EPA reviews corn rootworm resistance to Cry3Bb1

On Jan. 17, the EPA released to the public an October 2012 Insect Resistance Management Team review and a January 17, 2013, memorandum summarizing that review. These documents present the EPA IRM Team’s scientific conclusions on the status of corn rootworm resistance to the Cry3Bb1 toxin in certain parts of the Corn Belt. 

The EPA places a high value on the efficacy of Plant Incorporated Protectant crops. To ensure that these very safe methods of insect control continue to be available long into the future, they have to be managed properly to prevent insects from developing resistance to the natural proteins being expressed. The EPA is committed to maintaining effective oversight of these products in order to preserve their substantial benefits to agriculture and the environment.

Based on a variety of data sources, the EPA IRM Team has concluded that corn rootworm may not be completely controlled by Cry3Bb1 in certain parts of the Corn Belt. While “confirmed resistance” as defined in registration documents has not been met, given the nature of the data, the manufacturer, Monsanto, has agreed to several actions and changes related to the registration of Cry3Bb1 products to address these matters. Examples of these actions include a commitment to conduct grower education programs demonstrating the value of crop rotation (e.g., to non-host crops such as soybean). Monsanto has also agreed to continue to measure changes in susceptibility and report the information annually to EPA. Additional information on these actions and changes can be found in a Jan. 17 memorandum titled “EPA’s Mitigation Actions to Address Concerns Related to Single-Trait Cry3Bb1 Products.”

EPA will be assessing resistance potential in the Corn Belt and evaluating Monsanto’s actions and submitted information; based on this ongoing oversight, EPA may take further action as appropriate.

In addition to the agreed upon actions and changes, EPA anticipates holding a Scientific Advisory Panel meeting in 2013 to discuss insect resistance management issues. 

The two memoranda referenced above and the Oct. 11, 2012, review, titled “BPPD IRM Team review of corn rootworm monitoring data and unexpected damage reports for Cry3Bb1 expressing Bt Corn and academic reports of Cry3Bb1 field failures as well as corn rootworm resistance” can be found at http://www.regulations.gov/ under docket number EPA-HQ-OPP-2011-0922. 

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