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Insect Resistance Management Fact Sheet for Bacillus thuringiensis (Bt) Corn Products
Resources
On This Page
- Bt Field Corn (and Popcorn) IRM Program
- Specific Structured Refuge Requirements
- Bt Sweet Corn IRM Program
- IRM Websites
- Contact Information
Bt Field Corn (and Popcorn) IRM Program
The IRM program that growers must follow for Bt field corn (and popcorn) has the following elements.
- Structured refuge requirements
- Growers agreements must be signed
- Growers must annually affirm that they will follow the IRM requirements
- Grower compliance program (conducted by registrants)
- Anonymous telephone surveys
- On-farm assessments
- Growers can report violations of the structured refuge requirements as “tips and complaints” to the seed company
- Remedial actions are required of growers who have deviations from the structured refuge requirements
- Resistance monitoring programs for Cry1Ab and Cry1F Bt corn (European corn borer, corn earworm, southwestern corn borer)and for Cry3Bb1, Cry34Ab1/35Ab1, mCry3Aa1 Bt corn (western corn rootworm)
- Bioassays (conducted by registrants)
- Growers are encouraged to report incidents of “unexpected damage” in the field
Specific Structured Refuge Requirements
- The specific structured requirements for corn borer-protected Bt (Cry1Ab and Cry1F) corn products are as follows:
- Structured refuges: 20% non-Lepidopteran Bt corn refuge in Corn Belt; 50% non-Lepidopteran Bt refuge in Cotton Belt
- Blocks
- Internal (i.e., within the Bt field)
- External (i.e., separate fields within ½ mile (¼ mile if possible) of the Bt field to maximize random mating)
- In-field Strips
- Strips must be at least 4 rows wide (preferably 6 rows) to reduce the effects of larval movement
- The specific structured requirements for corn rootworm-protected Bt (Cry3Bb1, Cry34Ab1/Cry35Ab1, modified Cry3A) corn products are summarized in the Table below.
| Single gene CRW products | Stacked CRW and Corn borer products | |
|---|---|---|
| % Refuge | 20 % (all regions) | 20 % (corn regions) 50% (cotton regions) |
| Refuge Deployment | Discrete CRW refuge | 2 options: 1) Common CRW/corn borer refuge 2) Descent CRW and corn borer refuges |
| Refuse Design | Adjacent field, Block, Perimeter, In-field Strip | For common refuge and discrete CRW refuge: Adjacent field, Block Perimeter, In-field Strip For discrete corn borer refuge: Separate fields can be sued in addition to other options |
| Refuge Distance (proximity to Bt crop) | Refuges adjacent to or within field | For shared refuge and discrete CRW refuge: Refuges adjacent to or within field For discrete corn borer refuge: Separate refuges must be within 1/2 mile (1/4 mile preferred) |
| Strip Width (in-field refuges) | At least 4 rows | At least 4 rows (for discrete corn borer refuges, at least 6 rows are recommended) |
Bt Sweet Corn IRM Program
- No Structured Refuge Requirements
- Growers must destroy any Bt (Cry1Ab) sweet corn stalks that remain in the fields following harvest. This activity must take place either immediately following harvest or a short period of time (a maximum of 1 month) later in accordance with local production practices. Stalk destruction prior to winter will insure that any larvae that happen to be present in the plants after harvest are eliminated.
- Growers are instructed to report any incident of unexpected levels of pest damage.
- All other aspects of the IRM Grower Education, Grower Agreement, Grower Affirmation, and Resistance Monitoring Programs are the same as for Bt field corn and popcorn products as discussed above.
For specific information on the Bt field corn, popcorn, and sweet corn IRM programs, go the following websites:
For further information contact:
Ombudsman, Biopesticides and Pollution Prevention Division (7511P)
Office of Pesticide Programs
Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, D.C. 20460