terms of yield performance, when 

compared to a non-Bt isoline hybrid treated with and without a chemical insecticide (Force 3G, applied 

at 5 ounces/1000 row feet). The following agronomic traits were evaluated: yield, grain density, percent 

moisture at harvest, accumulated growing degree-days to 50% silk, accumulated growing degree-days to 

50% shed, percent stalk lodging, root lodging, plant height, ear height, and staygreen; these traits were 

evaluated to determine the overall health and harvestability of a hybrid. Trials were conducted in four 

locations (see WCRW efficacy trial description above), using a randomized complete block design with 

three replicates per location, twelve treatments per replicate, and four rows per treatment. At plant 

growth stage V2, plants were artificially infested with WCRW eggs at a rate of 1,000 eggs per plant. 

Results show that the DAS-59122-7 corn hybrid provided similar agronomic performance against CRW 

when compared to the isoline hybrid with and without applied insecticide. Yields were not statistically 

different among treatments, despite relatively high rootworm pressure (1,000 eggs per plant). 

Dow and Pioneer conducted additional agronomic performance trials in 2003. Performance of 

Cry34/35Ab1 CRW-protected hybrids (two expressing the single Event DAS-59122-7 and two 
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expressing DAS-59122-7 x Event TC1507 (Cry1F)) were compared to that of near-isogenic hybrids 

containing Event TC1507 and near-isogenic hybrids containing no transgenes. An elite hybrid was also 

included in the trials. The Pioneer trials were planted at 7 locations, and the Dow evaluations at 12 and 

13 locations (Dow completed 2 different experiments). Trials took place throughout the U.S. Corn Belt 

and fields were managed according to standard agronomic practices. Trials utilized randomized 

complete block design, with three replicates per location and two rows per plot. It is not clear if fields 

had been planted to corn prior to experiment initiation and/or whether rootworm pressure was severe in 

field trial locations. 

Results indicate that hybrids with and without event DAS-59122-7 performed similarly for most 

agronomic traits; however, expression of the Cry34/35Ab1 proteins in Event DAS-59122-7 CRWprotected corn was shown to confer advantages in yield and root lodging in some locations with high 

rootworm pressure. Agronomic performance may have been affected by base genetics of different 

hybrids and genetic variability in Cry34/35Ab1 corn hybrid lines. 

ii. BPPD Review

Agronomic performance of Cry34/35Ab1 CRW-protected hybrids, two containing Event DAS-59122-7 

stacked with Event TC1507 expressing Cry1F (Herculex® I) and two containing only Event DAS59122-7, was compared to that of near-isogenic hybrids containing Event TC1507 and near-isogenic 

hybrids containing no transgenes. An elite hybrid was also included in the trials. Based on the review of 

all of the agronomic trials conducted in 2003, the following conclusions can be made. With low CRW 

pressure, Event DAS-59122-7 (Cry34/35Ab1 CRW-protected corn) performed similarly to conventional 

corn hybrids treated with insecticides. There was no yield drag associated with Event DAS-59122-7. 

Under high CRW pressure, however, some Event DAS-59122-7 corn hybrids were shown to confer 

advantages, in some locations, in both yield and root lodging over that of non-transgenic corn treated 

with granular insecticides. There were no significant differences between stacked Cry34/35Ab1/Cry1F 

corn hybrids and Cry34/35Ab1 corn hybrids. The overall range of values for the measured agronomic 

parameters are all within the range of values obtained for traditional corn hybrids and do not indicate 

increased weediness. 

 d. Economic Benefits

i. Summary of Submitted Information

Economic benefit analyses were conducted to evaluate the impact of Cry34/35Ab1 CRW-protected corn 

hybrids (Event DAS-59122-7) on grower profitability, compared to various insect management 

alternatives. The following paragraphs describe the considerations/assumptions used to develop the 

benefits analyses. 

Several key assumptions were developed for economic modeling based on data collected by universities 

on insecticide performance under various corn rootworm densities. Published information was used to 

predict relationships between root damage in untreated corn and expected root damage in insecticide-
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treated corn for granular, liquid, and seed treatments. Separate equations were developed using the 0–3 

nodal injury scale (25 locations, 1999–2002) and the 1–6 Hills & Peters scale (45 locations, 1997–2001). 

The relationship between Event DAS-59122-7 and control root ratings was determined from 12 Dow 

and Pioneer trials conducted in 2003. Based on slopes of the regression equations, the most effective to 

least effective product classes in reducing root damage are as follows: (1) Event DAS-59122-7 hybrids, 

(2) granular insecticides, (3) liquid insecticides, and (4) seed treatments. 

The relationship between root ratings and grain yield has been extensively studied under both artificial 

infestations and natural populations. The economic thresholds for insecticide use typically are exceeded 

at a root rating of 3 or higher (1–6 scale) but can be higher or lower depending upon environmental 

conditions. There is also data that conventional breeding programs and planting rates influence the yield 

response to corn rootworm damage. To predict the relationship between root damage and yield, data 

from 10 corn rootworm trials conducted by Iowa State University (Oleson et al. 2000, 2001, 2002, and 

2003) were evaluated. The predicted difference in yield between insecticide-treated and untreated plots 

increases linearly with level of damage in untreated check plots over a range from 0 to 37 bushels per 

acre. Regression analysis from 37 university yield trials from Nebraska, Minnesota, Indiana, 

Pennsylvania, Illinois, and Iowa provide a similar equation from the 1–6 rating scale with predicted 

yield losses ranging from 0.6 to 39.5 bushels per acre. 

Another key concern of growers is that rootworm feeding increases the risk of lodging. Lodged 

cornfields yield less both due to direct physiological losses and to increased harvest losses. Two 

additional harvest costs associated with lodging are labor costs due to reduced harvest speed and 

increased fuel usage if the field must be harvested in one direction. For this economics assessment, the 

relationship between level of root damage and lodging was determined using insecticide treatments and 

untreated check plots (1–6 scale: 13 locations, Figure 6; 0–3 scale, 18 University trials and 49 Pioneer 

strip trials). Although several other factors (e.g., soil moisture level, wind speed, and root re-growth) 

influence the severity of lodging, root ratings were fairly good at predicting level of root lodging with R2

values of 0.3 and 0.6.

Cropping Scenarios

Three different farming operations were evaluated, using partial budget analysis, to illustrate the 

potential value that Cry34/35Ab1 CRW-protected corn hybrids may bring to the grower. Three farming 

situations were analyzed: (1) moderate pressure rootworm in continuous corn, (2) high pressure 

rootworm in rotated corn, and (3) moderate pressure rootworm in rotated corn. Variable costs for corn 

following soybeans and continuous corn include fertilizers, herbicides, insecticide, crop insurance, 

tillage, planting, harvest, and drying. These variable costs were based on values reported by Duffy and 

Smith (2003) for 150 bushels per acre and a corn price of $2.10 was used in all situations. Note: Tables 

6–8 were revised by the applicant, per the Agency’s request, to more accurately reflect variable costs. 

 Example 1: Moderate corn rootworm pressure, corn following corn 

Traditionally, corn planted in fields where corn was planted in prior years is considered to be at 

moderate risk for rootworm infestations throughout the central Corn Belt, including Nebraska 

and parts of Iowa, Illinois, and Kansas. A high proportion of corn growers treat their continuous 
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corn acres with a planting-time application of granular or liquid insecticides applied at the full, 

labeled rate. Adult beetle management, which involves scouting and typically two aerial 

applications of insecticide, is also implemented in parts of Nebraska, Colorado, Kansas, and 

South Dakota (Meinke 1996). Recently, high rate seed treatment options have become available 

and are included in this analysis. 

If left untreated, moderate rootworm pressure is expected to reduce harvestable yield 15 bushes 

per acre. Based on modeling assumptions, neither a two-application adult control program nor 

use of high rate seed treatments increased variable returns over the control despite improved 

standability and yield (Table 6). In contrast, use of Event DAS-59122-7 or full, labeled rates of 

granular insecticides are expected to return from $10 to $14 per acre more than untreated fields. 

Use of the full, labeled rate of liquid insecticides returned slightly less than Event DAS-59122-7 

or granular insecticides ($9–$12 per acre over untreated fields). 

Example 2: High corn rootworm pressure, corn following soybeans 

In east central Illinois and northwestern Indiana, fields of corn following soybeans are at high 

risk for root damage due to an eastern variant of the WCRW. If fields in this region have not 

been scouted, growers are advised to apply a planting-time insecticide at full, labeled rate. It is 

not unusual to have untreated 1st year cornfields average two or more nodes of roots destroyed, 

resulting in high levels of lodging. In a situation where first-year corn is infested with high 

populations of corn rootworms, harvestable yield is predicted to be reduced by 37 bushes per 

acre if no treatment is applied. Liquid insecticides and high rate seed treatments are not as 

effective in reducing losses and lodging as granular insecticides. High, consistent efficacy 

against even high rootworm pressure gives Event DAS-59122-7 a significant economic 

advantage over granular ($6–$13/acre), liquid ($16–$23/acre), and seed treatment options ($37–

$40/acre)(Table 7). 

Example 3: Moderate corn rootworm pressure, corn following soybeans

The eastern variant of the WCRW is considered a moderate risk to corn in northeastern Indiana 

and northern Illinois. This moderate risk area is expanding into southern Wisconsin, 

southwestern Michigan, and western Ohio. In addition, extended diapause by the northern corn 

rootworm is placing first-year corn in southern Minnesota, northern Iowa, and southwestern 

South Dakota at significant risk to damage. Both granular and liquid planting-time applications 

are being used in fields, particularly in fields with a history of root lodging. Frequently, growers 

elect to use a reduced rate of insecticide if rootworm pressure in the first-year corn is moderate. 

If first-year corn is infested with moderate populations of corn rootworm, use of either hybrids 

containing Event DAS-59122-7, a reduced rate of granular insecticides, or reduced rates of liquid 

insecticides is expected to increase variable returns $10 to $17 per acre over the untreated field 

(Table 8). Use of reduced rate of granular insecticide is slightly more profitable ($2 to $7) than 

either Event DAS-59122-7 or a reduced rate of liquid insecticides. 
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Table 6. Economic Analysis of Moderate Pressure Corn Rootworm in Corn Following Corn.

Untreated DAS59122-7 Granular 

Insecticide 

Liquid 

Insecticide 

High rate 

IST 

Adult Control 

CRW Damage 

 

Root rating (0-3)1 1.0 0.08 0.20 0.36 0.67 0.20

 % Lodged2 23% 2% 5% 8% 15% 5%

Variable Cost -----------------------------$/acre-----------------------------

Seed @ 30,000/acre3 $37.50 $37.50 $37.50 $37.50 $37.50 $37.50

CRW premium 0 $13.13– 

16.88 

0 0 0 0

Low rate IST $4.50 $4.50 0 0 0 $4.50

Scouting 0 0 0 0 0 $7.00

Insecticide 0 0 $12.00–15.00 $12.00–

15.00 

$17.25 $12.80–16.00

Insecticide equipment 

& application 

0 0 $2.00 $2.00 0 $6.00

Other variable costs4 $155.00 $155.00 $155.00 $155.00 $155.00 $155.00

Fuel adjustment5 0 0 0 0 0 0

Labor adjustment6 $0.55 0 0 0 $0.55 0

Harvest adjustment7 -$2.44 -$0.15 -$0.40 -$0.70 -$1.80 -$0.70

 SUBTOTAL 

$195.11 $209.98–

213.73 

$206.10–

209.10 

$205.80–

208.80 

$208.50 $222.10–225.30

Yield -----------------------------bushels/acre-----------------------------

Maximum yield 150 150 150 150 150 150

Harvest loss from 

lodging8

-3 0 0 0 -3 0

CRW loss9 -12 -1 -3 -4 -8 -4

 SUBTOTAL 

135 149 147 146 139 146

-----------------------------$/acre-----------------------------

Gross Returns @ 

$2.10/bushel 

$283.50 $312.90 $308.70 $306.60 $291.90 $306.60

Returns over Variable 

Cost 

$88.39 $99.17–

102.92 

$99.60–102.60 $97.80–

100.80 

$83.40 $81.30–84.50

1 Moderate pressure defined as root damage rating (RDR) of 1 on 0–3 rating scale in untreated field. Expected RDR in DAS-59122-7. Expected 

RDR in insecticide & IST treatments. 2

 % lodging = 0.4175 + 22.083*RDR. 

3 Planting rate is 30,000 kernels per acre; seed cost for 80,000 kernels/unit is $100.00. 4 Includes costs for fertilizer, lime, herbicide, drying, storage, machinery, harvest, insurance, and interest (Duffy and Smith 2003) for 150 

 bushels/acre production. 

5

 Fuel adjustment: 50% of normal combine cost @ $7.87/acre (Duffy and Smith 2003) if lodging is >40%. 

6

 Labor adjustment for harvesting lodged corn: $9.00/hour; normal combine speed 4.5 mph; for lodging >10% but <40%, combine speed 

 reduced by 25%; for lodging >40%, combine speed reduced by 50%. 7

 Variable costs for harvest (hauling, drying, and handling) reduced $0.16/bushel for yields below 150 bushels/acre. 8 Assumes 2% loss for lodging >10% but <40% and 5% loss for lodging >40%. 9

 CRW loss: Change in yield = 12.254*RDR . 
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Table 7. Economic Analysis of High Pressure Corn Rootworm in Corn Following Soybean.

Untreated DAS59122-7 Granular 

Insecticide 

Liquid 

Insecticide 

High rate IST 

CRW Damage 

 

Root rating (0-3)1 2.5 0.08 0.20 0.36 1.70

 % Lodged2 56% 5% 12% 20% 38%

Variable Cost -----------------------------$/acre----------------------------- 

Seed @ 30,000/acre3 $37.50 $37.50 $37.50 $37.50 $37.50

CRW premium 0 $13.13–

16.88 

0 0 0

Low rate IST $4.50 $4.50 0 0 0

Insecticide 0 0 $12.00–15.00 $12.00–15.00 0

Insecticide equipment & 

application 

0 0 $2.00 $2.00 0

Other variable costs4 $139.00 $139.00 $139.00 $139.00 $139.00

Fuel adjustment5 $3.93 0 0 0 0

Labor adjustment6 $1.65 0 $0.55 $0.55 $0.55

Harvest adjustment7 -$6.10 -$0.37 -$1.48 -$2.24 -$3.77

SUBTOTAL 

$180.48 $193.76–

197.51 

$189.57–192.57 $188.81–191.81 $190.53

Yield -----------------------------bushels/acre-----------------------------

Maximum yield 150 150 150 150 150

Harvest loss from lodging8 -7 0 -3 -3 -3

CRW loss9 -31 -2 -6 -11 -21

SUBTOTAL 

112 148 141 136 126

-----------------------------$/acre-----------------------------

Gross Returns @ 

$2.10/bushel 

$234.90 $310.17 $295.54 $285.62 $265.49

Returns over Variable Cost $54.42 $112.66–

115.66 

$102.97–105.97 $93.81–96.81 $74.96

1 High pressure defined as RDR of 2.5 on 0–3 rating scale in untreated field. Expected RDR in DAS-59122-7. Expected RDR in insecticides & 

 IST treatments. 

2

 % lodging = 0.4175 + 22.083*RDR. 

3 Planting rate is 30,000 kernels per acre; seed cost for 80,000 kernels/unit is $100.00. 4 Includes costs for fertilizer, lime, herbicide, drying, storage, machinery, harvest, insurance, and interest (Duffy and Smith 2003) for 150 

 bushels/acre production. 

5

 Fuel adjustment: 50% of normal combine cost @ $7.87/acre (Duffy and Smith 2003) if lodging is >40%. 

6

 Labor adjustment for harvesting lodged corn: $9.00/hour; normal combine speed 4.5 mph; for lodging >10% but <40%, combine speed reduced 

 by 25%; for lodging >40%, combine speed reduced by 50%. 7

 Variable costs for harvest (hauling, drying, and handling) reduced $0.16/bushel for yields below 150 bushels/acre. 8 Assumes 2% loss for lodging >10% but <40% and 5% loss for lodging >40%. 9

 CRW loss: Change in yield = 12.254*RDR . 
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Table 8. Economic Analysis of Moderate Pressure Corn Rootworm in Corn Following Soybean.

Untreated DAS59122-7 Granular 

Insecticide 

Liquid 

Insecticide 

High rate IST 

CRW Damage 

 

Root rating (0-3)1 1.0 0.08 0.2 0.4 0.7

 % Lodged2 23 2 5 8 15

Variable Cost -----------------------------$/acre-----------------------------

Seed @ 30,000/acre3 $37.50 $37.50 $37.50 $37.50 $37.50

CRW premium 0 $13.13–

16.88 

0 0 0

Low rate IST $4.50 $4.50 0 0 0

Insecticide 0 0 $9.00–11.25 $9.00–11.25 $17.25

Insecticide equipment & 

application 

0 0 $2.00 $2.00 0

Other variable costs4 $139.00 $139.00 $139.00 $139.00 $139.00

Fuel adjustment5 0 0 0 0 0

Labor adjustment6 $0.55 0 0 0 $0.55

Harvest adjustment7 -$2.44 -$0.15 -$0.40 -$0.70 -$1.80

SUBTOTAL 

$174.61 $193.98–

197.73 

$187.10–

189.35 

$186.80–

189.05 

$192.50

Yield -----------------------------bushels/acre-----------------------------

Maximum yield 150 150 150 150 150

Harvest loss from lodging8 -3 0 0 0 -3

CRW loss9 -12 1 3 4 8

SUBTOTAL 

135 149 147 146 139

-----------------------------$/acre-----------------------------

Gross Returns @ 

$2.10/bushel 

$282.97 $313.07 $309.74 $305.77 $291.41

Returns over Variable Cost $108.36 $115.34–

119.09 

$120.39–

122.64 

$116.72–

118.97 

$98.91

1 Moderate pressure defined as RDR of 1 on 0–3 rating scale in untreated field. Expected RDR in DAS-59122-7. Expected RDR in insecticide & 

 IST treatments . 

2

 % lodging = 0.4175 + 22.083*RDR. 

3 Planting rate is 30,000 kernels per acre; seed cost for 80,000 kernels/unit is $100.00. 4 Includes costs for fertilizer, lime, herbicide, drying, storage, machinery, harvest, insurance, and interest (Duffy and Smith 2003) for 150 

 bushels/acre production. 

5

 Fuel adjustment: 50% of normal combine cost @ $7.87/acre (Duffy and Smith 2003) if lodging is >40%. 

6 Labor adjustment for harvesting lodged corn: $9.00/hour; normal combine speed 4.5 mph; for lodging >10% but <40%, combine speed reduced 

 by 25%; for lodging >40%, combine speed reduced by 50%. 7

 Variable costs for harvest (hauling, drying, and handling) reduced $0.16/bushel for yields below 150 bushels/acre. 8 Harvest loss: assumes 2% loss for lodging >10% but <40% and 5% loss for lodging >40%. 9

 CRW loss: Change in yield = 12.254*RDR . 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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ii. BPPD Review

Dow and Pioneer analyzed three different farming operations to illustrate the economic benefits that 

Event DAS-59122-7 (Cry34/35Ab1) corn hybrids may provide to growers. Per the Agency’s request, 

Dow and Pioneer revised the original tables (Tables 19–21; Master Record Identification Number 

(MRID No.) 461239-21) to include variable cost adjustments, based on predicted yield, for hauling, 

drying, and handling. By using a static value for variable costs (original tables), economic models were 

slightly biased in favor of higher yielding treatments (Cry34/35Ab1 corn hybrids) and against lower 

yielding treatments because static values do not consider the effect that yield has on operating costs. The 

revised tables showed increased returns over variable costs for the untreated corn hybrids and high-rate 

insecticide treatments but had minimal impact on other treatments (Tables 6–8). 

BPPD agrees with Dow and Pioneer’s analysis of the economic benefits that Event DAS-59122-7 corn 

hybrids may provide to growers. Potential benefits include higher corn yields, reduced expenditures on 

insecticides and insecticide application, and the potential for lower harvest costs due to reduced lodging. 

Additional costs associated with Event DAS-59122-7 include higher seed prices and use of a refuge. Net 

benefits depend on the severity of the corn rootworm problem and on the price of Event DAS-59122-7 

seed. Models suggest that, in continuous corn fields with moderate CRW pressure, hybrids containing 

Event DAS-59122-7 and insecticide-treated non-transgenic varieties should provide similar returns 

(Table 6). In contrast, slightly higher returns are predicted in corn-soybean rotations with high rootworm 

pressure (Table 7). Additional benefits, which are not quantified in these models, include the potential 

for more predictable yields and reduced exposure to insecticides. Future models should also consider the 

cost-benefit of resistance management programs. 

 e. Practical Benefits

i. Summary of Submitted Information

Cry34/35Ab1 (Event DAS-59122-7) corn offers many practical advantages to corn growers over other 

CRW control measures. First, longer season varieties can be used, because later planting dates, which 

have traditionally helped to mitigate CRW damage, are unnecessary. Second, compared to use of 

chemical insecticides, growers should be able to plant more quickly because they won’t have to stop and 

refill the insecticide boxes. Third, insecticidal seed treatments may be applied to Cry34/35Ab1 seeds to 

permit control of associated pests such as wireworm, grub, maggots, and cutworms, providing protection 

against multiple pests. Fourth, planting Cry34/35Ab1 corn is expected to save the grower money in 

application, insecticide, labor, fuel, equipment, storage, and packaging disposal costs (no pesticide 

containers). Fifth, Cry34/35Ab1 corn is labeled for general use and thus, provides an alternative to 

restricted use products. Sixth, Cry34/35Ab1 corn is expected to provide the grower and other 

occupational workers greater safety, as well as fewer adverse environmental impacts, compared to use of 

chemical insecticides. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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ii. BPPD Review

BPPD agrees that Cry34/35Ab1 corn offers many practical advantages to corn growers over 

conventional insecticides, as stated above. 

 f. Market Adoption and Pesticide Use Reduction

i. Summary of Submitted Information

It is expected that growers who plant Cry34/35Ab1 CRW-protected corn will significantly reduce use of 

chemical insecticides for rootworm control. The addition of commercially available Cry34/35Ab1 corn 

will benefit growers for the following reasons: (1) corn varieties containing the Cry34/35Ab1 CRWprotected corn will compete with Cry3Bb1 corn varieties, creating price competition among transgenic 

CRW control technologies; and (2) corn varieties containing the Cry34/35Ab1 offer alternatives to 

current Cry3Bb1 CRW-protected corn varieties in terms of plant genetics and performance attributes. 

ii. BPPD Review

Rootworm damage may cost U.S. corn growers $1 billion annually in control costs and crop losses 

(Gianessi et al. 2002). In the year 2000, almost 8 million pounds of CRW insecticide, costing $172 

million, were applied to 14 million acres or 17% of U.S. corn acreage ($12.29 per acre). CRW-infested 

acreage is projected to increase from approximately 31.8 million acres in 2005 to 39 million acres by 

2013 (Table 9). 

Grower demand for CRW control technologies is influenced by the level of CRW infestation (acreage 

and degree of infestation), comparative cost-benefit of competing CRW control technologies, U.S. and 

global market acceptance and approval of a technology, and other regulatory constraints (e.g., refuge 

requirements). BPPD anticipates, through evaluation of National Agricultural Statistics Service (NASS) 

(of the United States Department of Agriculture) and Doane® Agricultural Services databases on CRW 

damage and control costs, that the market for transgenic in-plant CRW protection will increase by 2.6% 

per year, reaching 18 to 19 million acres by the year 2013 (Table 9). 

Anticipated economic and pesticide use reduction benefits of Cry34/35Ab1 corn largely depend on 

market penetration. Introduction of commercially available Cry34/35Ab1 corn hybrids is expected to 

create price competition among commercially available transgenic CRW-protected corn products and 

will offer a greater variety of plant genetics and performance attributes to growers. 

Increased adoption of transgenic CRW-protected corn products is expected to result in reduced use of 

many of the chemical insecticides registered for CRW control, which are highly toxic to humans and the 

environment, are in Special Review, and have restricted use labels. The chemical insecticides (larvicides 

and adulticides) subject to the greatest use reduction following adoption of transgenic CRW-protected 

hybrids are the following: organophosphates (chlorpyrifos, tebupirimphos, terbufos, methyl parathion, 

and chlorethoxyfos), pyrethroids (tefluthrin, cyfluthrin, bifenthrin, and lambda cyhalothrin), carbamates 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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(carbofuran), and pyrazoles (fipronil) (Table 10). Adoption of transgenic CRW-protected corn products 

is not expected to result in reduced use of seed treatments (nicotinoids); however, seed treatment 

products are generally less toxic than at-plant and post-plant products. 

Table 9. Projected Acreage with Corn Rootworm Infestation and Breakdown of Associated 

 CRW Control Practices for the Years 2000 to 2013 (Note: Information Presented for 

 2000 and 2002 Reflect Actual Infestation and Insect Control Tactics).

Acres Infested Acres Treated CRW-Protected 

Bt Corn Acreage 

Conventional 

Treatments 

Year 

-----------------------------------------acreage x 106---------------------------------------- 

2000 28.0 14.0 0.0 14.0 

20011 - - - - 

2002 29.5 14.7 0.0 14.7 

2003 30.2 15.1 1.0 14.1 

2004 31.0 15.5 2.5 13.0 

2005 31.8 15.9 4.0 11.9 

2006 32.6 16.3 6.0 10.3 

2007 33.5 16.7 7.2 9.5 

2008 34.3 17.2 8.6 8.5 

2009 35.2 17.6 10.4 7.2 

2010 36.1 18.1 11.9 6.1 

2011 37.1 18.5 13.7 4.8 

2012 38.0 19.0 15.8 3.2 

2013 39.0 19.5 16.8 2.7 

Annual Growth 

Rate 

2.58% 2.58% 16.8% -14.36% 

1

 The Agency does not have data for the 2001 growing season. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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Table 10. Use of Chlorpyrifos, Phorate, Tefluthrin, and Terbufos Insecticides for Rootworm 

 Control in Corn.

Chlorpyrifos Phorate Tefluthrin Terbufos

Source of data1 G U-97 U-03 G U-97 U-03 G U-97 U-03 G U-97 U-03

State

. ----------------------------1,000 pounds active ingredient ------------------------------

--------------- 

Colorado 7 - 2 12 1 - 218 125 

Illinois 810 2,105 747 120 – 68 57 205 466 1,117 – 

Indiana 299 267 621 62 36 31 93 558 – 473 

Iowa 1,044 1,248 366 114 – 71 35 – 366 922 – 

Kansas 91 – 19 – 226 

Maryland 45 5 11 

Michigan 135 153 146 47 15 – 155 – – 

Minnesota 265 - 214 129 – 21 – – 206 – – 

Missouri 232 315 106 25 – 1 – – 23 

Nebraska 294 382 - 134 68 270 76 879 748 246 

New York 216 80 147 11 24 – 

North Dakota 48 1 107 – 

Ohio 363 429 67 36 – 46 – – – – 

Oklahoma 1 2 14 

Pennsylvania 132 151 15 – 15 21 31 – 

South Dakota 480 – – 226 10 7 – 502 – 

Texas 50 44 – 5 512 228 

Wisconsin 286 254 96 70 – 32 32 43 385 – – 

Total - sum of rows 4,750 5,153 2,638 1,037 – – 558 432 454 4,681 2,787 1,072

Total - as reported in 

USDA 5,341 3,024 522 523 3,200 1,660 1 G = Gianessi et al. (2002), data from 1997 

 U-97 = USDA/NASS (1998), data for 1997 

 U-03 = USDA/NASS (2004), data for 2003 

2 A - indicates that usage data not published for this active ingredient 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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195

 g. Direct and Indirect Economic Benefits 

 i. Summary of Submitted Information

Shifting from conventional CRW control technologies to Cry34/35Ab1 CRW-protected corn is expected 

to provide direct economic benefits to farmers, by lessening the costs associated with pest control; 

transgenic corn seed is generally less expensive than chemical pesticide control programs. Indirect 

benefits are also expected to result from adoption of Cry34/35Ab1 CRW-protected corn. Benefits may 

include reduced energy consumption, resulting from a decline in the manufacture, transport, and 

application of chemical insecticides. Waste products, arising from pesticide manufacturing and residual 

chemical stocks, may also be reduced pending a decline in chemical pesticide manufacture and sales. 

Dow and Pioneer calculated indirect economic benefits based on reduced chemical insecticide use 

following adoption of Cry34/35Ab1 technology. Chemical insecticides consume roughly 2.25 x 108

British thermal units (BTU) per ton for manufacture and distribution, and approximately 94,000 BTU 

per acre are used for a single pesticide application. Estimated energy savings are approximately 660,000 

barrels of crude oil (3.83 x 1012 BTU), assuming a targeted adoption of 23.4 x 106

 acres Cry34/35Ab1 Bt

corn by 2014. These calculations are based on 2.25 x 106 BTU/ton of [active ingredient] pesticide for 

manufacturing and distribution, and 94,000 BTU/acre for application (one application per acre). Using 

Gianessi et al. (2002)’s 14.5 million pound (7,250 tons) estimate of applied CRW insecticide (annually), 

estimated annual energy savings would be: [(7,250 tons)(2.25 x 108 BTU/ton) + (23.4 x 106

acres)(94,000 BTU/acre) = 3.83 x 1012 BTU, at 5.8 x 106

 BTU/barrel of oil = 660,000 barrels of oil per 

year. 

 ii. BPPD Review

BPPD agrees with Dow and Pioneer’s conclusion that indirect economic benefits will be obtained from 

adoption of Cry34/35Ab1 CRW-protected corn. However, the applicants’ estimates of energy savings 

may be inflated. There are four assumptions to check: (1) energy for pesticide manufacturing and 

distribution; (2) amount of pesticide applied; (3) energy for application; and (4) number of acres. BPPD 

agrees with the applicants’ conclusions on assumptions 1, 2, and 4. However, assumption 3 (“energy for 

application”) may be over estimateda

. A value within the range of 15,730 to 25,220 BTU/acre may be 

more accurate than the applicants’ estimate of 94,000 BTU/acre.

 

a From Bhat et al. (1994), energy to manufacture insecticides is estimated to be 210.7 x 106

 BTU/ton and for formulation, packaging, and 

transportation ranges from 11.2 to 33.5 x 106

 BTU/ton of active ingredient. An estimate of 2.25 x 108 BTU/ton of [active ingredient] 

pesticide for manufacturing and distribution is valid. From a number of crop budgets, application on corn is typically assumed to be done 

using a 50-foot boom sprayer pulled by a 60-horsepower (hp) tractor that covers 25.6 acres/hour. A 60-hp tractor consumes 2.64 gallons of 

fuel/hour based on the American Society of Agricultural Engineers (ASAE 2001) standards for calculating fuel consumption (0.044 gallons 

of diesel/horsepower-hour). The American Agricultural Economics Association (2000) methodology for estimating costs of farming 

incorporates the ASAE standards and also assumes that powered equipment, such as tractors, operate 10% longer than is needed for the 

actual field operation. Thus, the 60-hp tractor would consume 2.904 gallons of diesel/machine hour in the field (402,760 BTU/machine 

hour based on 138,690 BTU/gallon of diesel). To calculate the area covered by the sprayer, assume it travels 6.5 miles per hour (mph) with 

a field efficiency of 0.65 (i.e., it does productive work 65% of the time) (ASAE 2001) [6.5 mph * 5280 ft/mi * 50 ft/(43,560 ft2

/acre) = 25.6 

acres/hour]. Based on 25.6 acres/hour, this is equivalent to 15,730 BTU/acre.
Bacillus thuringiensis Cry34/35Ab1 Corn 

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196

h. Human Health Benefits

 i. Summary of Submitted Information

Cry34/35Ab1 CRW-protected corn is expected to be safer for handlers, applicators, farmers, and the 

public than chemical pesticides in current use. Twenty-five of the 39 registered conventional insecticides 

used to control CRW are classified as “Restricted Use,” 12 have the “Danger” label classification, and 

several are in Agency Special Review (e.g., dimethoate, phorate, and terbufos). Further, each year there 

are confirmed reports of human illness associated with these registered chemical insecticides. 

Adoption of Cry34/35Ab1 corn hybrids has the potential to reduce occupational, farmer, and public 

health risks associated with the manufacture, transportation, storage, handling, application, and disposal 

of conventional insecticides, by providing a safer alternative for CRW control. 

ii. BPPD Review

BPPD has concluded that the Cry34Ab1 and Cry35Ab1 proteins are unlikely to be allergens and that 

there is reasonable certainty of no harm from aggregate exposure to the proteins as expressed in corn. 

(see the Human Health Assessment and Product Characterization chapters of this Biopesticides 

Registration Action Document (BRAD) for more information on potential human health effects.) 

 i. Environmental Benefits

i. Summary of Submitted Information

All of the major chemicals used for CRW control can cause major adverse environmental effects under 

conditions of normal use. Further, these chemicals can spread via spray drift and runoff, contaminating 

both land and water bodies and impacting non-target organisms. Fifteen of these products are labeled as 

“toxic,” 6 as “highly toxic,” 1 as “very highly toxic,” and 14 as “extremely toxic” to birds, fish, and 

other wildlife. Several of the synthetic insecticides, in particular organophosphates and synthetic 

pyrethroids, exhibit moderate to high toxicity to terrestrial non-target species. Of special concern are 

methyl parathion and carbofuran, both of which are implicated in bird kills. The three top CRW 

insecticides (Table 11)—terbufos, chlorpyrifos, and tefluthrin—account for the majority of the acres 

treated (63%) for CRW control. These three CRW insecticides pose greater ecological risk than do 

Cry34/35Ab1 CRW-protected corn hybrids. 

In contrast, the Cry34/35Ab1 protein is essentially non-toxic to non-target species, including endangered 

and beneficial species. The Cry34Ab1 and Cry35Ab1 proteins rapidly degrade soil, off-target exposure 

to non-target species through pollen or soil residues will be insignificant, and there is a minimum 

potential for runoff; exposure to Cry34Ab1 and Cry35Ab1 is minimal or non-existent. Reduced runoff 

reduces environmental pollution. The ecological risk assessment and characterization of the Cry34Ab1 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

197

and Cry35Ab1 proteins, as expressed in corn, suggests that these proteins pose no significant ecological 

risk to non-target species, including endangered and beneficial species. 

ii. BPPD Review

See BPPD’s Cry34/35Ab1 CRW-protected corn hybrid Environmental Assessment chapter in this 

BRAD for more information on the potential for ecological effects. 

Table 11. Comparison of Ecological Risks Associated with Terbufos, Chlorpyrifos, and 

 Tefluthrin.

Endpoint Terbufos Chlorpyrifos Tefluthrin

Mammalian Acute RQ 50 1 0.008 

Avian Acute RQ 0.27 0.55 0.0001 

Fish acute RQ 11 2 0.77 

Freshwater invertebrate RQ 50 20 0.77 

Marine/Estuarine Invertebrate RQ 53 162 0.87 a Risk is defined as the risk quotient (RQ) >level of concern (LOC). RQ = Toxicity/Exposure. LOC = 1 

 j. Insect Resistance Management Benefits

 i. Summary of Submitted Information

There is concern about the ability of target pests to evolve resistance to CRW control mechanisms, 

including crop rotation, chemical insecticides, and CRW-protected Bt-corn products. Currently, the 

favored management practice for CRW control is crop rotation, specifically corn-soybean rotations, 

complimented by application of chemical insecticides (e.g., pyrethroids, organophosphates, carbamates, 

and pyrazoles) and, more recently, neonicotinoids as seed treatments. Due to continuous use of a small 

number of active ingredients, CRW has developed resistance to a number of these chemical control 

products. The recent development of the NCRW extended diapause and WCRW soybean resistant 

variants have further reduced the efficacy of crop rotation and chemical control options. Since 

Cry34/35Ab1 CRW-protected corn presents a new mode of action and has good efficacy against CRW, 

introduction of this corn product is expected to extend the durability of existing rootworm control 

measures, including other commercially available CRW-protected Bt-corn products (e.g., MON 863). To 

ensure the long-term efficacy of Cry34/35Ab1 CRW-protected corn hybrids, an insect resistance 

management plan should be implemented. 

 ii. BPPD Review

See BPPD’s Cry34/35Ab1 Insect Resistance Management chapter of this BRAD for the analysis of the 

dose, mode of action, durability modeling, and the proposed insect resistance management plan for 

Cry34/35Ab1 CRW-protected corn hybrids. 
Bacillus thuringiensis Cry34/35Ab1 Corn 

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198

3. References 

AAEA.2000. Commodity Costs and Returns Estimation Handbook, American Agricultural Economics 

 Association, Ames, Iowa. 

ASAE. 2001. ASAE Standards, 48th Edition, American Society of Agricultural Engineers, St. Joseph, 

 Michigan. 

Bhat MG, English BC, Turhollow AF, Nyangito HO. 1994. Energy in Synthetic Fertilizers and 

 Pesticides: Revisited. Available from: 

http://www.osti.gov/bridge/purl.cover.jsp;jsessionid=B5046E886528DE6ADC405B64E9E49731

?purl=/10120269-p6yhLc/webviewable/.

Duffy M, Smith D. 2003. Estimated costs of crop production in Iowa - 2003. FM 1712. Iowa State 

 University, University Extension, Ames, IA. 

Gianessi LP, Silvers CS, Sankula S, Carpenter JE. 2002. Plant Biotechnology: Current and Potential 

 Impact for Improving Pest Management in U.S. Agriculture: An Analysis of 40 Case Studies. 

 Available from: http://www.ncfap.org/40casestudies.html. 

Levine E, Oloumi-Sadeghi H. 1991. Management of Diabroticite rootworms in corn. Annual Review of 

 Entomology 36:229–255. 

Meinke LJ. 1996. Adult corn rootworm management. University of Nebraska-Lincoln publication no. 

 MP63-C. 

Meinke LJ, Siegfried BD, Wright RJ, Chandler LD. 1998. Adult susceptibility of Nebraska western corn 

rootworm (Coleoptera: Chrysomelidae) populations to selected insecticides. Journal of 

Economic Entomology 91(3):594–600. 

MRID No. 461227-01. Bing J, Coats I, Davis P. 2003. Public Interest Document for Pioneer Brand Bt 

 Cry34/35Ab1 Corn Construct PHP 17662. Project Number: PHI/2003/059. Unpublished study 

 prepared by Pioneer Hi-Bred International, Incorporated, 607 pages. 

MRID No. 461239-21. Bing J, Coats I, Ernest A. 2003. Public Interest Document for Mycogen Brand 

 B.t. Cry34/35Ab1 Construct PHP17662 Insecticidal Crystal Protein as Expressed in Corn. 

 Project Number: GH/C/5704, 5,704 pages. 

 

Oleson JD. 1998. Joint Meeting, Entomological Society of America and American Phytopathological 

 Society, Display Presentation, D428 Linear Scale for Evaluating Corn Rootworm Larval Injury. 

 November 8–12, Las Vegas, Nevada. Available from: 

 http://www.ent.iastate.edu/pest/rootworm/nodeinjury/nodeinjury.html. 
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Oleson JD, Nowatzki TM, Wilson TA, Tollefson JJ. 2000. Corn rootworm larval control, 1999. 

 Arthropod Mgmt. Test, v. 25, rep F50. 

Oleson JD, Nowatzki TM, Wilson TA, Park Y, Tollefson JJ. 2001. Corn rootworm larval control, 2000. 

 Arthropod Mgmt. Test, v. 26, rep F33. 

Oleson JD, Nowatzki TM, Wilson TA, Park Y, Tollefson JJ. 2002. Evaluation of soil insecticides for 

 control of corn rootworm larvae, 2001. Arthropod Mgmt. Test, v. 27, rep F27. 

Oleson JD, Wilson TA, Park Y, Tollefson JJ. 2003. Evaluation of soil insecticides for control of corn 

 rootworm larvae, 2002. Arthropod Mgmt. Test, v. 28, rep F32. 

Scharf ME, Meinke LJ, Siegfried BD, Wright RJ, Chandler LD. 1999. Carbaryl susceptibility, 

 diagnostic concentration determination, and synergism for U.S. populations of western corn 

 rootworm (Coleoptera: Chrysomelidae). Journal of Economic Entomology 92(1):33–39. 

USDA/NASS. 1998. Agricultural Chemical Usage: 1997 Field Crops Summary. Available from: 

 http://usda.mannlib.cornell.edu/usda/nass/AgriChemUsFC//1990s/1998/AgriChemUsFC-05-20-

 1998.pdf 1998. 

USDA/NASS. 2004. Agricultural Chemical Usage: 2003 Field Crops Summary. Available from: 

 http://usda.mannlib.cornell.edu/usda/nass/AgriChemUsFC//2000s/2004/AgriChemUsFC-05-20-

 2004.pdf. 

U.S. EPA. 2005. EPA Public Interest Finding and Review of the Benefits Associated with Cry34/35 

 Rootworm-Protected Field Corn Products for the Section 3(c)(7)(C) Full Commercial 

 Registration. Memorandum from T. Milofsky, S.R. Matten, Ph.D., and E.B. Brandt to M. 

 Mendelsohn dated July 5, 2005. 

Zhu KY, Wilde GE, Higgins RA, Sloderbeck PE, Buschman LL, Shufran RA, Whitworth RJ, Starkey 

 SR, He F. 2001. Evidence of evolving carbaryl resistance in western corn rootworm (Coleoptera: 

 Chrysomelidae) in areawide-managed cornfields in north central Kansas. Journal of Economic 

 Entomology 94(4):929–934. 
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III. REGULATORY POSITION FOR EVENT DAS-59122-7 CORN 

A. Initial Registration (August 31, 2005)

Pursuant to section 3(c)(7)(C) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the 

Environmental Protection Agency (EPA) may conditionally register a new pesticide active ingredient for 

a period of time reasonably sufficient for the generation and submission of required data that are lacking 

because insufficient time has elapsed since the imposition of the data requirement for those data to be 

developed. EPA may grant such conditional registration only if EPA determines that (1) the use of the 

pesticide product during the period of the conditional registration will not cause any unreasonable 

adverse effect on the environment, and (2) the registration and use of the pesticide during the conditional 

registration is in the public interest. EPA determines that all of these criteria have been fulfilled. 

The first criterion under FIFRA section 3(c)(7)(C), as mentioned above, has been met because 

insufficient time has elapsed since the imposition of the requirements for the following data: 

1. Independent laboratory analytical method validation. 

 2. Field degradation studies evaluating accumulation and persistence of the Cry34Ab1 and 

 Cry35Ab1 proteins in several different soils in various strata. 

 3. Laboratory toxicity test with Orius insidiosus (minute pirate bug). 

 4. Laboratory toxicity test with carabid (ground beetle). 

 5. Multi-year non-target organism field studies. 

The applicants submitted and/or cited data sufficient for EPA to determine that conditional registration 

of the Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins and the genetic material necessary for 

their production (plasmid insert PHP17662) in Event DAS-59122-7 corn (Organization for Economic 

Cooperation and Development (OECD) Unique Identifier: DAS-59122-7) under FIFRA section 

3(c)(7)(C) will not result in unreasonable adverse effects to the environment, as discussed above. The 

applicants submitted and/or cited satisfactory data pertaining to the proposed use. The human health 

effects and non-target organism effects data are considered sufficient for the period of the conditional 

registration. These data demonstrate that no foreseeable human health hazards or environmental effects 

are likely to arise from the use of the products and, furthermore, that the risk of resistance developing to 

the Cry34Ab1 and Cry35Ab1 proteins during the conditional registrations is not expected to be 

significant. 

Registration of the Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins and the genetic material 

necessary for their production (plasmid insert PHP17662) in Event DAS-59122-7 corn (OECD Unique 

Identifier: DAS-59122-7) is in the public interest for the following reasons: 

1. Cry34/35Ab1-protected corn provides effective control of key rootworm pests of field corn and 

may prove more efficacious than chemical insecticides presently registered for this purpose. 
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2. Economic models suggest that, under conditions of high rootworm pressure, use of 

Cry34/35Ab1-protected corn will provide greater net returns to farmers. Cost benefits include 

reduced expenditures on insecticides, application equipment, and personnel, complimented by 

greater potential corn yields. Under high rootworm pressure, these benefits are expected to 

outweigh the higher cost of seed. 

3. Registration of Cry34/35Ab1-protected corn is expected to result in further reduction of 

chemical insecticide use by growers. This is of special importance since many pesticides 

registered for corn rootworm (CRW) control are highly toxic to humans and the environment, 

while Cry34/35Ab1-expressing corn poses no foreseeable human health or environmental risks. 

4. Cry34/35Ab1 corn will be the second CRW-protected corn trait on the market (the first was 

Cry3Bb1). The availability of multiple CRW-protected corn products will increase grower 

choice and price competition, resulting in lower seed prices for consumers and higher adoption 

rates. 

5. The Cry34/35Ab1 CRW-protected corn will provide a different mode of action and extend the 

durability of other CRW control measures, including other Bacillus thuringiensis CRWprotected corn hybrids. 

In view of these minimal risks and the clear benefits related to the Bacillus thuringiensis Cry34Ab1 and 

Cry35Ab1 proteins and the genetic material necessary for their production (plasmid insert PHP17662) in 

Event DAS-59122-7 corn (OECD Unique Identifier: DAS-59122-7), EPA believes that the use of the 

products during the limited period of the conditional registrations will not cause any unreasonable 

adverse effects. 

Although the data with respect to this particular new active ingredient are satisfactory, they are not 

sufficient to support an unconditional registration under FIFRA section 3(c)(5). Additional data are 

necessary to evaluate the risk posed by the continued use of these products. Consequently, EPA is 

imposing the data requirements specified earlier in this chapter. 

EPA has determined, as explained in section II(E) of this Biopesticides Registration Action Document 

(BRAD), that the third criterion for a FIFRA section 3(c)(7)(C) conditional registration has been 

fulfilled because use of the Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins and the genetic 

material necessary for their production (plasmid insert PHP17662) in Event DAS-59122-7 corn (OECD 

Unique Identifier: DAS-59122-7) under these registrations is in the public interest. 

The submitted data, in support of these registrations under FIFRA section 3(c)(7)(C), have been 

reviewed and determined to be adequate. Studies mentioned above are included in the terms, conditions, 

and limitations of these registrations. These registrations will not cause unreasonable adverse effects to 

man or the environment and are in the public interest. 

The expiration date of the registrations has been set to September 30, 2010. 
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B. 2010 Update 

Section 3(c)(7)(A) of FIFRA provides for the registration or amendment of a pesticide when the 

pesticide and proposed use “...are identical or substantially similar to any currently registered pesticide 

and use thereof, or differ only in ways that would not significantly increase the risk of unreasonable 

adverse effects on the environment, and (ii) approving the registration or amendment in the manner 

proposed by the applicant would not significantly increase the risk of any unreasonable adverse effect on 

the environment.” Unreasonable adverse effects on the environment are defined under section 2(bb) of 

FIFRA as “... any unreasonable risk to man or the environment, taking into account the economic, 

social, and environmental costs and benefits of the use of any pesticide...” Thus, pursuant to section 

3(c)(7)(A), EPA may conditionally register a pesticide if (1) the pesticide and its proposed use are 

identical or substantially similar to a currently registered pesticide; or (2) the pesticide and its proposed 

use differ only in ways that would not significantly increase the risk of unreasonable adverse effects; and 

(3) approving the registration would not significantly increase the risk of any unreasonable adverse 

effect. 

The Agency concludes that the following Cry34/35Ab1 corn product registrations, set to expire in 

September or October 2010 and described in-depth throughout this BRAD, meet both criteria (1) and 

(2): 

 (1) Event DAS-59122-7 Corn (EPA Reg. Nos. 68467-5 and 29964-4) 

 (2) Herculex® XTRA Insect Protection Corn (EPA Reg. Nos. 68467-6 and 29964-5) 

 (3) 1507 x 59122 x MON 810 (EPA Reg. No. 29964-8) 

 (4) 59122 x MON 810 (EPA Reg. No. 29964-9) 

All of these Cry34/35Ab1 corn products are identical in both composition and use (field corn) to plantincorporated protectants that are currently registered. Thus, criterion (1) has been fulfilled. 

With regard to criterion (2), the Agency maintains, as was previously determined for the original 

registration of these particular products, that cultivation of Cry34/35Ab1-containing corn will not cause 

unreasonable adverse effects on the environment. The conditional environmental effects data, submitted 

in response to terms and conditions of registration and summarized in section II(C)(2)(b) of this BRAD, 

strengthen the Agency’s initial position and also confirm that long-term effects on non-target organisms 

are not anticipated. Lastly, the continued use of these products will likely still provide many of the 

benefits as were evaluated in section II(E) of this BRAD to support the 2005 registration of Event DAS59122-7 corn (e.g., reduction in use of conventional insecticides that are highly toxic to both humans 

and the environment). 
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In conclusion, as the expiring Cry34/35Ab1 products (i.e., Event DAS-59122-7, Herculex® XTRA 

Insect Protection Corn, 1507 x 59122 x MON 810, and 59122 x MON 810) have met the required 

criteria under section 3(c)(7)(A) of FIFRA, the Agency is proposing to amend these registrations to 

extend their respective expiration datesa as follows: 

Product Name (EPA Reg. No.) Proposed Expiration Date 

Event DAS-59122-7 Corn (68467-5) 5 years after amendment (~September 2015) 

Event DAS-59122-7 Corn (29964-4) 5 years after amendment (~September 2015) 

Herculex® XTRA Insect Protection Corn (68467-6) 5 years after amendment (~September 2015) 

Herculex® XTRA Insect Protection Corn (29964-5) 5 years after amendment (~September 2015) 

1507 x 59122 x MON 810 (29964-8) 5 years after amendment (~October 2015) 

59122 x MON 810 (29964-9) 5 years after amendment (~October 2015) 

Although data provided were satisfactory to make the determinations required by section 3(c)(7)(A) of 

FIFRA, they were not sufficient to support an unconditional registration under FIFRA section 3(c)(5). 

Additional data, specifically in relation to aquatic invertebrate testing and insect resistance management, 

are necessary for a finding of registrability under FIFRA section 3(c)(5) and will remain as terms or 

conditions for the purposes of the proposed amendments. 

 

a

 See section III(C) of this BRAD for an explanation describing how the proposed expiration dates were determined. 
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C. Period of Registration 

In the 2001 Bt Corn reassessment, EPA determined that it was appropriate to amend the then-existing 

registrations to extend the period of registration of those products to an expiration date of October 15, 

2008. All of the products being assessed at that time were efficacious against lepidopteran pests. EPA 

based this action on the finding that use of Cry1Ab or Cry1F expressed in corn will not significantly 

increase the risk of unreasonable adverse effects on the environment “for the limited time period of 7 

additional years (to October 15, 2008).” These registrations were later amended to extend the period of 

registration to an expiration date of September 30, 2010. EPA subsequently granted time-limited 

registrations to products efficacious against coleopteran corn rootworm pests. For example, EPA 

registered Cry3Bb1 on February 24, 2003, to May 1, 2004, and extended that registration twice, to 

February 24, 2008, and September 30, 2010. 

As set forth elsewhere in this document, EPA’s primary concern for the Bt protected transgenic corn 

products is the possibility that target pests will develop resistance to one or more of the plantincorporated protectant (PIP) toxins. Development of resistance to a Bt toxin would be a grave adverse 

effect, and, for over 15 years, EPA has imposed stringent requirements intended to countermand the 

potential development of resistance. Registrants similarly have been busily developing various products, 

product mixes (i.e., so-called “pyramids” and “stacks”), and resistance strategies, to maximize 

agronomic benefits and address resistance management issues. The result has been a vast array of 

product combinations and, occurring over the past couple of years, a re-emergence of varying refuge 

requirements for different products. 

As discussed in the 2001 Bt PIP BRAD (at IID13), the earliest Bt corn registrations did not include 

mandatory refuge requirements. There was a lack of scientific consensus as to what the appropriate 

refuge requirement should be, and, it was assumed that the limited market penetration of these early 

crops would be so low as to guarantee that adequate natural refuges would be available from 

neighboring non-Bt corn fields. From 1995 to 1997, Bt corn registrations included voluntary refuge 

requirements of 0% to 20% in the Corn Belt. In 1999, the Agricultural Biotechnology Stewardship 

Technical Committee (ABSTC), in conjunction with the National Corn Growers Association, proposed 

uniform insect resistance management (IRM) requirements for Bt corn registrations. With some 

modifications, this proposal, put in place for the 2000 growing season, formed the baseline IRM 

requirements for almost all Bt corn registrations for the better part of a decade: farmers were required to 

plant a 20% refuge that could be treated for insects, or a 50% treated refuge in cotton-growing areas; all 

refuges to be planted within one-half mile of the Bt corn field. 

These uniform requirements brought certainty and consistency to the market after the initial period 

where many Bt corn products had different refuge requirements. Recently, however, as product 

developers have begun to conceive of products with different combinations of “pyramided” products 

(i.e., products containing two or more toxins efficacious against the same pest) and “stacked” products 

(i.e., products combining toxins efficacious against different pests), the refuge requirements have begun 

to vary. For example, certain products require a 20% external refuge; some products permit a 5% 
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external refuge; one product incorporates a 10% seed blend refuge; we have applications in process for 

products that propose to incorporate a 5% seed blend refuge; and other permutations are possible. 

Given the profusion of various toxin combinations and refuge options, we can no longer proceed on the 

basis that, as concerns insect resistance management, all products are equal. It was a relatively simple 

proposition when the default requirement of a 20% sprayed refuge applied to almost all of the Bt corn 

crops in the market. Under those circumstances, the relative durability of products against the 

development of resistance was functionally equivalent, and, as a consequence, imposing functionally 

equivalent registration periods was appropriate. That is now no longer the case. 

As part of our continually evolving regulatory approach to the continually evolving product mix 

wrought by developers, we think it appropriate to revise our regulatory requirements in scientifically 

defensible ways to reflect the actual level of risks posed by the products that we regulate. Here, for 

example, where we’ve determined that a particular product, or category of products, likely will pose less 

risk of insect resistance developing to a particular PIP protein, we think it appropriate to grant that 

particular product, or category of products, a registration for a period greater than that granted a 

corresponding product that poses a greater risk of insect resistance developing. This approach is 

reflective of complementary principles: first, to ensure that we apply our limited resources to the 

products that pose greater risk of adverse effects to the environment; and, second, to conserve the 

resources that registrants and applicants must expend in amending the registrations of products that pose 

less risk of adverse effects to the environment. 

The scheme that we propose to follow will include registration periods of five, eight, and twelve years; a 

fifteen-year registration period will also be available, if adequately supported by our science assessment. 

In this scheme, (i) a product with a single PIP toxin, and a 20% external refuge, qualifies for a five-year 

registration; (ii) a product with pyramided PIP toxins (i.e., two or more toxins with distinct, non-cross 

reacting modes of action), that are non-high dose (the definition for a high dose product remains 

unchanged), with either a seed blend or external refuge, qualifies for an eight-year registration; (iii) a 

product with pyramided PIP toxins (i.e., two or more toxins with distinct, non-cross reacting modes of 

action), that are high-dose, with either a seed blend or external refuge, qualifies for a twelve-year 

registration; (iv) a product with pyramided PIP toxins (i.e., two or more toxins with distinct non-cross 

reacting modes of actions), with either a seed blend or external refuge, that has been determined by 

EPA’s science assessment to be 150% as durable as the baseline single toxin product with a 20% 

external refuge, would qualify for a fifteen-year registration. Products determined by EPA’s science 

assessment to be less than 100% as durable as the baseline single toxin product with a 20% external 

refuge would not qualify for a five-year registration and the registration period for such products will be 

determined on a case-by-case basis consistent with the level of risk they pose. Similarly, instances where 

other risk issues may arise, or where novel resistance concerns may be present, would also be 

determined on a case-by-case basis. 
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APPENDIX A

GLOSSARY OF ACRONYMS AND ABBREVIATIONS 

AAEA American Agricultural Economics Association 

ABSTC Agricultural Biotechnology Stewardship Technical Committee 

ADP adenosine diphosphate 

AIBS American Institute of Biological Sciences 

ANOVA analysis of variance 

AP alkaline phosphatase 

APHIS Animal and Plant Health Inspection Service (of the United States Department of Agriculture) 

ARS Agricultural Research Service (of the United States Department of Agriculture) 

ASAE American Society of Agricultural Engineers 

BCW black cutworm 

BLAST Basic Local Alignment Search Tool 

BLASTP BLAST search that compares an amino acid query sequence with others stored in protein 

sequence databases 

BPPD Biopesticides and Pollution Prevention Division 

BRAD/BRADs Biopesticides Registration Action Document/Biopesticides Registration Action Documents 

BSA bovine serum albumin 

Bt/B.t. Bacillus thuringiensis

BTU British thermal units 

bw body weight 

°C Celsius (degrees) 

CAP/CAPs Compliance Assurance Program/Compliance Assurance Programs 

CEW corn earworm 

CLA corn leaf aphid 

CFR Code of Federal Regulations 

cm centimeter/centimeters 

Codex Codex Alimentarius Commission 

CRW corn rootworm 

CVs coefficients of variation 

Da Dalton/Daltons 

DNA deoxyribonucleic acid 

DT50 half-life 

DT90 time until 90% decay 

EC50 growth inhibition 

ECB European corn borer 

ED50 median effective dose (produces desired effect in 50% of population) 

EDSP Endocrine Disruptor Screening Program 

EEC Estimated Environmental Concentration 

ELISA/ELISAs enzyme-linked immunosorbent assay/enzyme-linked immunosorbent assays 

EPA Environmental Protection Agency (the Agency) 

EPA Reg. No. Environmental Protection Agency Registration Number 

EPA Reg. Nos. Environmental Protection Agency Registration Numbers 

ESI MS/MS electrospray ionization tandem mass spectrometry 

FAW fall armyworm 

FFDCA Federal Food, Drug, and Cosmetic Act 
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GLOSSARY OF ACRONYMS AND ABBREVIATIONS, CONTINUED 

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act 

FR Federal Register 

ft foot/feet 

ft/mi feet per mile 

ft2/acre square feet per acre 

g gram/grams 

GI50 50% growth inhibition 

GIPSA Grain Inspection, Packers and Stockyards Administration (of the United States Department of 

 Agriculture) 

GM genetically modified 

ha hectare/hectares 

HEEC Highest Estimated Environmental Concentration 

HGT horizontal gene transfer 

hp horsepower 

HPLC high-performance liquid chromatography 

IA Iowa 

IC insecticidal crystal 

ICP/ICPs insecticidal crystal protein/insecticidal crystal proteins 

IL Illinois 

ILV independent laboratory validation 

IN Indiana 

IRM insect resistance management 

ISBN International Standard Book Number 

KM Michaelis-Menten constant 

kb kilobase 

kDa kiloDalton 

kg kilogram/kilograms 

L liter/liters 

LC50 median lethal concentration. A statistically derived concentration of a 

 substance that can be expected to cause death in 50% of test animals. It is 

 usually expressed as the weight of substance per weight or volume of water, 

 air, or feed (e.g., mg/L, mg/kg, or ppm). 

LD50 median lethal dose. A statistically derived single dose that can be expected to cause 

 death in 50% of the test animals when administered by the route indicated (oral, 

 dermal, inhalation). It is expressed as a weight of substance per unit weight of 

 animal (e.g., mg/kg). 

LLC limited liability company 

LOAEC Lowest Observed Adverse Effect Concentration 

LOC Level of Concern 

LOQ limit of quantitation 

m meter/meters 

MALDI-TOF-MS matrix-assisted laser desorption/ionization time-of-flight mass spectrometry 

MCRW Mexican corn rootworm 

μg microgram/micrograms 

μg/cm2 micrograms per square centimeter 

μg/g micrograms per gram 

μL microliter/microliters 
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GLOSSARY OF ACRONYMS AND ABBREVIATIONS, CONTINUED

mg milligram/milligrams 

mg/kg milligrams per kilogram 

mg/mL milligrams per milliliter 

MHD maximum hazard dose 

mL milliliter/milliliters 

MN Minnesota 

MO Missouri 

MOA mode of action 

mol/L moles per liter 

mol/mol moles to moles 

mph miles per hour 

MRID No./MRID Nos. Master Record Identification Number/Master Record Identification Numbers 

MRL/MRLs maximum residue level/maximum residue levels 

N/A not applicable 

NAS National Academy of Sciences 

NASS National Agricultural Statistics Service (of the United States Department of Agriculture) 

NCBI National Center for Biotechnology Information 

NCEAS National Center for Ecological Analysis and Synthesis 

NCRW northern corn rootworm 

NE Nebraska 

ng nanograms/nanograms 

ng/mg nanograms per milligram 

NIS Node Injury Scale 

nM nanomolar 

NOAEL No Observed Adverse Effect Level 

OCSPP Office of Chemical Safety and Pollution Prevention 

OECD Organization for Economic Cooperation and Development 

OPP Office of Pesticide Programs 

OPPTS Office of Prevention, Pesticides, and Toxic Substances 

ORF open reading frame 

PAT/pat phosphinothricin acetyltransferase 

PBS phosphate buffered saline 

PC Code Pesticide Chemical Code 

PCA Phased Compliance Approach 

PCR polymerase chain reaction 

PIP/PIPs plant-incorporated protectant/plant-incorporated protectants 

ppm parts per million 

RDR root damage rating 

RIP/RIPs ribosomal inhibition protein/ribosomal inhibition proteins 

RNA ribonucleic acid 

RQ risk quotient 

RRA relative rate of adaptation 

RSD relative standard deviation 

SAP Scientific Advisory Panel (the Panel) 

SCRW southern corn rootworm 

SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis 

SGF simulated gastric fluid 
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GLOSSARY OF ACRONYMS AND ABBREVIATIONS, CONTINUED 

SSA Sublethal Seedling Assay 

SWCB southwestern corn borer 

T-DNA transfer deoxyribonucleic acid 

TEP total extractable protein 

TGAI technical grade of the active ingredient 

TX Texas 

tr truncated 

U.S. United States 

USDA United States Department of Agriculture 

Vmax maximum velocity of the reaction 

VIPs vegetative insecticidal proteins 

WBCW western bean cutworm 

WCRW western corn rootworm 

WI Wisconsin 

w/w weight-to-weight 
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Table 1. Currently Registered PIPs Expressing Cry34Ab1 and Cry35Ab1 Proteins. 

EPA 

Registration 

Number 

Registration Name Company and Address Active 

Ingredient(s) 

Initial Date of Registration 

524-581 MON 89034 x TC1507 x MON 88017 x 

DAS-59122-7 (or SmartStaxTM) 

Monsanto Company 

800 North Lindbergh Boulevard 

St. Louis, MO 63167 

 Cry1A.105 

 Cry2Ab2 

 Cry1F 

 Cry3Bb1 

 Cry34Ab1 

 Cry35Ab1 

July 20, 2009 

524-584 MON 89034 x DAS-59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only. 

Monsanto Company 

800 North Lindbergh Boulevard 

St. Louis, MO 63167 

 Cry1A.105 

 Cry2Ab2 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 

524-586 MON 88017 x DAS-59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only. 

Monsanto Company 

800 North Lindbergh Boulevard 

St. Louis, MO 63167 

 Cry3Bb1 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 

524-588 MON 89034 x TC1507 x DAS-59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only. 

Monsanto Company 

800 North Lindbergh Boulevard 

St. Louis, MO 63167 

 Cry1A.105 

 Cry2Ab2 

 Cry1F 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 

524-589 MON 89034 x MON 88017 x DAS59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only. 

Monsanto Company 

800 North Lindbergh Boulevard 

St. Louis, MO 63167 

 Cry1A.105 

 Cry2Ab2 

 Cry3Bb1 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 

524-590 TC1507 x MON 88017 x DAS-59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only. 

Monsanto Company 

800 North Lindbergh Boulevard 

St. Louis, MO 63167 

 Cry1F 

 Cry3Bb1 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 

29964-4* Herculex® Rootworm Insect Protection Pioneer Hi-Bred International, 

Incorporated 

7100 N.W. 62nd Avenue 

P.O. Box 1000 

Johnston, IA 50131-1000 

 Cry34Ab1 

 Cry35Ab1 

August 31, 2005 

29964-5* Herculex® XTRA Insect Protection Pioneer Hi-Bred International, 

Incorporated 

7100 N.W. 62nd Avenue 

P.O. Box 1000 

Johnston, IA 50131-1000 

 Cry1F 

 Cry34Ab1 

 Cry35Ab1 

October 27, 2005 
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EPA 

Registration 

Number 

Registration Name Company and Address Active 

Ingredient(s) 

Initial Date of Registration 

29964-6* Optimum® AcreMaxTM 1 

Note: This registration is a seed blend. 

Pioneer Hi-Bred International, 

Incorporated 

7100 N.W. 62nd Avenue 

P.O. Box 1000 

Johnston, IA 50131-1000 

 Cry1F 

 Cry34Ab1 

 Cry35Ab1 

April 30, 2010 

29964-8** 1507 x 59122 x MON 810 Pioneer Hi-Bred International, 

Incorporated 

7100 N.W. 62nd Avenue 

P.O. Box 1000 

Johnston, IA 50131-1000 

 Cry1F 

 Cry34Ab1 

 Cry35Ab1 

 Cry1Ab 

February 24, 2010 

29964-9** 59122 x MON 810 Pioneer Hi-Bred International, 

Incorporated 

7100 N.W. 62nd Avenue 

P.O. Box 1000 

Johnston, IA 50131-1000 

 Cry34Ab1 

 Cry35Ab1 

 Cry1Ab 

February 24, 2010 

29964-10* Optimum® AcreMaxTM RW 

Note: This registration is a seed blend. 

Pioneer Hi-Bred International, 

Incorporated 

7100 N.W. 62nd Avenue 

P.O. Box 1000 

Johnston, IA 50131-1000 

 Cry34Ab1 

 Cry35Ab1 

April 30, 2010 

68467-5* Herculex® RW Insect Protection Mycogen Seeds 

c/o Dow AgroSciences LLC 

9330 Zionsville Road 

Indianapolis, IN 46268-1054 

 Cry34Ab1 

 Cry35Ab1 

August 31, 2005 

68467-6* Herculex® XTRA Insect Protection Mycogen Seeds 

c/o Dow AgroSciences LLC 

9330 Zionsville Road 

Indianapolis, IN 46268-1054 

 Cry1F 

 Cry34Ab1 

 Cry35Ab1 

October 27, 2005 

68467-7 MON 89034 x TC1507 x MON 88017 x 

DAS-59122-7 (or SmartStaxTM) 

Mycogen Seeds 

c/o Dow AgroSciences LLC 

9330 Zionsville Road 

Indianapolis, IN 46268-1054 

 Cry1A.105 

 Cry2Ab2 

 Cry1F 

 Cry3Bb1 

 Cry34Ab1 

 Cry35Ab1 

July 20, 2009 

68467-9 MON 89034 x TC1507 x DAS-59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only.

Mycogen Seeds 

c/o Dow AgroSciences LLC 

9330 Zionsville Road 

Indianapolis, IN 46268-1054 

 Cry1A.105 

 Cry2Ab2 

 Cry1F 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 

68467-10 MON 89034 x MON 88017 x DAS59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only. 

Mycogen Seeds 

c/o Dow AgroSciences LLC 

9330 Zionsville Road 

Indianapolis, IN 46268-1054 

 Cry1A.105 

 Cry2Ab2 

 Cry3Bb1 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 

68467-11 MON 89034 x DAS-59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only. 

Mycogen Seeds 

c/o Dow AgroSciences LLC 

9330 Zionsville Road 

Indianapolis, IN 46268-1054 

 Cry1A.105 

 Cry2Ab2 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 
Bacillus thuringiensis Cry34/35Ab1 Corn 

 Biopesticides Registration Action Document (BRAD) July 2010 

212

EPA 

Registration 

Number 

Registration Name Company and Address Active 

Ingredient(s) 

Initial Date of Registration 

68467-13 MON 88017 x DAS-59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only. 

Mycogen Seeds 

c/o Dow AgroSciences LLC 

9330 Zionsville Road 

Indianapolis, IN 46268-1054 

 Cry3Bb1 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 

68467-15 TC1507 x MON 88017 x DAS-59122-7 

Note: This registration is for breeding 

purposes, agronomic testing, increasing 

inbred seed stocks, and producing hybrid 

seed only. 

Mycogen Seeds 

c/o Dow AgroSciences LLC 

9330 Zionsville Road 

Indianapolis, IN 46268-1054 

 Cry1F 

 Cry3Bb1 

 Cry34Ab1 

 Cry35Ab1 

December 14, 2009 

*Registration expires September 30, 2010. 

**Registration expires October 31, 2010.