. UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

Elizabeth Owens, Ph.D. 

Chair 

Agricultural Biotechnology Stewardship Technical Committee 

c/o Pioneer · 

7100 NW 62"d Avenue 

Johnston, TA 50131-1000 

Dear Dr. Owens: 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

September 3, 2014 

We are writing to initiate discussions with Bt corn registrants (via the Agricultural 

Biotechnology Stewardship Technical Committee) on improvements to corn rootworm resistance 

management. As you are aware, ABSTC and EPA share a common interest in preserving the 

durability of Bt corn traits to control corn rootworm. Along these lines, the Agency convened a 

Science Advisory Panel (SAP) meeting in December 2013 to address scientific uncertainties 

associated with corn rootworm resistance monitoring. These discussions will follow from the 

recommendations made by the panel in its report dated March 5, 2014. 

To aid in starting the discussions, the Agency is enclosing a set of proposals developed by the 

Biopesticides and Pollution Prevention Division to enhance current resistance management and 

monitoring programs for corn rootworm. These proposals are consistent with the SAP's 

guidance and cover five aspects of IRM, including the following: 

• Integrated Pest Management (IPM) as a component of corn rootworm resistance 

management 

• Responses to unexpected damage in Bt corn fields 

• Elimination of the requirement for annual random sampling of corn rootworm 

from the Corn Belt 

• Use of on-plant assays for resistance determinations 

• Enhancements to current remedial action plans 

The Agency's goal is to have improvements in place for the 2015 growing season. To meet this 

goal, we are asking that you submit a response to the attached proposal by September 21,2014. 

EPA would like to finalize the agreement/enhancements to the affected Bt corn products by 

October 31, 2014. 
If you would like to schedule a meeting to discuss this further after you've responded to our 

proposal, or if you have any questions or concerns, please contact Alan Reynolds 

(reynolds.alan@epa.gov; 703-605-0515). 

Enclosure 

Sincerely, 

· mberly Nesci, Chief 

Microbial Pesticides Branch 

Biopesticide and Pollution Prevention Division 

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EPA Framework for PIP Registrants: 

Proposal to Address Key SAP Recommendations for Corn Rootworm (CRW) IRM 

Draft Date: 8/27/14 

Overall Goal: BPPD has identified five areas of improvement for corn rootworm resistance management. These 

measures are needed to increase t he durability of CRW Bt PIPs (so as to reduce the potential need for 

remediation), and to improve on current abilit ies to detect and respond to cases of resistance. BPPD is targeting 

these improvements to be in place for the 2015 growing season. 

1) Utilize an IPM approach to CRW resistance management 

• Rationale: 

o Given the documented cases of field resistance to some Bt traits, refuge alone has not been 

sufficient to manage CRW resistance to Bt corn; 

o The SAP concluded (and EPA agrees) that sound IPM practices may reduce the potential for 

resistance (and hence remediation). 

• Goals: 

o IPM stewardship program. Registrants must supplement IRM (refuges) with IPM techniques. 

This can be implemented by registrants as a stewardship program as part of the terms of 

registration that must include the following specific IPM approaches: 

• Crop rotation with no more than two consecutive years of Bt corn (preferably rotating 

to soybean). Rotation can be accomplished on a farm-wide basis or field-by-field within 

a farm; 

• Use of multiple Bt modes of action for CRW control, preferably in pyramided varieties (4 

Bt PIPs are currently registered: Cry3Bb1, Cry34/35, mCry3A, and eCry3.1Ab); AND 

• Use of non-Bt (conventional) corn with insecticide use for CRW management; 

o Adoption targets. The stewardship program must establish adoption targets for the IPM 

elements (i.e.,% of growers and total corn acres planted with each company's seed using each 

IPM approach), as defined below. A two t ier system is envisioned, with separate targets for high 

risk areas (i.e., t he "Red Zone") and lower risk areas (i.e., the "fringe" of the Corn Belt). 

IPM Adoption (%of total acres) 

High Risk Areas Lower Risk Areas 

OveraiiiPM participation 70 50 

Tactics to be used among 

IPM participants: 

- Crop rotation 50 33 

- Mult iple modes of 

25 33 

action/pyramids 

- Non-Bt corn w/SAI 25 33 

Use of single toxin PIPs No more than 10% No more than 20% 

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o Annual report ing. The program would require annual reporting to EPA of success in meeting the 

IPM targets (i.e., how many growers chose to implement crop rotation, pyramids, etc.). Each 

company would report data individually based for their customers (surveys could be conducted 

similar to those done for refuge compliance). BPPD will analyze the reports and tabulate data 

across the industry as a whole; 

o Single trait PIPs. The stewardship program and reporting must include information on progress 

towards replacement of single-trait CRW commercial PIP products; 

• Non-starter: 

o Soi l-applied insecticides (SAl). SAis must be prohibited from use in combination with Bt corn for 

controlling corn rootworm. This can be done via bag tag language, grower guides, and terms of 

registration. 

• Challenges to be addressed: 

o Need for coordination between companies, particularly among growers who may purchase seed 

from more than one company (a program analogous to the existing compliance assurance 

program could address this challenge); 

o Need for means to address neighboring farms; 

o Implementation of SAl prohibition. 

2) Implement a proactive strategy to detect unexpected damage (UXD) in Bt corn fields 

• Rationale: 

o UXD is the f irst real indicator of potential resistance; 

o Cases of resistance to date have been documented by collecting CRW from damaged fields; 

o Effective and t imely responses to UXD may aid remediation (if resistant CRW are responsible). 

• Goals: 

o Damage thresholds. Revise terms and conditions to require the use of damage thresholds to 

trigger CRW sampling for resistance determinations: 1.0 Node Injury Score (NIS) for single traits 

and 0.5 NIS for pyramids; 

o Adult collection. Revise term and conditions to require collection of adults from the damaged 

site (or same field if collections are delayed that season) and that those adults be tested for 

resistance with on-plant assays (see #4 below); 

o Immediate implementation of BMPs. Revise terms and conditions to require, in cases of UXD, 

that BMPs be implemented immediately (i.e., before resistance confirmation) to mitigate the 

spread of a potentially resistant population. BMPs are essentially the same IPM practices that 

were detailed in #1 above but may include beetle bombing to reduce egg laying the next year. 

o Target adoption level for BMPs. At least 75%, similar to the IPM targets for high risk areas in #1 

above. 

• Challenges to be addressed: 

o Many elements are currently in place (e.g., damage triggers and BMPs for UXD) but there is a 

need for standardization across the industry; 

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o Need for improvement of detection capabilities in high risk areas- better scouting, possibly 

involving crop consultants, university extension personnel, company representatives (registrants 

currently rely solely on growers to report UXD); 

o Mechanism for reporting UXD cases and their resolut ion to EPA. One possible tool could be to 

use EPA's Central Data Exchange (COX). COX is a secure means to report information to EPA 

(used in the Air program) and could be used to tabulate UXD damage reports by toxin and 

geographic location. This information could be used in inform remedial action strategies (see #5 

below). 

3) Remove requirement for annual monitoring of CRW populations randomly sampled from the Corn Belt 

• Rationale: 

o EPA has concluded that data aren't meaningful unless populations are tracked over time; 

o Panel recommended tracking individual populations or discrete geographic locations based on 

high risk factors, but such tracking will be inefficient and unlikely to detect resistance before 

field failure; 

o BPPD believes it will be more effective to focus instead on proactive detection and response to 

UXD (#2 above). 

• Goals: 

o Industry to modify terms of registration to remove annual sampling requirements (coupled with 

improvements to UXD scouting detailed in #2 above). 

4) Improve resistance confirmation process by replacing artificial diet bioassays with "on-plant" assays 

• Rationale: 

o EPA has concluded that diet bioassays have not been helpful for regulatory purposes- data are 

too variable to reliably draw conclusions about resistance; 

o EPA believes that on-plant assays represent a more realistic exposure scenario and can serve as 

a diagnostic tool; 

o EPA understands that two on-plant assays have been developed (with methodology in the public 

literature) to confirm resistance: single on-plant assay (Gassmann) and Sublethal Seedling assay 

(Pioneer). 

• Goals: 

o Industry to modify terms of registration to mandate the use of an on-plant assay and resistance 

confirmation criteria; 

o Resistance is confirmed by comparing a population's response on Bt vs. non-Bt corn and/or with 

a susceptible control population (2 statistically significant comparisons are needed to confirm 

resistance); 

• Challenges to be addressed: 

o How to ensure consistent resistance determination standards with two separate assays (single 

on-plant vs. SSA); 

o Adaptation of the on-plant assays for the different registered Bt toxins, particularly the SSA 

which was developed for Cry34/35 corn; 

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o Transition for companies currently using the diet bioassay. 

S) Enhance current remedial action (RA) plans (in the event of documented resistance) 

• Rationale: 

o The panel recommended that specific, implementable RA plans be developed prior to resistance 

confirmation (currently registrants are required to work with EPA to develop a plan ex post 

facto); 

o The goals of RA are to 1) contain (and extirpate if possible) resistant populations, and 2) 

preserve the durability of Bt CRW traits in areas where they are still effective. 

• Goals: 

o Remedial action plans. Registrants must develop and submit RA plans to be in place prior to 

resistance development; 

o Standards. Remedial action plans must identify industry-wide standards as follows: 

• Timing: RA plan must ensure action (IPM-based BMPs from #2 above) occurs 

immediately in response to UXD (i.e., within the growing season) and should continue in 

subsequent seasons unless resistance is disconfirmed; 

• BMPs: RA plan must require the following specific steps taken for UXD and/or 

resistance: 

• Adult CRW treatment ("beetle bombing") in UXD damage fields (same season); 

• Crop rotation (preferred), use of alternate Bt modes of action, use of pyramided 

varieties, or non-Bt corn (with insecticides) in subsequent seasons; 

• Geography: RA plan must describe how to define the scope of RA. The RA area as 

defined in the plan must include not just the affected field but surrounding fields and 

farms within the dispersal range of CRW. (This could also be informed by UXD reports 

received by COX - see #2 above). 

o Data needs. Addit ional research is needed to improve RA including CRW dispersal in simulation 

models to assess the potential spread of resistant populations and would entertain revised plans 

based on the results of any such research; 

o Notification system. RA plan must require cases of documented resistance to be publ icly 

reported on web site (either by ABSTC, the individual company, or EPA). This would help 

growers make informed decisions about CRW management options. 

• Challenges to be addressed: 

o Defining the remediation zone, which could involve mult iple farms and customers from different 

registrants; 

o Need for coordination between companies; 

o Need for additional research to scientifically delineate remediation areas (the SAP also proposed 

a number of techniques to do this); 

o Encouraging growers to implement effective measures (e.g., crop rotation) that may differ from 

their farming practices. 

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