Corn: Bt Growers React to EPA Rootworm Management Proposal – DTN

    Adult western corn rootworm.

    Nestled below the soil, western corn rootworm eggs across the Midwest are mere weeks away from hatching, oblivious to the stir they are creating aboveground this spring.

    A month has passed since the Environmental Protection Agency (EPA) closed the public comment period on its regulatory proposal to slow the development of Bt resistance in the western corn rootworm. By targeting all use of corn containing Bt rootworm proteins, the proposal would govern almost every corn grower in the U.S., but would be particularly influential in the Midwest, where the rootworm is prevalent.

    The EPA’s proposed rules would require Bt-corn growers to use certain pest management practices such as crop rotation and the use of non-Bt corn hybrids. The proposal has generated a small, but passionate response of 91 public comments from the agricultural community.

    By and large, agricultural players such as seed companies, industry groups, farmers and crop consultants condemned the new rules as an infringement on farmers’ freedom to operate. Yet other groups — primarily academics and industry watchdog groups — asked the EPA to consider even more stringent policies, including increasing required plant refuges, setting higher pest management quotas, and arming the new rules with real regulatory teeth.


    The EPA proposal was released on Jan. 28 as part of the agency’s scheduled registration review of Bt traits on the market. In an effort to slow the steady development of rootworm resistance to Bt corn traits, the proposal would require seed companies that sell Bt corn to ensure that set percentages of their customers use approved integrated pest management (IPM) tactics. Those include crop rotation, planting non-Bt hybrids with a soil insecticide, and rotating the types of Bt proteins used in their fields.

    The proposal establishes a “red zone,” where corn rootworm pressure and Bt-resistance is especially prevalent, namely parts of Iowa, Illinois, Nebraska, western Indiana, southwestern Wisconsin, southern Minnesota, and eastern South Dakota.

    Here, Bt-seed companies would have to ensure that 70% of their customers were using these IPM practices. Beyond the “red zone” areas, companies would have to prove that 50% of their customers were using IPM practices. In addition to these quotas, the new rules propose banning the use of soil-applied insecticide on corn products with Bt rootworm traits and limiting the use of single-protein Bt corn products.

    The EPA is now reviewing public comments on these rules, which are scheduled to be finalized by the end of 2015, along with the agency’s registration review of Bt corn.


    The EPA’s proposed mandatory IPM quotas received criticism from industry players such as Syngenta, Valent USA, Burrus Seeds, the American Soybean Association, state Corn Growers’ Associations, farmers, entomologists, and even government agencies such as USDA and the National Association of State Departments of Agriculture.

    USDA deemed the quota system overly prescriptive and possibly unenforceable. Companies successfully monitoring the practice of IPM by growers “may not be achievable,” Director of USDA’s Office of Pest Management Policy Sheryl Kunickis wrote to the EPA. “Short of having seed company representatives walk the fields of farmers who opt not to purchase their products in a given year, individual registrants may not be able to determine if a particular farmer has adopted crop rotation practices or simply switched to a competitor’s seed.”

    Forcing farmers to rotate crops every two years was particularly concerning to some commenters. A group of Nebraska entomologists cited a number of factors driving the state’s farmers to continuous corn, such as irrigation profitability, livestock production, ethanol production, and soil types. “Because of these factors, continuous corn at some level will remain part of the Nebraska agricultural system for the foreseeable future,” they wrote to the EPA.

    A group of entomologists from the eastern and north-central U.S. added that crop rotation no longer controls the corn rootworm in parts of northeastern Illinois and northwestern and north-central Indiana, where researchers have confirmed rootworm populations with resistance to both crop rotation and two Bt proteins, Cry3Bb1 and mCry3A.

    Along with USDA, this group of entomologists also expressed deep skepticism that industry players such as companies, farmers, and Extension agents will share data and information on resistance problems in the field, as the EPA proposal would require. “The suggestion that companies should coordinate with respect to their interactions with customers raises some issues around the sharing of confidential business information as well as, potentially, antitrust considerations,” wrote USDA’s Kunickis.

    The EPA’s proposed ban to keep growers from using soil-applied insecticide (SAI) in combination with corn hybrids containing Bt rootworm traits has also become a focal point for many growers and industry groups.

    Banning this practice is grounded in academic research, which has shown that it can encourage the development of resistance. However, farmer, company, and crop consultant comments stressed a continued need for insecticides to control the rootworm and secondary pests.

    The National Association of State Departments of Agriculture stressed that restricting the use of soil-applied insecticides might not fall under the legal scope of the EPA’s division of Biopesticides and Pollution Prevention, which produced the proposal.

    USDA’s Kunickis also voiced disapproval of the proposed ban, but added that “USDA recognizes that there is no economic benefit to the grower in adding an insecticide on top of a Bt trait that is working” and recommends instead “an educational effort designed to dissuade growers from ill-informed use of SAI.”


    Some entomologists and industry watchdog groups called for stricter rules for Bt-corn users. Greg Jaffe, director of biotechnology at the Center for Science in the Public Interest, said Bt users’ history of “pitiful compliance” with the agency’s initial refuge requirements should guide the EPA’s approach to these new rules. “EPA cannot afford to do the same thing again for implementing IPM practices to prevent CRW resistance,” he wrote. “The adoption targets are the proper way forward and those targets need to be memorialized in the terms of registration with each registrant.”

    Jaffe recommended enforcing the integrated pest management quotas with third-party inspections and serious penalties: “If a particular developer does not achieve the adoption targets for its farmer customers, financial penalties and/or restriction on seed sales should result.”

    Jaffe also proposed making crop rotation a mandatory label requirement on Bt seed. He dismissed concerns about limiting farmer freedom, noting that crop rotation remains the number-one-recommended practice for discouraging resistance. “…Such a prescriptive requirement will be memorializing what the vast majority of farmers either do or should do,” he wrote.

    On top of the EPA’s proposed IPM quotas, University of Arizona entomologists Bruce Tabashnik and Yves Carriere called for greatly increasing Bt corn refuge requirements to 50% for single-protein products and 20% for “pyramided” products with two rootworm proteins.

    IPM practices can lower rootworm populations, but they don’t change the frequency of resistant individuals in those populations, Tabashnik explained to DTN. “It’s useful to apply IPM, but to really make a difference in slowing the trajectory of resistance, you must increase refuge percentage,” he said.

    The pyramided Bt-protein products championed by the EPA proposal can help slow Bt resistance in the rootworm, but their refuge requirement of only 5% is far too low, Tabashnik added. Since all of the pyramided products on the market contain at least one Bt protein that the rootworm has developed resistance to in some areas, some farmers will be essentially relying on just one Bt protein for protection, with a tiny refuge, he noted.

    Tabashnik and Carriere also called for upping the mandatory IPM quotas to 100% in high-risk areas and 75% for all other growers. “I agree that enforcement would be problematic, but our point is that a target adoption rate should be very high,” Tabashnik said. “Why aim low?”

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