EPA's Proposed Framework to Delay Corn Rootworm

Severe root pruning to Bt plants in Cass County, IL, June 2012. (Photo: M. Gray).

Severe root pruning to Bt plants in Cass County, IL, June 2012. (Photo: M. Gray)

With farmers facing corn rootworm (CRW) resistance in at least 13 states, the Environmental Protection Agency (EPA or Agency) has proposed a framework earlier in the year to improve the corn rootworm resistance management program.

According to the Agency, the proposed framework would change the way farmers use Bt corn in order to slow the development of resistance. Some environmental groups, however, question whether the plan goes far enough.

EPA’s Goal

Expressly, EPA wants “to prolong the durability and effectiveness of [plants with Bt pesticide genetically engineered into corn] to control the corn rootworm pest.” Resistance in Bt corn is documented in parts of Iowa and Illinois but EPA believes that other parts of the Corn Belt, where corn rootworm infestations are common and the use of Bt corn is high, are also at risk for resistance. These areas are known as the corn rootworm “red zone” and include portions of Iowa, Illinois, Nebraska, western Indiana, southwestern Wisconsin, southern Minnesota, and eastern South Dakota. Other corn-growing regions such as Colorado, Kansas, Missouri, New York, South Dakota and Wisconsin, may also be at risk of resistance, though not to the same extent as areas in the “red zone.”

Proposed Changes

In December 2013, the agency convened a panel of experts, a Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel (FIFRA SAP), that issued recommendations guiding the Agency’s current proposed recommendations for manufacturers of Bt corn.

In areas at risk for corn rootworm resistance, the proposal would require crop rotation (no more than two consecutive years of planting Bt corn, rotating to soybean), use of corn varieties containing more than one Bt protein, or other Integrated Pest Management (IPM) strategies and stewardship for corn rootworm (e.g., use of conventional corn). The EPA proposed setting adoption rates for IPM approaches at 70% for high risk areas (“red zones”), and 50% for lower risk areas (“Fringe” of the Cornbelt area). Another proposal is to develop and implement a strategy to better detect and address areas of resistance as they emerge (e.g., using better scouting with crop consultants, university extension personnel, and company representatives rather than the current method where manufacturers rely solely on growers to report unexpected damage to Bt corn fields).

The agency has also proposed improving scientific tests and sampling to study the problem and more reliably ensure that resistance to the Bt corn proteins is identified. The Agency further proposed an annual reporting of success in meeting the IPM targets (i.e., how many growers chose to implement crop rotation, pyramids, etc.). The idea is that each biotech seed company would report data individually based on their customers experience (surveys could be conducted similar to those done for refuge compliance).

The EPA also proposed prohibiting soil applied insecticides from being used in combination with Bt corn for controlling corn rootworm (e.g., bag tag language, grower guides, and terms of registration).

Not Far Enough

The problem with the EPA’s proposal, says Center for Food Safety (CFS), an environmental non-profit, is that it “requires significant strengthening in order to be effective.” For example, CFS recommended in its comments to the Agency that the EPA raise the rotation requirements substantially to 100% and 75% of higher and lower risk areas respectively from EPA’s 70/50 proposal. The group also criticized the corn/soy crop rotation decision stating that “there is no good reason to single out soybeans as a rotation partner for Bt corn,” especially when “[s]imple corn/soy rotations have fostered rapid emergence of rotation-resistant corn rootworm.” CFS also argues that corn resistances can be delayed by “increasing the size of required refugia.” The group recommended “a substantial increase in refuge requirements (whether block refugia or refuge in a bag) to 50% for single-toxin Bt corn and 20% for pyramids.”

Public sector etymologists, among other things, proposed higher adoption targets for Integrated Pest Management approaches. The scientists proposed treating low resistance risk areas as high risk and high risk areas as the “Cow is out of the barn” situation. “Now that rootworm Bt resistance is widespread in the western and central Corn Belt, formerly high-risk areas are no longer at risk for resistance, rather, they are confirmed. The problem cannot be reversed; maintenance by mitigating future damage is the best case scenario.”

Some farmers and farming trade groups objected to the EPA’s proposed framework viewing it as an imposition on their freedom to farm and expressed concern about the availability of non-gmo corn. Concerns over yield from non-gmo corn were also raised (even though higher yields of GMO crops has been hotly contested). A non-gmo farmer, however, countered these arguments by stating that they are “scare tactics” and that in fact GMO traits reduce farmers’ reliance on Integrated Pest Management.

Some commentators suggested doing away with GMOs as an alternative way of dealing with resistance, asking the EPA to ban Bt corn and to do away with GMOs entirely. At least one commentator also urged the EPA to consider the impact of genetic engineering on non-target animals.